diff --git a/bin/commit b/bin/commit
new file mode 100755
index 0000000..55aff07
--- /dev/null
+++ b/bin/commit
@@ -0,0 +1,13 @@
+#!/bin/sh
+TYPE=$(gum choose "fix" "feat" "docs" "style" "refactor" "test" "chore" "revert")
+SCOPE=$(gum input --placeholder "scope")
+
+# Since the scope is optional, wrap it in parentheses if it has a value.
+test -n "$SCOPE" && SCOPE="($SCOPE)"
+
+# Pre-populate the input with the type(scope): so that the user may change it
+SUMMARY=$(gum input --value "$TYPE$SCOPE: " --placeholder "Summary of this change")
+DESCRIPTION=$(gum write --placeholder "Details of this change (CTRL+D to finish)")
+
+# Commit these changes
+gum confirm "Commit changes?" && git add -A && git commit -m "$SUMMARY" -m "$DESCRIPTION"
diff --git a/bin/nb b/bin/nb
new file mode 100755
index 0000000..340e57b
--- /dev/null
+++ b/bin/nb
@@ -0,0 +1,25477 @@
+#!/usr/bin/env bash
+###############################################################################
+# __          _
+# \ \   _ __ | |__
+#  \ \ | '_ \| '_ \
+#  / / | | | | |_) |
+# /_/  |_| |_|_.__/
+#
+# [nb] Command line and local web note-taking, bookmarking, and archiving with
+# plain text data storage, encryption, filtering and search, pinning, #tagging,
+# Git-backed versioning and syncing, Pandoc-backed conversion, global and local
+# notebooks, customizable color themes, [[wiki-style linking]], plugins, and
+# more in a single portable, user-friendly script.
+#
+# ❯ https://github.com/xwmx/nb
+# ❯ https://xwmx.github.io/nb
+#
+# Based on Bash Boilerplate: https://github.com/xwmx/bash-boilerplate
+#
+# Copyright (c) 2015-present William Melody ┯ hi@williammelody.com
+#                                           ┕ https://www.williammelody.com
+#
+# Overview
+# ========
+#
+# - Configuration and Setup
+# - Helpers: Group 1 (alphabetical order)
+# - Subcommands: Group 1 (alphabetical order)
+# - Plugins
+# - Option Parsing
+# - _main() / Dispatch
+# - Helpers: Group 2 (alphabetical order)
+# - Subcommands: Group 2 (alphabetical order)
+# - Subcommands: Group 3 (alphabetical order)
+#
+# Target Bash Version:              5   (target,   recommended)
+# Minimum Recommended Bash Version: 4   (fallback, recommended)
+# Minimum Tested Bash Version:      3.2 (fallback, deprecated)
+#
+# AGPLv3
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+###############################################################################
+
+###############################################################################
+# Shell Options & Strict Mode
+#
+# More Information:
+#   https://github.com/xwmx/bash-boilerplate#bash-strict-mode
+#   https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html
+#   https://www.gnu.org/software/bash/manual/html_node/The-Shopt-Builtin.html
+#   https://tldp.org/LDP/abs/html/options.html
+###############################################################################
+
+set -o errexit
+set -o noglob
+set -o nounset
+set -o pipefail
+
+set +o noclobber
+
+shopt -s extglob
+
+IFS=$'\n\t'
+
+###############################################################################
+# Environment
+###############################################################################
+
+# $_VERSION
+#
+# The most recent program version.
+_VERSION="7.1.1"
+
+# $_ME
+#
+# This program's basename.
+_ME="$(basename "${0}")"
+
+# $_MY_DIR
+#
+# The directory containing $_ME.
+_MY_DIR="$(cd "$(dirname "${0}")"; pwd)"
+
+# $_MY_PATH
+#
+# This program's full path.
+_MY_PATH="${_MY_DIR}/${_ME}"
+
+# $_CURRENT_WORKING_DIR
+#
+# The current working directory in which the program was invoked.
+_CURRENT_WORKING_DIR="${PWD}"
+
+# $_REPO
+#
+# The <user>/<repo> identifier for this project's git repository.
+_REPO="xwmx/nb"
+
+# $_REPO_MAIN_BRANCH
+#
+# The name of the main branch in this project's git repository.
+_REPO_MAIN_BRANCH="master"
+
+# $_REPO_RAW_URL
+#
+# The base URL for raw files.
+_REPO_RAW_URL="https://raw.githubusercontent.com/${_REPO}/${_REPO_MAIN_BRANCH}"
+
+###############################################################################
+# Utilities
+###############################################################################
+
+# _command_exists()
+#
+# Usage:
+#   _command_exists <name>
+#
+# Exit / Error / Return Status:
+#   0 (success, true) If a command <name> is defined in the current environment.
+#   1 (error,  false) If not.
+#
+# More Information:
+#   http://stackoverflow.com/a/677212
+_command_exists() {
+  if [[ "${1:-}" == "w3m" ]]
+  then # Detect WSL 1 (https://stackoverflow.com/a/38859331), where w3m errors.
+    [[ -f /proc/version ]] && grep -q Micro /proc/version && return 1
+  fi
+
+  hash "${1}" 2>/dev/null
+}
+
+# _contains()
+#
+# Usage:
+#   _contains <query> <list-item>...
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If the item is included in the list.
+#   1 (error,  false)  If not.
+#
+# Example:
+#   _contains "${_query}" "${_list[@]}"
+_contains() {
+  local _query="${1:-}"
+
+  shift
+
+  if [[ -z "${_query}"  ]] ||
+     [[ -z "${*:-}"     ]]
+  then
+    return 1
+  fi
+
+  local __element=
+  for   __element in "${@}"
+  do
+    [[ "${__element}" == "${_query}" ]] && return 0
+  done
+
+  return 1
+}
+
+# _resolve_symlink()
+#
+# Usage:
+#   _resolve_symlink <path>
+#
+# Description:
+#   Resolve the real path or target for a symbolic link.
+_resolve_symlink() {
+  if hash "realpath" 2>/dev/null
+  then
+    realpath "${@:-}"
+  else
+    readlink "${@:-}"
+  fi
+}
+
+# _sed_i()
+#
+# Usage:
+#   _sed_i <sed-argument>...
+#
+# Description:
+#   `sed -i` takes an extension on macOS, but that extension can cause errors
+#   in GNU `sed`. Detect which `sed` is available and call it with the
+#   appropriate arguments.
+#
+# More Information:
+#   https://stackoverflow.com/q/43171648
+#   https://stackoverflow.com/a/16746032
+_sed_i() {
+  if sed --help >/dev/null 2>&1
+  then # GNU
+    sed -i    "${@}"
+  else # BSD
+    sed -i '' "${@}"
+  fi
+}
+
+# _tput()
+#
+# Usage:
+#   _tput <tput options>...
+#
+# Description:
+#   Run `tput` commands, with fallbacks to termcap names for FreeBSD and
+#   `stty` and escape sequences when `tput` is not found.
+_tput() {
+  if _command_exists "tput"
+  then
+    # More info: https://stackoverflow.com/a/64214019
+    case "${1:-}" in
+      cols)
+        if tput cols  &>/dev/null
+        then
+          tput cols
+        elif tput co  &>/dev/null
+        then
+          tput co
+        else
+          printf "80\\n"
+        fi
+
+        return 0
+        ;;
+      lines)
+        if tput lines &>/dev/null
+        then
+          tput lines
+        elif tput li  &>/dev/null
+        then
+          tput li
+        else
+          printf "20\\n"
+        fi
+
+        return 0
+        ;;
+      setaf|smul)
+        ((${_COLOR_ENABLED:-1}))  || return 0
+        ;;
+    esac
+
+    tput "${@:-}" 2>/dev/null     || {
+      case "${1:-}" in
+        sgr0)
+          tput me
+          ;;
+        smul)
+          tput us
+          ;;
+        setaf)
+          tput AF "${@:2}"
+          ;;
+      esac
+    } 2>/dev/null || printf ""
+  else
+    case "${1:-}" in
+      cols|lines)
+        {
+          stty size 2>/dev/null   || printf "20 80\\n"
+        } | if [[ "${1:-}" == "cols" ]]
+            then
+              cut -d " " -f 2
+            else
+              cut -d " " -f 1
+            fi
+        ;;
+      setaf)
+        printf '\033[38;5;%sm'  "${2:-}"
+        ;;
+      sgr0)
+        printf '\033[m'
+        ;;
+      smul)
+        printf '\033[4m'
+        ;;
+    esac
+  fi
+}
+
+###############################################################################
+# Debug
+###############################################################################
+
+# _debug()
+#
+# Usage:
+#   _debug <command> <options>...
+#
+# Description:
+#   Execute a command and print to standard error. The command is expected to
+#   print a message and should typically be either `echo`, `printf`, or `cat`.
+#
+# Example:
+#   _debug printf "Debug info. Variable: %s\\n" "$0"
+__DEBUG_COUNTER=0
+__DEBUG_START_TIME=
+_debug() {
+  # Usage: __debug_get_timestamp
+  __debug_get_timestamp() {
+    if hash "gdate" 2>/dev/null
+    then
+      gdate +%s%3N
+    elif date --version >/dev/null 2>&1
+    then
+      date +%s%3N
+    else
+      return 1
+    fi
+  }
+
+  if ((${_USE_DEBUG:-0}))
+  then
+    __DEBUG_COUNTER=$((__DEBUG_COUNTER+1))
+    printf "🐛  %s" "${__DEBUG_COUNTER} "
+
+    "${@}"
+
+    if [[ -n "${__DEBUG_START_TIME:-}" ]]
+    then
+      printf "⏱  %s\\n" "$(($(__debug_get_timestamp)-__DEBUG_START_TIME))"
+    elif __DEBUG_START_TIME="$(__debug_get_timestamp)"
+    then
+      printf "⏱  0\\n"
+    fi
+
+    printf "―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――\\n"
+  fi 1>&2
+}
+
+###############################################################################
+# Error Messages
+###############################################################################
+
+# _exit_1()
+#
+# Usage:
+#   _exit_1 <command>
+#
+# Description:
+#   Exit with status 1 after executing the specified command with output
+#   redirected to standard error. The command is expected to print a message
+#   and should typically be either `echo`, `printf`, or `cat`.
+_exit_1() {
+  {
+    [[ "${1:-}" == "_help" ]] || printf "%s " "$(_tput setaf 1)!$(_tput sgr0)"
+
+    "${@}"
+  } 1>&2
+
+  exit 1
+}
+
+# _warn()
+#
+# Usage:
+#   _warn <command>
+#
+# Description:
+#   Print the specified command with output redirected to standard error.
+#   The command is expected to print a message and should typically be either
+#   `echo`, `printf`, or `cat`.
+_warn() {
+  {
+    printf "%s " "$(_tput setaf 1)!$(_tput sgr0)"
+
+    "${@}"
+  } 1>&2
+}
+
+###############################################################################
+# Option Helpers
+###############################################################################
+
+# _option_get_value()
+#
+# Usage:
+#   _option_get_value <option> <value>
+#
+# Description:
+#   Given a flag (e.g., -e | --example) return the value or exit 1 if value
+#   is blank or appears to be another option.
+_option_get_value() {
+  local _option="${1:-}"
+  local _value="${2:-}"
+
+  if [[ -n "${_value:-}" ]] && [[ ! "${_value:-}" =~ ^- ]]
+  then
+    printf "%s\\n" "${_value}"
+  else
+    _exit_1 printf                          \
+      "%s requires a valid argument.\\n"    \
+      "$(_color_primary "${_option}")"
+  fi
+}
+
+# _option_value_is_present()
+#
+# Usage:
+#   _option_value_is_present <value>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  The argument is present and does not match as an option
+#                      flag.
+#   1 (error,  false)  The argument is blank or matches as an option flag.
+_option_value_is_present() {
+  [[ -n "${1:-}" ]] && [[ ! "${1:-}" =~ ^-  ]]
+}
+
+###############################################################################
+# Configuration
+###############################################################################
+
+# Configuration File ####################################### Configuration File
+
+# $NBRC_PATH
+#
+# Default: `$HOME/.nbrc`
+#
+# The location of the .nbrc configuration file.
+export NBRC_PATH="${NBRC_PATH:-"${HOME}/.${_ME}rc"}"
+
+# Handle symlinked NBRC_PATH.
+if [[ -L "${NBRC_PATH}" ]]
+then
+  NBRC_PATH="$(_resolve_symlink "${NBRC_PATH}")"
+fi
+
+# Source rc file.
+if [[ -e "${NBRC_PATH}" ]]
+then
+  source "${NBRC_PATH}"
+fi
+
+# Base Configuration ####################################### Base Configuration
+
+# $NB_DIR
+#
+# Default: `$HOME/.nb`
+#
+# The location of the directory that contains the notebooks.
+export NB_DIR="${NB_DIR:-"${HOME}/.${_ME}"}"
+
+# Handle symlinked NB_DIR.
+if [[ -L "${NB_DIR:-}"      ]]
+then
+  NB_DIR="$(_resolve_symlink "${NB_DIR}")"
+fi
+
+# Validate that NB_DIR exists and is writable.
+if [[ -z "${NB_DIR:?}"      ]] ||
+   [[    "${NB_DIR}" == "/" ]] ||
+   {
+     [[   -e "${NB_DIR}"    ]] &&
+     [[ ! -w "${NB_DIR}"    ]]
+   }
+then
+  _exit_1 cat <<HEREDOC
+NB_DIR is not valid:
+  ${NB_DIR}
+
+Remove any NB_DIR settings in .${_ME}rc to reset to default:
+  ${NBRC_PATH}
+
+NB_DIR settings prompt:
+  ${_ME} settings nb_dir
+HEREDOC
+fi
+
+# $NB_AUDIO_TOOL
+#
+# Default: '' (first available)
+#
+# Example Values: 'mplayer', 'afplay'
+export NB_AUDIO_TOOL="${NB_AUDIO_TOOL:-}"
+
+# $NB_AUTO_SYNC
+#
+# Default: '1'
+#
+# When set to '1', each `_git checkpoint()` call will automativally run
+# `$_ME sync`. To disable this behavior, set the value to '0'.
+export NB_AUTO_SYNC="${NB_AUTO_SYNC:-1}"
+
+# $NB_DATA_TOOL
+#
+# Default: '' (first available)
+#
+# Example Values: 'visidata', 'sc-im'
+export NB_DATA_TOOL="${NB_DATA_TOOL:-}"
+
+# $NB_DEFAULT_EXTENSION
+#
+# Default: 'md'
+#
+# Example Values: 'md' 'org'
+export NB_DEFAULT_EXTENSION="${NB_DEFAULT_EXTENSION:-md}"
+
+# $NB_DIRECTORY_TOOL
+#
+# Default: '' (nb browse)
+#
+# Example Values: 'ranger', 'mc'
+export NB_DIRECTORY_TOOL="${NB_DIRECTORY_TOOL:-}"
+
+# $NB_ENCRYPTION_TOOL
+#
+# Default: 'openssl'
+#
+# Supported Values: 'gpg' 'openssl'
+export NB_ENCRYPTION_TOOL="${NB_ENCRYPTION_TOOL:-openssl}"
+
+# $NB_FOOTER
+#
+# Default: '1'
+#
+# Supported Values: '0' '1'
+export NB_FOOTER="${NB_FOOTER:-1}"
+
+# $NB_GUI_BROWSER
+#
+# Default: ''
+#
+# Example Value: 'firefox'
+export NB_GUI_BROWSER="${NB_GUI_BROWSER:-}"
+
+# $NB_HEADER
+#
+# Default: '2'
+#
+# Supported Values: '0' '1' '2' '3'
+export NB_HEADER="${NB_HEADER:-2}"
+
+# $NB_IMAGE_TOOL
+#
+# Default: '' (first available)
+#
+# Example Values: 'imgcat', 'catimg'
+export NB_IMAGE_TOOL="${NB_IMAGE_TOOL:-}"
+
+# $NB_SERVER_HOST
+#
+# Default: 'localhost'
+export NB_SERVER_HOST="${NB_SERVER_HOST:-localhost}"
+
+# $NB_SERVER_PORT
+#
+# Default: '6789'
+export NB_SERVER_PORT="${NB_SERVER_PORT:-6789}"
+
+# $NB_SYNTAX_THEME
+#
+# Default: 'base16'
+#
+# Supported Values: Theme names listed with `bat --list-themes`
+export NB_SYNTAX_THEME="${NB_SYNTAX_THEME:-base16}"
+
+# $_GIT_ENABLED
+#
+# Default: '1'
+#
+# Supported Values: '0' '1'
+export _GIT_ENABLED="${_GIT_ENABLED:-1}"
+
+# limit ################################################################# limit
+
+# $NB_LIMIT
+#
+# Default: '15'
+#
+# Set to a positive number to limit the output of `nb` and `nls` to that value.
+# Set to "auto" to automatically limit output to the current terminal height.
+# Subtract an auto limit offset for multiline prompts with `auto-<number>`.
+#
+# Supported Values:
+#   - <number>
+#   - auto-<number>
+#   - auto-<number>
+#
+# Example Values:
+#   - 15
+#   - auto
+#   - auto-2
+case "${NB_LIMIT:-}" in
+  auto*)
+    export _AUTO_LIMIT="${NB_LIMIT#auto}"
+    _AUTO_LIMIT="${_AUTO_LIMIT:-0}"
+
+    export NB_LIMIT="${NB_LIMIT}"
+    ;;
+  *)
+    export _AUTO_LIMIT=
+    export NB_LIMIT="${NB_LIMIT:-15}"
+  ;;
+esac
+
+# $EDITOR ############################################################# $EDITOR
+
+# $EDITOR
+#
+# The terminal editor command for editing items.
+export EDITOR="${EDITOR:-}"
+
+__set_editor() {
+  local _editors=(
+    code
+    subl
+    micro
+    mate
+    macdown
+    nano
+    pico
+    vim
+    vi
+    emacs
+  )
+
+  if [[   -z "${EDITOR:-}" ]]
+  then
+    if [[ -n "${VISUAL:-}" ]]
+    then
+      EDITOR="${VISUAL}"
+    else
+      local __editor=
+      for   __editor in "${_editors[@]}"
+      do
+        if hash "${__editor}" 2>/dev/null
+        then
+          EDITOR="${__editor}"
+
+          break
+        fi
+      done
+    fi
+
+    if [[ -z "${EDITOR:-}" ]]
+    then
+      cat <<HEREDOC
+Command line text editor not found. Set the \$EDITOR variable in your
+environment or in the \`${_ME}\` configuration file located at:
+  ${NBRC_PATH}
+
+More information about setting \$EDITOR:
+  https://askubuntu.com/q/432524
+
+\`${_ME}\` uses text editors with command line support, such as:
+
+- Visual Studio Code
+    https://code.visualstudio.com
+- Sublime Text
+    https://www.sublimetext.com
+- Atom
+    https://atom.io
+- MacDown
+    https://macdown.uranusjr.com
+- Vim
+    https://en.wikipedia.org/wiki/Vim_(text_editor)
+- Emacs
+    https://en.wikipedia.org/wiki/Emacs
+- TextMate
+    https://macromates.com
+- nano
+    https://en.wikipedia.org/wiki/GNU_nano
+- or many of these:
+    https://en.wikipedia.org/wiki/List_of_text_editors
+HEREDOC
+      exit 1
+    fi
+  fi
+}; __set_editor
+
+# Indicators ####################################################### Indicators
+
+# $NB_INDICATOR_<type>
+#
+# Description:
+#   Reassign or turn off file type indicator icons.
+#
+# Examples:
+#   # reassign pinned indicator
+#   export NB_INDICATOR_PINNED="💖"
+#
+#   # turn off bookmark indicators
+#   export NB_INDICATOR_BOOKMARK=""
+#
+# Parameter Expansion:
+#   |    | set / not blank | set / blank |    unset    |
+#   ----------------------------------------------------
+#   | -  |    parameter    |    blank    | replacement |
+#   | :+ |   replacement   |    blank    |    blank    |
+
+# $NB_INDICATOR_AUDIO
+export  NB_INDICATOR_AUDIO="${NB_INDICATOR_AUDIO-🔉}"
+export _NB_INDICATOR_AUDIO="${NB_INDICATOR_AUDIO:+"${NB_INDICATOR_AUDIO} "}"
+
+# $NB_INDICATOR_BOOKMARK
+export  NB_INDICATOR_BOOKMARK="${NB_INDICATOR_BOOKMARK-🔖}"
+export _NB_INDICATOR_BOOKMARK="${NB_INDICATOR_BOOKMARK:+"${NB_INDICATOR_BOOKMARK} "}"
+
+# $NB_INDICATOR_DOCUMENT
+export  NB_INDICATOR_DOCUMENT="${NB_INDICATOR_DOCUMENT-📄}"
+export _NB_INDICATOR_DOCUMENT="${NB_INDICATOR_DOCUMENT:+"${NB_INDICATOR_DOCUMENT} "}"
+
+# $NB_INDICATOR_EBOOK
+export  NB_INDICATOR_EBOOK="${NB_INDICATOR_EBOOK-📖}"
+export _NB_INDICATOR_EBOOK="${NB_INDICATOR_EBOOK:+"${NB_INDICATOR_EBOOK} "}"
+
+# $NB_INDICATOR_ENCRYPTED
+export  NB_INDICATOR_ENCRYPTED="${NB_INDICATOR_ENCRYPTED-🔒}"
+export _NB_INDICATOR_ENCRYPTED="${NB_INDICATOR_ENCRYPTED:+"${NB_INDICATOR_ENCRYPTED} "}"
+
+# $NB_INDICATOR_FOLDER
+export  NB_INDICATOR_FOLDER="${NB_INDICATOR_FOLDER-📂}"
+export _NB_INDICATOR_FOLDER="${NB_INDICATOR_FOLDER:+"${NB_INDICATOR_FOLDER} "}"
+
+# $NB_INDICATOR_IMAGE
+export  NB_INDICATOR_IMAGE="${NB_INDICATOR_IMAGE-🌄}"
+export _NB_INDICATOR_IMAGE="${NB_INDICATOR_IMAGE:+"${NB_INDICATOR_IMAGE} "}"
+
+# $NB_INDICATOR_PINNED
+export  NB_INDICATOR_PINNED="${NB_INDICATOR_PINNED-📌}"
+export _NB_INDICATOR_PINNED="${NB_INDICATOR_PINNED:+"${NB_INDICATOR_PINNED} "}"
+
+# $NB_INDICATOR_TODO
+export  NB_INDICATOR_TODO="${NB_INDICATOR_TODO-✔️ }"
+export _NB_INDICATOR_TODO="${NB_INDICATOR_TODO:+"${NB_INDICATOR_TODO} "}"
+
+# $NB_INDICATOR_TODO_DONE
+export  NB_INDICATOR_TODO_DONE="${NB_INDICATOR_TODO_DONE-✅}"
+export _NB_INDICATOR_TODO_DONE="${NB_INDICATOR_TODO_DONE:+"${NB_INDICATOR_TODO_DONE} "}"
+
+# $NB_INDICATOR_VIDEO
+export  NB_INDICATOR_VIDEO="${NB_INDICATOR_VIDEO-📹}"
+export _NB_INDICATOR_VIDEO="${NB_INDICATOR_VIDEO:+"${NB_INDICATOR_VIDEO} "}"
+
+# Color ################################################################# Color
+
+# $_COLOR_ENABLED
+#
+# Default: '1'
+#
+# Supported Values: '0' '1'
+export _COLOR_ENABLED="${_COLOR_ENABLED:-1}"
+
+# $NB_COLOR_THEME
+#
+# Default: 'nb'
+#
+# The color theme.
+export NB_COLOR_THEME="${NB_COLOR_THEME:-nb}"
+
+case "${NB_COLOR_THEME}" in
+  nb)
+    : # Colors assigned as default values below.
+    ;;
+  blacklight)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-39}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-56}"
+    ;;
+  console)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-40}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-28}"
+    ;;
+  desert)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-179}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-95}"
+    ;;
+  electro)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-200}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-62}"
+    ;;
+  forest)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-29}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-59}"
+    ;;
+  lavender)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-183}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-61}"
+    ;;
+  mage)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-199}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-55}"
+    ;;
+  mint)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-43}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-60}"
+    ;;
+  ocean)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-75}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-26}"
+    ;;
+  raspberry)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-162}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-90}"
+    ;;
+  smoke|monochrome)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-248}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-241}"
+    ;;
+  unicorn)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-183}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-153}"
+    ;;
+  utility)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-227}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-8}"
+    ;;
+  1)
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-164}"
+    export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-60}"
+    ;;
+esac
+
+export _NB_COLOR_THEMES=(
+  blacklight
+  console
+  desert
+  electro
+  forest
+  nb
+  ocean
+  raspberry
+  smoke
+  unicorn
+  utility
+)
+
+# User defined themes can be installed in the $NB_DIR/.plugins directory.
+# Themes have an .nb-theme extension and contain a single if statment
+# assigning the color environment variables to tput ANSI color numbers.
+#
+# Example:
+#
+#     # filename: ~/.nb/.plugins/example.nb-theme
+#     if [[ "${NB_COLOR_THEME}" == "example" ]]
+#     then
+#       export NB_COLOR_PRIMARY=68
+#       export NB_COLOR_SECONDARY=8
+#     fi
+#
+#  To view a list of available color numbers, run `nb settings colors`
+__load_themes() {
+  if [[   -d "${NB_DIR}/.themes"  ]] &&
+     [[ ! -e "${NB_DIR}/.plugins" ]]
+  then # migrate legacy .themes directory. TODO: Remove.
+    mv "${NB_DIR}/.themes" "${NB_DIR}/.plugins"
+  fi
+
+  if [[ -d "${NB_DIR}/.plugins"   ]]
+  then
+    set +f
+    local __file=
+    for   __file in "${NB_DIR}/.plugins"/*."${_ME}"-theme*
+    do
+      if [[ -e "${__file}"        ]]
+      then
+        local _basename=
+        _basename="$(basename "${__file}")"
+
+        local _name="${_basename%%.*}"
+
+        _NB_COLOR_THEMES+=("${_name}")
+
+        source "${__file}"
+      fi
+    done
+    set -f
+  fi
+}; __load_themes
+
+# $NB_COLOR_PRIMARY
+#
+# Default: Value depends on terminal capabilities.
+#
+# Set highlighting color. This should be set to an xterm color number, usually
+# a value between 1 and 256. For a table of common colors and their numbers
+# run:
+#   nb settings colors
+#
+# Supported Values: [0..255+]
+__set_color_primary() {
+  local _colors=
+  _colors="$(_tput colors)"
+
+  if [[ -n "${_colors}" ]] && [[ "${_colors}" -gt 8 ]]
+  then
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-69}"
+  else
+    export NB_COLOR_PRIMARY="${NB_COLOR_PRIMARY:-4}"
+  fi
+}; __set_color_primary
+
+# $NB_COLOR_SECONDARY
+#
+# Default: '8'
+#
+# Color for lines and other accents. This should be set to an xterm color
+# number, usually a value between 1 and 256. For a table of common colors and
+# their numbers, run:
+#   nb settings colors
+#
+# Supported Values: [0..255+]
+export NB_COLOR_SECONDARY="${NB_COLOR_SECONDARY:-8}"
+
+# Color Variables
+#
+# Avoid multiple tput calls by assigning output to variables.
+export _TPUT_SGR0=
+if [[ -n "${TMUX:-}" ]]
+then
+  # Avoid `tmux` and `less` quirks: https://unix.stackexchange.com/a/446541
+  _TPUT_SGR0="$(printf '\033[m')"
+else
+  _TPUT_SGR0="$(_tput sgr0)"
+fi
+
+export _TPUT_COLOR_PRIMARY=
+       _TPUT_COLOR_PRIMARY="$(_tput setaf "${NB_COLOR_PRIMARY}")"
+
+export _TPUT_COLOR_SECONDARY=
+       _TPUT_COLOR_SECONDARY="$(_tput setaf "${NB_COLOR_SECONDARY}")"
+
+export _TPUT_SETAF_8=
+       _TPUT_SETAF_8="$(_tput setaf 8)"
+
+export _TPUT_SMUL=
+       _TPUT_SMUL="$(_tput smul)"
+
+# _color_brackets()
+#
+# Usage:
+#   _color_brackets <string>
+#
+# Description:
+#   Print <string> with surrounding color brackets.
+_color_brackets() {
+  if ! ((_COLOR_ENABLED))
+  then
+    printf "[%s]" "${1:-}"
+
+    return 0
+  fi
+
+  printf "%s%s[%s%s%s]%s"     \
+    "${_TPUT_SGR0}"           \
+    "${_TPUT_SETAF_8}"        \
+    "${_TPUT_COLOR_PRIMARY}"  \
+    "${1:-}"                  \
+    "${_TPUT_SETAF_8}"        \
+    "${_TPUT_SGR0}"
+}
+
+# _color_muted()
+#
+# Usage:
+#   _color_muted <string>
+#
+# Print the given string with the muted color.
+_color_muted() {
+  if ! ((_COLOR_ENABLED))
+  then
+    printf "%s" "${1:-}"
+
+    return 0
+  fi
+
+  printf "%s%s%s%s"     \
+    "${_TPUT_SGR0}"     \
+    "${_TPUT_SETAF_8}"  \
+    "${1:-}"            \
+    "${_TPUT_SGR0}"
+}
+
+# _color_primary()
+#
+# Usage:
+#   _color_primary <string> [--underline]
+#
+# Description:
+#   Use `tput` to highlight the given string.
+_color_primary() {
+  if ! ((_COLOR_ENABLED))
+  then
+    printf "%s\\n" "${1:-}"
+
+    return 0
+  fi
+
+  if [[ "${2:-}" == "--underline" ]]
+  then
+    printf "%s%s%s%s%s\\n"        \
+      "${_TPUT_SGR0}"             \
+      "${_TPUT_SMUL}"             \
+      "${_TPUT_COLOR_PRIMARY}"    \
+      "${1:-}"                    \
+      "${_TPUT_SGR0}"
+  else
+    printf "%s%s%s%s\\n"          \
+      "${_TPUT_SGR0}"             \
+      "${_TPUT_COLOR_PRIMARY}"    \
+      "${1:-}"                    \
+      "${_TPUT_SGR0}"
+  fi
+}
+
+# _color_secondary()
+#
+# Usage:
+#   _color_secondary <string>
+#
+# Description:
+#   Highlight the given string using the accent color.
+_color_secondary() {
+  if ! ((_COLOR_ENABLED))
+  then
+    printf "%s\\n" "${1:-}"
+
+    return 0
+  fi
+
+  printf "%s%s%s\\n" "${_TPUT_COLOR_SECONDARY}" "${1:-}" "${_TPUT_SGR0}"
+}
+
+# Unset CLICOLOR_FORCE to avoid unexpected color output in `ls` et al.
+unset CLICOLOR_FORCE
+
+# Current Notebook ########################################### Current Notebook
+
+# $NB_NOTEBOOK_PATH
+#
+# Default: `$NB_DIR/home`
+#
+# The path to the current notebook.
+export NB_NOTEBOOK_PATH="${NB_NOTEBOOK_PATH:-"${NB_DIR}/home"}"
+
+# $_GLOBAL_NOTEBOOK_PATH
+#
+# The path of the current global notebook.
+export _GLOBAL_NOTEBOOK_PATH=
+
+# $_LOCAL_NOTEBOOK_PATH
+#
+# The path of the local notebook, if one is found. The current working
+# directory and all parents are searched.
+export _LOCAL_NOTEBOOK_PATH=
+
+# __set_notebook_paths()
+#
+# Usage:
+#   __set_notebook_paths
+#
+# Description:
+#   Set the the notebook path variables to reflect the current environment.
+__set_notebook_paths() {
+  __set_local_notebook_path() {
+    if [[ "${PWD}" == "/" ]]
+    then
+      cd "${_CURRENT_WORKING_DIR}"
+
+      return 0
+    elif [[ -d "${PWD}/.git"    ]] &&
+         [[ -f "${PWD}/.index"  ]]
+    then
+      _LOCAL_NOTEBOOK_PATH="${PWD}"
+
+      cd "${_CURRENT_WORKING_DIR}"
+
+      return 0
+    else
+      cd ..
+      __set_local_notebook_path
+    fi
+  }; __set_local_notebook_path
+
+  __set_global_notebook_path() {
+    if [[   -e "${NB_DIR}/.current"                 ]]
+    then
+      local _global_notebook_name=
+      _global_notebook_name="$(<"${NB_DIR}/.current")"
+
+      if [[ -d "${NB_DIR}/${_global_notebook_name}" ]]
+      then
+        _GLOBAL_NOTEBOOK_PATH="${NB_DIR}/${_global_notebook_name}"
+      fi
+    fi
+  }; __set_global_notebook_path
+
+  if [[     -n "${_LOCAL_NOTEBOOK_PATH:-}"          ]]
+  then
+    NB_NOTEBOOK_PATH="${_LOCAL_NOTEBOOK_PATH}"
+  else
+    NB_NOTEBOOK_PATH="${_GLOBAL_NOTEBOOK_PATH}"
+  fi
+}; __set_notebook_paths
+
+# Cache & Temp ################################################### Cache & Temp
+
+# $_NB_CACHE_PATH
+#
+# The full path to the cache directory.
+export _NB_CACHE_PATH="${NB_DIR}/.cache"
+
+if [[   -d "${NB_DIR}"          ]] &&
+   [[ ! -e "${_NB_CACHE_PATH}"  ]]
+then
+  mkdir -p "${_NB_CACHE_PATH}"
+fi
+
+# $TMPDIR
+#
+# Reset $TMPDIR if it's set to the current working directory by npm.
+if [[ "${TMPDIR:-}" == "${PWD}" ]]
+then
+  export TMPDIR="/tmp"
+fi
+
+# $_NB_TEMP_DIRECTORY
+#
+# The full path to the temp directory.
+export _NB_TEMP_DIRECTORY
+_NB_TEMP_DIRECTORY="$(mktemp -d)"
+
+# $_NB_TEMP_PIDS
+#
+# A list of PIDS that should be terminated on exit.
+_NB_TEMP_PIDS=()
+
+# _temp()
+#
+# Usage:
+#   _temp cache [clear]
+#   _temp cleanup
+#   _temp directory
+#   _temp file [<basename> | <relative-path> | <extension>] [--touch]
+#   _temp pid <pid>
+#
+# Subcommands:
+#   cache       Print the full path to the cache directory, or optionally clear
+#               the cache.
+#   cleanup     Force delete the temp directory.
+#   directory   Print the full path the the temp directory.
+#   file        Initialize a temporary file path.
+#   pid         Specify a process ID that should be terminated on exit.
+#
+# Description:
+#   Manage temp and cache files and directories.
+_temp() {
+  # Usage: _temp_validate_path <path>
+  _temp_validate_path() {
+    [[ -n "${1:?}"              ]] &&
+    [[    "${1}" != "/"         ]] &&
+    [[    "${1}" != "${HOME}"   ]] &&
+    [[    "${1}" != "${PWD}"    ]] &&
+    [[ -e "${1}"                ]]
+  }
+
+  local _subcommand="${1:-}"
+
+  case "${_subcommand}" in
+    cache)
+      if [[ "${2:-}" == "clear" ]]
+      then
+        if _temp_validate_path "${_NB_CACHE_PATH:?}"
+        then
+          rm -r "${_NB_CACHE_PATH:?}"
+          mkdir -p "${_NB_CACHE_PATH}"
+        fi
+      else
+        printf "%s\\n" "${_NB_CACHE_PATH}"
+      fi
+      ;;
+    cleanup)
+      if _temp_validate_path "${_NB_TEMP_DIRECTORY:?}"
+      then
+        rm -rf "${_NB_TEMP_DIRECTORY:?}"
+      fi
+
+      local __pid=
+      for   __pid in "${_NB_TEMP_PIDS[@]:-}"
+      do
+        [[ -n "${__pid:-}" ]] || continue
+
+        kill "${__pid}" 2>/dev/null || :
+      done
+      ;;
+    directory)
+      printf "%s\\n" "${_NB_TEMP_DIRECTORY:-}"
+      ;;
+    file)
+      local _extension=
+      local _relative_path=
+      local _touch=0
+
+      local __arg=
+      for   __arg in "${2:-}" "${3:-}"
+      do
+        case "${__arg}" in
+          "")       :                           ;;
+          --touch)  _touch=1                    ;;
+          \.*)      _extension="${__arg:-}"     ;;
+          *)        _relative_path="${__arg:-}" ;;
+        esac
+      done
+
+      local _temp_file_path=
+
+      if [[ -z  "${_relative_path:-}"       ]]
+      then
+        _temp_file_path="${_NB_TEMP_DIRECTORY}/${RANDOM}${_extension:-}"
+      else
+        _temp_file_path="${_NB_TEMP_DIRECTORY}/${_relative_path:-}"
+      fi
+
+      if [[     "${_relative_path:-}" =~ /  ]]
+      then
+        mkdir -p "${_temp_file_path%/*}"
+      fi
+
+      if ((_touch))
+      then
+        touch "${_temp_file_path}"
+      fi
+
+      printf "%s\\n" "${_temp_file_path:-}"
+      ;;
+    pid)
+      _NB_TEMP_PIDS+=("${2:?}")
+      ;;
+  esac
+}
+
+trap "_temp cleanup"                        EXIT
+trap "exit"                                 INT
+trap 'printf "\\n"; _temp cleanup; exit 0'  SIGINT
+trap 'printf "\\n"; _temp cleanup; exit 0'  SIGTERM
+
+###############################################################################
+# Configuration Validation
+###############################################################################
+
+# _validate_configuration()
+#
+# Usage:
+#   _validate_configuration
+#
+# Description:
+#   Check the runtime environment and display an error message when running in
+#   an unsupported configuration.
+_validate_configuration() {
+  if { ((${NB_BASH_UPDATE_PROMPT_ENABLED:-0}))        ||
+       {
+         [[ "${BASH_VERSINFO[0]:-999999999}" -lt 4 ]] &&
+         ((${NB_BASH_UPDATE_PROMPT_ENABLED:-1}))
+       }
+     }                                                &&
+     _command_exists "brew"                           &&
+     {
+       # command initiated by user
+       [[ -t 1                          ]]            ||
+       ((${NB_TEST_MOCK_TTY:-0}))
+     }
+  then
+    local _config_file_path="${NB_DIR}/.nb-bash-3-enabled"
+
+    if [[ -e "${_config_file_path}"     ]]
+    then
+      local _config_file_version=
+      _config_file_version="$(head -n 1 "${_config_file_path:-}")"
+
+      if [[ "${_config_file_version:-}" != "${_VERSION}" ]] ||
+         ((${NB_BASH_UPDATE_PROMPT_ENABLED:-0}))
+      then
+        rm "${_config_file_path:?}"
+      fi
+    fi
+
+    if [[ ! -e "${_config_file_path:-}" ]]  &&
+       ((${NB_BASH_UPDATE_PROMPT_ENABLED:-1}))
+    then
+      local _color_me=
+      _color_me="$(_color_muted '`')$(_color_primary "${_ME}")$(_color_muted '`')"
+
+      {
+        printf "Update Bash\\n"
+        printf "%s\\n" "$(_color_muted  "-------------")"
+
+        cat <<HEREDOC
+${_color_me} works best with the current version of Bash.
+
+${_color_me} can $(_color_primary "update") your system to $(_color_primary "Bash 5") via Homebrew
+or you can proceed with $(_color_muted "Bash 3.2").
+
+Answering $(_color_primary "y") or $(_color_primary "yes") will run the following command:
+
+  $(_color_primary "brew install bash")
+
+This command could take a minute to run.
+HEREDOC
+      } | _warn printf "%s\\n" "$(cat)"
+
+      while true
+      do
+        local __yn=
+
+        if _contains "-y"     "${@:-}" ||
+           _contains "--yes"  "${@:-}"
+        then
+          __yn="y"
+        else
+          printf "%s\\n" "$(_color_muted "------------------------")"
+
+          IFS='' read -r -e -d $'\n' -p   \
+"$(_color_primary "Update") to Bash 5?  $(_color_brackets "y/N") " __yn
+        fi
+
+        case "${__yn}" in
+          [Yy]*)
+            printf "\\n"
+
+            _warn printf "Updating Bash%s\\n\\n" "$(_color_muted "...")"
+
+            if brew install bash
+            then
+              printf "\\n"
+
+              {
+                printf "%s\\n"    "$(_color_muted  "------------------")"
+                printf "  %s to %s!\\n"         \
+                  "$(_color_primary "Updated")" \
+                  "$(_color_primary "Bash 5")"
+                printf "  %s\\n"  "$(_color_muted  "------------------")"
+              } | _warn printf "%s\\n" "$(cat)"
+
+              printf "\\n"
+            else
+              printf "\\n"
+
+              _warn printf "Unable to update to Bash 5.\\n\\n"
+            fi
+
+
+            if [[ -e "${_config_file_path:?}" ]]
+            then
+              rm "${_config_file_path:?}"
+            fi
+
+            break
+            ;;
+          *)
+            cat <<HEREDOC > "${_config_file_path:?}"
+${_VERSION}
+
+This presence of this file indicates that Bash 3 support is enabled.
+HEREDOC
+
+            printf "\\n"
+
+            {
+              printf "%s\\n" "$(_color_muted    "-------------------------")"
+              printf                          "  Bash 3.2 support enabled.\\n"
+              printf "%s\\n" "$(_color_muted  "  -------------------------")"
+            } | _warn printf "%s\\n" "$(cat)"
+
+            printf "\\n"
+
+            break
+            ;;
+        esac
+      done
+    fi
+  fi
+}
+
+if [[ -e "${NB_DIR:-}" ]]
+then
+  _validate_configuration "${@:-}"
+fi
+
+###############################################################################
+# Helpers: Group 1                                             Helpers: Group 1
+# ----------------                                             ----------------
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+# $_BT
+#
+# Backtick with ANSI-C quoting for string building.
+_BT=$'`'
+
+# $_CHEVRON_LEFT
+#
+# A left-pointing chevron character.
+_CHEVRON_LEFT="❮"
+
+# $_CHEVRON_RIGHT
+#
+# A right-pointing chevron character.
+_CHEVRON_RIGHT="❯"
+
+# $_COLUMNS
+#
+# The terminal width in number of columns (characters).
+_COLUMNS="$(_tput cols)"
+
+# $_FILE_TYPES
+#
+# An array of supported aggregate file types.
+_FILE_TYPES=(archive audio bookmark document folder image text video)
+
+# $_IGNORE_PATTERNS
+#
+# An array of filename patterns to ignore, formatted as `sed -e` arguments.
+_IGNORE_PATTERNS=(
+  -e '/~$/d'
+  -e '/^#.*#$/d'
+  -e '/\.swa?p$/d'
+  -e '/^\.#*/d'
+)
+
+# $_MD
+#
+# Middle dot character.
+_MD="·"
+
+# $_NBSP
+#
+# No-break space character.
+_NBSP=" "
+
+# $_NEWLINE
+#
+# Newline with ANSI-C quoting for string building.
+_NEWLINE=$'\n'
+
+# $_SLASH
+#
+# Slash with ANSI-C quoting for string building support and macOS Bash
+# string substitution.
+_SLASH=$'/'
+
+# _URL_PATTERNS
+#
+# Patterns for matching URLs.
+#
+# https://en.wikipedia.org/wiki/List_of_URI_schemes
+export _URL_PATTERNS=(
+  "([.a-z0-9+-]+)://[^[:space:]]+"
+  "(afp|attachment|platform):/[^[:space:]]+"
+  "aim:[^[:space:]]+\?[^[:space:]]+"
+  "(dab|fm):[^[:space:]]+\.[^[:space:]]+\.[^[:space:]]+"
+  "(data|geo):[^[:space:]]+,[^[:space:]]+"
+  "doi:10\.[^[:space:]]+"
+  "(msnim|things):[^[:space:]]+\?[^[:space:]]+"
+  "(feed|mvn|paparazzi|view-source):https?://[^[:space:]]+"
+  "git@[^[:space:]]+:[^[:space:]]+"
+  "gtalk:chat[^[:space:]]+"
+  "(im|mailto|reload|sips?|xmpp):[^[:space:]]+@[^[:space:]]+"
+  "jar:[^[:space:]]+!/[^[:space:]]+"
+  "magnet:\?xt=urn:[^[:space:]]+"
+  "maps:q=[^[:space:]]+"
+  "(sms|tel):\+[0-9]+"
+  "(jdbc|spotify|urn):[^[:space:]]+:[^[:space:]]+"
+  "tag:[^[:space:]]+,[^[:space:]]+:[^[:space:]]+"
+  "ymsgr:sendIM?[^[:space:]]+"
+  # TODO: develop strategy to avoid matching notebook: selectors
+  # "(apt|amss|barion|bitcoin|callto|cid|dns|drm|fax|gg):[^[:space:]]+"
+  # "(go|iax|javascript|message|mid|mvn|news|openpgp4fpr):[^[:space:]]+"
+  # "(palm|pres|proxy|psyc|query|session|shc|skype):[^[:space:]]+"
+  # "(stuns?|trueconf|turns?|ws|xfire):[^[:space:]]+"
+  # "itms:"
+)
+
+# Fallbacks for non-unicode environments.
+if [[ ! "${LANG:-x}" =~ (utf-|UTF-) ]]
+then
+  _CHEVRON_LEFT="<"
+  _CHEVRON_RIGHT=">"
+  _MD="-"
+fi
+
+# _alias_subcommand()
+#
+# Usage:
+#   _alias_subcommand <subcommand> <alias>
+#
+# Description:
+#   Create an <alias> of <subcommand>. NOTE: aliases also have to be added to
+#   the $_SUBCOMMANDS variable.
+_alias_subcommand() {
+  local _alias="${2:-}"
+  local _subcommand="${1:-}"
+
+  if [[ -z "${_alias:-}" ]]
+  then
+    return 1
+  fi
+
+  shopt -u extglob
+
+  eval "_describe_${_alias}() { _describe_${_subcommand}  \"\${@:-}\"; }"
+  eval "_${_alias}()          { _${_subcommand}           \"\${@:-}\"; }"
+
+  shopt -s extglob
+}
+
+# _file_is_archive()
+#
+# Usage:
+#   _file_is_archive <path>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is an archive.
+#   1 (error,  false)  if not.
+export _ARCHIVE_FILE_EXTENSIONS=(
+  7z
+  apk
+  bz2
+  dmg
+  gz
+  lz
+  rar
+  s7z
+  sit
+  sitx
+  sparsebundle
+  tar
+  tgz
+  tbz2
+  tlz
+  txz
+  xz
+  zip
+  zipx
+  Z
+)
+_file_is_archive() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  LC_ALL=C _contains "${_file_type}" "${_ARCHIVE_FILE_EXTENSIONS[@]}"
+}
+
+# _file_is_audio()
+#
+# Usage:
+#   _file_is_audio (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is an audio file.
+#   1 (error,  false)  if not.
+export _AUDIO_FILE_EXTENSIONS=(
+  aac
+  aiff
+  flac
+  m4a
+  mp3
+  ogg
+  wav
+)
+_file_is_audio() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  LC_ALL=C _contains "${_file_type}" "${_AUDIO_FILE_EXTENSIONS[@]}"
+}
+
+# _file_is_bookmark()
+#
+# Usage:
+#   _file_is_bookmark (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true) If file is a bookmark.
+#   1 (error,  false) if not.
+export _BOOKMARK_FILE_EXTENSIONS=(
+  bookmark.md
+  bookmark.md.enc
+)
+_file_is_bookmark() {
+  # Use explicit matching for legacy bookmark name support.
+  [[ "${1:-}" =~ ([(-|.)]bookmark.md|[(-|.)]bookmark.md.enc) ]]
+}
+
+# _file_is_document()
+#
+# Usage:
+#   _file_is_document (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is a Word, Open Office, PDF, or other document.
+#   1 (error,  false)  if not.
+export _DOCUMENT_FILE_EXTENSIONS=(
+  doc
+  docx
+  odt
+  pdf
+  rtf
+  xls
+  xlsx
+)
+_file_is_document() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  LC_ALL=C _contains "${_file_type}" "${_DOCUMENT_FILE_EXTENSIONS[@]}"
+}
+
+# _file_is_encrypted()
+#
+# Usage:
+#   _file_is_encrypted <path>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is encrypted.
+#   1 (error,  false)  if not.
+export _ENCRYPTED_FILE_EXTENSIONS=(
+  enc
+)
+_file_is_encrypted() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  # `file` with 'soft' test is slow, so avoid calling it.
+  LC_ALL=C _contains "${_file_type}" "${_ENCRYPTED_FILE_EXTENSIONS[@]}" ||
+    {
+      ! LC_ALL=C _contains "${_file_type}"  \
+        "${_TEXT_FILE_EXTENSIONS[@]}"       \
+        "${_IMAGE_FILE_EXTENSIONS[@]}"      \
+        "${_DOCUMENT_FILE_EXTENSIONS[@]}"   \
+        "${_AUDIO_FILE_EXTENSIONS[@]}"      \
+        "${_VIDEO_FILE_EXTENSIONS[@]}"      &&
+        if _command_exists "file"
+        then
+          [[ "$(file "${_file_path:-}"      \
+                  --exclude=apptype         \
+                  --exclude=encoding        \
+                  --exclude=tokens          \
+                  --exclude=cdf             \
+                  --exclude=compress        \
+                  --exclude=elf             \
+                  --exclude=tar)" =~ (encrypted|openssl) ]]
+        else
+          return 1
+        fi
+    }
+}
+
+# _file_is_image()
+#
+# Usage:
+#   _file_is_image (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is an image.
+#   1 (error,  false)  if not.
+export _IMAGE_FILE_EXTENSIONS=(
+  afphoto
+  ai
+  bmp
+  gif
+  heic
+  ind
+  indd
+  jpg
+  jpeg
+  png
+  psd
+  raw
+  svg
+  svgz
+  tif
+  tiff
+  webp
+)
+_file_is_image() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  LC_ALL=C _contains "${_file_type}" "${_IMAGE_FILE_EXTENSIONS[@]}"
+}
+
+# _file_is_text()
+#
+# Usage:
+#   _file_is_text <path>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is text.
+#   1 (error,  false)  if not.
+#
+# Resources:
+#   Markdown: https://superuser.com/a/285878
+export _TEXT_FILE_EXTENSIONS=(
+  bash
+  bib
+  coffee
+  css
+  go
+  html
+  js
+  json
+  jsx
+  latex
+  markdown
+  md
+  mdown
+  mdwn
+  mdtxt
+  mdtext
+  mkd
+  mkdn
+  org
+  py
+  rb
+  Rmd
+  rst
+  scss
+  sh
+  sql
+  tex
+  text
+  textile
+  ts
+  tsx
+  txt
+  xml
+)
+_file_is_text() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  # Avoid calling `file` for better performance.
+  LC_ALL=C _contains "${_file_type}" "${_TEXT_FILE_EXTENSIONS[@]}" ||
+    {
+      ! LC_ALL=C _contains "${_file_type}"  \
+        "${_IMAGE_FILE_EXTENSIONS[@]}"      \
+        "${_DOCUMENT_FILE_EXTENSIONS[@]}"   \
+        "${_ENCRYPTED_FILE_EXTENSIONS[@]}"  \
+        "${_AUDIO_FILE_EXTENSIONS[@]}"      \
+        "${_VIDEO_FILE_EXTENSIONS[@]}"      \
+        "${_ARCHIVE_FILE_EXTENSIONS[@]}"        &&
+        [[ !    "${_file_type}" =~ \.epub$  ]]  &&
+        [[ ! -d "${_file_path:-}"           ]]  &&
+        if _command_exists "file"
+        then
+          [[ "$(file "${_file_path:-}"      \
+                  --exclude=apptype         \
+                  --exclude=encoding        \
+                  --exclude=tokens          \
+                  --exclude=cdf             \
+                  --exclude=compress        \
+                  --exclude=elf             \
+                  --exclude=tar             \
+                  -b --mime-type)" =~ ^text ]]
+        else
+          return 0
+        fi
+    }
+}
+
+# _file_is_todo()
+#
+# Usage:
+#   _file_is_todo (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true) If file is a todo.
+#   1 (error,  false) if not.
+export _TODO_FILE_EXTENSIONS=(
+  todo.md
+  todo.md.enc
+)
+_file_is_todo() {
+  [[ "${1:-}" =~ (todo\.md|todo\.md\.enc) ]]
+}
+
+# _file_is_video()
+#
+# Usage:
+#   _file_is_video (<path> | <filename>)
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If file is a video file.
+#   1 (error,  false)  if not.
+export _VIDEO_FILE_EXTENSIONS=(
+  avi
+  flv
+  m4p
+  m4v
+  mp2
+  mp4
+  mov
+  mpeg
+  mpg
+  qt
+  webm
+  wmv
+)
+_file_is_video() {
+  local _file_path="${1:-}"
+  local _file_type="${_file_path##*.}"
+
+  LC_ALL=C _contains "${_file_type}" "${_VIDEO_FILE_EXTENSIONS[@]}"
+}
+
+# _get_content()
+#
+# Usage:
+#   _get_content <path> [--title]
+#
+# Options:
+#   --title  Print the title or nothing if a title is not found.
+#
+# Description:
+#   Print the title or first line of the text document at <path>. When a title
+#   is not found, print the first line, prefixed with '__first_line:'.
+#
+#   Supports both Markdown h1 styles, YAML front matter, Org Mode, and LaTeX.
+#
+#   - Markdown
+#     - Supported:
+#       - # This is a Title
+#       - This is a Title
+#         ===============
+#       - ---
+#         title: This is a Title
+#         ---
+#     - https://daringfireball.net/projects/markdown/syntax#header
+#     - https://jekyllrb.com/docs/front-matter/
+#   - Org Mode
+#     - Supported:
+#       - #+TITLE: This is a Title
+#     - https://orgmode.org/guide/Export-Settings.html
+#   - LaTeX
+#     - Supported:
+#       - \title{This is a Title}
+_get_content() {
+  local _counter=0
+  local _first_line=
+  local _in_code_block=0
+  local _in_front_matter=0
+  local _maybe_title=
+  local _path="${1:-}"
+  local _title=
+
+  if [[ "${2:-}" == --title ]]
+  then
+    local _only_title=1
+  else
+    local _only_title=0
+  fi
+
+  if [[   -z "${_path}" ]]
+  then
+    return 1
+  elif [[ -d "${_path}" ]]
+  then
+    return 0
+  elif [[ -e "${_path}" ]]
+  then
+
+    # `awk` `_get_first_line` alternative
+    # -----------------------------------
+    #       awk -f - "${_path}" <<'HEREDOC'
+    # (state == 0) && /^---$/ { state=1; next }
+    # (state == 1) && /^---$/ { state=0; next }
+    # (state == 0) && /^```/  { state=1; next }
+    # (state == 1) && /^```/  { state=0; next }
+    #
+    # (state == 0) && /^./    { print; exit   }
+    # HEREDOC
+
+    if [[ "${_path}" =~ (\.md$|\.markdown$) ]]
+    then
+      local               __line=
+      while IFS= read -r  __line || [[ -n "${__line:-}"     ]]
+      do
+        if [[ "${__line}" =~ ^([[:space:]]*#[[:space:]]+)   ]] &&
+           ! ((_in_code_block))
+        then # line starts with an atx-style H1
+          _title="${__line#"${BASH_REMATCH[1]:-}"}"
+
+          if [[ "${_title}" =~ ([[:space:]]+#[[:space:]]*)$ ]]
+          then
+            _title="${_title%"${BASH_REMATCH[1]:-}"}"
+          fi
+
+          # `sed` alternative
+          # -----------------
+          # _title="$(
+          #   printf "%s\\n" "${__line}"    \
+          #     | sed                       \
+          #       -e 's/^[[:space:]]*# //'  \
+          #       -e 's/ #$//'
+          #   )"
+
+          break
+        elif [[ "${__line}" =~ ^---$    ]]
+        then # start or end of front matter block
+          if ((_in_front_matter))
+          then
+            _in_front_matter=0
+          else
+            _in_front_matter=1
+          fi
+        elif [[ "${__line}" =~ ^\`\`\`  ]]
+        then # start or end of code block
+          if ((_in_code_block))
+          then
+            _in_code_block=0
+          else
+            _in_code_block=1
+          fi
+        elif ((_in_front_matter))   &&  [[ "${__line}" =~ ^title\:  ]]
+        then # front matter title
+          _title="$(printf "%s\\n" "${__line}" | LC_ALL=C sed 's/^title: //')"
+
+          break
+        elif ! ((_in_front_matter)) && ! ((_in_code_block))
+        then
+          if [[ -z "${_maybe_title:-}"  ]]  &&  [[ -n "${__line:-}" ]]
+          then  # potential setext-style H1
+            _maybe_title="${__line}"
+          elif [[ -n "${_maybe_title:-}"            ]] &&
+               [[ "${__line}" =~ ^[[:space:]]*\=+$  ]]
+          then # underline for setext-style H1 on previous line
+            _title="$(
+              printf "%s\\n" "${_maybe_title}" | LC_ALL=C sed 's/^[[:space:]]*//'
+            )"
+
+            break
+          elif [[ -n "${_maybe_title:-}"        ]]
+          then # in normal content, title not found
+            if ! ((_only_title))
+            then
+              if [[ "${#_maybe_title}" -gt 500  ]]
+              then
+                _first_line="${_maybe_title:0:500}..."
+              else
+                _first_line="${_maybe_title}"
+              fi
+            fi
+
+            if [[ ! "${_maybe_title}"  =~ ^\[   ]]
+            then # only break with first non-link line
+              break
+            fi
+          else
+            continue
+          fi
+        fi
+      done < "${_path}"
+
+      if [[ -z "${_title:-"${_first_line:-}"}"  ]] &&
+         [[ -n "${_maybe_title:-}"              ]]
+      then
+        _first_line="${_maybe_title:-}"
+      fi
+    elif [[ "${_path}"    =~ (\.latex$|\.tex$)  ]]
+    then
+      local               __line=
+      while IFS= read -r  __line  ||  [[ -n "${__line:-}" ]]
+      do
+        _counter="$((_counter+1))"
+
+        if [[ "${__line}" =~  ^\\title\{        ]]
+        then
+          _title="$(
+            printf "%s\\n" "${__line}" | LC_ALL=C sed 's/\\title{\(.*\)}/\1/'
+          )"
+
+          break
+        elif [[ -n "${__line:-}"      ]]
+        then
+          if [[ -z "${_first_line:-}" ]]
+          then
+            _first_line="${__line}"
+          fi
+
+          if [[ ! "${__line}" =~ ^\\  ]] &&
+             [[ "${_counter}" -gt 20  ]]
+          then
+            break
+          fi
+        else
+          continue
+        fi
+      done < "${_path}"
+    elif [[   "${_path}" =~ \.org$    ]]
+    then
+      local               __line=
+      while IFS= read -r  __line  ||  [[ -n "${__line}"   ]]
+      do
+        _counter="$((_counter+1))"
+
+        # NOTE: Titles can be defined with multiple #+TITLE: lines.
+        if [[ "${__line}" =~ ^\#\+TITLE\: ]]
+        then
+          if [[ -n "${_title:-}"          ]]
+          then
+            _title="${_title} "
+          fi
+
+          _title+="$(printf "%s\\n" "${__line}" | LC_ALL=C sed 's/^#+TITLE: //')"
+        elif [[ -n "${__line:-}"      ]]
+        then
+
+          if [[ -z "${_first_line:-}" ]]
+          then
+            _first_line="${__line}"
+          fi
+
+          if [[ ! "${__line}" =~ ^\#  ]] &&
+             [[ "${_counter}" -gt 10  ]]
+          then
+            break
+          fi
+        else
+          continue
+        fi
+      done < "${_path}"
+    elif ! ((_only_title))        &&
+         LC_ALL=C _contains "${_path##*.}" "${_TEXT_FILE_EXTENSIONS[@]}"
+    then
+      local               __line=
+      while IFS= read -r  __line  ||  [[ -n "${__line:-}" ]]
+      do
+        if [[ -n "${__line:-}"        ]]
+        then
+          if [[ "${#__line}" -gt 500  ]]
+          then
+            _first_line="${__line:0:500}..."
+          else
+            _first_line="${__line}"
+          fi
+
+          break
+        fi
+      done < "${_path}"
+    fi
+
+    if [[ -n "${_title:-}"    ]]
+    then
+      printf "%s\\n" "${_title/%$'\r'}"
+    elif ! ((_only_title)) && [[ -n "${_first_line:-}"    ]]
+    then
+      printf "%s\\n" "__first_line:${_first_line/%$'\r'}"
+    fi
+  fi
+}
+
+# _get_id_selector()
+#
+# Usage:
+#   _get_id_selector <path> | <selector> [--notebook]
+#
+# Options:
+#   --notebook  Always include the notebook name in the output.
+#
+# Description:
+#   Convert a <path> or <selector> to valid selector constructed with ids,
+#   which are resolved first during selector resolution. This function gives
+#   precedence to folder names in input.
+_get_id_selector() {
+  local _folder_path=
+  local _id_selector=
+  local _notebook_name=
+  local _notebook_path=
+  local _relative_path=
+  local _selector="${1:-}"
+  local _selector_relative_path=
+  local _trailing_slash=0
+
+  case "${2:-}" in
+    --notebook) local _always_include_notebook=1 ;;
+    *)          local _always_include_notebook=0 ;;
+  esac
+
+  if [[ -z "${_selector:-}"     ]]
+  then
+    return 0
+  fi
+
+  if [[ "${_selector:-}" =~ /$  ]]
+  then
+    _trailing_slash=1
+  fi
+
+  if [[ "${_selector:-}" =~ ^/  ]]
+  then # selector is full path
+    if [[ "${_selector}" =~ ^${NB_DIR}      ]]
+    then
+      local _path_with_notebook="${_selector#"${NB_DIR}"/}"
+      _notebook_name="${_path_with_notebook%%/*}"
+      _notebook_path="${NB_DIR}/${_notebook_name}"
+
+      if [[ "${_path_with_notebook:-}" =~ / ]]
+      then
+        _selector_relative_path="${_path_with_notebook#*/}"
+      fi
+    else
+      _notebook_name="local"
+
+      _notebook_path="$(
+        cd "${_selector%/*}"    &&
+          __set_notebook_paths  &&
+          _notebooks current --path --no-color
+      )"
+
+      if [[ "${_selector:-}" == "${_notebook_path:-}" ]]
+      then
+        _selector_relative_path=
+      else
+        _selector_relative_path="${_selector#"${_notebook_path}"/}"
+      fi
+    fi
+  else
+    if [[ "${_selector:-}" =~ :   ]]
+    then
+      _notebook_name="${_selector%%:*}"
+      _selector_relative_path="${_selector#*:}"
+    else
+      _selector_relative_path="${_selector:-}"
+    fi
+  fi
+
+  if [[ -z "${_notebook_path:-}"  ]]
+  then
+    case "${_notebook_name:-}" in
+      local) _notebook_path="$(_notebooks --local --path --no-color)" ;;
+      *)     _notebook_path="${NB_DIR}/${_notebook_name}"             ;;
+    esac
+  fi
+
+  local _parent_folder_path=
+
+  if [[ -n "${_notebook_name:-}"  ]]
+  then
+    _id_selector+="${_notebook_name}:"
+    _parent_folder_path="${_notebook_path:-}"
+  else
+    _parent_folder_path="$(_notebooks current --path)"
+
+    if ((_always_include_notebook))
+    then
+      if _notebooks current --local
+      then
+        _id_selector+="local:"
+      else
+        _id_selector+="${_parent_folder_path##*/}:"
+      fi
+    fi
+  fi
+
+  local _id_path=
+
+  if [[ -n "${_selector_relative_path:-}" ]]
+  then
+    local _selector_segments=()
+
+    IFS="/" read -ra _selector_segments <<< "${_selector_relative_path:-}"
+
+    local i=
+    for ((i=0; i < ${#_selector_segments[@]}; i++))
+    do
+      local _segment_id=
+
+      if [[ "${i}" -eq "$((${#_selector_segments[@]} - 1))" ]]
+      then # it's the last segment
+        if [[ "${_selector_segments[i]:-}" =~ ^[0-9]+$      ]] &&
+           ! ((_trailing_slash))
+        then
+          _segment_id="${_selector_segments[i]:-}"
+        fi
+      fi
+
+      if [[ -z "${_segment_id:-}"         ]]
+      then
+        _segment_id="$(
+          _index get_id                   \
+            "${_selector_segments[i]:-}"  \
+            "${_parent_folder_path}"      || :
+        )"
+      fi
+
+      local _segment_basename=
+
+      if [[ -z "${_segment_id:-}"                     ]] &&
+         [[ "${_selector_segments[i]:-}"  =~ ^[0-9]+$ ]]
+      then
+        _segment_basename="$(
+          _index get_basename             \
+            "${_selector_segments[i]:-}"  \
+            "${_parent_folder_path}" 2>/dev/null || :
+        )"
+
+        if [[ -n "${_segment_basename:-}" ]]
+        then
+          _segment_id="${_selector_segments[i]:-}"
+        fi
+      fi
+
+      if [[ -z "${_segment_id:-}" ]]
+      then
+        return 1
+      fi
+
+      if [[ -z "${_id_path:-}"    ]]
+      then
+        _id_path+="${_segment_id}"
+      else
+        _id_path+="/${_segment_id}"
+      fi
+
+      _parent_folder_path+="/${_segment_basename:-${_selector_segments[i]:-}}"
+    done
+  fi
+
+  if [[ -n "${_id_path:-}"        ]] &&
+     [[ !  "${_id_path}" == "/"   ]]
+  then
+    _id_selector+="${_id_path}"
+  fi
+
+  if ((_trailing_slash))
+  then
+    _id_selector+="/"
+  fi
+
+  printf "%s\\n" "${_id_selector:-}"
+}
+
+# _get_visible_length()
+#
+# Usage:
+#   _get_visible_length <string> [<extra-length>]
+#
+# Describe:
+#   Calculate the apparent length of <string>, with byte and character
+#   calculations for handling unicode characters.
+#
+# More Information:
+#   https://stackoverflow.com/a/31009961
+_get_visible_length() {
+  local _extra_length="${2:-0}"
+  local _string="${1:-}"
+
+  _LANG="${LANG:-}" _LC_ALL="${LC_ALL:-}"
+
+  local _length_chars=
+  _length_chars="${#_string}"
+
+  LANG=C LC_ALL=C
+
+  local _length_bytes=
+  _length_bytes="${#_string}"
+
+  LANG="${_LANG:-}" LC_ALL="${_LC_ALL:-}"
+
+  local _difference=
+  _difference=$(((_length_bytes-_length_chars)/3))
+
+  local _calculated_length=
+  _calculated_length=$((_length_chars+_difference))
+
+  if ((_extra_length))
+  then
+    _calculated_length=$((_calculated_length+_extra_length))
+  fi
+
+  printf "%s\\n" "${_calculated_length:-0}"
+}
+
+# _highlight_syntax_if_available()
+#
+# Usage:
+#   _highlight_syntax_if_available [<path> | <extension>]
+#
+# Description:
+#   If `bat` or Pygments is available, use it to highlight syntax. When neither
+#   is available, pipe through `cat`.
+#
+# References:
+#   https://github.com/sharkdp/bat
+#   https://pygments.org/
+_highlight_syntax_if_available() {
+  # Usage: _highlight_syntax_with_extension <extension>
+  _highlight_syntax_with_extension() {
+    ! _contains "${1:-}" "db" # TODO
+  }
+
+  local _extension=
+  local _path=
+
+  if [[ "${1:-}" =~ / ]]
+  then
+    _path="${1}"
+  elif [[ -n "${1:-}" ]]
+  then
+    _extension="${1}"
+  else
+    _extension="md"
+  fi
+
+  if ! ((_COLOR_ENABLED))
+  then
+    if [[ -n "${_path:-}"   ]]
+    then
+      cat "${_path}"
+    else
+      cat
+    fi
+
+    return 0
+  fi
+
+  if hash "bat" 2>/dev/null
+  then
+    local _arguments=()
+
+    if [[ -n "${_path:-}"   ]]
+    then
+      _arguments+=("${_path}")
+    elif _highlight_syntax_with_extension "${_extension}"
+    then
+      _arguments+=("--language" "${_extension}")
+
+      if ! printf "" | bat  --color     always          \
+                            --language  "${_extension}" \
+                            --paging    never           \
+                            --plain                     \
+                            2>/dev/null
+      then
+        cat
+
+        return 0
+      fi
+    fi
+
+    bat "${_arguments[@]}"  \
+      --color   always      \
+      --paging  never       \
+      --plain               \
+      --theme "${NB_SYNTAX_THEME:-base16}"
+  elif hash "highlight" 2>/dev/null
+  then
+    local _arguments=("-O" "ansi")
+
+    if [[ -n "${_path:-}"   ]]
+    then
+      _arguments+=("${_path}")
+    elif _highlight_syntax_with_extension "${_extension}"
+    then
+      _arguments+=("--syntax" "${_extension}")
+    fi
+
+    highlight "${_arguments[@]}"
+  elif ((_COLOR_ENABLED)) && hash "pygmentize" 2>/dev/null
+  then # pygments is installed.
+    local _arguments=("-O" "style=default" "-f" "terminal")
+
+    if [[ -n "${_path:-}"   ]]
+    then
+      _arguments+=("${_path}")
+    elif _highlight_syntax_with_extension "${_extension}"
+    then
+      _arguments+=("-l" "${_extension}")
+    fi
+
+    pygmentize "${_arguments[@]}" 2>/dev/null
+  else
+    if [[ -n "${_path:-}"   ]]
+    then
+      cat "${_path}"
+    else
+      cat
+    fi
+  fi
+}
+
+# _join()
+#
+# Usage:
+#   _join <delimiter> <list-item>...
+#
+# Description:
+#   Print a string containing all <list-item> arguments separated by
+#   <delimeter>.
+#
+# Example:
+#   _join "${_delimeter}" "${_list[@]}"
+#
+# More Information:
+#   https://stackoverflow.com/a/17841619
+_join() {
+  local _delimiter="${1:-}"
+
+  shift
+
+  local _joined_string="${1:-}"
+
+  shift
+
+  local __element=
+  for   __element in "${@:-}"
+  do
+    [[ -n "${__element:-}" ]] || continue
+
+    _joined_string+="${_delimiter:-}${__element:-}"
+  done
+
+  printf "%s\\n" "${_joined_string}"
+}
+
+# _less_prompt()
+#
+# Usage:
+#   _less_prompt
+#
+# Description:
+#   The prompt to display in `less`.
+_less_prompt() {
+  local _prompt="\
+> scroll for more, h for help, or q to quit"
+
+  if [[ "${_COLUMNS}" -gt 81 ]]
+  then
+    _prompt="\
+> scroll for more, f / b to jump ↓ / ↑, h for help, or q to quit"
+  fi
+
+  printf "%s\\n" "${_prompt}"
+}
+
+# _list_files()
+#
+# Usage:
+#   _list_files <path> [--reverse] [--sort] [--standard-input] [--type <type>]
+#
+# Description:
+#   List files in the current notebook or filenames from standard input.
+_list_files() {
+  local _path=
+  local _read_from_standard_input=0
+  local _reverse=0
+  local _sort=0
+  local _type=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --reverse)
+        _reverse=1
+        ;;
+      --sort)
+        _sort=1
+        ;;
+      --standard-input)
+        _read_from_standard_input=1
+        ;;
+      --type)
+        if _option_value_is_present "${2:-}"
+        then
+          _type="${2}"
+
+          shift
+        fi
+        ;;
+      --[A-Za-z]*)
+        _type="${1:2}"
+        ;;
+      [^-]*)
+        if [[ -z "${_path:-}" ]] && [[ "${1:-}" =~ ^/ ]]
+        then
+          _path="${1}"
+        fi
+    esac
+
+    shift
+  done
+
+  if [[ -z "${_path:-}"   ]]
+  then
+    _path="$(_notebooks current --path)"
+  fi
+
+  if ((_read_from_standard_input)) && _piped_input
+  then
+    cat
+  elif ((_sort))
+  then
+    cat "${_path}/.index"
+  else
+    ls -t -1 "${_path}"
+  fi | {
+    if ((_reverse))
+    then
+      # https://stackoverflow.com/a/744093
+      sed '1!G;h;$!d'
+    else
+      cat
+    fi
+  } | {
+    if [[ -n "${_type:-}" ]]
+    then
+      local __extension=
+      local _grep_patterns=()
+
+      case "${_type}" in
+        bookmark|bookmarks)
+          grep --color=never    \
+            -e '\.bookmark\.'   \
+            -e '\-bookmark\.'
+          ;;
+        book|books)
+          grep --color=never -e 'epub$'
+          ;;
+        note|notes)
+          for __extension in "${_TEXT_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "${__extension}$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}" \
+            | grep --color=never -v                 \
+                -e '\.bookmark\.'                   \
+                -e '\-bookmark\.'
+          ;;
+        folder|folders|directory|directories)
+          local         __line=
+          while read -r __line
+          do
+            if [[ -d "${_path}/${__line}" ]]
+            then
+              printf "%s\\n" "${__line}"
+            fi
+          done
+          ;;
+        archive)
+          for __extension in "${_ARCHIVE_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "${__extension}$" "-e" "${__extension}.enc$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        audio|music)
+          for __extension in "${_AUDIO_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "${__extension}$" "-e" "${__extension}.enc$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        document|documents|doc|docs)
+          for __extension in "${_DOCUMENT_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$" "-e" "\.${__extension}\.enc$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        encrypted)
+          for __extension in "${_ENCRYPTED_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        image|images|picture|pictures)
+          for __extension in "${_IMAGE_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$" "-e" "\.${__extension}\.enc$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        text|txt)
+          for __extension in "${_TEXT_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        todo|todos)
+          for __extension in "${_TODO_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        video|videos)
+          for __extension in "${_VIDEO_FILE_EXTENSIONS[@]}"
+          do
+            _grep_patterns+=("-e" "\.${__extension}$" "-e" "\.${__extension}\.enc$")
+          done
+
+          grep --color=never "${_grep_patterns[@]}"
+          ;;
+        *)
+          grep --color=never -e "\.${_type}$"
+          ;;
+      esac
+    else
+      cat
+    fi
+  }
+}
+
+# _open_in_gui_app()
+#
+# Usage:
+#   _open_in_gui_app <url> | <path>
+#
+# Description:
+#   Open <url> or <path> in the system GUI web browser or application for the
+#   given file type.
+_open_in_gui_app() {
+  local _target="${1:-}"
+
+  [[ -n "${_target:-}" ]] || return 1
+
+  if _command_exists "xdg-open"
+  then
+    xdg-open "${_target}"
+  elif _command_exists "open"
+  then
+    open "${_target}"
+  elif _command_exists "wslview"
+  then
+    wslview "${_target}"
+  else
+    return 1
+  fi
+}
+
+# _pager()
+#
+# Usage:
+#   _pager
+#
+# Description:
+#   Display standard input in the preferred pager, `less`, `bat`, or `cat`.
+_pager() {
+  local _less_options=()
+  _less_options=(-R --CLEAR-SCREEN --prompt="$(_less_prompt)")
+
+  if [[ -n  "${PAGER:-}"          ]]
+  then
+    local _pager_command=()
+    IFS=" " read -r -a _pager_command <<< "${PAGER:-}"
+
+    if [[   "${PAGER:-}" =~ less  ]]
+    then
+      "${_pager_command[@]:-less}" "${_less_options[@]:-}"
+    else
+      "${_pager_command[@]:-cat}"
+    fi
+  elif _command_exists "less"
+  then
+    less "${_less_options[@]:-}"
+  elif _command_exists "bat"
+  then
+    bat --style numbers,grid
+  else
+    cat
+  fi
+}
+
+# _pandoc()
+#
+# Usage:
+#   _pandoc [--standard-input | <path>] [<pandoc-options>]
+#
+# Description:
+#   Interact with pandoc, using iconv when available.
+_pandoc() {
+  if ! _command_exists "pandoc"
+  then
+    _warn printf "%spandoc%s not found.\\n" "${_BT}" "${_BT}"
+
+    return 1
+  fi
+
+  local _pandoc_arguments=()
+  local _path=
+  local _read_from_standard_input=0
+
+  case "${1:-}" in
+    --standard-input)
+      _read_from_standard_input=1
+      ;;
+    *)
+      _path="${1:-}"
+      ;;
+  esac
+
+  shift
+
+  [[ -n "${1:-}" ]] && _pandoc_arguments=("${@}")
+
+  if _command_exists "iconv"          &&  {
+       ((_read_from_standard_input))  ||  _file_is_text "${_path:-}"
+     }
+  then
+    {
+      if ((_read_from_standard_input))
+      then
+        iconv -c -t utf-8
+      else
+        iconv -c -t utf-8 "${_path}"
+      fi
+    } | {
+      if [[ -n "${_pandoc_arguments[*]:-}"  ]]
+      then
+        pandoc "${_pandoc_arguments[@]:-}" --wrap=preserve
+      else
+        pandoc --wrap=preserve
+      fi
+    } | {
+      iconv -f utf-8
+    }
+  else
+    if ! ((_read_from_standard_input))
+    then
+      _pandoc_arguments=("${_path}" "${_pandoc_arguments[@]:-}")
+    fi
+
+    if [[ -n "${_pandoc_arguments[*]:-}"    ]]
+    then
+      pandoc "${_pandoc_arguments[@]:-}"
+    else
+      pandoc
+    fi
+  fi
+}
+
+# _piped_input()
+#
+# Usage:
+#   _piped_input
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If piped input is present.
+#   1 (error,  false)  If the current input is interactive (eg, a shell).
+_piped_input() {
+  [[ ! -t 0 ]]
+}
+
+# _print_line()
+#
+# Usage:
+#   _print_line <text> [--muted] [--no-wrap] [--visible-length [<extra-length>]
+#
+# Description:
+#   Print a line of dashes the length of <text>.
+#
+# More Information:
+#   https://wiki.bash-hackers.org/commands/builtin/printf
+_print_line() {
+  local _extra_length=0
+  local _muted=0
+  local _text=
+  local _visible_length=0
+  local _wrap_line=1
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --muted*) _muted=1              ;;
+      --no*w*)  _wrap_line=0          ;;
+      --vis*)   _visible_length=1     ;;
+      *)
+        case "${_text:-}" in
+          '') _text="${1:-}"          ;;
+          *)  _extra_length="${1:-}"  ;;
+        esac
+        ;;
+    esac
+
+    shift
+  done
+
+  local _text_length=
+
+  if ((_visible_length))
+  then
+    _text_length="$(
+      _get_visible_length "${_text:-}" "${_extra_length:-0}"
+    )"
+  else
+    _text_length="${#_text}"
+  fi
+
+  local _full_width_line=0
+
+  if ! ((_wrap_line)) && {
+       [[ -z "${_text_length:-}"                    ]] ||
+       [[    "${_text_length:-}" -gt "${_COLUMNS}"  ]]
+     }
+  then
+    _full_width_line=1
+  fi
+
+  local _line=
+
+  if ((_full_width_line))
+  then
+    printf -v _line "%*s" "${_COLUMNS}" ""
+  else
+    printf -v _line "%*s" "${_text_length}" ""
+  fi
+
+  if ((_muted))
+  then
+    _color_muted "${_line// /-}"
+  else
+    _color_secondary "${_line// /-}"
+  fi |  if ((_full_width_line))
+        then
+          tr -d '\n'
+        else
+          cat
+        fi
+}
+
+# _print_padding()
+#
+# Usage:
+#   _print_padding <line> <columns> [<aligned>]
+#
+# Description:
+#   Print a string of spaces that can be used as left padding to
+#   center-align <line>. <aligned> is an optional boolean that can
+#   be used to print no padding, returning an empty string.
+_print_padding() {
+  local _padding_centered="${3:-1}"
+  local _padding_columns="${2:-}"
+  local _padding_line="${1:-}"
+
+  local _padding_line_length="${#_padding_line}"
+
+  local _padding_amount=$(( (_padding_columns-_padding_line_length) / 2 ))
+
+  if ((_padding_centered)) && ((_padding_amount))
+  then
+    printf "%-${_padding_amount}s" " "
+  fi
+}
+
+# _print_welcome()
+#
+# Usage:
+#   _print_welcome
+#
+# Description:
+#   Print the welcome message.
+_print_welcome() {
+  local _padding=
+  _padding="$(_print_padding " / / | | | | |_) |" "${_COLUMNS}")"
+
+  _print_line "$(printf "%-${_COLUMNS}s" '.')"
+
+  cat <<HEREDOC
+${_padding}$(_color_primary "Welcome") to
+${_padding}__          _
+${_padding}\ \   _ __ | |__
+${_padding} \ \ | '_ \| '_ \\
+${_padding} / / | | | | |_) |
+${_padding}/_/  |_| |_|_.__/
+HEREDOC
+
+  _print_line "$(printf "%-${_COLUMNS}s" '.')"
+}
+
+# _selector_get_identifier()
+#
+# Usage:
+#   _selector_get_identifier <selector>
+#
+# Description:
+#   Print the identifier (non-notebook) portion of a selector.
+_selector_get_identifier() {
+  local _selector="${1:-}"
+
+  if [[   "${_selector:-}" =~ :     ]] &&
+     [[ ! "${_selector:-}" =~ /.*:  ]]
+  then
+    printf "%s\\n" "${_selector#*:}" # strip notebook name
+  else
+    printf "%s\\n" "${_selector:-}"
+  fi
+}
+
+# _selector_resolve_folders()
+#
+# Usage:
+#   _selector_resolve_folders <selector> [<notebook-path>] [--build]
+#
+# Options:
+#   --build  Build a new path that includes segments that don't exist yet.
+#
+# Description:
+#   Resolve a selector path, which can be a mix of folder names and ids.
+_selector_resolve_folders() {
+  local _build_path=0
+  local _folder_relative_path=
+  local _notebook_path=
+  local _selector=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      --build)
+        _build_path=1
+        ;;
+      *)
+        if [[ -z "${_selector:-}"   ]]
+        then
+          _selector="${__arg}"
+        else
+          _notebook_path="${__arg}"
+        fi
+        ;;
+    esac
+  done
+
+  local _selector_path="${_selector#*:}"
+
+  if [[ "${_selector}" =~ :         ]]
+  then
+    local _selector_notebook_path=
+    _selector_notebook_path="$(
+      _notebooks show "${_selector%%:*}" --path 2>/dev/null || :
+    )"
+
+    if [[ -n "${_selector_notebook_path:-}"     ]]
+    then
+      _notebook_path="${_selector_notebook_path}"
+    fi
+  fi
+
+  if [[ -z "${_notebook_path:-}"    ]]
+  then
+    _notebook_path="$(_notebooks current --path)"
+  fi
+
+  if [[ "${_selector_path}" =~ ^/   ]]
+  then
+    _selector_path="${_selector_path#"${_notebook_path}"/}"
+  fi
+
+  if [[ ! "${_selector_path}"  =~ / ]]
+  then
+    if ((_build_path))
+    then
+      _build_path=0
+      _selector_path="${_selector_path}/"
+    else
+      return 0
+    fi
+  fi
+
+  while [[ "${_selector_path}" =~ / ]]
+  do
+    local _folder_name=
+    local _parent_folder_path=
+    local _selector_segment="${_selector_path%%\/*}"
+
+    if [[ -z "${_folder_relative_path:-}"       ]]
+    then
+      _parent_folder_path="${_notebook_path}"
+    else
+      _parent_folder_path="${_notebook_path}/${_folder_relative_path}"
+    fi
+
+    if [[ -n "${_selector_segment:-}"           ]]
+    then
+      if [[ "${_selector_segment}" =~ ^[0-9]+$  ]]
+      then # folder name might be an id
+        _folder_name="$(
+          _index get_basename "${_selector_segment:?}" "${_parent_folder_path:?}" ||
+            printf "%s\\n" "${_selector_segment:?}"
+        )"
+      fi
+
+      if [[ -z "${_folder_name:-}"              ]]
+      then
+        _folder_name="${_selector_segment}"
+      fi
+
+      if [[ -d "${_parent_folder_path:?}/${_folder_name:?}" ]] ||
+         ((_build_path))
+      then
+        if [[ -z "${_folder_relative_path:-}"   ]]
+        then
+          _folder_relative_path="${_folder_name}"
+        else
+          _folder_relative_path+="/${_folder_name}"
+        fi
+
+        _selector_path="${_selector_path#*/}"
+
+        continue
+      fi
+    fi
+
+    return 1
+  done
+
+  printf "%s\\n" "${_folder_relative_path:-}"
+}
+
+# _selector_resolve_path()
+#
+# Usage:
+#   _selector_resolve_path <selector> [<notebook-path>] [--full | --relative]
+#                          [--skip-titles]
+#
+# Options:
+#   --full  Print the full path.
+#
+# Description:
+#   Determine relative path of the file that is identified by the given <id>,
+#   <filename>, <path>, or <title> and is in the current notebook or a
+#   notebook specified with a colon prefix.
+#
+#   Examples:
+#     1
+#     example.md
+#     title
+#     relative/path/to/example.md
+#     /path/to/example.md
+#     notebook:1
+#     notebook:example.md
+#     notebook:title
+#     notebook:relative/path/to/example.md
+#     notebook:/path/to/example.md
+_selector_resolve_path() {
+  local _identifier=
+  local _notebook_path=
+  local _print_full_path=0
+  local _relative_path=
+  local _selector=
+  local _skip_titles=0
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg:-}" in
+      --full)
+        _print_full_path=1
+        ;;
+      --skip-titles)
+        _skip_titles=1
+        ;;
+      [^-]*)
+        if [[ -z "${_selector:-}"   ]]
+        then
+          _selector="${__arg%/}" # strip trailing /
+        else
+          _notebook_path="${__arg:-}"
+        fi
+        ;;
+    esac
+  done
+
+  if [[ -n "${_selector}"           ]]
+  then
+    if [[ -z "${_notebook_path:-}"  ]] &&
+       [[ "${_selector}" =~ (:|^/)  ]]
+    then
+      _notebook_path="$(
+        _notebooks show "${_selector}" --path 2>/dev/null || :
+      )"
+    fi
+
+    if [[ -z "${_notebook_path:-}"  ]]
+    then
+      _notebook_path="$(
+        _notebooks current --path 2>/dev/null || :
+      )"
+    fi
+
+    _identifier="$(_selector_get_identifier "${_selector}")"
+    _identifier="${_identifier%/}" # strip trailing /
+
+    if [[ -e "${_identifier}"                     ]] &&
+       [[ "${_identifier}" =~ ^${_notebook_path}  ]]
+    then # <selector> is a full path in the current notebook
+      _relative_path="${_identifier/${_notebook_path}}"
+      _relative_path="${_relative_path#\/}"
+    elif [[ "${_identifier}" =~ ^/  ]] &&
+         [[ -e "${_identifier:-}"   ]]
+    then # <selector> is a full path in a different notebook
+      _notebook_path="$(
+        _notebooks show "${_identifier}" --path 2>/dev/null
+      )"
+
+      _relative_path="${_identifier/"${_notebook_path}"\//}"
+    elif [[ -e  "${_notebook_path}/${_identifier}"  ]] &&
+         [[ !   "${_identifier}" =~ ^[0-9]+$        ]]
+    then # <selector> is a relative path with a non-numeric filename
+      _relative_path="${_identifier}"
+    else
+      local _folder_path="${_notebook_path}"
+      local _folder_relative_path=
+      _folder_relative_path="$(
+        _selector_resolve_folders "${_selector}" "${_notebook_path}"
+      )" || return 0
+
+      if [[ -n "${_folder_relative_path:-}"     ]]
+      then
+        _folder_path="${_notebook_path}/${_folder_relative_path}"
+      fi
+
+      _identifier="${_identifier##*/}"
+
+      if [[ -e "${_folder_path}/${_identifier}" ]] &&
+         [[ !  "${_identifier}" =~ ^[0-9]+$     ]]
+      then # <selector> is relative path with a non-numeric filename
+        _relative_path="${_folder_relative_path}/${_identifier}"
+      elif [[ "${_identifier}" =~ ^[0-9]+$      ]]
+      then # <selector> is an id
+        local _basename=
+        _basename="$(_index get_basename "${_identifier}" "${_folder_path}")"
+
+        if [[ -n "${_basename:-}"                     ]]
+        then
+          if [[ -n "${_folder_relative_path:-}"       ]]
+          then
+            _relative_path="${_folder_relative_path}/${_basename}"
+          else
+            _relative_path="${_basename}"
+          fi
+        elif [[ -e "${_notebook_path}/${_identifier}" ]]
+        then # <selector> is a relative path with numeric filename
+          _relative_path="${_identifier}"
+        fi
+      elif ! ((_skip_titles))
+      then # <selector> might be a title
+        local _maybe_title="${_identifier##*\/}"
+
+        _relative_path="$(
+          {
+            _list_files "${_folder_path}"
+          } | {
+            local         __filename=
+            while read -r __filename || [[ -n "${__filename:-}" ]]
+            do
+              local _title=
+              _title="$(
+                _get_content "${_folder_path}/${__filename}" --title
+              )"
+
+              if [[ -n "${_title}"                    ]] &&
+                 [[ "${_title}" == "${_maybe_title}"  ]]
+              then
+                local _full_path="${_folder_path}/${__filename}"
+
+                printf "%s\\n" "${_full_path/"${_notebook_path}"\//}"
+
+                break
+              fi
+            done
+          }
+        )"
+      fi
+    fi
+  fi
+
+  if [[ -n "${_identifier:-}" ]] && [[ -z "${_relative_path:-}" ]]
+  then
+    return 0
+  elif ((_print_full_path))
+  then
+    printf "%s\\n" "$(_join "/" "${_notebook_path}" "${_relative_path:-}")"
+  else
+    printf "%s\\n" "${_relative_path:-}"
+  fi
+}
+
+# _spinner()
+#
+# Usage:
+#   _spinner <pid>
+#
+# Description:
+#   Display an ascii spinner while <pid> is running.
+#
+# Example Usage:
+#   ```
+#   _spinner_example() {
+#     printf "Working..."
+#     (sleep 1) &
+#     _spinner $!
+#     printf "Done!\\n"
+#   }
+#   (_spinner_example)
+#   ```
+#
+# More Information:
+#   http://fitnr.com/showing-a-bash-spinner.html
+_spinner() {
+  local _delay=0.1
+  local _pid="${1:-}"
+  local _spin_string="|/-\\"
+
+  if [[ -z "${_pid:-}" ]]
+  then
+    _exit_1 printf "Usage: _spinner <pid>\\n"
+  fi
+
+  while ps a | awk '{print $1}' | grep -q "${_pid}"
+  do
+    local _temp="${_spin_string#?}"
+
+    if ((_COLOR_ENABLED))
+    then
+      printf " %s%s[%s%c%s]%s"    \
+        "${_TPUT_SGR0}"           \
+        "${_TPUT_SETAF_8}"        \
+        "${_TPUT_COLOR_PRIMARY}"  \
+        "${_spin_string}"         \
+        "${_TPUT_SETAF_8}"        \
+        "${_TPUT_SGR0}"
+
+      printf "\b\b\b\b\b\b\b\b"
+    fi
+
+    sleep ${_delay}
+
+    _spin_string="${_temp}${_spin_string%"${_temp}"}"
+  done
+
+  if ((_COLOR_ENABLED))
+  then
+    printf "        \b\b\b\b\b\b\b\b"
+  fi
+
+  return 0
+}
+
+# _string_is_email()
+#
+# Usage:
+#   _string_is_email <string>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If the string is recognized as an email address.
+#   1 (error,  false)  if not.
+_string_is_email() {
+  [[ "${1:-}" =~ ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]+$ ]]
+}
+
+# _string_is_url()
+#
+# Usage:
+#   _string_is_url <string>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If the string is a recognized URL.
+#   1 (error,  false)  if not.
+_string_is_url() {
+  [[ -z "${1:-}" ]] && return 1
+
+  local _url_match_patterns=()
+
+  local __url_match_pattern=
+  for   __url_match_pattern in "${_URL_PATTERNS[@]}"
+  do
+    _url_match_patterns+=(-e "^${__url_match_pattern}$")
+  done
+
+  printf "%s\\n" "${1:-}" | grep -E -q --color=never "${_url_match_patterns[@]:-}"
+}
+
+# _wrap()
+#
+# Usage:
+#   _wrap [on | off]
+#
+# Description:
+#   Turn on line wrapping / automatic margins.
+_wrap() {
+  if [[ "${1:-}" == "off"  ]]
+  then
+    # NOTE: `tput` vs escape sequence:
+    # https://unix.stackexchange.com/a/558771
+    # https://unix.stackexchange.com/a/515938
+    # https://superuser.com/a/189068
+
+    # tput rmam
+    printf '\033[?7l'
+  elif [[ "${1:-}" == "on" ]]
+  then
+    # tput smam
+    printf '\033[?7h'
+  fi
+}
+
+###############################################################################
+# describe
+###############################################################################
+
+# describe()
+#
+# Usage:
+#   describe <name> <description>
+#   describe --get <name>
+#
+# Options:
+#   --get  Print the description for <name> if one has been set.
+#
+# Examples:
+# ```
+#   describe "list" <<HEREDOC
+# Usage:
+#   ${_ME} list
+#
+# Description:
+#   List items.
+# HEREDOC
+#
+# describe --get "list"
+# ```
+#
+# Set or print a description for a specified command or function <name>. The
+# <description> text can be passed as the second argument or as standard input.
+#
+# To make the <description> text available to other functions, `describe()`
+# assigns the text to a variable with the format `$____DESCRIBE_<name>`.
+#
+# When the `--get` option is used, the description for <name> is printed, if
+# one has been set.
+describe() {
+  set +e
+  [[ -z "${1:-}"          ]] &&
+    _exit_1 printf "describe(): <name> required.\\n"
+
+  if [[ "${1}" == "--get" ]]
+  then # get ------------------------------------------------------------------
+    [[ -z "${2:-}"        ]] &&
+      _exit_1 printf "describe(): <description> required.\\n"
+
+    local _name="${2:-}"
+    local _describe_var="____DESCRIBE_${_name//-/_}"
+
+    if [[ !   "${_name}" =~ ^\-               ]] &&
+       [[     "${_name}" =~ ^[A-Za-z0-9_-]+$  ]] &&
+       [[ -n  "${!_describe_var:-}"           ]]
+    then
+      printf "%s\\n" "${!_describe_var}"
+    elif _command_exists "_describe_${_name:-}"
+    then
+      "_describe_${_name:-}"
+    else
+      printf "No additional information for \`%s\`\\n" "${_name}"
+    fi
+  else # set ------------------------------------------------------------------
+    if [[ -n "${2:-}"     ]]
+    then # argument is present
+      read -r -d '' "____DESCRIBE_${1//-/_}" <<HEREDOC
+${2}
+HEREDOC
+
+      eval "_describe_${1}() { printf \"%s\\n\" \"${2:-}\"; }"
+    else # no argument is present, so assume piped input
+      local _describe_var="____DESCRIBE_${1//-/_}"
+
+      read -r -d '' "${_describe_var}"
+
+      eval "_describe_${1}() { printf \"%s\\n\" \"${!_describe_var:-}\"; }"
+    fi
+  fi
+  set -e
+}
+
+# Support legacy `desc` name.
+desc() { describe "${@}"; }
+
+###############################################################################
+# Subcommands: Group 1                                     Subcommands: Group 1
+# --------------------                                     --------------------
+#
+# `ls` and dependencies.
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+# count · ############################################################# · count
+
+_describe_count() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} count [<notebook>:][<folder-path>/]
+
+$(_color_primary "Description"):
+  Print the number of items in the first level of the current notebook,
+  <notebook>, or the folder at <folder-path>.
+HEREDOC
+}
+_count() {
+  local _list_files_options=()
+  local _selector=
+  local _skip_unmatched_selector=0
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --skip-unmatched-selector)
+        _skip_unmatched_selector=1
+        ;;
+      --type)
+        _list_files_options+=("${1}")
+        _list_files_options+=(_option_get_value "${1}" "${2:-}")
+
+        shift
+        ;;
+      -*|/*)
+        _list_files_options+=("${1}")
+        ;;
+      *)
+        _selector="${1}"
+        ;;
+    esac
+
+    shift
+  done
+
+  if [[ -n "${_selector:-}"         ]]
+  then
+    local _selector_path=
+    _selector_path="$(_selector_resolve_path "${_selector}" --full)"
+
+    if [[ -z "${_selector_path:-}"  ]]
+    then
+      if ! ((_skip_unmatched_selector))
+      then
+        _warn printf "Not found: %s\\n" "$(_color_primary "${_selector:-}")"
+
+        return 1
+      fi
+    else
+      _list_files_options+=("${_selector_path:-}")
+    fi
+  fi
+
+  _list_files "${_list_files_options[@]:-}" | wc -l | tr -d ' '
+}
+
+# git · ################################################################# · git
+
+_describe_git() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} git [checkpoint [<message>] | dirty]
+  ${_ME} git <git-options>...
+
+$(_color_primary "Subcommands"):
+  checkpoint    Create a new git commit in the current notebook and sync with
+                the remote if \`${_ME} set auto_sync\` is enabled.
+  dirty         0 (success, true) if there are uncommitted changes in the
+                current notebook. 1 (error, false) if the notebook is clean.
+
+$(_color_primary "Description"):
+  Run \`git\` commands within the current notebook directory.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-git-sync
+  ${_README_URL}#-revision-history
+
+$(_color_primary "See Also"):
+  ${_ME} help history
+  ${_ME} help remote
+  ${_ME} help run
+  ${_ME} help status
+  ${_ME} help sync
+
+$(_color_primary "Examples"):
+  ${_ME} git status
+  ${_ME} git diff
+  ${_ME} git log
+  ${_ME} example:git status
+HEREDOC
+}
+_git() {
+  # _git_autosyncable()
+  #
+  # Usage:
+  #   _git_autosyncable [<notebook-path>]
+  #
+  # Exit / Error / Return Status:
+  #   0 (success, true)  If autosync should trigger.
+  #   1 (error,  false)  If autosync should not trigger.
+  _git_autosyncable() {
+    ((_GIT_ENABLED)) || return 1
+
+    local _last_fetch_timestamp=
+    local _maybe_fetch_timestamp=
+    local _notebook_path="${1:-}"
+
+    if [[ -z "${_notebook_path}" ]]
+    then
+      _notebook_path="$(_notebooks current --path)"
+    fi
+
+    if ! ((NB_AUTO_SYNC))
+    then # autosync not enabled.
+      return 1
+    fi
+
+    if ! git -C "${_notebook_path}" config --get remote.origin.url &>/dev/null
+    then # there is no remote configured.
+      return 1
+    fi
+
+    if [[ ! -e "${_notebook_path}/.git/FETCH_HEAD" ]]
+    then # no previous fetches, but has an origin and autosync is enabled.
+      return 0
+    fi
+
+    if _maybe_fetch_timestamp="$(
+         stat -c %Y "${_notebook_path}/.git/FETCH_HEAD" 2>/dev/null
+       )"
+    then # GNU
+      _last_fetch_timestamp="${_maybe_fetch_timestamp}"
+    elif _maybe_fetch_timestamp="$(
+           gstat -c %Y "${_notebook_path}/.git/FETCH_HEAD" 2>/dev/null
+         )"
+    then # GNU prefixed
+      _last_fetch_timestamp="${_maybe_fetch_timestamp}"
+    else
+      _last_fetch_timestamp="$(
+        stat -f '%m' "${_notebook_path}/.git/FETCH_HEAD"
+      )"
+    fi
+
+    local _current_timestamp=
+    _current_timestamp="$(date +%s)"
+
+    local _diff=
+    _diff=$((_current_timestamp-_last_fetch_timestamp))
+
+    [[ "${_diff}" -gt 60 ]]
+  }
+
+  # _git_checkpoint()
+  #
+  # Usage:
+  #   _git_checkpoint <notebook-path> <commit-message>
+  #
+  # Description:
+  #   Commit all files in <notebook-path> with the provided <commit-message>.
+  _git_checkpoint() {
+    ((_GIT_ENABLED)) || return 0
+
+    # Usage: _git_checkpoint_commit <notebook-path> <message>
+    _git_checkpoint_commit() {
+      local _message="${2:-}"
+      local _notebook_path="${1:-}"
+
+      if [[ -z "${_notebook_path:-}" ]] || [[ -z "${_message:-}" ]]
+      then
+        _exit_1 printf \
+           "Usage: _git_checkpoint_commit <message> <notebook-path>"
+      fi
+
+      git -C "${_notebook_path}" add --all &&
+        git -C "${_notebook_path}" commit -a -m "${_message}"
+    }
+
+    local _message=
+    local _notebook_path=
+    local _show_spinner=0
+
+    local __arg=
+    for   __arg in "${@:-}"
+    do
+      case "${__arg}" in
+        --spinner)
+          _show_spinner=1
+          ;;
+        *)
+          if [[ -z "${_notebook_path}"  ]] &&
+             [[ "${__arg}" =~ ^/        ]] &&
+             [[ -d "${__arg}"           ]]
+          then
+            _notebook_path="${__arg}"
+          elif [[ -z "${_message}" ]]
+          then
+            _message="${__arg}"
+          fi
+          ;;
+      esac
+    done
+
+    if [[ -z "${_notebook_path:-}" ]]
+    then
+      _notebook_path="$(_notebooks current --path)"
+    fi
+
+    if [[ -z "${_message}" ]]
+    then
+      _message="[${_ME}] Commit"
+    fi
+
+    if ((NB_AUTO_SYNC))
+    then
+      (
+        {
+          # only sync when the index is dirty
+          if _git dirty "${_notebook_path}"
+          then
+            _git_checkpoint_commit "${_notebook_path}" "${_message}" &>/dev/null
+          fi && GIT_TERMINAL_PROMPT=0 _git sync "${_notebook_path}"  &>/dev/null
+        } || :
+      ) &
+    else
+      (
+        _git_checkpoint_commit "${_notebook_path}" "${_message}" &>/dev/null ||
+          return 0
+      ) &
+    fi
+
+    if ((_show_spinner))
+    then
+      _spinner  ${!}
+    fi
+
+    wait        ${!}
+    return      ${?}
+  }
+
+  # _git_dirty()
+  #
+  # Usage:
+  #   _git_dirty [<notebook-path>]
+  #
+  # Exit / Error / Return Status:
+  #   0 (success, true)  If there are uncommitted changes in <notebook-path>
+  #                      or the current notebook.
+  #   1 (error,  false)  If <notebook-path> or the current notebook is clean.
+  _git_dirty() {
+    ((_GIT_ENABLED)) || return 1
+
+    local _target_path="${1:-}"
+
+    if [[ -z "${_target_path:-}" ]]
+    then
+      _target_path="$(_notebooks current --path)"
+    fi
+
+    [[ -n "$(git -C "${_target_path}" status --porcelain)" ]]
+  }
+
+  # _git_out_of_sync()
+  #
+  # Usage:
+  #   _git_out_of_sync [<notebook-path>]
+  #
+  # Exit / Error / Return Status:
+  #   0 (success, true)  If <notebook-path> or the current notebook is out of
+  #                      sync with the remote.
+  #   1 (error,  false)  If <notebook-path> or the current notebook is synced
+  #                      with the remote.
+  _git_out_of_sync() {
+    ((_GIT_ENABLED)) || return 1
+
+    local _notebook_path="${1:-}"
+
+    if [[ -z "${_notebook_path:-}" ]]
+    then
+      _notebook_path="$(_notebooks current --path)"
+    fi
+
+    git -C "${_notebook_path}" status | grep -q 'diverged'
+  }
+
+  # _git_required()
+  #
+  # Usage:
+  #   _git_required
+  #
+  # Description:
+  #   Exit with `_exit_1` if `git` isn't found.
+  _git_required() {
+    ((_GIT_ENABLED)) || return 0
+
+    if ! _command_exists "git"
+    then
+      _exit_1 cat <<HEREDOC
+Welcome to $(_color_primary "${_ME}")!
+
+Git is required, but wasn't found. Install Git, then run \`${_ME}\` again.
+
+About Git: $(_color_primary "https://git-scm.com")
+HEREDOC
+    fi
+
+    local _git_name=
+    _git_name="$(git config --global --includes user.name   || printf '')"
+
+    local _git_email=
+    _git_email="$(git config --global --includes user.email || printf '')"
+
+    if [[ -z "${_git_name:-}"   ]]  ||
+       [[ -z "${_git_email:-}"  ]]
+    then
+      cat <<HEREDOC
+Welcome to $(_color_primary "${_ME}")!
+
+Git requires some additional setup before using $(_color_primary "${_ME}").
+Enter the name and email address you'd like to use with Git.
+Edits you make are attributed to this name and email address.
+HEREDOC
+      if [[ -z "${_git_name:-}"   ]]
+      then
+        while true
+        do
+          local __name=
+          IFS='' read -r -e -d $'\n' -p "$(_color_primary "Name"):  " __name
+
+          if [[ -n "${__name:-}"  ]]
+          then
+            git config --global user.name "${__name}"
+
+            break
+          fi
+        done
+      fi
+
+      if [[ -z "${_git_email:-}"  ]]
+      then
+        while true
+        do
+          local __email=
+          IFS='' read -r -e -d $'\n' -p "$(_color_primary "Email"): " __email
+
+          if [[ -n "${__email:-}" ]]
+          then
+            git config --global user.email "${__email}"
+
+            break
+          fi
+        done
+      fi
+    fi
+  }
+
+  # _git_sync()
+  #
+  # Usage:
+  #   _git_sync [<notebook-path>]
+  #
+  # Description:
+  #   Sync <notebook-path> or the current notebook with the remote.
+  _git_sync() {
+    local _notebook_path="${1:-}"
+    local _prompt="${GIT_TERMINAL_PROMPT:-1}"
+
+    if _contains "--skip-prompt" "${1:-}" "${2:-}"
+    then
+      _prompt=0
+    fi
+
+    if [[ -z "${_notebook_path:-}"  ]]
+    then
+      _notebook_path="$(_notebooks current --path)"
+    fi
+
+    local _remote_url=
+
+    if ! _remote_url="$(git -C "${_notebook_path}" remote get-url origin 2>/dev/null)" ||
+       [[ -z "${_remote_url:-}"     ]]
+    then
+      return 0
+    fi
+
+    local _git_branch=
+    _git_branch="$(git -C "${_notebook_path}" rev-parse --abbrev-ref HEAD 2>/dev/null)"
+
+    local _branch_query_succeeded=0
+
+    local _remote_branches=
+    _remote_branches=($(
+      git -C "${_notebook_path}" ls-remote --heads "${_remote_url}" 2>/dev/null \
+        | LC_ALL=C sed "s/.*\///g"
+    )) && _branch_query_succeeded=1
+
+    if ! GIT_TERMINAL_PROMPT=0 git -C "${_notebook_path}" fetch origin "${_git_branch}" &>/dev/null
+    then
+      if _contains "${_git_branch}" "${_remote_branches[@]:-}" ||
+         ! ((_branch_query_succeeded))
+      then
+        if ((_prompt))
+        then # fetch again, displaying git prompt and/or errors after newline
+          printf "\\n"
+
+          if ! GIT_TERMINAL_PROMPT=1 git -C "${_notebook_path}" fetch origin "${_git_branch}"
+          then
+            exit 1
+          fi
+        else
+          return 1
+        fi
+      fi
+    fi
+
+    if ((_prompt))
+    then
+      if ! _contains "${_git_branch}" "${_remote_branches[@]:-}"  ||
+         ! git -C "${_notebook_path}" show-branch                 \
+           "remotes/origin/${_git_branch}" > /dev/null 2>&1       ||
+         {
+           local _local_branch_root_hash=
+           _local_branch_root_hash="$(
+             git -C "${_notebook_path}" rev-list --max-parents=0  \
+               "${_git_branch}"
+           )"
+
+           local _remote_branch_root_hash=
+           _remote_branch_root_hash="$(
+             git -C "${_notebook_path}" rev-list --max-parents=0  \
+               "remotes/origin/${_git_branch}"
+           )"
+
+           [[ "${_local_branch_root_hash:-}" != "${_remote_branch_root_hash:-}" ]]
+         }
+      then
+        printf "\\n"
+
+        _remote set "${_remote_url}" "${_git_branch}" --skip-preamble
+
+        _git_branch="$(git -C "${_notebook_path}" rev-parse --abbrev-ref HEAD)"
+      fi
+    fi
+
+    if git -C "${_notebook_path}" show-branch \
+         "remotes/origin/${_git_branch}"      \
+         > /dev/null 2>&1                     &&
+         ! git -C "${_notebook_path}" rebase "origin/${_git_branch}" &>/dev/null
+    then
+      local _merge_error=1
+
+      local _conflicted_files=
+      _conflicted_files=($(
+        GIT_PAGER='' git -C "${_notebook_path}" diff --name-only --diff-filter=U
+      ))
+
+      local _conflicted_binary_files=()
+      local _conflicted_text_files=()
+
+      if [[ -n "${_conflicted_files[*]:-}" ]]
+      then
+        local __maybe_index_relative_path=
+        for   __maybe_index_relative_path in "${_conflicted_files[@]}"
+        do
+          if [[ "${__maybe_index_relative_path}" =~ (^.index$|/.index$) ]]
+          then
+            # Remove git conflict markers to keep both.
+            # More info: https://stackoverflow.com/a/55187779
+            _sed_i              \
+              -e '/^<<<<<<</d'  \
+              -e '/^>>>>>>>/d'  \
+              -e '/=======/d'   \
+              "${_notebook_path}/${__maybe_index_relative_path}"
+
+            git -C "${_notebook_path}" add "${__maybe_index_relative_path}"
+          fi
+        done
+
+        local __relative_path=
+        for   __relative_path in "${_conflicted_files[@]}"
+        do
+          [[ "${__relative_path}" =~ (^.index$|/.index$) ]] && continue
+
+          if _file_is_text "${__relative_path}"
+          then
+            _conflicted_text_files+=("${__relative_path}")
+
+            git -C "${_notebook_path}" add                \
+              "${__relative_path}"
+          else
+            git -C "${_notebook_path}" checkout           \
+              "origin/${_git_branch}" -- "${__relative_path}"
+
+            local _conflicted_file=
+            _conflicted_file="$(
+              _notebooks show "${_notebook_path}"         \
+                --filename  "${__relative_path%%.*}--conflicted-copy.${__relative_path#*.}"
+            )"
+
+            _conflicted_binary_files+=("${_conflicted_file}")
+
+            git -C "${_notebook_path}" mv                 \
+              "${__relative_path}" "${_conflicted_file}"
+
+            git -C "${_notebook_path}" checkout           \
+              "${_git_branch}" -- "${__relative_path}"
+
+            git -C "${_notebook_path}" add "${_conflicted_file}"
+            git -C "${_notebook_path}" add "${__relative_path}"
+          fi
+        done
+
+        GIT_EDITOR=true git -C "${_notebook_path}" rebase \
+          --continue &>/dev/null                          &&
+            _merge_error=0
+      fi
+
+      if ((_merge_error))
+      then
+        git -C "${_notebook_path}" rebase --abort
+
+        _warn printf                                              \
+          "Merge conflict. Use \`%s git\` to merge manually.\\n"  \
+          "${_ME}"
+
+        return 1
+      else
+        local _notebook_name=
+        _notebook_name="$(_notebooks show "${_notebook_path}" --name)"
+
+        if ((${#_conflicted_text_files[@]}))
+        then
+          printf "\\n"
+
+          _warn cat <<HEREDOC
+Files containing conflicts:
+
+$(printf "  %s\\n" "${_conflicted_text_files[@]/#/${_notebook_name}:}")
+
+Resolve conflicts with \`${_ME} edit\`. More info: \`${_ME} help sync\`
+HEREDOC
+        fi
+
+        if ((${#_conflicted_binary_files[@]}))
+        then
+          printf "\\n"
+
+          _warn cat <<HEREDOC
+Conflicted copies of binary files:
+
+$(printf "  %s\\n" "${_conflicted_binary_files[@]/#/${_notebook_name}:}")
+HEREDOC
+        fi
+      fi
+    fi
+
+    GIT_TERMINAL_PROMPT="${GIT_TERMINAL_PROMPT:-1}" \
+      git -C "${_notebook_path}" push               \
+      --set-upstream                                \
+      origin "${_git_branch}"                       \
+      &>/dev/null || {
+        _warn printf "Unable to push to remote.\\n"
+
+        return 1
+      }
+  }
+
+  case "${1:-}" in
+    *autosync*)
+      _git_autosyncable "${2:-}"
+      ;;
+    checkpoint)
+      shift
+
+      _git_checkpoint "${@:-}"
+      ;;
+    dirty)
+      _git_dirty "${2:-}"
+      ;;
+    out*of*sync|o|oos|out)
+      _git_out_of_sync "${2:-}"
+      ;;
+    required|setup)
+      _git_required
+      ;;
+    sync)
+      _git_sync "${2:-}" "${3:-}"
+      ;;
+    *)
+      local _notebook_path=
+      _notebook_path="$(_notebooks current --path)"
+
+      if [[ -n "${1:-}" ]]
+      then
+        git -C "${_notebook_path}" "${@}"
+      else
+        git -C "${_notebook_path}"
+      fi
+      ;;
+  esac
+}
+
+# help · ############################################################### · help
+
+export _README_URL="https://github.com/xwmx/nb"
+
+_describe_help() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} help [<subcommand>] [-p | --print]
+  ${_ME} help [-c | --colors] | [-r | --readme] | [-s | --short] [-p | --print]
+
+$(_color_primary "Options"):
+  -c, --colors  View information about color themes and color settings.
+  -p, --print   Print to standard output / terminal.
+  -r, --readme  View the \`${_ME}\` README file.
+  -s, --short   Print shorter help without subcommand descriptions.
+
+$(_color_primary "Description"):
+  Print the program help information. When a subcommand name is passed, print
+  the help information for the subcommand.
+
+$(_color_primary "Examples"):
+  ${_ME} help
+  ${_ME} help add
+  ${_ME} help import
+  ${_ME} h notebooks
+  ${_ME} h e
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} h
+HEREDOC
+}
+_help() {
+  local _arguments=()
+  local _color_help=0
+  local _readme=0
+  local _shell=0
+  local _short=0
+  local _use_pager=1
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      +) _help "add"    && return 0 ;;
+      -) _help "delete" && return 0 ;;
+      --pager)
+        _use_pager=1
+        ;;
+      -p|--print|--dump|--skip*pager|--no*pager)
+        _use_pager=0
+        ;;
+      -r|*readme*|*README*)
+        _readme=1
+        ;;
+      --shell)
+        _shell=1
+        ;;
+      -s|--short)
+        _short=1
+        ;;
+      -c|*color*|*colour*|*theme*)
+        _color_help=1
+        ;;
+      *)
+        _arguments+=("${__arg}")
+        ;;
+    esac
+  done
+
+  if ! ((_COLOR_ENABLED))
+  then
+    _TPUT_COLOR_PRIMARY=""
+    _TPUT_SETAF_8=""
+    _TPUT_SGR0=""
+  fi
+
+  if ((_readme))
+  then
+    _download_from                          \
+      "${_REPO_RAW_URL}/README.md"          \
+        | if _command_exists "pandoc"       &&
+             _web_browser --check
+          then
+            _pandoc                         \
+              --standard-input              \
+              --from  markdown              \
+              --to    html                  \
+              | _web_browser
+
+            return 0
+          else
+            _highlight_syntax_if_available  \
+              | if ((_use_pager))
+                then
+                  _pager
+                else
+                  cat
+                fi
+          fi
+  else
+    if ((_color_help))
+    then
+      # NOTE: this screen mirrors the content from README.md#-color-themes:
+      # https://github.com/xwmx/nb#-color-themes
+      _color_primary  " __          _                     _"
+      _color_primary  " \ \   _ __ | |__         ___ ___ | | ___  _ __ ___"
+      _color_primary  "  \ \ | '_ \| '_ \   _   / __/ _ \| |/ _ \| '__/ __|"
+      _color_primary  "  / / | | | | |_) | (_) | (_| (_) | | (_) | |  \__ \\"
+      _color_primary  " /_/  |_| |_|_.__/       \___\___/|_|\___/|_|  |___/"
+      printf "\\n"
+      _color_secondary \
+                      " ---------------------------------------------------"
+      printf "\\n"
+      cat <<HEREDOC
+\`${_ME}\` uses color to highlight various interface elements, including ids,
+the current notebook name, the shell prompt, and divider lines.
+
+\`${_ME}\` includes several built-in color themes and also supports user-defined
+themes. The current color theme can be set using \`${_ME} set color_theme\`:
+
+    $(_color_primary "${_ME} set color_theme")
+
+Custom color themes are \`${_ME}\` plugins with a \`.${_ME}-theme\` file extension.
+A theme is defined with a single \`if\` statement indicating the name and
+assigning the color environment variables to \`tput\` ANSI color numbers:
+
+    $(_color_secondary "# turquoise.${_ME}-theme")
+    $(_color_primary "if [[ \"\${NB_COLOR_THEME}\" == ${_TPUT_SGR0}\"turquoise\"${_TPUT_COLOR_PRIMARY} ]]")
+    $(_color_primary "then")
+    $(_color_primary "  export NB_COLOR_PRIMARY=${_TPUT_SGR0}43${_TPUT_COLOR_PRIMARY}")
+    $(_color_primary "  export NB_COLOR_SECONDARY=${_TPUT_SGR0}38${_TPUT_COLOR_PRIMARY}")
+    $(_color_primary "fi")
+
+View this theme as a complete file
+
+    $(_color_primary "https://github.com/xwmx/nb/blob/master/plugins/turquoise.${_ME}-theme")
+
+Themes can be installed using the \`${_ME} plugins\` subcommand:
+
+    $(_color_muted ">") $(_color_primary "${_ME} plugins install https://github.com/xwmx/nb/blob/master/plugins/turquoise.${_ME}-theme")
+    $(_color_secondary "Plugin installed:")
+    $(_color_secondary "/home/example/.${_ME}/.plugins/turquoise.${_ME}-theme")
+
+Once a theme is installed, use it with \`${_ME} set color_theme\`:
+
+    $(_color_muted ">") $(_color_primary "${_ME} set color_theme turquoise")
+    $(_color_secondary "NB_COLOR_THEME set to turquoise")
+
+The primary and secondary colors can also be overridden individually,
+making color themes easily customizable:
+
+    $(_color_secondary "# open the settings prompt for the primary color")
+    $(_color_primary "${_ME} set color_primary")
+
+    $(_color_secondary "# open the settings prompt for the secondary color")
+    $(_color_primary "${_ME} set color_secondary")
+
+To view a table of available colors and numbers, run:
+
+    $(_color_primary "${_ME} settings colors")
+
+To set the syntax highlighting color theme, use:
+
+    $(_color_primary "${_ME} set syntax_theme")
+
+HEREDOC
+    elif [[ -z "${_arguments[*]:-}" ]] || ((_short))
+    then
+      _color_primary        " __          _"
+      _color_primary        " \ \   _ __ | |__"
+      _color_primary        "  \ \ | '_ \| '_ \\"
+      _color_primary        "  / / | | | | |_) |"
+      _color_primary        " /_/  |_| |_|_.__/"
+
+      printf        \
+        "\\n %s\\n" \
+        "$(_color_secondary  "------------------")"
+
+      cat <<HEREDOC
+
+$(_color_brackets "${_ME}") Command line and local web note-taking, bookmarking, and archiving with
+plain text data storage, encryption, filtering and search, pinning, #tagging,
+Git-backed versioning and syncing, Pandoc-backed conversion, global and local
+notebooks, customizable color themes, [[wiki-style linking]], plugins, and more
+in a single portable, user-friendly script.
+
+$(_color_primary "Help"):
+  ${_ME} help               Display this help information.
+  ${_ME} help <subcommand>  View help information for <subcommand>.
+  ${_ME} help --colors      View information about color settings.
+  ${_ME} help --readme      View the \`${_ME}\` README file.
+
+$(_color_primary "Usage"):
+  ${_ME}
+  ${_ME} [<ls-options>...] [<id> | <filename> | <path> | <title> | <notebook>]
+  ${_ME} [<url>] [<bookmark options>...]
+  ${_ME} add [<notebook>:][<folder-path>/][<filename>] [<content>]
+         [-b | --browse] [-c <content> | --content <content>] [--edit]
+         [-e | --encrypt] [-f <filename> | --filename <filename>]
+         [--folder <folder-path>] [--tags <tag1>,<tag2>...]
+         [-t <title> | --title <title>] [--type <type>]
+  ${_ME} add bookmark [<bookmark-options>...]
+  ${_ME} add folder [<name>]
+  ${_ME} add todo [<todo-options>...]
+  ${_ME} archive [<notebook>]
+  ${_ME} bookmark [<ls-options>...]
+  ${_ME} bookmark [<notebook>:][<folder-path>/] <url>
+              [-c <comment> | --comment <comment>] [--edit] [-e | --encrypt]
+              [-f <filename> | --filename <filename>] [--no-request]
+              [-q <quote> | --quote <quote>] [--save-source]
+              [-r (<url> | <selector>) | --related (<url> | <selector>)]...
+              [-t <tag1>,<tag2>... | --tags <tag1>,<tag2>...] [--title <title>]
+  ${_ME} bookmark [list [<list-options>...]]
+  ${_ME} bookmark (edit | delete | open | peek | url)
+              ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} bookmark search <query>
+  ${_ME} browse [<notebook>:][<folder-path>/][<id> | <filename> | <title>]
+            [-g | --gui] [-n | --notebooks] [-p | --print] [-q | --query <query>]
+            [-s | --serve] [-t <tag> | --tag <tag> | --tags <tag1>,<tag2>...]
+  ${_ME} browse add [<notebook>:][<folder-path>/][<filename>]
+            [-c <content> | --content <content>] [--tags <tag1>,<tag2>...]
+            [-t <title> | --title <title>]
+  ${_ME} browse delete ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} browse edit ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} completions (check | install [-d | --download] | uninstall)
+  ${_ME} copy ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [[<notebook>:][<folder-path>/]<filename>]
+  ${_ME} count [<notebook>:][<folder-path>/]
+  ${_ME} delete ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])...
+            [-f | --force]
+  ${_ME} do ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+        [<task-number>]
+  ${_ME} edit ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [-c <content> | --content <content>] [--edit]
+          [-e <editor> | --editor <editor>] [--overwrite] [--prepend]
+  ${_ME} export ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            <path> [-f | --force] [<pandoc options>...]
+  ${_ME} export notebook <name> [<path>]
+  ${_ME} export pandoc ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            [<pandoc options>...]
+  ${_ME} folders (add | delete) [<notebook>:][<folder-path>/]<folder-name>
+  ${_ME} folders <list-options>...
+  ${_ME} git [checkpoint [<message>] | dirty]
+  ${_ME} git <git-options>...
+  ${_ME} help [<subcommand>] [-p | --print]
+  ${_ME} help [-c | --colors] | [-r | --readme] | [-s | --short] [-p | --print]
+  ${_ME} history [<notebook>:][<folder-path>/][<id> | <filename> | <title>]
+  ${_ME} import [copy | download | move] (<path>... | <url>) [--convert]
+            [<notebook>:][<folder-path>/][<filename>]
+  ${_ME} import notebook <path> [<name>]
+  ${_ME} init [<remote-url> [<branch>]] [--author] [--email <email>]
+          [--name <name>]
+  ${_ME} list [-e [<length>] | --excerpt [<length>]] [--filenames]
+          [-n <limit> | --limit <limit> | --<limit>] [--no-id]
+          [--no-indicator] [-p <number> | --page <number>] [--pager]
+          [--paths] [-s | --sort] [-r | --reverse] [--tags]
+          [-t <type> | --type <type> | --<type>]
+          [<notebook>:][<folder-path>/][<id> | <filename> | <path> | <query>]
+  ${_ME} ls [-a | --all] [-b | --browse] [-e [<length>] | --excerpt [<length>]]
+        [--filenames] [-g | --gui] [-n <limit> | --limit <limit> | --<limit>]
+        [--no-footer] [--no-header] [--no-id] [--no-indicator]
+        [-p <number> | --page <number>] [--pager] [--paths] [-s | --sort]
+        [-r | --reverse] [--tags] [-t <type> | --type <type> | --<type>]
+        [<notebook>:][<folder-path>/][<id> | <filename> | <path> | <query>]
+  ${_ME} move ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          ([<notebook>:][<path>] | --reset | --to-bookmark | --to-note |
+          --to-title | --to-todo) [-f | --force]
+  ${_ME} notebooks [<name> | <query>] [--ar | --archived] [--global] [--local]
+               [--names] [--paths] [--unar | --unarchived]
+  ${_ME} notebooks add ([<name>] [<remote-url> [<branch>... | --all]]) [--author]
+                   [--email <email>] [--name <name>]
+  ${_ME} notebooks (archive | open | peek | status | unarchive) [<name>]
+  ${_ME} notebooks author [<name> | <path>] [--email <email>] [--name <name>]
+  ${_ME} notebooks current [--path | --selected | --filename [<filename>]]
+                       [--global | --local]
+  ${_ME} notebooks delete <name> [-f | --force]
+  ${_ME} notebooks (export <name> [<path>] | import <path>)
+  ${_ME} notebooks init [<path> [<remote-url> [<branch>]]] [--author]
+                    [--email <email>] [--name <name>]
+  ${_ME} notebooks rename <old-name> <new-name>
+  ${_ME} notebooks select <selector>
+  ${_ME} notebooks show (<name> | <path> | <selector>) [--ar | --archived]
+                    [--escaped | --name | --path | --filename [<filename>]]
+  ${_ME} notebooks use <name>
+  ${_ME} open ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} peek ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} pin  ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} plugins [<name>] [--paths]
+  ${_ME} plugins install [<path> | <url>] [--force]
+  ${_ME} plugins uninstall <name> [--force]
+  ${_ME} remote [branches [<url>] | remove | rename [<branch-name>] <name>]
+  ${_ME} remote [delete <branch-name> | reset <branch-name>]
+  ${_ME} remote set <url> [<branch-name>]
+  ${_ME} run <command> [<arguments>...]
+  ${_ME} search ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            <query>... [-a | --all] [--and <query>] [--or <query>]
+            [-l | --list] [--path] [-t <tag1>,<tag2>... | --tag <tag1>,<tag2>...]
+            [-t | --tags] [--type <type> | --<type>] [--utility <name>]
+  ${_ME} set [<name> [<value>] | <number> [<value>]]
+  ${_ME} settings [colors [<number> | themes] | edit | list [--long]]
+  ${_ME} settings (get | show | unset) (<name> | <number>)
+  ${_ME} settings set (<name> | <number>) <value>
+  ${_ME} shell [<subcommand> [<options>...] | --clear-history]
+  ${_ME} show ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [[-a | --added] | [--authors] | [-b | --browse] | --filename | --id |
+          --info-line | --path | [-p | --print] | --relative-path | [-r |
+          --render] | --title | --type [<type>] | [-u | --updated]] [--no-color]
+  ${_ME} show <notebook>
+  ${_ME} status [<notebook>]
+  ${_ME} subcommands [add <name>...] [alias <name> <alias>]
+                 [describe <name> <usage>]
+  ${_ME} sync [-a | --all]
+  ${_ME} tasks ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+           [open | closed]
+  ${_ME} todo add [<notebook>:][<folder-path>/][<filename>] <title>
+              [--description <description>] [--due <date>]
+              [-r (<url> | <selector>) | --related (<url> | <selector>)]
+              [--tags <tag1>,<tag2>...] [--task <title>]...
+  ${_ME} todo do   ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+               [<task-number>]
+  ${_ME} todo undo ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+               [<task-number>]
+  ${_ME} todos [<notebook>:][<folder-path>/] [open | closed]
+  ${_ME} todos tasks ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+                 [open | closed]
+  ${_ME} unarchive [<notebook>]
+  ${_ME} undo ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [<task-number>]
+  ${_ME} unpin ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} unset (<name> | <number>)
+  ${_ME} update
+  ${_ME} use <notebook>
+  ${_ME} -h | --help | help [<subcommand> | --readme]
+  ${_ME} -i | --interactive [<subcommand> [<options>...]]
+  ${_ME} --no-color
+  ${_ME} --version | version
+HEREDOC
+
+      if ! ((_short))
+      then
+        cat <<HEREDOC
+
+$(_color_primary "Subcommands"):
+  (default)    List notes and notebooks. This is an alias for \`${_ME} ls\`.
+               When a <url> is provided, create a new bookmark.
+  add          Add a note, folder, or file.
+  archive      Archive the current or specified notebook.
+  bookmark     Add, open, list, and search bookmarks.
+  browse       Browse and manage linked items in terminal and GUI browsers.
+  completions  Install and uninstall completion scripts.
+  copy         Copy or duplicate an item.
+  count        Print the number of items in a notebook or folder.
+  delete       Delete a note.
+  do           Mark a todo or task as done.
+  edit         Edit a note.
+  export       Export a note to a variety of different formats.
+  folders      Add, delete, and list folders.
+  git          Run \`git\` commands within the current notebook.
+  help         View help information for the program or a subcommand.
+  history      View git history for the current notebook or a note.
+  import       Import a file into the current notebook.
+  init         Initialize the first notebook.
+  list         List notes in the current notebook.
+  ls           List notebooks and notes in the current notebook.
+  move         Move or rename a note.
+  notebooks    Manage notebooks.
+  open         Open a bookmarked web page or notebook folder, or edit a note.
+  peek         View a note, bookmarked web page, or notebook in the terminal.
+  pin          Pin an item so it appears first in lists.
+  plugins      Install and uninstall plugins and themes.
+  remote       Configure the remote URL and branch for the notebook.
+  run          Run shell commands within the current notebook.
+  search       Search notes.
+  settings     Edit configuration settings.
+  shell        Start the \`${_ME}\` interactive shell.
+  show         Show a note or notebook.
+  status       Print notebook status information.
+  subcommands  List, add, alias, and describe subcommands.
+  sync         Sync local notebook with the remote repository.
+  tasks        List tasks in todos, notebooks, folders, and other items.
+  todo         Manage todos and tasks.
+  unarchive    Unarchive the current or specified notebook.
+  undo         Mark a todo or task as not done.
+  unset        Return a setting to its default value.
+  unpin        Unpin a pinned item.
+  update       Update \`${_ME}\` to the latest version.
+  use          Switch to a notebook.
+  version      Display version information.
+
+$(_color_primary "Notebook Usage"):
+  ${_ME} <notebook>:[<subcommand>] [<identifier>] [<options>...]
+  ${_ME} <subcommand> <notebook>:<identifier> [<options>...]
+
+$(_color_primary "Program Options"):
+  -h, --help          Display this help information.
+  -i, --interactive   Start the \`${_ME}\` interactive shell.
+  --no-color          Print without color highlighting.
+  --version           Display version information.
+
+$(_color_primary "More Information"):
+  https://github.com/${_REPO}
+
+$(_color_primary "Sponsor & Donate"):
+  https://github.com/sponsors/xwmx
+  https://paypal.me/WilliamMelody
+
+$(_color_primary "Created By"):
+  William Melody
+  https://github.com/xwmx
+  https://www.williammelody.com
+
+$(_color_primary "Contributors"):
+  https://github.com/xwmx/nb/graphs/contributors
+
+HEREDOC
+      fi
+    else
+      printf "%s\\n" "$(describe --get "${_arguments[@]}")"
+    fi | {
+      if ((_shell))
+      then
+        LC_ALL=C sed -e "s/^  ${_ME} /  /" -e "/^  ${_ME}$/d"
+      else
+        cat
+      fi
+    } | {
+      if ((_color_help))
+      then
+        cat
+      else
+        local _replacement_pattern="${_TPUT_SGR0}${_TPUT_SETAF_8}\1${_TPUT_SGR0}"
+
+        LC_ALL=C sed -E                                                               \
+-e "/^\ \ |\[\[wiki\-style\ linking\]\]/s/(\[|\]|\(|\)|\|)/${_replacement_pattern}/g" \
+-e "s/#tag/${_TPUT_SGR0}${_TPUT_SETAF_8}#${_TPUT_SGR0}tag/g"                          \
+-e "s/(currently\ set\ to: )(.*)/\1${_TPUT_SGR0}${_TPUT_COLOR_PRIMARY}\2${_TPUT_SGR0}/g"
+      fi
+    } | {
+      LC_ALL=C sed -e "s/\`/${_TPUT_SGR0}${_TPUT_SETAF_8}\`${_TPUT_SGR0}/g"
+    } | {
+      if ((_use_pager))
+      then
+        _pager
+      else
+        cat
+      fi
+    }
+  fi
+}
+_alias_subcommand "help" "h"
+
+# index · ############################################################# · index
+
+_describe_index() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} index add <filename>
+  ${_ME} index delete <filename>
+  ${_ME} index get_basename <id>
+  ${_ME} index get_id <filename>
+  ${_ME} index get_max_id
+  ${_ME} index rebuild [--ancestors]
+  ${_ME} index reconcile [--ancestors] [--commit]
+  ${_ME} index show
+  ${_ME} index update <existing-filename> <new-filename>
+  ${_ME} index verify
+  ${_ME} index <subcommand> <options>... [<folder-path>]
+
+$(_color_primary "Options"):
+  --ancestors   Perform the action on all folders within the notebook that
+                are ancestors of the current folder.
+  --commit      Commit changes to git.
+
+$(_color_primary "Subcommands"):
+  add           Add <filename> to the index.
+  delete        Delete <filename> from the index.
+  get_basename  Print the filename / basename at the specified <id>.
+  get_id        Get the id for <filename>.
+  get_max_id    Get the maximum id for the folder.
+  rebuild       Rebuild the index, listing files by last modified, reversed.
+                Some ids will change. Prefer \`${_ME} index reconcile\`.
+  reconcile     Remove duplicates and update index for added and deleted files.
+  show          Print the index.
+  update        Overwrite the <existing-filename> entry with <new-filename>.
+  verify        Verify that the index matches the folder contents.
+
+$(_color_primary "Description"):
+  Manage the index for the current folder or the folder at <folder-path>,
+  which can be passed as the final argument to any \`index\` subcommand.
+
+  \`index\` is used internally by \`${_ME}\` and using it manually will
+  probably corrupt the index. If something goes wrong with an index,
+  fix it with \`${_ME} index reconcile\`.
+
+  An index is a text file named '.index' in any folder within a notebook.
+  .index contains a list of filenames and the line number of each filename
+  represents the id. .index files are included in the git repository so
+  ids are preserved across systems.
+HEREDOC
+}
+_index() {
+  local _ancestors=0
+  local _commit_changes=0
+  local _folder_path=
+  local _subcommand="${1:-}"
+
+  case "${_subcommand:-}" in
+    get_max_id|show|verify)
+      _folder_path="${2:-}"
+      ;;
+    rebuild|reconcile)
+      shift
+
+      local __arg=
+      for   __arg in "${@:-}"
+      do
+        case "${__arg:-}" in
+          --ancestors)
+            _ancestors=1
+            ;;
+          --commit|--checkpoint)
+            _commit_changes=1
+            ;;
+          *)
+            _folder_path="${__arg:-}"
+            ;;
+        esac
+      done
+      ;;
+    add|delete|get_basename|get_id)
+      _folder_path="${3:-}"
+      ;;
+    update)
+      _folder_path="${4:-}"
+      ;;
+    *)
+      [[ -d "${1:-}" ]] && _folder_path="${1:-}"
+      ;;
+  esac
+
+  _folder_path="${_folder_path:-"${NB_NOTEBOOK_PATH}"}"
+
+  local _index_path="${_folder_path}/.index"
+  local _notebook_path="${NB_NOTEBOOK_PATH}"
+
+  if [[ ! "${_folder_path:-}" =~ ^${NB_NOTEBOOK_PATH} ]]
+  then
+    local _notebook_and_relative_path="${_folder_path#"${NB_DIR}"/}"
+    _notebook_path="${NB_DIR}/${_notebook_and_relative_path%%/*}"
+  fi
+
+  if [[ ! -e "${_index_path}" ]]
+  then
+    case "${_subcommand}" in
+      add)
+        _index reconcile "${_folder_path}" --ancestors
+        ;;
+      rebuild|reconcile)
+        :
+        ;;
+      *)
+        _index reconcile "${_folder_path}" --ancestors --commit
+        ;;
+    esac
+  fi
+
+  case "${_subcommand}" in
+    add)
+      local _basename="${2:-}"
+
+      if [[ -z "${_basename}" ]]
+      then
+        _exit_1 _help index
+      fi
+
+      if [[ ! -e "${_folder_path}/${_basename}" ]]
+      then
+        _exit_1 printf "File not found: %s\\n" "${_folder_path}/${_basename}"
+      fi
+
+      if ! grep -q "^${_basename}$" "${_index_path}"
+      then
+        {
+          printf "%s\\n" "${_basename}" | sed -E "${_IGNORE_PATTERNS[@]:-}"
+        } >> "${_index_path}"
+      fi
+      ;;
+    delete)
+      local _basename="${2:-}"
+
+      if [[ -z "${_basename}" ]]
+      then
+        _exit_1 _help index
+      fi
+
+      if grep -q "^${_basename}$" "${_index_path}"
+      then
+        _sed_i -e "s/^${_basename}$//g" "${_index_path}"
+      else
+        return 1
+      fi
+      ;;
+    get_basename)
+      # Usage: _index_get_basename <id> <index-path>
+      _index_get_basename() {
+        if [[ -z "${1:-}" ]] || [[ "${1:-}" == "0" ]]
+        then
+          return 1
+        fi
+
+        sed "${1:-}q;d" "${2:-}"
+      }
+
+      local _id_number="${2:-}"
+      if [[ -z "${_id_number}"  ]]
+      then
+        _exit_1 _help index
+      fi
+
+      local _basename=
+      _basename="$(_index_get_basename "${_id_number}" "${_index_path}")"
+
+      if [[ -z "${_basename}"   ]]
+      then
+        _index reconcile &&
+          _basename="$(_index_get_basename "${_id_number}" "${_index_path}")"
+      fi
+
+      if [[ -z "${_basename}"   ]]
+      then
+        return 1
+      else
+        printf "%s\\n" "${_basename}"
+      fi
+      ;;
+    get_id)
+      # Usage: _index_get_id <basename> <index-path>
+      _index_get_id() {
+        # Alternatives:
+        # awk 'match($0,v){print NR; exit}' v="^${1:-}$" "${2:-}"
+        # git -C "${3:?}" grep  \
+        #   --line-number       \
+        #   --no-color          \
+        #   -e "^${1:?}$"       \
+        #   "${2:?}"            \
+        #   | cut -d: -f2
+        # grep -n "^${1:-}$" "${2:-}"                         | cut -d: -f1
+        # rg --color=never --line-number "^${1:-}$" "${2:-}"  | cut -d: -f1
+        sed -n "/^${1:-}$/=" "${2:-}"
+      }
+
+      local _basename="${2:-}"
+
+      if [[ -z "${_basename}" ]]
+      then
+        _help index
+
+        return 1
+      fi
+
+      local _id=
+      _id="$(_index_get_id "${_basename}" "${_index_path}")"
+
+      if [[ -z "${_id}" ]]
+      then
+        _index reconcile &&
+          _id="$(_index_get_id "${_basename}" "${_index_path}")"
+      fi
+
+      if [[ -z "${_id}" ]]
+      then
+        return 1
+      else
+        printf "%s\\n" "${_id}"
+      fi
+
+      # Alternative
+      # -----------
+
+      # local _basename="${2:-}"
+      # local _id=
+
+      # if [[ -z "${_basename}" ]]
+      # then
+      #   _help index
+      #
+      #   return 1
+      # fi
+
+      # _index_get_id "${_basename:-}" "${_index_path:-}" | {
+      #   read -r _id
+
+      #   if [[ -n "${_id:-}"   ]]
+      #   then
+      #     printf "%s\\n" "${_id:-}"
+      #   else
+      #     _index reconcile &&
+      #       _index_get_id "${_basename:-}" "${_index_path:-}" | {
+      #           read -r _id
+
+      #           if [[ -n "${_id:-}" ]]
+      #           then
+      #             printf "%s\\n" "${_id:-}"
+      #           else
+      #             return 1
+      #           fi
+      #         }
+      #   fi
+      # }
+      ;;
+    get_max_id)
+      wc -l < "${_index_path}" | tr -d '[:space:]'
+
+      printf "\\n"
+      ;;
+    rebuild)
+      local _top_path="${_folder_path:?}"
+
+      if ((_ancestors))
+      then
+        _top_path="${_notebook_path:?}"
+      fi
+
+      local _rebuild_type="Rebuild"
+
+      if [[ ! -e "${_folder_path:?}/.index" ]]
+      then
+        _rebuild_type="Initialize"
+      fi
+
+      local _current_folder_path="${_folder_path:?}"
+
+      while [[ "${_current_folder_path:?}" =~ ${_top_path:?} ]]
+      do
+        {
+          ls -t -r "${_current_folder_path:?}"
+        } | {
+          sed -E "${_IGNORE_PATTERNS[@]:-}"
+        } > "${_current_folder_path:?}/.index"
+
+        _current_folder_path="${_current_folder_path%/*}"
+      done  &&
+        _git checkpoint "${_notebook_path}" "[${_ME}] ${_rebuild_type:-Rebuild} Index"
+
+      return 0
+      ;;
+    reconcile)
+      # Usage: _index_reconcile_remove_duplicates <index-path>
+      _index_reconcile_remove_duplicates() {
+        local _reconcile_index_path="${1:-}"
+        [[ -z "${_reconcile_index_path:-}" ]] && return 1
+
+        local _temp_file=
+        _temp_file="$(_temp file)"
+
+        exec 3> "${_temp_file}"
+        exec 4< "${_temp_file}"
+
+        rm "${_temp_file:?}"
+
+        # Remove duplicates and preserve newlines.
+        awk '!NF || !seen[$0]++' "${_reconcile_index_path}" >&3
+        cat <&4 > "${_reconcile_index_path}"
+
+        exec 3>&-
+        exec 4<&-
+      }
+
+      local _top_path="${_folder_path:?}"
+
+      [[ -d "${_top_path}" ]] || return 0
+
+      if ((_ancestors))
+      then
+        _top_path="${_notebook_path:?}"
+      fi
+
+      local _current_folder_path="${_folder_path:?}"
+
+      while [[ "${_current_folder_path:?}" =~ ^${_top_path} ]]
+      do
+        if [[ ! -e "${_current_folder_path:?}/.index"       ]]
+        then
+          {
+            ls -t -r "${_current_folder_path:?}"
+          } | {
+            sed -E "${_IGNORE_PATTERNS[@]:-}"
+          } > "${_current_folder_path:?}/.index"
+        fi
+
+        local -a _index_list=()
+        _index_list=($(<"${_current_folder_path:?}/.index"))
+
+        local -a _file_list=()
+        _file_list=($(
+          {
+            ls -t -r "${_current_folder_path:?}"
+          } | {
+            sed -E "${_IGNORE_PATTERNS[@]:-}"
+          }
+        ))
+
+        _index_reconcile_remove_duplicates "${_current_folder_path:?}/.index"
+
+        local -a _index_file_list_diff=()
+        _index_file_list_diff=($(
+          printf "%s\\n"          \
+            "${_index_list[@]:-}" \
+            "${_file_list[@]:-}"  \
+            | sort                \
+            | uniq -u
+        ))
+
+        local -a _diff_in_index=()
+        _diff_in_index=($(
+          printf "%s\\n"                    \
+            "${_index_list[@]:-}"           \
+            "${_index_file_list_diff[@]:-}" \
+            | sort                          \
+            | uniq -d                       \
+            | uniq
+        ))
+
+        local __item=
+        for   __item in "${_diff_in_index[@]:-}"
+        do
+          if [[ -n "${__item}" ]]
+          then
+            _contains "${__item}" "${_file_list[@]:-}" ||
+              _index delete "${__item}" "${_current_folder_path:?}"
+          fi
+        done
+
+        local -a _diff_in_file_list=()
+        _diff_in_file_list=($(
+          printf "%s\\n"                    \
+            "${_file_list[@]:-}"            \
+            "${_index_file_list_diff[@]:-}" \
+            | sort                          \
+            | uniq -d                       \
+            | uniq
+        ))
+
+        local __item=
+        for   __item in "${_diff_in_file_list[@]:-}"
+        do
+          if [[ -n "${__item}" ]]
+          then
+            _contains "${__item}" "${_index_list[@]:-}" ||
+              _index add "${__item}" "${_current_folder_path:?}"
+          fi
+        done
+
+        _current_folder_path="${_current_folder_path%/*}"
+      done
+
+      if ((_commit_changes))
+      then
+        _git checkpoint "${_notebook_path}" "[${_ME}] Reconcile Index"
+      fi
+      ;;
+    show)
+      cat "${_index_path}"
+      ;;
+    update)
+      local _new_basename="${3:-}"
+      local _old_basename="${2:-}"
+
+      if [[ -z "${_old_basename}" ]] || [[ -z "${_new_basename}" ]]
+      then
+        _exit_1 _help index
+      fi
+
+      if grep -q "^${_old_basename}$" "${_index_path}"
+      then
+        _sed_i -e "s/^${_old_basename}$/${_new_basename}/g" "${_index_path}"
+      else
+        return 1
+      fi
+      ;;
+    verify)
+      local _valid=1
+
+      local -a _index_list=()
+      _index_list=($(<"${_index_path}"))
+
+      local -a _file_list=()
+      _file_list=($(
+        {
+          ls -t -r "${_folder_path}"
+        } | {
+          sed -E "${_IGNORE_PATTERNS[@]:-}"
+        }
+      ))
+
+      local -a _index_file_list_diff=()
+      _index_file_list_diff=($(
+        printf "%s\\n"          \
+          "${_index_list[@]:-}" \
+          "${_file_list[@]:-}"  \
+          | sort                \
+          | uniq -u
+      ))
+
+      if [[ -n "${_index_file_list_diff[*]:-}" ]]
+      then
+        _valid=0
+      fi
+
+      local __item=
+      for   __item in $(printf "%s\\n" "${_index_list[@]:-}" | uniq -c)
+      do
+        local _count=
+        _count="$(printf "%s\\n" "${__item}" | awk '{print $1}')"
+
+        if [[ "${_count}" -gt 1 ]]
+        then
+          _valid=0
+
+          break
+        fi
+      done
+
+      if ! ((_valid))
+      then
+        _warn                                                               \
+          printf "Index corrupted. To fix, run:\\n  %s index reconcile\\n"  \
+          "${_ME}"
+
+        return 1
+      else
+        return 0
+      fi
+      ;;
+    *)
+      :
+      ;;
+  esac
+}
+
+# init · ############################################################### · init
+
+_describe_init() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} init [<remote-url> [<branch>]] [--author] [--email <email>]
+          [--name <name>]
+
+$(_color_primary "Options"):
+  --author         Display the local email and name config prompt.
+  --email <email>  Set the local commit author email address to <email>.
+  --name  <name>   Set the local commit author name to <name>.
+
+$(_color_primary "Description"):
+  Initialize the initial "home" notebook and generate a configuration file at:
+
+      ${NBRC_PATH}
+
+  Pass optional <remote-url> and <branch> arguments to create the initial
+  "home" notebook using a clone of an existing notebook.
+
+$(_color_primary "See Also"):
+  ${_ME} help notebooks
+
+$(_color_primary "Examples"):
+  ${_ME} init
+  ${_ME} init https://github.com/example/example.git
+  ${_ME} init https://github.com/example/example.git example-branch
+HEREDOC
+}
+_init() {
+  # Usage: _init_create_home_notebook [<url> [<branch>]] [--author]
+  #                                   [--email <email>] [--name <name>]
+  _init_create_home_notebook() {
+    local _author=0
+    local _author_arguments=()
+    local _remote_branch=
+    local _remote_url=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --author) _author=1 ;;
+        --email|--name)
+          _author=1
+          _author_arguments+=("${1:-}")
+
+          if _option_value_is_present "${2:-}"
+          then
+            _author_arguments+=("${2:-}")
+
+            shift
+          fi
+          ;;
+        *)
+          if   [[ -z "${_remote_url:-}"     ]] &&
+               _string_is_url "${1:-}"
+          then
+            _remote_url="${1:-}"
+          elif [[ -z "${_remote_branch:-}"  ]]
+          then
+            _remote_branch="${1:-}"
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    ((_author)) && _author_arguments+=("${NB_DIR}/home")
+
+    if   [[ -n "${_remote_url:-}"     ]]
+    then
+      if [[ -n "${_remote_branch:-}"  ]]
+      then
+        git clone --no-local --single-branch --branch "${_remote_branch:-}" \
+          "${_remote_url}"                                                  \
+          "${NB_DIR}/home"
+      else
+        git clone --no-local --single-branch "${_remote_url}" "${NB_DIR}/home"
+      fi && if ((_author))
+            then
+              _notebooks author "${_author_arguments[@]:-}"
+            fi
+    else
+      {
+        mkdir -p  "${NB_DIR}/home"
+      } && {
+        if ((_GIT_ENABLED))
+        then
+          git -C  "${NB_DIR}/home" init   &>/dev/null
+        fi
+      } && {
+        if ((_author))
+        then
+          _notebooks author "${_author_arguments[@]:-}"
+        fi
+      } && {
+        touch  "${NB_DIR}/home/.index"
+      } && {
+        _git checkpoint "${NB_DIR}/home" "[${_ME}] Initialize"
+      }
+    fi
+
+    _notebooks use "home" 1>/dev/null
+
+    # printf "Created notebook:           %s\\n" "$(_color_primary "home")"
+  }
+
+  # Usage: _init_create_nb_dir
+  _init_create_nb_dir() {
+    if    [[ -d "${NB_DIR}" ]]
+    then
+      printf "Data directory exists:      %s\\n" "$(_color_primary "${NB_DIR}")"
+    elif  [[ -e "${NB_DIR}" ]]
+    then
+      _exit_1 cat <<HEREDOC
+Unable to set up the $(_color_primary "${_ME}") data directory. File exists at:
+${NB_DIR}
+HEREDOC
+    else
+      mkdir -p "${NB_DIR}"
+      printf "Created data directory:     %s\\n" "$(_color_primary "${NB_DIR}")"
+    fi
+  }
+
+  # Usage: _init_create_rc_file
+  _init_create_rc_file() {
+    if [[ -e "${NBRC_PATH}" ]]
+    then
+      printf "Configuration file exists:  %s\\n" \
+        "$(_color_primary "${NBRC_PATH}")"
+    else
+      cat <<HEREDOC > "${NBRC_PATH}"
+#!/usr/bin/env bash
+###############################################################################
+# .${_ME}rc
+#
+# Configuration file for \`${_ME}\`, a command line note-taking, bookmarking,
+# and knowledge base application with encryption, search, Git-backed syncing,
+# and more in a single portable script.
+#
+# Edit this file manually or manage settings using the \`${_ME} settings\`
+# subcommand. Configuration options are set as environment variables, eg:
+#   export NB_ENCRYPTION_TOOL=gpg
+#
+# https://github.com/${_REPO}
+###############################################################################
+HEREDOC
+      printf "Created configuration file: %s\\n" "$(_color_primary "${NBRC_PATH}")"
+    fi
+  }
+
+  # Usage: _init_print_header
+  _init_print_header() {
+    printf "%s%s\\n" "$(_color_primary "Initializing")" "$(_color_muted "...")"
+  }
+
+  if [[ -e "${NB_DIR}" ]] && [[ ! -d "${NB_DIR}" ]]
+  then
+    _exit_1 printf "NB_DIR exists and is not a directory: %s\\n" \
+      "$(_color_primary "${NB_DIR}")"
+  fi
+
+  if [[ -d "${_GLOBAL_NOTEBOOK_PATH}" ]]
+  then
+    _exit_1 cat <<HEREDOC
+$(_color_primary "${_ME}") already initialized. To initialize a local notebook, use:
+  $(_color_primary "${_ME} notebooks init")
+More Information:
+  $(_color_primary "${_ME} help notebooks")
+HEREDOC
+  fi
+
+  _print_welcome                            &&
+    _init_print_header          1>/dev/null &&
+    _init_create_nb_dir         1>/dev/null &&
+    _init_create_rc_file        1>/dev/null &&
+    _validate_configuration     "${@:-}"    &&
+    _init_create_home_notebook  "${@:-}"
+}
+
+# list · ############################################################### · list
+
+_describe_list() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} list [-e [<length>] | --excerpt [<length>]] [--filenames]
+          [-n <limit> | --limit <limit> | --<limit>] [--no-id]
+          [--no-indicator] [-p <number> | --page <number>] [--pager]
+          [--paths] [-s | --sort] [-r | --reverse] [--tags]
+          [-t <type> | --type <type> | --<type>]
+          [<notebook>:][<folder-path>/][<id> | <filename> | <path> | <query>]
+
+$(_color_primary "Options"):
+  -e, --excerpt [<length>]        Print an excerpt <length> lines long under
+                                  each note's filename [default: 3].
+  --filenames                     Print the filename for each note.
+  -n, --limit <limit>, --<limit>  The maximum number of notes to list.
+  --no-id                         Don't include the id in list items.
+  --no-indicator                  Don't include the indicator in list items.
+  -p, --page <number>             The page to view in the list paginated by
+                                  a <limit> option or \`${_ME} set limit\`.
+  --pager                         Display output in the pager.
+  --paths                         Print the full path to each item.
+  -s, --sort                      Order notes by id.
+  -r, --reverse                   List items in reverse order.
+  --tags                          List tags in the notebook or folder.
+  -t, --type <type>, --<type>     List items of <type>. <type> can be a file
+                                  extension or one of the following types:
+                                  archive, audio, book, bookmark, document,
+                                  folder, image, note, text, video
+
+$(_color_primary "Description"):
+  List notes in the current notebook.
+
+  When <id>, <filename>, <path>, or <title> are present, the listing for the
+  matching note is displayed. When no match is found, titles and filenames
+  are searched for any that match <query> as a case-insensitive regular
+  expression.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#listing--filtering
+
+$(_color_primary "Indicators"):
+  ${_NB_INDICATOR_AUDIO:-} Audio
+  ${_NB_INDICATOR_EBOOK:-} Book
+  ${_NB_INDICATOR_BOOKMARK:-} Bookmark
+  ${_NB_INDICATOR_ENCRYPTED:-} Encrypted
+  ${_NB_INDICATOR_FOLDER:-} Folder
+  ${_NB_INDICATOR_IMAGE:-} Image
+  ${_NB_INDICATOR_DOCUMENT:-} PDF, Word, or Open Office document
+  ${_NB_INDICATOR_VIDEO:-} Video
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help ls
+  ${_ME} help pin
+  ${_ME} help search
+  ${_ME} help unpin
+
+$(_color_primary "Examples"):
+  ${_ME} list
+  ${_ME} list example.md -e 10
+  ${_ME} list --excerpt --no-id
+  ${_ME} list --filenames --reverse
+  ${_ME} list "^Example.*"
+  ${_ME} list --10
+  ${_ME} list --type document
+  ${_ME} example:list
+HEREDOC
+}
+_list() {
+  local _error_on_empty=0
+  local _excerpt_length=3
+  local _force_line_wrap=0
+  local _limit=
+  local _line_wrap=1
+  local _list_filenames=0
+  local _list_paths=0
+  local _no_id=0
+  local _only_pinned=0
+  local _page=1
+  local _paginate=0
+  local _print_excerpt=0
+  local _print_indicators=1
+  local _print_notebook_selectors=0
+  local _recursive=0
+  local _recursive_arguments=()
+  local _reverse=0
+  local _selector_arguments=()
+  local _sort=0
+  local _type=
+  local _use_pager=0
+  local _with_pinned=0
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -a|--all)
+        _limit=
+        ;;
+      -e|--excerpt)
+        _print_excerpt=1
+        _recursive_arguments+=("--excerpt")
+
+        if _option_value_is_present "${2:-}"
+        then
+          _excerpt_length="${2:-}"
+          _recursive_arguments+=("${2:-}")
+
+          shift
+        fi
+        ;;
+      --*empty)
+        _error_on_empty=1
+        _recursive_arguments+=("--error-on-empty")
+        ;;
+      --filename*)
+        _list_filenames=1
+        _recursive_arguments+=("--filenames")
+        ;;
+      --limit|-n|--num|--number|--per*)
+        if _option_value_is_present "${2:-}"
+        then
+          _limit="${2:-}"
+
+          shift
+        fi
+        ;;
+      --no*color)
+        _COLOR_ENABLED=0
+        ;;
+      --no-id*|--noid*|--no*index)
+        _no_id=1
+        _recursive_arguments+=("--no-id")
+        ;;
+      --no*indicator*|--no*icon*|--no*emoji*|--no*unicode*)
+        _print_indicators=0
+        _recursive_arguments+=("--no-indicators")
+        ;;
+      --no*wrap|--truncate)
+        _line_wrap=0
+        _recursive_arguments+=("--no-wrap")
+        ;;
+      --notebook-selectors)
+        _print_notebook_selectors=1
+        ;;
+      -p|--page)
+        _page="$(_option_get_value "${1}" "${2:-}")"
+        ((_page))               || _page=1
+        [[ -z "${_limit:-}" ]]  && _limit="${NB_LIMIT}"
+        _paginate=1
+
+        shift
+        ;;
+      --pager|--less)
+        _use_pager=1
+        ;;
+      --path*)
+        _list_paths=1
+        _recursive_arguments+=("--paths")
+        ;;
+      --pinned)
+        _only_pinned=1
+        _with_pinned=1
+        _recursive_arguments+=("--pinned")
+        ;;
+      --recursive|--tree)
+        _recursive=1
+        ;;
+      -r|--reverse)
+        _reverse=1
+        ;;
+      -s|--sort)
+        _sort=1
+        ;;
+      --tags|--hashtags)
+        _search "${_selector_arguments[@]:-}" "${@:-}"
+
+        return 0
+        ;;
+      --titles)
+        : # Do nothing. This is the default behavior.
+        ;;
+      -t|--type)
+        _type="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --with*pinned)
+        _with_pinned=1
+        ;;
+      --wrap)
+        _force_line_wrap=1
+        _recursive_arguments+=("--wrap")
+        ;;
+      *)
+        if   [[   "${1:-}" =~ ^-+[0-9]+$  ]]
+        then
+          _limit="${1##*-}"
+        elif [[   "${1:-}" =~ ^--         ]]
+        then
+          if ! _contains "${1:-}" "--ar" "--archived" "--unar" "--unarchived"
+          then
+            _type="${1:2}"
+          fi
+        else
+          _selector_arguments+=("${1:-}")
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  local _filter_patterns=()
+  local _folder_relative_path=
+  local _selector=
+  local _selector_basename=
+
+  local __argument=
+  for   __argument in "${_selector_arguments[@]:-}"
+  do
+    if [[   -z "${__argument:-}"  ]]
+    then
+      continue
+    elif [[ -n "${_selector:-}"   ]]
+    then # selector has already been set
+      _filter_patterns+=("${__argument}")
+    elif [[ "${__argument}" =~ :$ ]]
+    then # argument appears to be a <notebook>: selector
+      local _selector_notebook_path=
+      _selector_notebook_path="$(_notebooks show "${__argument}" --path)"
+
+      if [[ -n "${_selector_notebook_path:-}"                   ]] &&
+         [[ "${_selector_notebook_path}" == "${_notebook_path}" ]]
+      then # argument is the notebook selected during program option parsing
+        _selector="${__argument}"
+      else
+        _filter_patterns+=("${__argument}")
+      fi
+    else
+      local _selector_relative_path=
+      _selector_relative_path="$(
+        # resolve selector relative path without a trailing /
+        _selector_resolve_path "${__argument%\/}" --relative
+      )"
+
+      if [[ "${__argument:-}" =~ ^/ ]]
+      then # selector is a full path
+        _selector="${__argument}"
+
+        local _selector_notebook_path=
+        _selector_notebook_path="$(
+          _notebooks show "${__argument}" --path 2>/dev/null || :
+        )"
+
+        if [[ -n  "${_selector_notebook_path:-}"                        ]] &&
+           [[ -d  "${_selector_notebook_path:-}"                        ]] &&
+           [[     "${_selector_notebook_path:-}" != "${_notebook_path}" ]]
+        then
+          _notebooks select "${_selector_notebook_path}"
+          _notebook_path="${_selector_notebook_path}"
+        fi
+
+        if [[ "${__argument}" =~ /$ ]] && [[ -d "${__argument}"   ]]
+        then
+          _selector_relative_path="${_selector_relative_path}/"
+          _folder_relative_path="${_selector_relative_path%\/*}"
+          _selector_basename="${_selector_relative_path##*\/}"
+        elif [[     "${_selector_relative_path}" =~ /             ]]
+        then
+          _folder_relative_path="${_selector_relative_path%\/*}"
+          _selector_basename="${_selector_relative_path##*\/}"
+        elif [[ -n  "${_selector_relative_path:-}"                ]]
+        then
+          _folder_relative_path=
+          _selector_basename="${_selector_relative_path}"
+        elif [[ "${__argument:-}" != "${_notebook_path:-}"        ]]
+        then
+          _filter_patterns+=("${__argument}")
+        fi
+      elif [[ "${__argument:-}" =~ /$                             ]]
+      then
+        if [[ -n "${_selector_relative_path:-}"                   ]]
+        then
+          if [[ -d "${_notebook_path}/${_selector_relative_path}" ]]
+          then # argument is a folder selector with trailing /
+            _folder_relative_path="${_selector_relative_path}"
+            _selector="${__argument}"
+            _selector_basename=
+          else # argument is a file selector
+            if [[ "${_selector_relative_path:-}" =~ /             ]]
+            then # argument is a nested file selector
+              _folder_relative_path="${_selector_relative_path%\/*}"
+            else # argument does not include a folder
+              _folder_relative_path=
+            fi
+
+            _selector="${__argument%\/}"
+            _selector_basename="${_selector_relative_path##*\/}"
+          fi
+        else # argument has a trailing slash and does not match an exsting path
+          _filter_patterns+=("${__argument}")
+        fi
+      elif [[ "${__argument:-}" =~ /            ]]
+      then
+        if [[ -n "${_selector_relative_path:-}" ]]
+        then # argument is a nested file or folder path
+          _folder_relative_path="${_selector_relative_path%\/*}"
+          _selector="${__argument}"
+          _selector_basename="${_selector_relative_path##*\/}"
+        else
+          # resolve selector relative path without final path segment
+          _selector_relative_path="$(
+            _selector_resolve_path "${__argument%\/*}" --relative
+          )"
+
+          if [[ -n "${_selector_relative_path:-}"                   ]] &&
+             [[ -d "${_notebook_path}/${_selector_relative_path:-}" ]]
+          then # folder path is selector, final path segment is filter pattern
+            _folder_relative_path="${_selector_relative_path}"
+            _selector="${__argument%\/*}"
+            _selector_basename=
+            _selector_relative_path="${_folder_relative_path:-}"
+
+            _filter_patterns+=("${__argument##*\/}")
+          else # argument does not resolve, treat as filter pattern
+            _filter_patterns+=("${__argument}")
+          fi
+        fi
+      else
+        if [[ -n "${_selector_relative_path:-}" ]]
+        then # argument is a root-level file or folder identifier
+          _folder_relative_path=
+          _selector="${__argument}"
+          _selector_basename="${_selector_relative_path##*\/}"
+        else
+          if [[ "${__argument:-}" =~ :          ]]
+          then # argument appears to include notebook selector
+            local _selector_notebook_path=
+            _selector_notebook_path="$(
+              _notebooks show "${__argument%%:*}" --path || :
+            )"
+
+            if [[ -n "${_selector_notebook_path:-}"                   ]] &&
+               [[ "${_selector_notebook_path}" == "${_notebook_path}" ]]
+            then # argument notebook selector matches the current notebook
+              _selector="${__argument%%:*}"
+              _filter_patterns+=("${__argument#*:}")
+            else
+              _filter_patterns+=("${__argument}")
+            fi
+          else
+            _filter_patterns+=("${__argument}")
+          fi
+        fi
+      fi
+    fi
+  done
+
+  local _filter_pattern=
+  _filter_pattern="$(_join "|" "${_filter_patterns[@]:-}")"
+
+  if [[ "${_selector:-}" =~ ^[^\/]+/ ]] && [[ -z "${_folder_relative_path:-}" ]]
+  then
+    _warn printf "Not found: %s\\n" "$(_color_primary "${_selector}")"
+
+    return 1
+  fi
+
+  local _list_files_options=()
+
+  [[ -n "${_type:-}" ]] && _list_files_options+=("--type" "${_type}")
+  ((_reverse))          && _list_files_options+=("--reverse")
+  ((_sort))             && _list_files_options+=("--sort")
+
+  local _list_path="${_notebook_path}"
+
+  # context variables
+
+  local _maybe_id_path_context=
+  local _maybe_selector_context=
+
+  if [[ -n "${_folder_relative_path:-}"                 ]] &&
+     [[ -e "${_notebook_path}/${_folder_relative_path}" ]]
+  then
+    _list_path="${_notebook_path}/${_folder_relative_path}"
+
+    _maybe_id_path_context="$(
+      _get_id_selector "${_folder_relative_path:-}/"
+    )"
+
+    _maybe_selector_context="${_folder_relative_path:-}/"
+  fi
+
+  if [[ ! -e "${_list_path}" ]]
+  then
+    _exit_1 printf "Not found: %s\\n" "$(
+      _color_primary "${_folder_relative_path:-"${_selector:-}"}"
+    )"
+  fi
+
+  if _notebooks current --selected || ((_print_notebook_selectors))
+  then
+    local _selected_notebook_name=
+    _selected_notebook_name="$(
+      _notebooks show "${_notebook_path}" --name --no-color
+    )"
+
+    _maybe_id_path_context="${_selected_notebook_name}:${_maybe_id_path_context:-}"
+
+    _maybe_selector_context="${_selected_notebook_name}:${_maybe_selector_context}"
+  fi
+
+  # recursive
+
+  # TODO: support --limit and any other loop-dependent features
+
+  _recursive_arguments+=("${_list_files_options[@]:-}")
+
+  if ((_recursive))
+  then
+    {
+      find "${_list_path}" -type d -not -path '*/\.*'
+    } | {
+      local         __folder_path=
+      while read -r __folder_path
+      do
+        [[ -z "${__folder_path:-}"                    ]] && continue
+        [[    "${__folder_path:-}" == "${_list_path}" ]] && continue
+
+        _list "${__folder_path}/"         \
+          "${_recursive_arguments[@]:-}"  \
+          --error-on-empty 2>/dev/null    || :
+      done
+    }
+  fi
+
+  # pinning
+
+  local _pinned_basenames=()
+
+  if ((_with_pinned))
+  then
+    if [[ -f "${_list_path}/.pindex"  ]]
+    then
+      _pinned_basenames=($(cat "${_list_path}/.pindex"))
+    fi
+
+    # Search-Based Pinning
+    #
+    # Display pinned items first in the list by matching against a pattern
+    # like "#pinned". To enable, assign a tag or other pattern to the
+    # $NB_PINNED_PATTERN environment variable.
+    #
+    # Example:
+    #   # file: ~/.nbrc
+    #   export NB_PINNED_PATTERN="#pinned"
+    if [[ -n "${NB_PINNED_PATTERN:-}" ]]
+    then
+      _pinned_basenames=($(
+        {
+          printf "%s\\n" "${_pinned_basenames[@]:-}"
+          GIT_PAGER='' git -C "${_list_path}"     \
+            grep                                  \
+            --color=never                         \
+            --extended-regexp                     \
+            --files-with-matches                  \
+            --ignore-case                         \
+            --max-depth 0                         \
+            --text                                \
+            -e "${NB_PINNED_PATTERN:-"#pinned"}"  \
+            "${_list_path}" 2>/dev/null || :
+        } | awk '!NF || !seen[$0]++'
+      ))
+    fi
+  fi
+
+  # TODO: External local variables used in pipeline.
+  #
+  # Not affected by list path:
+  #
+  # ${_excerpt_length}
+  # ${_limit}
+  # ${_list_files_options[@]}
+  # ${_with_pinned}
+  #
+  # Affected by list path / selector (Display):
+  #
+  # ${_maybe_selector_context}
+  #
+  # Affected by list path / selector (Logic):
+  #
+  # ${_filter_pattern}
+  # ${_folder_relative_path}
+  # ${_list_path}
+  # ${_maybe_selector_context}
+  # ${_pinned_basenames[@]}
+  # ${_selector_arguments[@]}
+  # ${_selector_basename}
+
+  # Use code blocks to capture all output for piping to pager.
+  {
+    if [[ -n "${_selector_basename:-}"        ]] &&
+       [[ "${#_selector_arguments[@]}" -le 1  ]]
+    then
+      printf "%s\\n" "${_selector_basename}"
+    else
+      if ((_with_pinned)) && ((${#_pinned_basenames[@]}))
+      then
+        {
+          printf "%s\\n" "${_pinned_basenames[@]:-}"
+        } | {
+          local         __pinned_basename=
+          while read -r __pinned_basename
+          do
+            if [[ -e "${_list_path:-}/${__pinned_basename:-}" ]]
+            then
+              printf "%s\\n" "${__pinned_basename:-}"
+            else
+              _sed_i -e "s/^${__pinned_basename}$//g" "${_list_path}/.pindex"
+              _sed_i -e '/^[[:space:]]*$/d'           "${_list_path}/.pindex"
+
+              if [[ ! -s "${_list_path}/.pindex"              ]]
+              then
+                rm -f "${_list_path}/.pindex"
+              fi
+
+              local _deleted_pin_relative_path="${__pinned_basename:-}"
+
+              if [[ -n "${_folder_relative_path:-}"           ]]
+              then
+                _deleted_pin_relative_path="${_folder_relative_path}/${__pinned_basename}"
+              fi
+
+              _git checkpoint "${_notebook_path}"                   \
+                "[${_ME}] Unpinned: ${_deleted_pin_relative_path}"
+            fi
+          done
+        } | {
+          _list_files "${_list_path}" "${_list_files_options[@]:-}" \
+            --standard-input  || :
+        }
+      fi
+
+      if ! ((_only_pinned))
+      then
+        _list_files "${_list_path}" "${_list_files_options[@]:-}" || :
+      fi
+    fi
+  } | {
+    sed -E "${_IGNORE_PATTERNS[@]:-}"
+  } | {
+    local _filenames_count=0
+    local _matches=0
+    local _paginated_count=0
+    local _pagination_max="$((_page * _limit))"
+    local _pagination_min="$(((_page * _limit) - _limit))"
+    local _pinned_basenames_seen=()
+    local _printed_count=0
+
+    local _max_id=
+    _max_id="$(_index get_max_id "${_list_path}")"
+
+    if ((_line_wrap))         &&
+       ((_COLOR_ENABLED))     &&
+       ! ((_list_filenames))  &&
+       ! ((_list_paths))      &&
+       ! ((_no_id))           &&
+       ! ((_force_line_wrap))
+    then
+      _line_wrap=0
+    fi
+
+    # begin main loop
+
+    local         __basename=
+    while read -r __basename
+    do
+      [[ -z "${__basename:-}" ]] && continue
+
+      _filenames_count=$((_filenames_count+1))
+
+      local _first_line=
+      local _maybe_title=
+      local _title_basename_or_path="${__basename}"
+      local _title_basename_or_path_color="${__basename}"
+
+      if [[ -z "${_filter_pattern:-}"                       ]] &&
+         [[ -n "${_selector_basename:-}"                    ]] &&
+         [[ "${__basename}" != "${_selector_basename}"      ]]
+      then
+        continue # exclude from list
+      elif ((_with_pinned)) &&
+           _contains "${__basename}" "${_pinned_basenames_seen[@]:-}"
+      then
+        continue # exclude from list
+      elif [[ -n "${_selector_basename}"                    ]] &&
+           [[ "${__basename:-}" == "${_selector_basename}"  ]]
+      then
+        # include in list
+        _matches=$((_matches+1))
+      elif [[ -n "${_filter_pattern:-}" ]]
+      then
+        # turn on case-insensitive matching
+        shopt -s nocasematch
+
+        if [[ -n "${_selector_basename}"                    ]] &&
+           [[ "${__basename:-}" == "${_selector_basename}"  ]]
+        then
+          # include in list
+          _matches=$((_matches+1))
+        elif [[ ! "${_filter_pattern}" =~ ^[0-9][0-9]$      ]] &&
+             [[ "${__basename:-}" =~ ${_filter_pattern}     ]]
+        then
+          # include in list
+          _matches=$((_matches+1))
+        else
+          _maybe_title="$(_get_content "${_list_path}/${__basename}")"
+
+          if [[ "${_maybe_title:-}" =~ ^__first_line:       ]]
+          then
+            _first_line="${_maybe_title#__first_line:}"
+            _maybe_title=
+          fi
+
+          if [[ "${_maybe_title:-}" =~ ${_filter_pattern}   ]]
+          then
+            # include in list
+            _matches=$((_matches+1))
+          else
+            continue # exclude from list
+          fi
+        fi
+
+        # turn off case-insensitive matching
+        shopt -u nocasematch
+      fi
+
+      local _pinned=0
+
+      if ((_with_pinned))
+      then
+        if _contains "${__basename}" "${_pinned_basenames[@]:-}"
+        then
+          _pinned=1
+          _pinned_basenames_seen+=("${__basename}")
+        elif ((_only_pinned))
+        then
+          continue
+        fi
+      fi
+
+      if ((_paginate))
+      then
+        _paginated_count=$((_paginated_count+1))
+
+        if   [[ "${_paginated_count}" -le "${_pagination_min}"  ]]
+        then
+          continue
+        elif [[ "${_paginated_count}" -gt "${_pagination_max}"  ]]
+        then
+          break
+        fi
+      fi
+
+      if [[   -n "${_limit:-}"                        ]] &&
+         [[      "${_printed_count}" -ge "${_limit}"  ]]
+      then # the limit has been reached
+        if [[ -n "${_filter_pattern:-}"               ]]
+        then
+          # keep looking for matches to count total
+          continue
+        else
+          if ((_only_pinned))
+          then
+            _filenames_count="${#_pinned_basenames[@]}"
+          else
+            _filenames_count="$(
+              _count "${_list_path}" "${_list_files_options[@]:-}"
+            )"
+          fi
+
+          break
+        fi
+      fi
+
+      if ((_list_paths))
+      then
+        _title_basename_or_path="${_list_path}/${__basename}"
+        _title_basename_or_path_color="${_list_path}/${__basename}"
+      elif ! ((_list_filenames))
+      then
+        if [[ -z "${_maybe_title}" ]]
+        then
+          _maybe_title="$(_get_content "${_list_path}/${__basename}")"
+        fi
+
+        if [[ -n "${_maybe_title}" ]]
+        then
+          if [[ "${_maybe_title}" =~ ^__first_line: ]]
+          then
+            _first_line="${_maybe_title#__first_line:}"
+            _maybe_title=
+          else
+            _title_basename_or_path="${_maybe_title}"
+            _title_basename_or_path_color="${_maybe_title}"
+          fi
+        fi
+      fi
+
+      local _extra_length=0
+      local _indicators=
+
+      if ((_print_indicators))
+      then
+        if ((_with_pinned)) && ((_pinned))
+        then
+          _indicators+="${_NB_INDICATOR_PINNED:-}"
+        fi
+
+        # TODO: `show --indicators` duplicated for performance
+        if [[ -d "${_list_path}/${__basename}" ]]
+        then
+          _indicators+="${_NB_INDICATOR_FOLDER:-}"
+        elif _file_is_bookmark "${_list_path}/${__basename}"
+        then
+          _indicators+="${_NB_INDICATOR_BOOKMARK:-}"
+        elif ! LC_ALL=C _contains "${__basename##*.}" "${_TEXT_FILE_EXTENSIONS[@]}"
+        then
+          if _file_is_image "${_list_path}/${__basename}"
+          then
+            _indicators+="${_NB_INDICATOR_IMAGE:-}"
+          elif _file_is_document "${_list_path}/${__basename}"
+          then
+            _indicators+="${_NB_INDICATOR_DOCUMENT:-}"
+          elif _file_is_video "${_list_path}/${__basename}"
+          then
+            _indicators+="${_NB_INDICATOR_VIDEO:-}"
+          elif _file_is_audio "${_list_path}/${__basename}"
+          then
+            _indicators+="${_NB_INDICATOR_AUDIO:-}"
+          elif [[ "${__basename}" =~ \.epub$ ]]
+          then
+            _indicators+="${_NB_INDICATOR_EBOOK:-}"
+          fi
+        fi
+
+        if _file_is_encrypted "${_list_path}/${__basename}"
+        then
+          _indicators+="${_NB_INDICATOR_ENCRYPTED:-}"
+        fi
+
+        if _file_is_todo "${_list_path}/${__basename}"
+        then
+          # TODO: review
+          if [[ "${_title_basename_or_path}" =~ \[x\]\  ]]
+          then
+            _indicators+="${_NB_INDICATOR_TODO_DONE% } "
+            _extra_length="1"
+          else
+            _indicators+="${_NB_INDICATOR_TODO% } "
+            _extra_length="-2"
+          fi
+
+          if ((_COLOR_ENABLED))
+          then
+            _title_basename_or_path_color="\
+${_title_basename_or_path_color/\[x\]/${_TPUT_SETAF_8}[${_TPUT_COLOR_PRIMARY}x${_TPUT_SETAF_8}]${_TPUT_SGR0}}"
+            _title_basename_or_path_color="\
+${_title_basename_or_path_color/\[$' '\]/${_TPUT_SETAF_8}[ ]${_TPUT_SGR0}}"
+          fi
+        fi
+      fi
+
+      local _item_info="${_indicators}${_title_basename_or_path}"
+      local _item_info_color="${_indicators}${_title_basename_or_path_color}"
+
+      if ! ((_list_filenames))  &&
+         ! ((_list_paths))      &&
+         ! ((_print_excerpt))   &&
+         [[ "${_title_basename_or_path}" == "${__basename}" ]]
+      then
+        if [[ -n "${_first_line:-}" ]]
+        then
+          _item_info="${_item_info} ${_MD} \"${_first_line}\""
+          _item_info_color="${_item_info_color} ${_MD} \"${_first_line}\""
+        fi
+      fi
+
+      local _info_line=
+      local _info_line_color=
+
+      if ((_no_id))
+      then
+        _info_line="${_item_info}"
+        _info_line_color="${_item_info_color}"
+      else
+        local _item_id=
+        # use `sed` directly instead of `_index get_id` for performance
+        _item_id="$(sed -n "/^${__basename:-}$/=" "${_list_path:-}/.index")"
+
+        if [[ -z "${_item_id:-}" ]]
+        then
+          _index reconcile "${_list_path:-}" --ancestors --commit
+
+          _item_id="$(sed -n "/^${__basename:-}$/=" "${_list_path:-}/.index")"
+        fi
+
+        local _item_identifier="${_maybe_selector_context:-}${_item_id:-}"
+        local _max_identifier="${_maybe_selector_context:-}${_max_id:-}"
+
+        local _brackets_identifier="[${_item_identifier:-}]"
+        # avoid calling `_color_brackets` for performance
+        local _brackets_identifier_color="\
+${_TPUT_SGR0}\
+${_TPUT_SETAF_8}\
+[\
+${_TPUT_COLOR_PRIMARY}\
+${_item_identifier:-}\
+${_TPUT_SETAF_8}\
+]\
+${_TPUT_SGR0}"
+
+        # use calculated number of spaces for nicer formatting
+        local _spaces_length=
+        _spaces_length=$(( ${#_max_identifier} - ${#_item_identifier} + 1 ))
+
+        local _spaces=
+        printf -v _spaces '%*s' "${_spaces_length}" ""
+
+        _info_line="${_brackets_identifier}${_spaces}${_item_info}"
+        _info_line_color="${_brackets_identifier_color}${_spaces}${_item_info_color}"
+      fi
+
+      if ! ((_line_wrap))
+      then
+        _wrap off
+      fi
+
+      if ((_COLOR_ENABLED))
+      then
+        printf "%s" "${_info_line_color}"
+      else
+        printf "%s" "${_info_line}"
+      fi
+
+      if ! ((_line_wrap))
+      then
+        _wrap on
+      fi
+
+      # end of line
+      printf "\\n"
+
+      if ((_print_excerpt))                   &&
+         [[ "${_excerpt_length}" =~ ^[0-9] ]] &&
+         _file_is_text "${_list_path}/${__basename}"
+      then # excerpt is specified with a non-zero digit, required by `head`
+        _print_line "${_info_line:-}"         \
+          --no-wrap                           \
+          --visible-length "${_extra_length:-0}"
+
+        if ((${_excerpt_length:-0}))
+        then
+          head -n "${_excerpt_length}" "${_list_path}/${__basename}" \
+            | _highlight_syntax_if_available "${__basename##*.}"
+
+          printf "\\n"
+        fi
+      fi
+
+      _printed_count=$((_printed_count+1))
+    done
+
+    # end main loop
+
+    if [[   -n "${_limit:-}"          ]] && ! ((_paginate))
+    then
+      if [[ -n "${_filter_pattern:-}" ]]
+      then
+        if [[ "${_matches:-0}"    -gt "${_limit}" ]] &&
+           [[ "${_printed_count}" -ge "${_limit}" ]]
+        then
+          local _label="matches"
+          local _omitted_count=
+          _omitted_count=$((_matches-_printed_count))
+
+          [[ "${_omitted_count}" -eq 1 ]] && _label="match"
+
+          printf "%s %s omitted. %s total.\\n"    \
+            "${_omitted_count}"                   \
+            "${_label}"                           \
+            "${_matches}"
+
+          return 0
+        fi
+      elif [[ "${_filenames_count}" -gt "${_limit}" ]] &&
+           [[ "${_printed_count}"   -ge "${_limit}" ]]
+      then
+        printf "%s omitted. %s total.\\n"         \
+          "$((_filenames_count-_printed_count))"  \
+          "${_filenames_count}"
+
+        return 0
+      fi
+    fi
+
+    if ! ((_printed_count)) && [[ -n "${_filter_pattern:-}"   ]]
+    then
+      local _filter_message=
+
+      if _notebooks current --selected
+      then
+        _filter_message="$(_color_primary "$(_notebooks current):")"
+      fi
+
+      if [[ -n "${_folder_relative_path:-}"     ]]
+      then
+        _filter_message="${_filter_message}$(_color_primary "${_folder_relative_path}/")"
+      fi
+
+      if [[ -n "${_filter_message:-}"           ]]
+      then
+        _filter_message="${_filter_message} "
+      fi
+
+      _filter_message="${_filter_message}$(_color_primary "${_filter_pattern:-}")"
+
+      if [[ -n "${_type:-}"                     ]]
+      then
+         _filter_message="${_filter_message} Type: $(_color_primary "${_type}")"
+      fi
+
+      _warn printf "Not found: %s\\n" "${_filter_message}"
+
+      return 1
+    fi
+
+    if ! ((_filenames_count)) && [[ -z "${_filter_pattern:-}" ]]
+    then
+      {
+        local _maybe_id_path_context_padded_left=
+        local _maybe_id_path_context_padded_right=
+
+        if [[ -n "${_maybe_id_path_context:-}"  ]]
+        then
+          _maybe_id_path_context="${_maybe_id_path_context//' '/\\ }"
+          _maybe_id_path_context_padded_left=" ${_maybe_id_path_context:-}"
+          _maybe_id_path_context_padded_right="${_maybe_id_path_context:-} "
+        fi
+
+        if [[ "${_type}" =~ (^bookmark$|^bookmarks$)    ]]
+        then
+          cat <<HEREDOC
+0 bookmarks.
+
+Add a bookmark:
+  $(_color_primary "${_ME} ${_maybe_id_path_context_padded_right:-}<url>")
+Help information:
+  $(_color_primary "${_ME} help bookmark")
+HEREDOC
+        elif [[ "${_type}" =~ (^todo$|^todos$)          ]]
+        then
+          cat <<HEREDOC
+0 todos.
+
+Add a todo:
+  $(_color_primary "${_ME} todo add${_maybe_id_path_context_padded_left:-} <title>")
+Help information:
+  $(_color_primary "${_ME} help todo")
+HEREDOC
+        elif [[ -n "${_type:-}" ]] || ((_only_pinned))
+        then
+          if _contains "${_type}" "bookmarks" "documents" "images" "videos" "folders"
+          then
+            _type="$(printf "%s\\n" "${_type}" | sed -e 's/s$//')"
+          fi
+
+          if ((_only_pinned))
+          then
+            cat <<HEREDOC
+0 pinned ${_type:+"${_type} "}items.
+
+Pin an item:
+  $(_color_primary "${_ME} pin ${_maybe_id_path_context:-}<id>")
+Help information:
+  $(_color_primary "${_ME} help")
+HEREDOC
+          else
+            if [[ "${_type:-}" =~ (^folder$|^folders$)  ]]
+            then
+              local _empty_type_label="folders"
+            else
+              local _empty_type_label="${_type} items"
+            fi
+
+            cat <<HEREDOC
+0 ${_empty_type_label}.
+
+Import a file:
+  $(_color_primary "${_ME} import (<path> | <url>)${_maybe_id_path_context_padded_left:-}")
+Help information:
+  $(_color_primary "${_ME} help import")
+HEREDOC
+          fi
+        else
+          cat <<HEREDOC
+0 items.
+
+Add a note:
+  $(_color_primary "${_ME} add${_maybe_id_path_context_padded_left:-}")
+Add a bookmark:
+  $(_color_primary "${_ME} ${_maybe_id_path_context_padded_right:-}<url>")
+Add a todo:
+  $(_color_primary "${_ME} todo add${_maybe_id_path_context_padded_left:-} <title>")
+Import a file:
+  $(_color_primary "${_ME} import (<path> | <url>)${_maybe_id_path_context_padded_left:-}")
+Help information:
+  $(_color_primary "${_ME} help")
+HEREDOC
+        fi
+      } | {
+        if ((_error_on_empty))
+        then
+          cat 1>&2
+
+          return 1
+        else
+          cat
+
+          return 0
+        fi
+      }
+    fi
+  } | if ((_use_pager))
+      then
+        _pager
+      else
+        cat
+      fi
+}
+
+# ls · ################################################################### · ls
+
+_describe_ls() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} ls [-a | --all] [-b | --browse] [-e [<length>] | --excerpt [<length>]]
+        [--filenames] [-g | --gui] [-n <limit> | --limit <limit> | --<limit>]
+        [--no-footer] [--no-header] [--no-id] [--no-indicator]
+        [-p <number> | --page <number>] [--pager] [--paths] [-s | --sort]
+        [-r | --reverse] [--tags] [-t <type> | --type <type> | --<type>]
+        [<notebook>:][<folder-path>/][<id> | <filename> | <path> | <query>]
+
+$(_color_primary "Options"):
+  -a, --all                       Print all items in the notebook. Equivalent
+                                  to no limit.
+  -b, --browse                    Open the specified item or current notebook
+                                  with \`browse\` in a terminal web browser.
+  -e, --excerpt [<length>]        Print an excerpt <length> lines long under
+                                  each note's filename [default: 3].
+  --filenames                     Print the filename for each note.
+  -g, --gui                       Open the specified item or current notebook
+                                  with \`browse\` in a GUI web browser.
+  -n, --limit <limit>, --<limit>  The maximum number of listed items.
+                                  [default: 15]
+  --no-footer                     Print without footer.
+  --no-header                     Print without header.
+  --no-id                         Don't include the id in list items.
+  --no-indicator                  Don't include the indicator in list items.
+  -p, --page <number>             The page to view in the list paginated by
+                                  a <limit> option or \`${_ME} set limit\`.
+  --pager                         Display output in the pager.
+  --paths                         Print the full path to each item.
+  -s, --sort                      Order notes by id.
+  -r, --reverse                   List items in reverse order.
+  --tags                          List tags in the notebook or folder.
+  -t, --type <type>, --<type>     List items of <type>. <type> can be a file
+                                  extension or one of the following types:
+                                  note, book, bookmark, document, archive,
+                                  image, video, audio, folder, text
+
+$(_color_primary "Description"):
+  List notebooks and notes in the current notebook, displaying note titles
+  when available. \`${_ME} ls\` is a combination of \`${_ME} notebooks\` and
+  \`${_ME} list\` in one view.
+
+  When <id>, <filename>, <path>, or <title> are present, the listing for the
+  matching note is displayed. When no match is found, titles and filenames
+  are searched for any that match <query> as a case-insensitive regular
+  expression.
+
+  Options are passed through to \`list\`. For more information, see
+  \`${_ME} help list\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#listing--filtering
+
+$(_color_primary "Indicators"):
+  ${_NB_INDICATOR_AUDIO:-} Audio
+  ${_NB_INDICATOR_EBOOK:-} Book
+  ${_NB_INDICATOR_BOOKMARK:-} Bookmark
+  ${_NB_INDICATOR_ENCRYPTED:-} Encrypted
+  ${_NB_INDICATOR_FOLDER:-} Folder
+  ${_NB_INDICATOR_IMAGE:-} Image
+  ${_NB_INDICATOR_DOCUMENT:-} PDF, Word, or Open Office document
+  ${_NB_INDICATOR_VIDEO:-} Video
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help list
+  ${_ME} help pin
+  ${_ME} help search
+  ${_ME} help unpin
+
+$(_color_primary "Examples"):
+  ${_ME}
+  ${_ME} --all
+  ${_ME} ls
+  ${_ME} ls example.md -e 10
+  ${_ME} ls --excerpt --no-id
+  ${_ME} ls --reverse
+  ${_ME} ls "^Example.*"
+  ${_ME} ls --10
+  ${_ME} ls --type document
+  ${_ME} example:
+  ${_ME} example: -ae
+  ${_ME} example:ls
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME}
+HEREDOC
+}
+_ls() {
+  # _ls_print_footer()
+  #
+  # Usage:
+  #   _ls_print_footer [<selector>]
+  _ls_print_footer() {
+    local _footer_line_hi=
+    local _footer_line_raw=
+    local _footer_separator_raw=" ${_MD}"
+    local _footer_test_line=
+    local _maybe_notebook=
+    local _maybe_selector_scope=
+    local _maybe_selector_scope_padded_left=
+    local _maybe_selector_scope_padded_right=
+    local _selector_path="${1:-}"
+
+    local _footer_separator_hi=
+    _footer_separator_hi="$(_color_primary "${_footer_separator_raw}")"
+
+    if _notebooks current --selected
+    then
+      _maybe_notebook="$(
+        _notebooks show "$(_notebooks current)" --escaped --no-color
+      ):"
+    fi
+
+    local _folder_id_path=
+    _folder_id_path="$(_get_id_selector "${_selector_path:-}")"
+
+    if [[ -n "${_maybe_notebook:-}" ]] ||
+       [[ -n "${_folder_id_path:-}" ]]
+    then
+      _maybe_selector_scope="${_maybe_notebook}${_folder_id_path}"
+      _maybe_selector_scope_padded_left=" ${_maybe_selector_scope}"
+      _maybe_selector_scope_padded_right="${_maybe_selector_scope} "
+    fi
+
+    local _notebook_command="${_ME} notebooks add <name>"
+
+    local _unarchived_notebook_count=0
+
+    set +f
+    local __path=
+    for   __path in "${NB_DIR}"/*
+    do
+      if [[ ! -f "${__path:?}/.archived"          ]]
+      then
+        _unarchived_notebook_count=$((_unarchived_notebook_count + 1))
+      fi
+
+      if [[ "${_unarchived_notebook_count}" -gt 1 ]]
+      then
+        if [[ -n "${_maybe_notebook:-}"           ]]
+        then
+          _notebook_command="${_ME} use ${_maybe_notebook%%:*}"
+        else
+          _notebook_command="${_ME} use <notebook>"
+        fi
+
+        break
+      fi
+    done
+    set -f
+
+    local _commands_raw=(
+      "${_CHEVRON_RIGHT} ${_ME}${_maybe_selector_scope_padded_left}"
+      "${_ME} add${_maybe_selector_scope_padded_left}"
+      "${_ME} ${_maybe_selector_scope_padded_right}<url>"
+      "${_ME} edit ${_maybe_selector_scope}<id>"
+      "${_ME} show ${_maybe_selector_scope}<id>"
+      "${_ME} open ${_maybe_selector_scope}<id>"
+      "${_ME} browse${_maybe_selector_scope_padded_left}"
+      "${_ME} todos${_maybe_selector_scope_padded_left}"
+      "${_ME} tasks${_maybe_selector_scope_padded_left}"
+      "${_ME} search ${_maybe_selector_scope_padded_right}<query>"
+      "${_notebook_command}"
+      "${_ME} settings"
+      "${_ME} help"
+    )
+
+    local _commands_hi=(
+      "$(_color_muted "${_CHEVRON_RIGHT}") $(_color_secondary "${_ME}${_maybe_selector_scope_padded_left}")"
+      "$(_color_secondary "${_commands_raw[1]}")"
+      "$(_color_secondary "${_commands_raw[2]}")"
+      "$(_color_secondary "${_commands_raw[3]}")"
+      "$(_color_secondary "${_commands_raw[4]}")"
+      "$(_color_secondary "${_commands_raw[5]}")"
+      "$(_color_secondary "${_commands_raw[6]}")"
+      "$(_color_secondary "${_commands_raw[7]}")"
+      "$(_color_secondary "${_commands_raw[8]}")"
+      "$(_color_secondary "${_commands_raw[9]}")"
+      "$(_color_secondary "${_commands_raw[10]}")"
+      "$(_color_secondary "${_commands_raw[11]}")"
+      "$(_color_secondary "${_commands_raw[12]}")"
+    )
+
+    _wrap off
+
+    _print_line "$(printf "%-${_COLUMNS}s" '.')" | tr -d '\n'
+
+    printf "%s" "${_TPUT_SGR0}"
+
+    _wrap on
+
+    printf "\\n"
+
+    local i=
+    for ((i=0; i < ${#_commands_raw[@]}; i++))
+    do
+      if [[ -z "${_footer_test_line}"                 ]]
+      then # first item in line
+        _footer_test_line="${_commands_raw[i]}"
+      else
+        _footer_test_line="${_footer_test_line}${_footer_separator_raw} ${_commands_raw[i]}"
+      fi
+
+      if [[ "${#_footer_test_line}" -gt "${_COLUMNS}" ]]
+      then # wrap to next line
+        printf "%s\\n" "${_footer_line_hi}"
+
+        # Start the line for the next iteration using the current name.
+        _footer_test_line="${_commands_raw[i]}"
+        _footer_line_hi="${_commands_hi[i]:-}"
+        _footer_line_raw="${_commands_raw[i]}"
+      else # add to line
+        if [[ -z "${_footer_line_hi}" ]]
+        then # first item in highlighted line
+          _footer_line_hi="${_commands_hi[i]:-}"
+          _footer_line_raw="${_commands_raw[i]}"
+        else
+          _footer_line_hi="${_footer_line_hi}${_footer_separator_hi} ${_commands_hi[i]:-}"
+          _footer_line_raw="${_footer_line_raw}${_footer_separator_raw} ${_commands_raw[i]}"
+        fi
+      fi
+
+      if [[ "${#_commands_raw[@]}" == $((i+1))        ]]
+      then # end of list
+        printf "%s\\n" "${_footer_line_hi}"
+      fi
+    done
+  }
+
+  # _ls_print_folder_header()
+  #
+  # Usage: _ls_print_folder_header <folder-path>
+  _ls_print_folder_header() {
+    [[ -z "${1:-}" ]] && return 0
+
+    # printf "${_NB_INDICATOR_FOLDER:-}" # TODO: Review
+
+    local _folder_separator=
+    _folder_separator="$(_color_muted "/")"
+
+    printf "%s\\n" "${1//\// ${_folder_separator} }"
+
+    _print_line "$(printf "%-${_COLUMNS}s" '.')" --muted
+
+    printf "\\n"
+  }
+
+  # _ls_print_header()
+  #
+  # Usage:
+  #   _ls_print_header <alignment>
+  #
+  # Description:
+  #   Build word-wrapping notebook line. `fold` doesn't account for
+  #   highlighting.
+  #
+  #   Simple version:
+  #     _notebooks --names            \
+  #       | tr '\n' ' '               \
+  #       | fold -s "-w$(tput cols)"  \
+  #       && printf "\\n"
+  _ls_print_header() {
+    local _alignment="${1:-}"
+    local _auto_align=1 # auto-align by default.
+    local _centered=0
+    local _justified=0
+    local _plain=0
+
+    [[ "${NB_HEADER}" == 2 ]] && _centered=1
+    [[ "${NB_HEADER}" == 3 ]] && _justified=1
+
+    case "${_alignment}" in
+      --auto*align)
+        _auto_align=1
+        _centered=0
+        _justified=0
+        ;;
+      --centered)
+        _auto_align=0
+        _centered=1
+        _justified=0
+        ;;
+      --justified)
+        _auto_align=0
+        _centered=0
+        _justified=1
+        ;;
+      --plain)
+        _plain=1
+        ;;
+    esac
+
+    local _separator=
+    local _separator_hi=
+
+    if ! ((_plain))
+    then
+      _separator=" ${_MD}"
+      _separator_hi="$(_color_muted "${_separator}")"
+    fi
+
+    local _current_notebook_name=
+    _current_notebook_name="$(_notebooks current)"
+
+    {
+      local _archived_count=0
+      local _unarchived_notebook_names=()
+
+      set +f
+      local __path=
+      for   __path in "${NB_DIR}"/*
+      do
+        if [[ -f "${__path:?}/.archived" ]]
+        then
+          _archived_count=$((_archived_count+1))
+        else
+          _unarchived_notebook_names+=("${__path##*\/}")
+        fi
+      done
+      set -f
+
+      if _notebooks current --local
+      then
+        printf "local\\n"
+      fi
+
+      printf "%s\\n" "${_unarchived_notebook_names[@]:-}"
+
+      if ((_archived_count))
+      then
+        printf "[%s archived]\\n" "${_archived_count}"
+      fi
+    } | {
+      local _line_hi=
+      local _line_number=0
+      local _line_raw=
+      local _output_line_raw=
+      local _padding=
+      local _test_line=
+
+      local         __header_name=
+      while read -r __header_name
+      do
+        local _maybe_highlighted_notebook_name=
+
+        if [[ "${_current_notebook_name}" == "${__header_name}" ]]
+        then
+          _maybe_highlighted_notebook_name="$(
+            _color_primary "${__header_name:-}" --underline
+          )"
+        else
+          _maybe_highlighted_notebook_name="${__header_name:-}"
+        fi
+
+        if [[ -z "${_test_line}"                  ]]
+        then # first item in line
+          _test_line="${__header_name}"
+        else
+          _test_line="${_test_line}${_separator} ${__header_name}"
+        fi
+
+        if [[ "${#_test_line}" -gt "${_COLUMNS}"  ]]
+        then # wrap to next line
+          # Use the existing value of $_line_[highlighted|raw] without the
+          # current name.
+          if ((_auto_align)) || ((_centered)) && ! ((_justified))
+          then
+            _centered=1
+            _padding="$(
+              _print_padding "${_line_raw}" "${_COLUMNS}" "${_centered}"
+            )"
+          fi
+
+          printf "%s%s%s\\n" "${_TPUT_SGR0}" "${_padding:-}" "${_line_hi:-}"
+          _output_line_raw="${_padding}${_line_raw}\\n"
+          _line_number=$((_line_number + 1))
+
+          # Start the line for the next iteration using the current name.
+          _test_line="${__header_name}"
+          _line_hi="${_maybe_highlighted_notebook_name:-}"
+          _line_raw="${__header_name}"
+        else # add to line
+          if [[ -z "${_line_hi}"                  ]]
+          then # first item in highlighted line
+            _line_hi="${_maybe_highlighted_notebook_name:-}"
+            _line_raw="${__header_name}"
+          else
+            _line_hi="${_line_hi}${_separator_hi} ${_maybe_highlighted_notebook_name:-}"
+            _line_raw="${_line_raw}${_separator} ${__header_name}"
+          fi
+        fi
+      done
+
+      if ((_line_number))  && ! ((_justified)) &&
+         ((_auto_align))   ||   ((_centered))
+      then
+        _centered=1
+      fi
+
+      _padding="$(
+        _print_padding "${_line_raw}" "${_COLUMNS}" "${_centered}"
+      )"
+
+      printf "%s%s\\n" "${_padding:-}" "${_line_hi:-}"
+      _output_line_raw="${_padding}${_line_raw}\\n"
+
+      _wrap off
+
+      if ((_centered))
+      then # print full-width line.
+        _print_line "$(printf "%-${_COLUMNS}s" '.')" | tr -d '\n'
+      else # print line the length of the first line.
+        _print_line "$(
+          # $_output_line_raw content is 2 characters too long. TODO: Review
+          printf "%s" "${_output_line_raw}" | sed 's/..$//'
+        )" | tr -d '\n'
+      fi
+
+      printf "%s" "${_TPUT_SGR0}"
+
+      _wrap on
+
+      printf "\\n"
+    }
+  }
+
+  local _all=0
+  local _arguments=()
+  local _delegate_to_browse=0
+  local _delegate_arguments=()
+  local _fast_exit=0
+  local _filter_patterns=()
+  local _header_flags=()
+  local _limit=
+  local _maybe_type=
+  local _selector=
+  local _selector_folder_path=
+  local _use_pager=0
+  local _with_pinned=1
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --added|--ar|--archived|--unar|--unarchived|--updated)
+        _delegate_arguments+=("${1}")
+        ;;
+      -a|--all)
+        _all=1
+        ;;
+      --auto*align|--centered|--justified|--plain)
+        _header_flags+=("${1}")
+        ;;
+      -b|--browse)
+        _delegate_to_browse=1
+        ;;
+      --content|--title)
+        if _option_value_is_present "${2:-}"
+        then
+          _delegate_arguments+=("${1}" "${2:-}")
+
+          shift
+        fi
+        ;;
+      --*exit*)
+        _fast_exit=1
+        ;;
+      -g|--gui)
+        _delegate_to_browse=1
+        _delegate_arguments+=("${1}")
+        ;;
+      --limit|-n|--num|--number|--per*)
+        _limit="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --pager|--less)
+        _use_pager=1
+        ;;
+      -l)
+        : # Ignore accidental ls -l  due to muscle memory.
+        ;;
+      --no*footer)
+        NB_FOOTER=0
+        ;;
+      --no*header)
+        NB_HEADER=0
+        ;;
+      -s|--sort|-r|--reverse)
+        _arguments+=("${1}")
+        _with_pinned=0
+        ;;
+      --tag*)
+        _delegate_arguments+=("${1}")
+
+        if _option_value_is_present "${2:-}"
+        then
+          _delegate_arguments+=("${2:-}")
+
+          shift
+        fi
+        ;;
+      -t|--type)
+        _maybe_type="$(_option_get_value "${1}" "${2:-}")"
+        _arguments+=("${1}" "${2:-}")
+
+        shift
+        ;;
+      --[A-Za-z]*)
+        _maybe_type="${1:2}"
+
+        _arguments+=("${1}")
+        ;;
+      -*)
+        if [[ "${1:-}" =~ ^-+[0-9]+$  ]]
+        then
+          _limit="${1##*-}"
+        else
+          _arguments+=("${1}")
+
+          if _option_value_is_present "${2:-}"
+          then
+            _arguments+=("${2:-}")
+
+            shift
+          fi
+        fi
+        ;;
+      \#*)
+        _delegate_arguments+=(--tag "${1}")
+        ;;
+      *:*)
+        local _selector_id=
+        _selector_id="$(_selector_get_identifier "${1}")"
+
+        if [[ -n "${_selector_id:-}"  ]]
+        then
+          _arguments+=("${_selector_id}")
+        fi
+
+        _selector="${1:-}"
+        _filter_patterns+=("${1}")
+        ;;
+      *)
+        if [[ -z "${_selector:-}"     ]]
+        then
+          _selector="${1}"
+        fi
+
+        _arguments+=("${1}")
+        _filter_patterns+=("${1}")
+        ;;
+    esac
+
+    shift
+  done
+
+  # Delegate to `add`, `show`, and other subcommands.
+
+  if ((${#_delegate_arguments[@]})) || ((_delegate_to_browse))
+  then
+    if ((_delegate_to_browse))
+    then
+      _defer "_browse" "${_arguments[@]:-}" "${_delegate_arguments[@]:-}"
+
+      return 0
+    else
+      local i=
+      for ((i=0; i < ${#_delegate_arguments[@]}; i++))
+      do
+        case "${_delegate_arguments[i]:-}" in
+          --ar*|--unar*)
+            _defer "_notebooks" list "${_delegate_arguments[@]:-}"
+
+            return 0
+            ;;
+          --added|--updated)
+            if [[ -n "${_selector:-}"     ]]
+            then
+              _defer "_show" "${_arguments[@]:-}" "${_delegate_arguments[@]:-}"
+
+              return 0
+            fi
+            ;;
+          --content|--title)
+            if _option_value_is_present "${_delegate_arguments[$((i+1))]:-}"
+            then
+              _defer "_add" "${_arguments[@]:-}" "${_delegate_arguments[@]:-}"
+
+              return 0
+            fi
+            ;;
+          --tag*)
+            ((_all)) && _delegate_arguments+=("--all")
+            _defer "_search"                \
+              "${_arguments[@]:-}"          \
+              "${_delegate_arguments[@]:-}" \
+              --list
+
+            return 0
+            ;;
+          *)
+            if [[ -n "${_arguments[i]:-}" ]]
+            then
+              _arguments+=("${_arguments[i]:-}")
+            fi
+            ;;
+        esac
+      done
+    fi
+  fi
+
+  # Build list options.
+
+  local _list_options=(${_arguments[@]:-})
+
+  if ((_with_pinned))
+  then
+    _list_options+=("--with-pinned")
+  fi
+
+  local _selector_relative_path="${_selector#*:}"
+
+  if [[ -n "${_limit:-}"                            ]]
+  then
+    _list_options+=("--limit" "${_limit}")
+  elif ! ((_all))                                       &&
+       [[ -z "${_AUTO_LIMIT:-}"                     ]]  &&
+       {
+         [[ -z "${_selector_relative_path:-}"       ]]  ||
+         {
+           [[ "${_selector_relative_path:-}" =~ /   ]]  &&
+           [[ -z "${_selector_relative_path##*\/}"  ]]  &&
+           [[ "${#_filter_patterns[@]}" -le 1       ]]
+         }
+       }
+  then
+    _list_options+=("--limit" "${NB_LIMIT}")
+  fi
+
+  # Resolve selector folders before printing header to minimize pause
+  # before printing list.
+
+  if [[ "${_selector:-}" =~ /             ]]
+  then
+    _selector_folder_path="$(_selector_resolve_folders "${_selector}" || :)"
+
+    if [[ -n "${_selector_folder_path:-}" ]]
+    then
+      _selector_folder_path="${_selector_folder_path}/"
+    fi
+  fi
+
+  # Determine whether to display header and footer.
+
+  local _display_header_and_footer=0
+
+  if [[ -z "${_arguments[*]:-}"           ]]  ||
+     {
+       [[ "${_selector:-}" =~ (/$|:$)     ]]  &&
+       [[ -n "${_selector_folder_path:-}" ]]  &&
+       [[ "${#_arguments[@]}" -le 1       ]]
+     }
+  then
+    _display_header_and_footer=1
+  fi
+
+  # Pre-load auto --limit header and footer.
+
+  local _footer=
+  local _header=
+
+  if [[ -n "${_AUTO_LIMIT:-}"             ]]  &&
+     ! ((_all))                               &&
+     ! _contains "--limit" "${_list_options[@]:-}"
+  then
+    local _available_lines=0
+    _available_lines="$(_tput lines)"
+
+    local _header_and_footer_line_count=0
+
+    if ((NB_HEADER)) && ((_display_header_and_footer))
+    then
+      _header="$(_ls_print_header "${_header_flags[@]:-}")"
+    fi
+
+    if ((NB_FOOTER)) && ((_display_header_and_footer))
+    then
+      _footer="$(_ls_print_footer "${_selector_folder_path:-}")"
+    fi
+
+    local _header_and_footer_line_count=0
+    _header_and_footer_line_count="$(
+      {
+        [[ -n "${_header:-}" ]] && printf "%s\\n" "${_header:-}"
+        [[ -n "${_footer:-}" ]] && printf "%s\\n" "${_footer:-}"
+
+        printf ""
+      } | wc -l | xargs
+    )"
+
+    local _auto_limit_adjustment="$((_AUTO_LIMIT - 2))"
+    local _auto_limit_amount=1
+
+    _auto_limit_amount="$((
+      ${_available_lines:-1}                -
+        ${_header_and_footer_line_count:-0} +
+        ${_auto_limit_adjustment:-0}
+    ))"
+
+    [[ "${_auto_limit_amount}" -gt 0 ]] || _auto_limit_amount=1
+
+    _list_options+=("--limit" "${_auto_limit_amount:-1}")
+  fi
+
+  local _list_error=
+
+  # NOTE: Pipeline structured to start List, Header, and Footer concurrently.
+  {
+    # List
+    # ----
+    {
+      # Capture error to variable while preserving standard output. More info:
+      # https://unix.stackexchange.com/a/474195
+      _list_error="$(
+        _list --error-on-empty "${_list_options[@]:-}" 2>&1 >&3 3>&-
+      )"
+    } 3>&1 || {
+      if [[ -n  "${_arguments[0]:-}"        ]]  &&
+         [[ !   "${_arguments[0]:-}" =~ ^-- ]]
+      then
+        local _maybe_notebook_name="${_arguments[0]:-}"
+
+        _maybe_notebook_name="$(
+          printf "%s\\n" "${_maybe_notebook_name}" | sed 's/\:$//'
+        )"
+
+        local _notebook_name=
+        _notebook_name="$(
+          _notebooks \
+            show "${_maybe_notebook_name:-}" --name --no-color 2>/dev/null || :
+        )"
+      fi
+
+      if [[ -n "${_notebook_name:-}"          ]]  &&
+         ! _notebooks current --selected          &&
+         [[ -d "${NB_DIR}/${_notebook_name}"  ]]
+      then
+        NB_NOTEBOOK_PATH="${NB_DIR}/${_notebook_name}"  \
+          _ls "${_arguments[@]:1}"
+
+        return 0
+      else
+        local _count_arguments=()
+
+        if [[ -n "${_selector:-}"   ]]
+        then
+          _count_arguments+=("${_selector}")
+        fi
+
+        if [[ -n "${_maybe_type:-}" ]]
+        then
+          _count_arguments+=("--${_maybe_type}")
+        fi
+
+        local _local_count=
+        _local_count="$(
+          _count "${_count_arguments[@]:-}" --skip-unmatched-selector || :
+        )"
+
+        if ! ((_local_count))                           &&
+           {
+             [[ -n  "${_selector_folder_path:-}"    ]]  ||
+             [[ !   "${_filter_patterns[*]:-}" =~ / ]]
+           }
+        then
+          {
+            _list "${_list_options[@]:-}"
+          } | {
+            if [[ -z "${_selector:-}"               ]]  ||
+               {
+                 [[ "${_selector:-}" =~ (/$|:$)     ]]  &&
+                 [[ "${#_filter_patterns[@]}" -eq 1 ]]
+               }
+            then # only container arguments
+              if ((NB_HEADER)) && [[ -n "${_maybe_type:-}"  ]]
+              then
+                _ls_print_header "${_header_flags[@]:-}"
+              fi
+
+              if ! ((${NB_FOLDER_HEADER:-0}))
+              then
+                _ls_print_folder_header "${_selector_folder_path:-}"
+              fi
+
+              cat
+
+              if ((NB_FOOTER)) && [[ -n "${_maybe_type:-}"  ]]
+              then
+                _ls_print_footer "${_selector_folder_path:-}"
+              fi
+            else
+              cat
+            fi
+          }
+        else
+          if [[ -n "${_list_error:-}" ]]
+          then
+            printf "%s\\n" "${_list_error}"
+
+            return 1
+          fi
+        fi
+      fi
+    }
+  } | {
+    # Header
+    # ------
+
+    if ((NB_HEADER)) && ((_display_header_and_footer))
+    then
+      if [[ -n "${_header:-}"             ]]
+      then
+        printf "%s\\n" "${_header:-}"
+      else
+        _ls_print_header "${_header_flags[@]:-}"
+      fi
+    fi
+
+    if [[ -n "${_selector_folder_path:-}" ]] &&
+       ((${NB_FOLDER_HEADER:-0}))            &&
+       ((_display_header_and_footer))
+    then
+      _ls_print_folder_header "${_selector_folder_path:-}"
+    fi
+
+    cat
+
+  } | {
+    # Footer
+    # ------
+
+    if ((NB_FOOTER))                  &&
+       ((_display_header_and_footer)) &&
+       [[ -z "${_footer:-}" ]]
+    then
+      _footer="$(_ls_print_footer "${_selector_folder_path:-}")"
+    fi
+
+    cat
+
+    if [[ -n "${_footer:-}" ]]
+    then # print preloaded footer
+      printf "%s\\n" "${_footer}"
+    fi
+  } | {
+    if ((_use_pager))
+    then
+      _pager
+    else
+      cat
+    fi
+  }
+
+  if ((_fast_exit))
+  then
+    exit 0
+  else
+    return 0
+  fi
+}
+
+# notebooks · ##################################################### · notebooks
+
+_describe_notebooks() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} notebooks [<name> | <query>] [--ar | --archived] [--global] [--local]
+               [--names] [--paths] [--unar | --unarchived]
+  ${_ME} notebooks add ([<name>] [<remote-url> [<branch>... | --all]]) [--author]
+                   [--email <email>] [--name <name>]
+  ${_ME} notebooks (archive | open | peek | status | unarchive) [<name>]
+  ${_ME} notebooks author [<name> | <path>] [--email <email>] [--name <name>]
+  ${_ME} notebooks current [--path | --selected | --filename [<filename>]]
+                       [--global | --local]
+  ${_ME} notebooks delete <name> [-f | --force]
+  ${_ME} notebooks (export <name> [<path>] | import <path>)
+  ${_ME} notebooks init [<path> [<remote-url> [<branch>]]] [--author]
+                    [--email <email>] [--name <name>]
+  ${_ME} notebooks rename <old-name> <new-name>
+  ${_ME} notebooks select <selector>
+  ${_ME} notebooks show (<name> | <path> | <selector>) [--ar | --archived]
+                    [--escaped | --name | --path | --filename [<filename>]]
+  ${_ME} notebooks use <name>
+
+$(_color_primary "Options"):
+  --all                    Add notebooks from all remote branches.
+  --ar, --archived         List archived notebooks, or return archival status
+                           with \`show\`.
+  --author                 Set the notebook's commit author email and name.
+  --email <email>          Set the notebook's commit author email to <email>.
+  --escaped                Print the notebook name with spaces escaped.
+  --filename [<filename>]  Print an available filename for the notebooks. When
+                           <filename> is provided, check for an existing file
+                           and provide a filename with an appended sequence
+                           number for uniqueness.
+  -f, --force              Skip the confirmation prompt.
+  --global                 List global notebooks or the notebook set globally
+                           with \`use\`.
+  --local                  Exit with 0 if current within a local notebook,
+                           otherwise exit with 1.
+  --name, --names          Print the notebook name.
+  --name <name>            Set the notebook's commit author name to <name>.
+  --path, --paths          Print the notebook path.
+  --selected               Exit with 0 if the current notebook differs from
+                           the current global notebook, otherwise exit with 1.
+  --unar, --unarchived     Only list unarchived notebooks.
+
+$(_color_primary "Subcommands"):
+  (default)  List notebooks.
+  add        Create a new global notebook. When <remote-url> is specified,
+             create one ore more new global notebook by cloning selected
+             or specified <branch>es from <remote-url>.
+             Aliases: \`${_ME} notebooks create\`, \`${_ME} notebooks new\`
+  archive    Set the current notebook or notebook <name> to "archived" status.
+  author     Configure the commit author email and name for the notebook.
+  current    Print the current notebook name or path.
+  delete     Delete a notebook.
+  export     Export the notebook <name> to the current directory or <path>,
+             making it usable as a local notebook.
+  import     Import the local notebook at <path> to make it global.
+  init       Create a new local notebook. Specify a <path> or omit to
+             initialize the current working directory as a local notebook.
+             Specify <remote-url> to clone an existing notebook.
+  open       Open the current notebook directory or notebook <name> in the
+             file browser, explorer, or finder.
+             Shortcut Alias: \`o\`
+  peek       Open the current notebook directory or notebook <name> in the
+             first tool found in the following list:
+             \`ranger\` [1], \`mc\` [2], \`vifm\` [3], \`joshuto\` [4], \`exa\` [5], or \`ls\`.
+             Shortcut Alias: \`p\`
+  rename     Rename a notebook. Aliases: \`move\`, \`mv\`
+  select     Set the current notebook from a colon-prefixed selector.
+             Not persisted. Selection format: <notebook>:<identifier>
+  status     Print the archival status of the current notebook or
+             notebook <name>.
+  show       Show and return information about a specified notebook.
+  unarchive  Remove "archived" status from the current notebook or notebook <name>.
+  use        Switch to a notebook.
+
+    1. https://ranger.github.io/
+    2. https://en.wikipedia.org/wiki/Midnight_Commander
+    3. https://vifm.info/
+    4. https://github.com/kamiyaa/joshuto
+    5. https://github.com/ogham/exa
+
+$(_color_primary "Description"):
+  Manage notebooks.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-notebooks
+
+$(_color_primary "See Also"):
+  ${_ME} help archive
+  ${_ME} help history
+  ${_ME} help move
+  ${_ME} help remote
+  ${_ME} help status
+  ${_ME} help sync
+  ${_ME} help unarchive
+  ${_ME} help use
+
+$(_color_primary "Examples"):
+  ${_ME} notebooks --names
+  ${_ME} notebooks add sample
+  ${_ME} notebooks add example https://github.com/example/example.git
+  ${_ME} nb current --path
+  ${_ME} nb archive example
+
+$(_color_primary "Shortcut Aliases"):
+  ${_ME} n
+  ${_ME} nb
+HEREDOC
+}
+_RESERVED_NOTEBOOK_NAMES=(
+  ".cache"
+  ".current"
+  ".plugins"
+  ".readme"
+  "readme"
+  "readme.md"
+)
+_notebooks() {
+  # _notebooks_add()
+  #
+  # Usage:
+  #   _notebooks_add ([<name>] [<remote_url> [<branch>... | --all]]) [--author]
+  #                  [--email <email>] [--name <name>]
+  _notebooks_add() {
+    local _author=0
+    local _author_arguments=()
+    local _clone_all_branches=0
+    local _name=
+    local _print_default_feedback=1
+    local _option_selected_remote_branches=()
+    local _remote_url=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --all)    _clone_all_branches=1 ;;
+        --author) _author=1             ;;
+        --email|--name)
+          _author=1
+          _author_arguments+=("${1:-}")
+
+          if _option_value_is_present "${2:-}"
+          then
+            _author_arguments+=("${2:-}")
+
+            shift
+          fi
+          ;;
+        *)
+          if _string_is_url "${1:-}"
+          then
+            _remote_url="${1:-}"
+          elif [[ -z "${_name:-}"         ]] &&
+               [[ -z "${_remote_url:-}"   ]]
+          then
+            _name="${1:-}"
+          else
+            _option_selected_remote_branches+=("${1:-}")
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -z "${_name:-}"                 ]] &&
+       [[ -z "${_remote_url:-}"           ]]
+    then
+      _exit_1 _help notebooks
+    fi
+
+    if   [[ -n "${_remote_url:-}"         ]]
+    then
+      local _git_options=(
+        --no-local
+        --single-branch
+      )
+    fi
+
+    if [[ -n "${_name:-}"                 ]]
+    then
+      _notebooks_validate_name "${_name}"
+
+      if [[ -e "${NB_DIR}/${_name}"       ]]
+      then
+        _exit_1 printf "Already exists: %s\\n" "$(_color_primary "${_name}")"
+      fi
+    fi
+
+    if [[ -n "${_remote_url:-}"           ]]
+    then
+      if [[ -n "${_name:-}"               ]] &&
+         ! ((${#_option_selected_remote_branches[@]}))
+      then
+        git clone "${_git_options[@]:-}"                  \
+          "${_remote_url}"                                \
+          "${NB_DIR}/${_name}"
+      elif [[ -n "${_name:-}"                             ]] &&
+           [[ "${#_option_selected_remote_branches[@]}" -eq 1    ]]
+      then
+        git clone "${_git_options[@]:-}"                  \
+          --branch "${_option_selected_remote_branches[0]:-}"    \
+          "${_remote_url}"                                \
+          "${NB_DIR}/${_name}"
+      else
+        local _current_notebook_path=
+        _current_notebook_path="$(_notebooks current --path)"
+
+        local _remote_branches=()
+
+        if [[ -n "${_option_selected_remote_branches[*]:-}" ]]
+        then
+          _remote_branches=("${_option_selected_remote_branches[@]}")
+        else
+          _remote_branches=($(
+            git -C "${_current_notebook_path}" ls-remote  \
+              --heads "${_remote_url:-}"                  \
+              2>/dev/null                                 \
+              | LC_ALL=C sed "s/.*\///g"
+          ))
+        fi
+
+        if ! ((${#_remote_branches[@]}))
+        then
+          _warn printf "No remote branches found.\\n"
+
+          return 1
+        else
+          local _selected_branches=()
+
+          _print_default_feedback=0
+
+          if ((${#_option_selected_remote_branches[@]}))
+          then
+            _selected_branches=("${_option_selected_remote_branches[@]:-}")
+          elif [[ "${#_remote_branches[@]}" -eq 1 ]]
+          then
+            _selected_branches=("${_remote_branches[0]:-}")
+          elif ((_clone_all_branches))
+          then
+            _selected_branches=("${_remote_branches[@]:-}")
+          fi
+
+          if ! ((${#_selected_branches[@]}))
+          then
+            printf      "Choose a remote branch:\\n"
+
+            _print_line "-----------------------"
+
+            local i=
+            for ((i=0; i < ${#_remote_branches[@]}; i++))
+            do
+              printf "%s %s\\n"                 \
+                "$(_color_brackets "$((i+1))")" \
+                "${_remote_branches[${i}]:-}"
+            done
+
+            printf "%s All Branches\\n"         \
+              "$(_color_brackets "$((i+1))")"
+
+            local _branch_prompt_response=
+
+            while true
+            do
+              IFS='' read -r -e -d $'\n' -p                                               \
+                "$(_color_primary "Choose a branch") or $(_color_primary "q") to quit: "  \
+                _branch_prompt_response
+
+              case "${_branch_prompt_response:-}" in
+                q*|exit)
+                  printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                  exit 0
+                  ;;
+                [0-9]*)
+                  if [[ -n "${_remote_branches[$((_branch_prompt_response - 1))]:-}" ]]
+                  then
+                    _branch_prompt_response="${_remote_branches[$((_branch_prompt_response - 1))]:-}"
+
+                    break
+                  elif [[ "${_branch_prompt_response}" -eq "$((${#_remote_branches[@]} + 1))" ]]
+                  then
+                    _clone_all_branches=1
+
+                    break
+                  fi
+                  ;;
+                *)
+                  if _contains "${_branch_prompt_response}" "${_remote_branches[@]}"
+                  then
+                    break
+                  fi
+              esac
+            done
+
+            if ((_clone_all_branches))
+            then
+              _selected_branches=("${_remote_branches[@]:-}")
+            else
+              _selected_branches=("${_branch_prompt_response:-}")
+            fi
+
+            _print_line "------------------------------------"
+          fi
+
+          if ! ((${#_selected_branches[@]}))
+          then
+            _selected_branches=("${_remote_branches[@]:-}")
+          fi
+
+          local _first=1
+
+          local __selected_branch=
+          for   __selected_branch in "${_selected_branches[@]:-}"
+          do
+            local _target_notebook_name=
+
+            if _contains "${__selected_branch:-}" "main" "master"
+            then
+              _target_notebook_name="${_remote_url##*/}"
+            else
+              _target_notebook_name="${__selected_branch:-}"
+            fi
+
+            local _target_notebook_path=
+            _target_notebook_path="$(
+              _get_unique_path "${NB_DIR}/${_target_notebook_name}"
+            )"
+
+            _target_notebook_name="${_target_notebook_path##*/}"
+
+            if ((_first))
+            then
+              _first=0
+            else
+              _print_line "------------------------------------"
+            fi
+
+            local _bk_name=  && _bk_name="$(_color_brackets "${_target_notebook_name}")"
+            local _hi_enter= && _hi_enter="$(_color_primary 'enter')"
+            local _hi_q=     && _hi_q="$(_color_primary 'q')"
+            local _hi_type=  && _hi_type="$(_color_primary 'type')"
+
+            cat <<HEREDOC
+Press ${_hi_enter} to use the selected name, ${_hi_type} a new name, or press ${_hi_q} to quit.
+
+HEREDOC
+
+            while true
+            do
+              local _target_notebook_prompt_response=
+
+              IFS='' read -r -e -d $'\n' -p \
+                "Name ${_bk_name}: "        \
+                _target_notebook_prompt_response
+
+              case "${_target_notebook_prompt_response:-}" in
+                '')
+                  break
+                  ;;
+                q*|exit)
+                  printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                  exit 0
+                  ;;
+                *)
+                  _target_notebook_name="${_target_notebook_prompt_response}"
+
+                  break
+                  ;;
+              esac
+            done
+
+            local _unique_notebook_path=
+            _unique_notebook_path="$(
+              _get_unique_path "${NB_DIR}/${_target_notebook_name:-}"
+            )"
+
+            _name="${_unique_notebook_path##*/}"
+
+            _notebooks_validate_name "${_name}" || return 1
+
+            git clone "${_git_options[@]:-}"    \
+              "${_remote_url}"                  \
+              --branch "${__selected_branch:-}" \
+              "${NB_DIR}/${_name}"              &&
+              printf "Added notebook: %s\\n" "$(_color_primary "${_name}")"
+          done && return 0
+        fi
+      fi
+    else
+      mkdir -p "${NB_DIR}/${_name}"                   &&
+        git -C "${NB_DIR}/${_name}" init &>/dev/null  &&
+        {
+          if ((_author))
+          then
+            _author_arguments+=("${NB_DIR}/${_name}")
+            _notebooks author "${_author_arguments[@]:-}"
+          fi
+        }                                             &&
+        touch "${NB_DIR}/${_name}/.index"             &&
+        _temp cache clear                             &&
+        _git checkpoint "${NB_DIR}/${_name}" "[${_ME}] Initialize"
+      fi                            &&
+        ((_print_default_feedback)) &&
+        printf "Added notebook: %s\\n" "$(_color_primary "${_name}")"
+  }
+
+  # Usage: _notebooks_add_new [<notebook>...]
+  _notebooks_add_new() {
+    local _notebook_list=("${@:-}")
+
+    [[ ! -d "${NB_DIR}" ]] && return 0
+
+    if [[ -z "${1:-}"   ]]
+    then
+      _notebook_list=($(ls -1 "${NB_DIR}"))
+    fi
+
+    local __notebook_name=
+    for   __notebook_name in "${_notebook_list[@]:-}"
+    do
+      if [[   -d "${NB_DIR}/${__notebook_name}"         ]]  &&
+         [[ ! -e "${NB_DIR}/${__notebook_name}/.index"  ]]
+      then
+        {
+          if ((_GIT_ENABLED))
+          then
+            git -C "${NB_DIR}/${__notebook_name}" init &>/dev/null
+          fi
+        } && touch "${NB_DIR}/${__notebook_name}/.index"    &&
+        _temp cache clear                                   &&
+        _git checkpoint "${NB_DIR}/${__notebook_name}" "[${_ME}] Initialize"
+      fi
+    done
+  }
+
+  # _notebooks_author()
+  #
+  # Usage:
+  #   _notebooks_author [--name [<name>]] [--email [<email>]] [--unset]
+  #                     [<notebook-path>]
+  #
+  # Description:
+  #   Print, set, and delete the <email> and <name> for git commit attribution
+  #   within the notebook.
+  _notebooks_author() {
+    local _email=0
+    local _name=0
+    local _new_local_email=
+    local _new_local_name=
+    local _print_current=0
+    local _selector=
+    local _skip_prompt=0
+    local _unset=0
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --email)
+          _email=1
+
+          if _option_value_is_present "${2:-}"
+          then
+            _new_local_email="${2:-}"
+
+            shift
+          fi
+          ;;
+        -f|--force|--skip*|-y|--yes)
+          _skip_prompt=1
+          ;;
+        --name)
+          _name=1
+
+          if _option_value_is_present "${2:-}"
+          then
+            _new_local_name="${2:-}"
+
+            shift
+          fi
+          ;;
+        --print|--current)
+          _print_current=1
+          ;;
+        --unset)
+          _unset=1
+          ;;
+        *)
+          if [[ -z "${_selector:-}"     ]]
+          then
+            _selector="${1:-}"
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    local _notebook_path=
+
+    if   [[ "${_selector:-}" =~ ^/      ]]
+    then
+      _notebook_path="${_selector:-}"
+    elif [[ "${_selector:-}" == "local" ]]
+    then
+      _notebook_path="$(_notebooks_current --local --path || :)"
+    elif [[ -n "${_selector:-}"         ]]
+    then
+      _notebook_path="${NB_DIR}/${_selector%%:*}"
+    fi
+
+    if [[ -z "${_notebook_path:-}"            ]]
+    then
+      _notebook_path="$(_notebooks_current --path)"
+    fi
+
+    if [[ "${_notebook_path:-}" =~ ^${NB_DIR} ]]
+    then
+      local _notebook_name="${_notebook_path##*/}"
+    else
+      local _notebook_name="local"
+    fi
+
+    local _global_email=
+    _global_email="$(
+      git -C "${_notebook_path:-}" config --global user.email || :
+    )"
+
+    local _global_name=
+    _global_name="$(
+      git -C "${_notebook_path:-}" config --global user.name  || :
+    )"
+
+    local _local_email=
+    _local_email="$(
+      git -C "${_notebook_path:-}" config --local user.email  || :
+    )"
+
+    local _local_name=
+    _local_name="$(
+      git -C "${_notebook_path:-}" config --local user.name   || :
+    )"
+
+    if ((_unset))
+    then
+      local _unset_output_present=0
+
+      if [[ -n "${_local_email:-}"  ]] && {
+           ((_email)) || ! ((_name))
+         }
+      then
+        _warn printf "Unsetting local email.\\n"
+        git -C "${_notebook_path:-}" config --unset user.email  || :
+        _unset_output_present=1
+      fi
+
+      if [[ -n "${_local_name:-}"   ]] && {
+           ((_name))  || ! ((_email))
+         }
+      then
+        _warn printf "Unsetting local name.\\n"
+        git -C "${_notebook_path:-}" config --unset user.name   || :
+        _unset_output_present=1
+      fi
+
+      ((_unset_output_present)) && printf "\\n"
+
+      printf "Updated author for: %s\\n" "$(
+        _color_primary "${_notebook_name}"
+      )"
+
+      _print_line "-------------------"
+
+      _notebooks_author "${_notebook_path}" --current
+
+      return 0
+    elif ((_print_current))
+    then
+      printf "%s" "$(_color_primary "email")"
+
+      if [[ -n "${_local_email:-}"        ]]
+      then
+        printf " (%s):  %s\\n" "$(_color_primary "local")" "${_local_email:-}"
+      else
+        printf " (%s): %s\\n" "$(_color_primary "global")" "${_global_email:-}"
+      fi
+
+      printf "%s" "$(_color_primary "name")"
+
+      if [[ -n "${_local_name:-}"         ]]
+      then
+        printf "  (%s):  %s\\n" "$(_color_primary "local")" "${_local_name:-}"
+      else
+        printf "  (%s): %s\\n" "$(_color_primary "global")" "${_global_name:-}"
+      fi
+
+      return 0
+    else
+      printf "Current author for: %s\\n" "$(
+        _color_primary "${_notebook_name}"
+      )"
+
+      _print_line "-------------------"
+
+      _notebooks_author "${_notebook_path}" --current
+
+      if [[ -n "${_new_local_email:-}"    ]] || [[ -n "${_new_local_name:-}" ]]
+      then
+        printf    "\\nUpdate:\\n"
+        _print_line  "-------"
+
+        if [[ -n "${_new_local_email:-}"  ]]
+        then
+          printf "local %s: %s\\n" "$(_color_primary "email")" "${_new_local_email:-}"
+        fi
+
+        if [[ -n "${_new_local_name:-}"   ]]
+        then
+          printf "local %s:  %s\\n" "$(_color_primary "name")" "${_new_local_name:-}"
+        fi
+      fi
+
+      if ! ((_skip_prompt))
+      then
+        while true
+        do
+          local __yn=
+          IFS='' read -r -e -d $'\n' -p   \
+"${_NEWLINE}$(_color_primary "Update?")  $(_color_brackets "y/N") " __yn
+
+          case "${__yn}" in
+            [Yy]*)
+              break
+              ;;
+            *)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+          esac
+        done
+
+        if [[ -z "${_new_local_email:-"${_new_local_name:-}"}" ]]
+        then
+          local _unset=
+          _unset=$(_color_primary "unset")
+
+          cat <<HEREDOC
+
+Enter a new value, ${_unset} to use the global value,
+or leave blank to keep the current value.
+
+HEREDOC
+
+          IFS='' read -r -e -d $'\n' -p             \
+"local $(_color_primary "email:") " _new_local_email
+
+          IFS='' read -r -e -d $'\n' -p             \
+"local $(_color_primary "name:")  " _new_local_name
+        fi
+      fi
+
+      if [[ -n "${_new_local_email:-}"    ]]
+      then
+        if _contains "${_new_local_email:-}" "global" "--unset" "unset"
+        then
+          git -C "${_notebook_path:-}" config --unset user.email  || :
+        else
+          git -C "${_notebook_path}" config --local \
+            user.email "${_new_local_email:-}"
+        fi
+      fi
+
+      if [[ -n "${_new_local_name:-}"     ]]
+      then
+        if _contains "${_new_local_name:-}" "global" "--unset" "unset"
+        then
+          git -C "${_notebook_path:-}" config --unset user.name   || :
+        else
+          git -C "${_notebook_path}" config --local \
+            user.name "${_new_local_name:-}"
+        fi
+      fi
+
+      if [[ -n "${_new_local_email:-"${_new_local_name:-}"}" ]]   || ! ((_skip_prompt))
+      then
+        printf "\\nUpdated author for: %s\\n" "$(
+          _color_primary "${_notebook_name}"
+        )"
+
+        _print_line "-------------------"
+
+        _notebooks_author "${_notebook_path}" --current
+      fi
+    fi
+  }
+
+  # _notebooks_current()
+  #
+  # Usage:
+  #   _notebooks_current (<name> | <path> | <selector>) [--global | --local]
+  #                      [--path | --scoped] [--filename]
+  _notebooks_current() {
+    local _file_path=
+    local _print_global=0
+    local _print_local=0
+    local _print_path=0
+    local _print_unique_file_path=0
+    local _return_selected=0
+    local _selector=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --global)
+          _print_global=1
+          ;;
+        --local)
+          _print_local=1
+          ;;
+        --path*)
+          _print_path=1
+          ;;
+        --scoped|--selected)
+          _return_selected=1
+          ;;
+        --filename|--basename|--file*path)
+          _print_unique_file_path=1
+
+          if _option_value_is_present "${2:-}"
+          then
+            _file_path="${2}"
+
+            shift
+          fi
+          ;;
+        [^-]*)
+          _selector="${1}"
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -n "${_selector:-}" ]]
+    then
+      _notebooks_select "${_selector}" || :
+    fi
+
+    if ((_print_local))
+    then
+      if [[ -n "${_LOCAL_NOTEBOOK_PATH:-}" ]]
+      then
+        if ((_print_path))
+        then
+          printf "%s\\n" "${_LOCAL_NOTEBOOK_PATH}"
+        else
+          return 0
+        fi
+      else
+        return 1
+      fi
+    elif ((_print_global))
+    then
+      if ((_print_path))
+      then
+        printf "%s\\n" "${_GLOBAL_NOTEBOOK_PATH}"
+      else
+        basename "${_GLOBAL_NOTEBOOK_PATH}"
+      fi
+    elif ((_print_path))
+    then
+      printf "%s\\n" "${NB_NOTEBOOK_PATH}"
+    elif ((_return_selected))
+    then
+      [[ "${NB_NOTEBOOK_PATH}" != "${_GLOBAL_NOTEBOOK_PATH}" ]] &&
+      [[ "${NB_NOTEBOOK_PATH}" != "${_LOCAL_NOTEBOOK_PATH}"  ]]
+    elif ((_print_unique_file_path))
+    then
+      _notebooks_show "${NB_NOTEBOOK_PATH}" --filename "${_file_path:-}"
+    else
+      if [[ -n "${_LOCAL_NOTEBOOK_PATH:-}"                      ]] &&
+         [[ "${NB_NOTEBOOK_PATH}" == "${_LOCAL_NOTEBOOK_PATH}"  ]]
+      then
+        printf "local\\n"
+      else
+        basename "${NB_NOTEBOOK_PATH}"
+      fi
+    fi
+  }
+
+  # _notebooks_delete()
+  #
+  # Usage:
+  #   _notebooks_delete <name>
+  _notebooks_delete() {
+    local _force=0
+    local _name=
+
+    local __arg=
+    for   __arg in "${@:-}"
+    do
+      case "${__arg}" in
+        -f|--force|--skip*|-y|--yes)
+          _force=1
+          ;;
+        *)
+          [[ -z "${_name:-}"  ]] && _name="${__arg%%:*}"
+          ;;
+      esac
+    done
+
+    if [[   -z  "${_name}"    ]]
+    then
+      _exit_1 _help notebooks
+    elif [[     "${_name}"    == "local"    ]] &&
+         [[ -n  "${_LOCAL_NOTEBOOK_PATH:-}" ]]
+    then
+      _exit_1 cat <<HEREDOC
+Use your system's shell or file explorer to delete local notebook directories.
+HEREDOC
+    fi
+
+    _notebooks_validate_name "${_name}"
+
+    if [[ ! -d "${NB_DIR}/${_name}"         ]] ||
+       [[ ! -e "${NB_DIR}/${_name}/.git"    ]] ||
+       [[ ! -e "${NB_DIR}/${_name}/.index"  ]]
+    then
+      _exit_1 printf "Notebook not found: %s\\n" "$(_color_primary "${_name}")"
+    fi
+
+    local _notebook_names=()
+    _notebook_names=($(_notebooks --names --no-color))
+
+    local _notebook_count=
+    _notebook_count="${#_notebook_names[@]}"
+
+    if ! ((_force))
+    then
+      if _command_exists "trash" && [[ "${OSTYPE}" =~ ^darwin ]]
+      then
+        printf "Moving to Trash: %s\\n" "$(_color_primary "${_name}")"
+      else
+        cat <<HEREDOC
+Deleting $(_color_primary "${_name}").
+
+This action cannot be undone. This will permanently delete the
+$(_color_primary "${_name}") notebook, all notes and files it contains,
+and the entire revision history.
+
+HEREDOC
+      fi
+
+      while true
+      do
+        local __response=
+        IFS='' read -r -e -d $'\n' -p \
+"Please type $(_color_primary "${_name}") to confirm: " __response
+
+        if [[ "${__response}"     == "${_name}"   ]]
+        then
+          break
+        else
+          printf "Exiting%s\\n" "$(_color_muted "...")"
+
+          exit 0
+        fi
+      done
+    fi
+
+    if [[ "$(_notebooks current)" ==  "${_name}"  ]] &&
+       [[ "${_notebook_count}"    -gt 1           ]]
+    then
+      if [[ "${_name}" != "home"  ]]
+      then
+        _notebooks use "home"
+      else
+        local __notebook=
+        for   __notebook in "${_notebook_names[@]:-}"
+        do
+          if [[ "${__notebook}"   !=    "$(_notebooks current)"   ]]
+          then
+            _notebooks use "${__notebook}"
+
+            break
+          fi
+        done
+      fi
+    fi
+
+    if _command_exists "trash"    &&    [[ "${OSTYPE}" =~ ^darwin ]]
+    then
+      trash "${NB_DIR:?}/${_name:?}"
+    else
+      if [[ -e "${NB_DIR:?}/${_name:?}" ]]
+      then
+        rm -r -f "${NB_DIR:?}/${_name:?}"
+      fi
+    fi &&
+      _temp cache clear &&
+      printf "Notebook deleted: %s\\n" "$(_color_primary "${_name}")"
+  }
+
+  # _notebooks_export()
+  #
+  # Usage:
+  #   _notebooks_export <name> [<path>]
+  _notebooks_export() {
+    local _name="${1:-}"
+
+    if [[ -z "${_name:-}"           ]]
+    then
+      _exit_1 _help "notebooks"
+    fi
+
+    _notebooks_validate_name "${_name}"
+
+    if [[ ! -d "${NB_DIR}/${_name}" ]]
+    then
+      _exit_1 printf "Notebook not found: %s\\n" "$(_color_primary "${_name}")"
+    fi
+
+    local _target_path="${2:-}"
+
+    if [[ -n "${_target_path:-}"    ]] && [[ ! "${_target_path}" =~ ^/ ]]
+    then
+      _target_path="${_CURRENT_WORKING_DIR}/${_target_path}"
+    fi
+
+    if [[ -n "${_target_path:-}"              ]] &&
+       [[ -d "${_target_path}"                ]] &&
+       [[ ! "${_target_path}" =~ \/${_name}$  ]]
+    then
+      _target_path="${_target_path}/${_name}"
+    fi
+
+    if [[ -z "${_target_path}"      ]]
+    then
+      _target_path="${_CURRENT_WORKING_DIR}/${_name}"
+    fi
+
+    _target_path="$(_get_unique_path "${_target_path}")"
+
+    cp -R "${NB_DIR}/${_name}" "${_target_path}"  &&
+      _temp cache clear                           &&
+      printf "Exported notebook %s to %s\\n"  \
+        "$(_color_primary "${_name}")"        \
+        "$(_color_primary "${_target_path}")"
+  }
+
+  # _notebooks_import()
+  #
+  # Usage:
+  #   _notebooks_import <path> [<name>]
+  _notebooks_import() {
+    local _path="${1:-}"
+
+    if [[ -z "${_path:-}"     ]]
+    then
+      _exit_1 _help "notebooks"
+    fi
+
+    local _basename=
+    _basename="$(basename "${_path}")"
+
+    if [[ ! "${_path}" =~ ^/  ]]
+    then
+      _path="${_CURRENT_WORKING_DIR}/${_path}"
+    fi
+
+    if [[ ! -d "${_path}"     ]]
+    then
+      _exit_1 printf "Not a directory: %s" "$(_color_primary "${_path}")"
+    fi
+
+    local _target_basename="${2:-}"
+
+    if [[   -z "${_target_basename:-}"  ]]
+    then
+      _target_basename="${_basename}"
+    fi
+
+    _notebooks_validate_name "${_target_basename}"
+
+    local _target_path=
+    _target_path="$(_get_unique_path "${NB_DIR}/${_target_basename}")"
+
+    cp -R "${_path}" "${_target_path}"  &&
+      _temp cache clear                 &&
+      _notebooks_add_new                &&
+      printf "Imported notebook: %s\\n" \
+        "$(_color_primary "$(basename "${_target_path}")")"
+  }
+
+  # _notebooks_init()
+  #
+  # Usage:
+  #   _notebooks_init [<path> [<remote_url> [<branch>]]
+  _notebooks_init() {
+    local _author=0
+    local _author_arguments=()
+    local _path=
+    local _remote_branch=
+    local _remote_url=
+    local _skip_prompt=0
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --author) _author=1 ;;
+        --email|--name)
+          _author=1
+          _author_arguments+=("${1:-}")
+
+          if _option_value_is_present "${2:-}"
+          then
+            _author_arguments+=("${2:-}")
+
+            shift
+          fi
+          ;;
+        -f|--force|--skip*|-y|--yes)
+          _skip_prompt=1
+          ;;
+        *)
+          if _string_is_url "${1:-}"    && [[ -z "${_remote_url:-}" ]]
+          then
+            _remote_url="${1:-}"
+          elif [[ -z "${_path:-}"   ]]  && [[ -z "${_remote_url:-}" ]]
+          then
+            _path="${1:-}"
+          else
+            _remote_branch="${1:-}"
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -n "${_remote_url:-}"     ]]  && [[ -z "${_path}"         ]]
+    then
+      _exit_1 printf                                                    \
+        "Must specify a <path> when cloning from <remote-url>.\\n%s\\n" \
+        "$(_help "notebooks")"
+    fi
+
+    if [[   -n "${_path:-}"         ]]
+    then
+      if [[ !   "${_path}" =~ ^/    ]]
+      then
+        _path="${_CURRENT_WORKING_DIR}/${_path}"
+      fi
+    else
+      _path="${_CURRENT_WORKING_DIR}"
+    fi
+
+    if [[ -d "${_path}"             ]]  &&
+       [[ -e "${_path}/.git"        ]]
+    then
+      local _error_message=
+
+      if [[ -f "${_path}/.index"    ]]
+      then
+        _error_message="Notebook exists: $(_color_primary "${_path}")"
+      else
+        _error_message="Git repository exists: $(_color_primary "${_path}")"
+      fi
+
+      _exit_1 printf "%s\\n" "${_error_message}"
+    fi
+
+    if [[ ! -e "${_path}"           ]]
+    then
+      mkdir -p "${_path}"
+    elif [[ "${HOME}" =~ ^${_path}  ]]
+    then
+      _exit_1 printf                                                    \
+        "Unable to turn top-level directory into local notebook: %s\\n" \
+        "$(_color_primary "${_path}")"
+    elif [[ -f "${_path}"           ]]
+    then
+      _exit_1 printf "File exists: %s\\n" "$(_color_primary "${_path}")"
+    elif [[ -d "${_path:-}"         ]]
+    then
+      printf "Directory exists: %s\\n" "$(_color_primary "${_path}")"
+
+      if [[ -n "${_remote_url:-}"   ]]
+      then
+        _exit_1 printf "Unable to clone to existing directory.\\n"
+      else
+        local _git_repository_count=0
+        _git_repository_count="$(
+          find "${_path}" -name .git -prune | wc -l | awk '$1=$1'
+        )"
+
+        if ((_git_repository_count))
+        then
+          _warn printf "This directory contains %s git repositories.\\n" \
+            "$(_color_primary "${_git_repository_count}")"
+        fi
+
+        if ! ((_skip_prompt))
+        then
+          while true
+          do
+            local __yn=
+            IFS='' read -r -e -d $'\n' -p \
+              "Initialize directory as a local notebook? $(_color_brackets "y/N") " __yn
+
+            case "${__yn}" in
+              [Yy]*)
+                break
+                ;;
+              *)
+                printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                exit 0
+                ;;
+            esac
+          done
+        fi
+      fi
+    fi
+
+    if [[ "${_path}" != "${_CURRENT_WORKING_DIR}" ]] &&
+       [[ -n "${_remote_url:-}"                   ]]
+    then
+      if [[ -n "${_remote_branch:-}"      ]]
+      then
+        git clone --no-local --single-branch --branch "${_remote_branch:-}" \
+          "${_remote_url}"                                                  \
+          "${_path}"
+      else
+        git clone --no-local --single-branch "${_remote_url}" "${_path}"
+      fi
+    else
+      git -C "${_path}" init &>/dev/null  &&
+        {
+          if ((_author))
+          then
+            _author_arguments+=("${_path}")
+            _notebooks author "${_author_arguments[@]:-}"
+          fi
+        } &&
+        touch "${_path}/.index"           &&
+        _git checkpoint "${_path}" "[${_ME}] Initialize"
+    fi
+
+    printf "Initialized local notebook: %s\\n" "$(_color_primary "${_path}")"
+  }
+
+  # _notebooks_list()
+  #
+  # Usage:
+  #   _notebooks_list [<name> | <query>] [--ar | --archived] [--local]
+  #                   [--global] [--names] [--paths] [--unar | --unarchived]
+  _notebooks_list() {
+    local _counter=0
+    local _notebook_color_enabled="${_COLOR_ENABLED}"
+    local _notebook_names=()
+    local _notebook_paths=()
+    local _only_archived=0
+    local _only_global=0
+    local _only_local=0
+    local _only_names=0
+    local _only_paths=0
+    local _only_unarchived=0
+    local _options=()
+    local _query_names=()
+
+    local __arg=
+    for   __arg in "${@:-}"
+    do
+      case "${__arg}" in
+        --archived|--global|--local|--name*|--no*color|--path*|--unarchived)
+          _options+=("${__arg}")
+          ;;
+      esac
+
+      case "${__arg}" in
+        --ar|--archived)
+          _only_archived=1
+          ;;
+        --global)
+          _only_global=1
+          ;;
+        --local)
+          _only_local=1
+          ;;
+        --name*)
+          _only_names=1
+          ;;
+        --no*color)
+          _notebook_color_enabled=0
+          ;;
+        --path*)
+          _only_paths=1
+          ;;
+        --unar|--unarchived)
+          _only_unarchived=1
+          ;;
+        *)
+          _query_names+=("${__arg}")
+          ;;
+      esac
+    done
+
+    if [[ -z "${NB_DIR}" ]] || [[ ! -e "${NB_DIR}"  ]]
+    then
+      exit 1
+    fi
+
+    _current_notebook_name="$(_notebooks current --name)"
+
+    if [[ -z "${_query_names[*]:-}"         ]]
+    then
+      _notebook_names=($(ls -1 "${NB_DIR}"))
+
+      _notebooks_add_new "${_notebook_names[@]:-}"
+
+      set +f
+      _notebook_paths=($(ls -1 -d "${NB_DIR}"/*))
+      set -f
+
+      if [[ -n "${_LOCAL_NOTEBOOK_PATH:-}"  ]]
+      then
+        _notebook_names=("local" "${_notebook_names[@]:-}")
+        _notebook_paths=("${_LOCAL_NOTEBOOK_PATH}" "${_notebook_paths[@]:-}")
+      fi
+    else
+      _notebooks_add_new
+
+      local __name=
+      for   __name in "${_query_names[@]}"
+      do
+        __name="${__name%:}"
+
+        _notebook_names+=("${__name}")
+
+        if [[ "${__name}" == "local"        ]]
+        then
+          _notebook_paths+=("${_LOCAL_NOTEBOOK_PATH}")
+        else
+          _notebook_paths+=("${NB_DIR}/${__name}")
+        fi
+      done
+    fi
+
+    local i=
+    for ((i=0; i < ${#_notebook_names[@]}; i++))
+    do
+      if [[ -e "${_notebook_paths[i]}/.git"                 ]]
+      then # it's a git repository.
+        local _notebook_line=
+        local _origin_url=
+
+        if [[     "${i}"                        == "0"      ]]  &&
+           [[     "${_notebook_names[i]:-}"     == "local"  ]]  &&
+           [[ -n  "${_LOCAL_NOTEBOOK_PATH:-}"               ]]
+        then # local notebook as first notebook
+          if ((_only_global))
+          then
+            continue
+          else
+            if ((_only_paths))
+            then
+              _notebook_line="${_notebook_paths[i]}"
+            elif ((_notebook_color_enabled))                    &&
+                 [[ "${_current_notebook_name}" == "local"  ]]
+            then
+              _notebook_line="$(_color_primary "local" --underline)"
+            else
+              _notebook_line="local"
+            fi
+          fi
+        elif ((_only_local))
+        then
+          if [[ -z "${_LOCAL_NOTEBOOK_PATH:-}"      ]]
+          then
+            return 1
+          else
+            continue
+          fi
+        else
+          if ((_only_paths))
+          then
+            _notebook_line="${_notebook_paths[i]}"
+          elif ! ((_notebook_color_enabled))
+          then
+            _notebook_line="${_notebook_names[i]}"
+          else
+            if [[ "${_current_notebook_name}" == "${_notebook_names[i]}" ]]
+            then # it's the current repository.
+              _notebook_line="$(_color_primary "${_notebook_names[i]}")"
+
+              if [[ "${#_notebook_names[@]}" -gt 1  ]]
+              then
+                _notebook_line="$(
+                  _color_primary "${_notebook_names[i]}" --underline
+                )"
+              fi
+            else
+              _notebook_line="${_notebook_names[i]}"
+            fi
+          fi
+        fi
+
+        if [[ -e "${_notebook_paths[i]}/.archived"  ]]
+        then
+          if ((_only_unarchived))
+          then
+            continue
+          elif ! ((_only_names)) && ! ((_only_paths))
+          then
+            _notebook_line="${_notebook_line} (archived)"
+          fi
+        elif ((_only_archived))
+        then
+          continue
+        fi
+
+        if ! ((_only_names)) && ! ((_only_paths))
+        then
+          _origin_url="$(
+            git -C "${_notebook_paths[i]}" config --get remote.origin.url || echo ''
+          )"
+
+          if [[ -n "${_origin_url:-}"   ]]
+          then
+            _notebook_line="${_notebook_line} (${_origin_url})"
+          fi
+        fi
+
+        if [[ -n "${_notebook_line:-}"  ]]
+        then
+          printf "%s\\n" "${_notebook_line:-}"
+
+          _counter=$((_counter+1))
+        fi
+      fi
+    done
+
+    if ! ((_counter))
+    then
+      if [[ -n "${_query_names[*]:-}"   ]]
+      then
+        {
+          local _query_pattern=
+          _query_pattern="$(_join "|" "${_query_names[@]:-}")"
+
+          {
+            _notebooks_list "${_options[@]:-}"  2>/dev/null
+          } | {
+            grep -i "${_query_pattern:-}"       2>/dev/null
+          }
+        } || {
+          _warn printf                  \
+            "Notebook not found: %s\\n" \
+            "$(_color_primary "${_query_names[*]}" | tr '\r\n' ' ')" &&
+              return 1
+        }
+      else
+        return 1
+      fi
+    fi
+  }
+
+  # _notebooks_notebook()
+  #
+  # Usage:
+  #   _notebooks_notebook [archive | open | peek | status | unarchive] <name>
+  _notebooks_notebook() {
+    local _notebook_name="${2%:}"
+    local _notebook_path=
+    local _subcommand="${1:-}"
+
+    if [[ -n "${_notebook_name:-}"  ]]
+    then
+      _notebooks_validate_name "${_notebook_name}"
+
+      _notebook_path="$(_notebooks "${_notebook_name}" --path)"
+    else
+      _notebook_name="$(_notebooks current)"
+      _notebook_path="$(_notebooks current --path)"
+    fi
+
+    if [[ -z "${_notebook_name:-}"  ]]
+    then
+      _exit_1 printf "Unable to determine notebook name.\\n"
+    fi
+
+    if [[ -z "${_notebook_path:-}"  ]]
+    then
+      _exit_1 printf "Unable to determine notebook path.\\n"
+    fi
+
+    if [[ -z "${_subcommand}"       ]]
+    then
+      printf "%s\\n" "${_notebook_name}"
+
+      return 0
+    fi
+
+    if [[ "${_subcommand:-}"    =~ (^open$|^o$) ]]
+    then
+      if _open_in_gui_app "${_notebook_path:-}"
+      then
+        return 0
+      else
+        _exit_1 printf                                                  \
+          "%s doesn't know how to open directories on this system.\\n"  \
+          "$(_color_primary "${_ME}")"
+      fi
+    elif [[ "${_subcommand:-}"  =~ (^peek$|^p$) ]]
+    then
+      if _command_exists "ranger"
+      then
+        ranger "${_notebook_path}"
+      elif _command_exists "mc"
+      then
+        mc "${_notebook_path}"
+      elif _command_exists "vifm"
+      then
+        vifm "${_notebook_path}"
+      elif _command_exists "exa"
+      then
+        exa -lah --git "${_notebook_path}"
+      else
+        # gnu || bsd
+        ls -lah --color=always "${_notebook_path}" 2>/dev/null ||
+          ls -lah -G "${_notebook_path}"
+      fi
+    else
+      local _dotfile_path="${_notebook_path}/.archived"
+
+      if [[   "${_subcommand}" == "archive"   ]]
+      then
+        if [[ ! -e "${_dotfile_path}"         ]]
+        then
+          touch "${_dotfile_path}" &&
+            _git checkpoint "${_notebook_path}" "[${_ME}] Archived"
+        fi
+
+        printf "%s archived.\\n" "$(_color_primary "${_notebook_name}")"
+      elif [[ "${_subcommand}" == "status"    ]]
+      then
+        if [[   -e "${_dotfile_path}"         ]]
+        then
+          printf "%s is archived.\\n" "$(_color_primary "${_notebook_name}")"
+        else
+          printf "%s is not archived.\\n" "$(_color_primary "${_notebook_name}")"
+        fi
+      elif [[ "${_subcommand}" == "unarchive" ]]
+      then
+        if [[   -e "${_dotfile_path}"         ]]
+        then
+          rm "${_dotfile_path:?}" &&
+            _git checkpoint "${_notebook_path}" "[${_ME}] Unarchived"
+        fi
+
+        printf "%s unarchived.\\n" "$(_color_primary "${_notebook_name}")"
+      fi
+    fi
+  }
+
+  # _notebooks_rename()
+  #
+  # Usage:
+  #   _notebooks_rename <old> <new>
+  _notebooks_rename() {
+    local _new="${2:-}"
+    local _old="${1:-}"
+
+    _notebooks_validate_name "${_old}"
+    _notebooks_validate_name "${_new}"
+
+    if [[ -z "${_old}" ]] || [[ -z "${_new}"  ]]
+    then
+      _exit_1 _help notebooks
+    elif [[ -n "${_LOCAL_NOTEBOOK_PATH:-}"    ]]
+    then
+      if [[ "${_old}" == "local" ]] || [[ "${_new}" == "local" ]]
+      then
+        _exit_1 cat <<HEREDOC
+"local" refers to the local notebook and can not be renamed.
+HEREDOC
+      fi
+    elif [[ ! -d "${NB_DIR}/${_old}"  ]]
+    then
+      _exit_1 printf "%s is not a valid notebook name.\\n"        \
+        "$(_color_primary "${_old}")"
+    elif [[ -e "${NB_DIR}/${_new}"    ]]
+    then
+      _exit_1 printf "A notebook named \"%s\" already exists.\\n" \
+        "$(_color_primary "${_new}")"
+    fi
+
+    mv "${NB_DIR}/${_old}" "${NB_DIR}/${_new}"
+
+    if [[ "$(cat "${NB_DIR}/.current")" == "${_old}" ]]
+    then
+      printf "%s\\n" "${_new}" > "${NB_DIR}/.current"
+    fi
+
+    _temp cache clear
+
+    printf "%s is now named %s\\n"  \
+      "$(_color_primary "${_old}")" \
+      "$(_color_primary "${_new}")"
+  }
+
+  # _notebooks_select()
+  #
+  # Usage:
+  #   _notebook_select <selector>
+  _notebooks_select() {
+    local _selector="${1:-}"
+
+    if [[ -z "${_selector:-}"       ]]
+    then
+      _exit_1 _help "notebooks"
+    fi
+
+    local _notebook_path=
+    _notebook_path="$(
+      _notebooks_show "${_selector:-}" --path 2>/dev/null || :
+    )"
+
+    if [[ -n "${_notebook_path:-}"  ]] &&
+       [[ -d "${_notebook_path:-}"  ]]
+    then
+      NB_NOTEBOOK_PATH="${_notebook_path}"
+
+      return 0
+    else
+      return 1
+    fi
+  }
+
+  # _notebooks_show()
+  #
+  # Usage:
+  #   _notebooks_show (<name> | <path> | <selector>) [--archived]
+  #                   [--escaped | --name | --path | --filename [<filename>]]
+  _notebooks_show() {
+    local _file_path=
+    local _local_notebook_path="${_LOCAL_NOTEBOOK_PATH:-}"
+    local _notebook_color_enabled=1
+    local _notebook_path=
+    local _only_name=0
+    local _only_path=0
+    local _print_escaped_name=0
+    local _print_unique_file_path=0
+    local _selector=
+    local _test_archived=0
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --archived)
+          _test_archived=1
+          ;;
+        --escaped)
+          _print_escaped_name=1
+          ;;
+        --name)
+          _only_name=1
+          ;;
+        --no*color)
+          _notebook_color_enabled=0
+          ;;
+        --path)
+          _only_path=1
+          ;;
+        --filename|--basename|--file*path)
+          _print_unique_file_path=1
+
+          if _option_value_is_present "${2:-}"
+          then
+            _file_path="${2}"
+
+            shift
+          fi
+          ;;
+        *)
+          if [[ -z "${_selector}"   ]]
+          then
+            _selector="${1:-}"
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -z "${_selector:-}"       ]]
+    then
+      _exit_1 _help "notebooks"
+    elif [[ "${_selector:-}" =~ ^/  ]]
+    then
+      local _maybe_notebook_path="${_selector}"
+
+      while [[ -n "${_maybe_notebook_path:-}"         ]] &&
+            ! {
+              [[ -d "${_maybe_notebook_path}/.git"    ]] &&
+              [[ -f "${_maybe_notebook_path}/.index"  ]]
+            } && {
+              {
+                [[    "${_maybe_notebook_path:-}"   =~ ^${NB_DIR}     ]]  &&
+                [[ !  "${_maybe_notebook_path%/*}"  == "${NB_DIR}"    ]]
+              } || {
+                [[ !  "${_maybe_notebook_path:-}"   =~ ^${NB_DIR}     ]]
+              }
+            }
+      do
+        _maybe_notebook_path="${_maybe_notebook_path%/*}"
+      done
+
+      if [[ -n "${_maybe_notebook_path:-}"    ]]
+      then
+        if [[ -n "${_local_notebook_path:-}"                          ]] &&
+           [[ "${_maybe_notebook_path}" == "${_local_notebook_path}"  ]]
+        then
+          _notebook_path="${_local_notebook_path%/}"
+        else
+          _notebook_path="${_maybe_notebook_path%/}"
+        fi
+      fi
+    elif [[ -n "${_selector:-}"               ]]
+    then
+      local _selector_notebook="${_selector%%:*}"
+
+      if [[ -n "${_selector_notebook:-}"      ]]
+      then
+        if [[ "${_selector_notebook:-}" == "local"  ]] &&
+           [[ -n "${_local_notebook_path:-}"        ]]
+        then
+          _notebook_path="${_local_notebook_path%/}"
+        elif [[ -d "${NB_DIR}/${_selector_notebook:-}/.git"    ]] &&
+             [[ -f "${NB_DIR}/${_selector_notebook:-}/.index"  ]]
+        then
+          _notebook_path="${NB_DIR}/${_selector_notebook%/}"
+        fi
+      fi
+    fi
+
+    if [[ -z "${_notebook_path:-}"            ]]
+    then
+      _warn \
+        printf "Notebook not found: %s\\n" "$(_color_primary "${_selector}")"
+
+      return 1
+    fi
+
+    if ((_only_path))
+    then
+      printf "%s\\n" "${_notebook_path}"
+
+      return 0
+    fi
+
+    if ((_test_archived))
+    then
+      if [[ -d "${_notebook_path}/.archived"  ]]
+      then
+        return 0
+      else
+        return 1
+      fi
+    fi
+
+    if ((_print_unique_file_path))
+    then
+      _get_unique_relative_path "${_file_path:-".${NB_DEFAULT_EXTENSION}"}"
+
+      return 0
+    fi
+
+    local _notebook_name=
+
+    if [[   "${_notebook_path}"   == "${_LOCAL_NOTEBOOK_PATH:-}"  ]] ||
+       [[ ! "${_notebook_path:-}" =~ ^${NB_DIR}                   ]]
+    then
+      _notebook_name="local"
+    else
+      _notebook_name="$(basename "${_notebook_path}")"
+    fi
+
+    if ((_only_name))
+    then
+      printf "%s\\n" "${_notebook_name}"
+
+      return 0
+    fi
+
+    local _escaped_name="${_notebook_name}"
+
+    if [[ "${_escaped_name}" =~ \         ]]
+    then
+      _escaped_name="$(
+        printf "%s\\n" "${_escaped_name}" | sed -e "s/ /\\\ /g"
+      )"
+    fi
+
+    if ((_print_escaped_name))
+    then
+      printf "%s\\n" "${_escaped_name:-}"
+
+      return 0
+    fi
+
+    if ((_notebook_color_enabled))        &&
+       [[ "${_notebook_path}" == "${NB_NOTEBOOK_PATH}"  ]]
+    then
+      _escaped_name="$(_color_primary "${_escaped_name}")"
+    fi
+
+    local _notebook_line="${_escaped_name}"
+
+    if [[ -e "${_notebook_path}/.archived"              ]]
+    then
+      _notebook_line="${_notebook_line} (archived)"
+    fi
+
+    local _remote_url=
+    _remote_url="$(
+      git -C "${_notebook_path}" config --get remote.origin.url || echo ''
+    )"
+
+    if [[ -n "${_remote_url:-}"           ]]
+    then
+      _notebook_line="${_notebook_line} (${_remote_url})"
+    fi
+
+    printf "%s\\n" "${_notebook_line}"
+  }
+
+  # _notebooks_use()
+  #
+  # Usage:
+  #   _notebooks_use <name>
+  _notebooks_use() {
+    local _name="${1%:}"
+
+    if [[ -z "${_name}"                   ]]
+    then
+      _exit_1 _help notebooks
+    fi
+
+    _notebooks_validate_name "${_name}"
+
+    if [[ -n "${_LOCAL_NOTEBOOK_PATH}"    ]]
+    then
+      _exit_1 cat <<HEREDOC
+Currently in a local notebook. To run a command in a global notebook,
+add the notebook name before the command name, separated by a colon:
+  ${_ME} <notebook>:<command> [options...]
+
+$(_color_primary "Examples"):
+  ${_ME} home:list
+  ${_ME} example:add --title "Example Title"
+  ${_ME} example:search "sample query"
+HEREDOC
+    fi
+
+    if [[ -e "${NB_DIR}/${_name}/.index"  ]]
+    then
+      printf "%s\\n" "${_name}" > "${NB_DIR}/.current"
+
+      _GLOBAL_NOTEBOOK_PATH="${NB_DIR}/${_name}"
+      NB_NOTEBOOK_PATH="${_GLOBAL_NOTEBOOK_PATH}"
+
+      printf "Now using: %s\\n" "$(_color_primary "${_name}")"
+    else
+      _exit_1 printf "Not found: %s\\n" "$(_color_primary "${_name}")"
+    fi
+  }
+
+  # Usage: _notebooks_validate_name <name>
+  _notebooks_validate_name() {
+    if _contains                                                \
+      "$(printf "%s\\n" "${1:-}" | tr '[:upper:]' '[:lower:]')" \
+      "${_RESERVED_NOTEBOOK_NAMES[@]}"
+    then
+      _warn printf "Name reserved: %s\\n" "$(_color_primary "${1:-}")"
+
+      return 1
+    else
+      return 0
+    fi
+  }
+
+  local _name="${2:-}"
+  local _subcommand="${1:-}"
+
+  if ! _contains "${_subcommand:-}" "add" "author" "current" "init" "list" "show"
+  then
+    _notebooks_add_new
+  fi
+
+  case "${_subcommand}" in
+    a|add|create|new)
+      shift
+
+      _notebooks_add      "${@:-}"
+      ;;
+    author|config*)
+      shift
+
+      _notebooks_author   "${@:-}"
+      ;;
+    export)
+      _notebooks_export   "${2:-}" "${3:-}"
+      ;;
+    import)
+      _notebooks_import   "${2:-}" "${3:-}"
+      ;;
+    init)
+      shift
+
+      _notebooks_init     "${@:-}"
+      ;;
+    current)
+      shift
+
+      _notebooks_current  "${@:-}"
+      ;;
+    d|delete)
+      _notebooks_delete   "${_name:-}" "${3:-}"
+      ;;
+    list)
+      shift
+
+      _notebooks_list     "${@:-}"
+      ;;
+    rename|mv|move)
+      _notebooks_rename   "${_name:-}" "${3:-}"
+      ;;
+    select)
+      _notebooks_select   "${2:-}"
+      ;;
+    s|show)
+      shift
+
+      _notebooks_show     "${@:-}"
+      ;;
+    u|use)
+      _notebooks_use      "${_name:-}"
+      ;;
+    archive|open|o|peek|p|status|unarchive)
+      _notebooks_notebook "${_subcommand}" "${_name:-}"
+      ;;
+    *)
+      _notebooks_list     "${@}"
+      ;;
+  esac
+}
+_alias_subcommand "notebooks" "n"
+_alias_subcommand "notebooks" "nb"
+_alias_subcommand "notebooks" "nbs"
+_alias_subcommand "notebooks" "notebook"
+_alias_subcommand "notebooks" "ns"
+
+# subcommands · ################################################# · subcommands
+
+_describe_subcommands() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} subcommands [add <name>...] [alias <name> <alias>]
+                 [describe <name> <usage>]
+
+$(_color_primary "Subcommands"):
+  add       Add a new subcommand.
+  alias     Create an <alias> of a given subcommand <name>, with linked help.
+            Note that aliases must also be added with \`subcommands add\`.
+  describe  Set the usage text displayed with \`${_ME} help <subcommand>\`.
+            This can be assigned as a heredoc, which is recommended, or
+            as a string argument.
+
+$(_color_primary "Description"):
+  List, add, alias, and describe subcommands. New subcommands, aliases, and
+  descriptions are not persisted, so \`add\`, \`alias\`, \`describe\` are
+  primarily for plugins.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-plugins
+
+$(_color_primary "See Also"):
+  ${_ME} help plugins
+HEREDOC
+}
+_subcommands() {
+  case "${1:-}" in
+    add)
+      if [[ -n "${2:-}" ]]
+      then
+        shift
+
+        NB_PLUGIN_SUBCOMMANDS+=("${@:-}")
+      fi
+      ;;
+    alias)
+      if [[ -n "${2:-}" ]] &&
+         [[ -n "${3:-}" ]]
+      then
+        _alias_subcommand "${2:-}" "${3:-}"
+      fi
+      ;;
+    describe)
+      shift
+
+      describe "${@:-}"
+      ;;
+    *)
+      printf "%s\\n" "${_DOCUMENTED_SUBCOMMANDS[*]}"
+      ;;
+  esac
+}
+_alias_subcommand "subcommands" "commands"
+
+###############################################################################
+# Plugins
+###############################################################################
+
+# $NB_PLUGIN_SUBCOMMANDS
+#
+# The list of subcommands exposed by plugins.
+NB_PLUGIN_SUBCOMMANDS=()
+
+# User defined plugins can be installed in the $NB_DIR/.plugins directory.
+# Plugins have a .nb-plugin or .nb-theme extension and are written in a
+# Bash-compatible shell scripting language.
+#
+# NOTE: Themes are loaded separately.
+__load_plugins() {
+  if [[ -d "${NB_DIR}/.plugins" ]]
+  then
+    set +f
+    local __file=
+    for   __file in "${NB_DIR}/.plugins"/*."${_ME}"-plugin*
+    do
+      [[ -f "${__file}"                           ]] || continue
+      [[    "${__file}"  =~ /copy.${_ME}-plugin$  ]] && continue
+
+      source "${__file}" 2>/dev/null || :
+    done
+    set -f
+  fi
+}; __load_plugins
+
+###############################################################################
+# Program Option Parsing
+###############################################################################
+
+# _normalize_options()
+#
+# Usage:
+#   _normalize_options <option>...
+#
+# Description:
+#   Iterate over options, breaking -ab into -a -b and --foo=bar into --foo bar
+#   also turns -- into --endopts to avoid issues with things like '-o-', the
+#   '-' should not indicate the end of options, but be an invalid option (or
+#   the argument to the option, such as wget -qO-)
+#
+# Source:
+#   https://github.com/e36freak/templates/blob/master/options
+_NORMALIZED_OPTIONS=()
+_normalize_options() {
+  local _character=
+  local _character_string=
+  local _options=()
+
+  while ((${#}))
+  do
+    case "${1}" in
+      # if option is of type -ab
+      -[!-]?*)
+        if  [[ -n "${_options[*]:-}" ]]                 &&
+            _contains "${_options[${#_options[@]}-1]}"  \
+            "--content"                                 \
+            "add"                                       \
+            "a"                                         \
+            "+"                                         \
+            "new"
+        then
+          _options+=("${1}")
+
+          shift
+        else
+          # loop over each character starting with the second
+          local i=
+          for ((i=1; i < ${#1}; i++))
+          do
+            _character="${1:i:1}"
+            _character_string+="${_character}"
+
+            if [[ ! "${_character}"     =~ [0-9]  ]] ||
+               [[ ! "${1:$((i + 1)):1}" =~ [0-9]  ]]
+            then
+              _options+=("-${_character_string}")
+              _character_string=
+            fi
+          done
+        fi
+        ;;
+      # if option is of type --foo=bar, split on first '='
+      --?*=*)
+        _options+=("${1%%=*}" "${1#*=}")
+        ;;
+      # end of options, stop breaking them up
+      --)
+        _options+=(--endopts)
+
+        shift
+
+        _options+=("${@}")
+
+        break
+        ;;
+      # otherwise, nothing special
+      *)
+        _options+=("${1}")
+        ;;
+    esac
+
+    shift
+  done
+
+  _NORMALIZED_OPTIONS=("${_options[@]}")
+}; _normalize_options "${@:-}"
+
+# set new positional parameters to altered options. Set default to blank.
+set -- "${_NORMALIZED_OPTIONS[@]:-}"
+
+# Usage: _print_normalized_options
+_print_normalized_options() {
+  printf "%s\\n" "${_NORMALIZED_OPTIONS[@]}"
+}
+
+# Parse Options ###############################################################
+
+# Initialize program option variables.
+_ARGUMENTS=()
+_SUBCOMMAND=
+_USE_DEBUG=0
+
+# $_SUBCOMMANDS
+#
+# All available subcommands.
+_SUBCOMMANDS=(
+  a
+  add
+  ar
+  archive
+  b
+  bk
+  bm
+  bookmark
+  bookmarks
+  br
+  browse
+  browser
+  bs
+  close
+  commands
+  completions
+  config
+  copy
+  count
+  create
+  d
+  delete
+  "do"
+  "done"
+  duplicate
+  e
+  edit
+  export
+  env
+  f
+  folder
+  folders
+  git
+  grep
+  h
+  help
+  helpers
+  history
+  i
+  import
+  index
+  init
+  list
+  ls
+  move
+  mv
+  n
+  nb
+  nbs
+  new
+  notebook
+  notebooks
+  ns
+  o
+  open
+  p
+  peek
+  pin
+  plugin
+  plugins
+  preview
+  q
+  r
+  remote
+  rename
+  reset
+  rm
+  run
+  s
+  search
+  set
+  settings
+  shell
+  show
+  st
+  stat
+  status
+  subcommands
+  sync
+  t
+  task
+  tasks
+  trash
+  to
+  todo
+  todos
+  u
+  unar
+  unarchive
+  undo
+  undone
+  unpin
+  unset
+  update
+  upgrade
+  use
+  version
+  view
+  ${NB_PLUGIN_SUBCOMMANDS[@]:-}
+)
+
+# $_DOCUMENTED_SUBCOMMANDS
+#
+# Primary subcommands that appear in documentation. For example, some aliases
+# are omitted from this list. This list is also used for tab completion.
+_DOCUMENTED_SUBCOMMANDS=(
+  +
+  -
+  add
+  archive
+  b
+  bookmark
+  browse
+  commands
+  completions
+  copy
+  count
+  delete
+  "do"
+  edit
+  export
+  env
+  folders
+  git
+  help
+  history
+  import
+  init
+  list
+  ls
+  move
+  mv
+  notebooks
+  open
+  peek
+  pin
+  plugins
+  preview
+  q
+  remote
+  rename
+  run
+  search
+  set
+  settings
+  shell
+  show
+  st
+  status
+  subcommands
+  sync
+  tasks
+  todo
+  u
+  unarchive
+  undo
+  unpin
+  unset
+  update
+  use
+  version
+  ${NB_PLUGIN_SUBCOMMANDS[@]:-}
+)
+
+# $_GIT_SUBCOMMANDS
+#
+# Subcommands that initiate background cleanup commits and sync with remotes.
+_GIT_SUBCOMMANDS=(
+  a
+  add
+  ar
+  archive
+  b
+  bk
+  bm
+  bookmark
+  bookmarks
+  br
+  browse
+  browser
+  bs
+  close
+  copy
+  count
+  create
+  d
+  delete
+  "do"
+  "done"
+  duplicate
+  e
+  edit
+  export
+  f
+  folder
+  folders
+  grep
+  i
+  import
+  list
+  ls
+  move
+  mv
+  n
+  nb
+  nbs
+  new
+  notebook
+  notebooks
+  ns
+  o
+  open
+  p
+  peek
+  pin
+  preview
+  q
+  rename
+  rm
+  s
+  show
+  search
+  t
+  task
+  tasks
+  to
+  todo
+  todos
+  u
+  unar
+  unarchive
+  undo
+  undone
+  unpin
+  use
+  view
+  ${NB_PLUGIN_SUBCOMMANDS[@]:-}
+)
+
+# $_SUBCOMMANDS_PATTERN
+#
+# The contents of the `$_SUBCOMMANDS` array, joined with '|'.
+_SUBCOMMANDS_PATTERN="^$(_join '$|^' "${_SUBCOMMANDS[@]}")$|^\+$|^\-$"
+
+# $_GIT_SUBCOMMANDS_PATTERN
+#
+# The contents of the `$_GIT_SUBCOMMANDS` array, joined with '|'.
+_GIT_SUBCOMMANDS_PATTERN="^$(_join '$|^' "${_GIT_SUBCOMMANDS[@]}")$|^\+$|^\-$"
+
+# _is_valid_subcommand()
+#
+# Usage:
+#   _is_valid_subcommand <name>
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If the given <name> is a valid subcommand name.
+#   1 (error,  false)  If not.
+_is_valid_subcommand() {
+  [[ -n "${1:-}" ]] &&  [[ "${1:-}" =~ ${_SUBCOMMANDS_PATTERN} ]]
+}
+
+# _parse_options()
+#
+# Usage:
+#   _parse_options <option>...
+#
+# Description:
+#   Parse program options.
+_parse_options() {
+  local _current_option=
+  local _non_option_arguments=()
+  local _previous_option=
+
+  while ((${#}))
+  do
+    _previous_option="${_current_option:-}"
+
+    _current_option="${1:-}"
+
+    shift
+
+    case "${_current_option}" in
+      -)
+        if [[ -z "${_SUBCOMMAND:-}"     ]]
+        then
+          _SUBCOMMAND="delete"
+        else
+          _ARGUMENTS+=("delete")
+        fi
+        ;;
+      +)
+        if [[ -z "${_SUBCOMMAND:-}"     ]]
+        then
+          _SUBCOMMAND="add"
+        else
+          _ARGUMENTS+=("add")
+        fi
+        ;;
+      -h|--help)
+        case "${_SUBCOMMAND:-}" in
+          git|run)
+            _ARGUMENTS+=("${_current_option}")
+            ;;
+          *)
+            if [[ -n "${_SUBCOMMAND:-}" ]]
+            then
+              _ARGUMENTS+=("${_SUBCOMMAND}")
+            fi
+
+            _SUBCOMMAND="help"
+            ;;
+        esac
+        ;;
+      --debug)
+        _USE_DEBUG=1
+        ;;
+      --no*color)
+        _COLOR_ENABLED=0
+        ;;
+      --no*git|--skip*git)
+        _GIT_ENABLED=0
+        ;;
+      --version)
+        if [[ -n "${_SUBCOMMAND:-}"     ]]
+        then
+          _ARGUMENTS+=("${_current_option}")
+        else
+          _SUBCOMMAND="version"
+        fi
+        ;;
+      -i|--interactive)
+        case "${_SUBCOMMAND:-}" in
+          git|run)
+            _ARGUMENTS+=("${_current_option}")
+            ;;
+          *)
+            _SUBCOMMAND="shell"
+            ;;
+        esac
+        ;;
+      --welcome)
+        _print_welcome
+        ;;
+      *:*)
+        if [[ ! "${_current_option:-}"  =~ ^-         ]] &&
+           [[ ! "${_previous_option:-}" =~ ^-         ]]
+        then
+          _non_option_arguments+=("${_current_option}")
+        fi
+
+        if [[ -z "${_SUBCOMMAND:-}"                   ]] &&
+            _string_is_url "${_current_option}"
+        then
+          _SUBCOMMAND="bookmark"
+          _ARGUMENTS+=("${_current_option}")
+        elif _notebooks current --selected
+        then
+          _ARGUMENTS+=("${_current_option}")
+        elif _contains "${_SUBCOMMAND:-"${1:-}"}" "copy" "move" "mv" "rename" &&
+             (($((${#_non_option_arguments[@]} - 1))))
+        then
+          _ARGUMENTS+=("${_current_option}")
+        elif [[ "${_SUBCOMMAND:-}" == "delete"        ]]
+        then
+          _ARGUMENTS+=("${_current_option}")
+        elif _contains "${_previous_option:-}" "-r" "--related" "--via" "--also"
+        then
+          _ARGUMENTS+=("${_current_option}")
+        else
+          local _selector_suffix="${_current_option#*:}"
+
+          if [[ -z "${_selector_suffix:-}"            ]] &&
+             [[ -n "${_SUBCOMMAND:-}"                 ]] &&
+             [[ ! "${_SUBCOMMAND}" =~ (^ls$|^list$)   ]]
+          then
+            _ARGUMENTS+=("${_current_option}")
+          else
+            if ! _notebooks select "${_current_option}"
+            then
+              if [[ -n "${_SUBCOMMAND:-}"             ]] ||
+                 [[    "${_previous_option}" =~ ^-    ]]
+              then
+                _ARGUMENTS+=("${_current_option}")
+
+                continue
+              else
+                _exit_1 printf                \
+                  "Notebook not found: %s\\n" \
+                  "$(_color_primary "${_current_option%%:*}")"
+              fi
+            fi
+
+            if _is_valid_subcommand "${_selector_suffix}"
+            then
+              _SUBCOMMAND="${_selector_suffix}"
+            else
+              if _string_is_url "${_selector_suffix}"
+              then
+                _SUBCOMMAND="bookmark"
+                _ARGUMENTS+=("${_selector_suffix}")
+              elif [[ "${_selector_suffix}" =~ ^-   ]]
+              then
+                _ARGUMENTS+=("${_selector_suffix}")
+              else
+                _ARGUMENTS+=("${_current_option}")
+              fi
+            fi
+          fi
+        fi
+        ;;
+      --endopts)
+        # Terminate option parsing.
+        break
+        ;;
+      *)
+        if [[     ! "${_previous_option}"   =~ ^-   ]]
+        then
+          if [[ -z "${_SUBCOMMAND:-}"               ]] &&
+             _is_valid_subcommand "${_current_option}"
+          then
+            _SUBCOMMAND="${_current_option}"
+          else
+            if [[ ! "${_current_option:-}"  =~ ^-   ]]
+            then
+              _non_option_arguments+=("${_current_option}")
+            fi
+
+            _ARGUMENTS+=("${_current_option}")
+          fi
+        else
+          _ARGUMENTS+=("${_current_option}")
+        fi
+        ;;
+    esac
+  done
+}; _parse_options "${@:-}"
+
+_debug printf "\${_SUBCOMMAND}:           '%s'\\n"  "${_SUBCOMMAND}"
+_debug printf "\${NB_NOTEBOOK_PATH}:      '%s'\\n"  "${NB_NOTEBOOK_PATH}"
+_debug printf "\${_LOCAL_NOTEBOOK_PATH}:  '%s'\\n"  "${_LOCAL_NOTEBOOK_PATH}"
+_debug printf "\${_ARGUMENTS[*]:-}:       '%s'\\n"  "${_ARGUMENTS[*]:-}"
+
+###############################################################################
+# Deprecated Functions and Variables
+#
+# TODO: Remove
+###############################################################################
+
+# _get_notebook_identifier()
+_get_notebook_identifier()  { _notebooks show "${@}" --escaped;   }
+
+# _get_selection_basename()
+_get_selection_basename()   { _show "${@}" --filename;            }
+
+# _get_unique_basename()
+_get_unique_basename()      { _get_unique_relative_path "${@:-}"; }
+
+# _set_selection_notebook() <selector>
+_set_selection_notebook()   {
+  if [[ "${1:-}" =~ : ]]
+  then
+    if _notebooks select "${1:-}"
+    then
+      _NOTEBOOK_PATH="${NB_NOTEBOOK_PATH}"
+    fi
+  elif [[ "${_NOTEBOOK_PATH:-}" != "${NB_NOTEBOOK_PATH}" ]]
+  then
+    _NOTEBOOK_PATH="${NB_NOTEBOOK_PATH}"
+  fi
+}
+
+# $_NOTEBOOK_PATH
+# shellcheck disable=SC2034
+export _NOTEBOOK_PATH="${_NOTEBOOK_PATH:-"${NB_NOTEBOOK_PATH}"}"
+
+# $_SCOPE
+# shellcheck disable=SC2034
+# _SCOPE="$(_notebooks current --name)"
+_SCOPE="$(basename "${NB_NOTEBOOK_PATH}")"
+
+# $_SCOPED
+# shellcheck disable=SC2034
+_SCOPED="$(
+  # if _notebooks current --selected
+  if [[ "${NB_NOTEBOOK_PATH}" != "${_GLOBAL_NOTEBOOK_PATH}" ]]
+  then
+    printf "1\\n"
+  else
+    printf "0\\n"
+  fi
+)"
+
+# color functions
+_color_dim()          { _color_muted    "${@:-}"; }
+_highlight()          { _color_primary  "${@:-}"; }
+_id_brackets_color()  { _color_brackets "${@:-}"; }
+
+###############################################################################
+# _defer()
+###############################################################################
+
+# $_DEFERRED_COMMAND
+#
+# The function and arguments to run after the script has loaded.
+_DEFERRED_COMMAND=()
+
+# _defer()
+#
+# Usage:
+#   _defer <name> [<argument>...]
+#
+# Description:
+#   Assign a command to run after the script has loaded.
+_defer() {
+  _DEFERRED_COMMAND=("${@:-}")
+}
+
+# _call_deferred_command()
+#
+# Usage:
+#   _call_deferred_command --group <num>
+#
+# Description:
+#   Call the deferred command.
+_call_deferred_command() {
+  [[ -z "${_DEFERRED_COMMAND[0]:-}" ]] && exit 0
+
+  local _group="${2:-}"
+  local _group_3_names=(
+    _ar _archive _b _bookmark _br _browse _browser _close _config _copy _do   \
+    _done _duplicate _f _folder _folders _h _help _helpers _set _plugin       \
+    _plugins _remote _reset _settings _shell _st _stat _status _sync _t _task \
+    _tasks _to _todo _todos _unar _unarchive _undo _undone _unset _update     \
+    _upgrade
+  )
+
+  if {
+       [[ "${_group:-}" -eq 2 ]] &&
+         _contains "${_DEFERRED_COMMAND[0]:-}" "${_group_3_names[@]}"
+     } || {
+       [[ "${_group:-}" -eq 3 ]] &&
+       ! _contains "${_DEFERRED_COMMAND[0]:-}" "${_group_3_names[@]}"
+     }
+  then
+    return 0
+  else
+    "${_DEFERRED_COMMAND[@]:-}"
+
+    return 0
+  fi
+}
+
+###############################################################################
+# _main()
+###############################################################################
+
+# _main()
+#
+# Usage:
+#   _main "$@"
+#
+# Description:
+#   Primary entry point for the program logic. Call this function at the end
+#   of the script after everything has been defined.
+_main() {
+  if [[ -z "${_SUBCOMMAND:-}" ]]
+  then
+    _SUBCOMMAND="ls"
+  fi
+
+  case "${_SUBCOMMAND}" in
+    init|sync)
+      _git required
+      _defer "_${_SUBCOMMAND}" "${@:-}"
+      ;;
+    commands|completions|env|git|h|help*|r|run|set|settings|subcommands|update|version)
+      _defer "_${_SUBCOMMAND}" "${@:-}"
+      ;;
+    *)
+      _git required
+
+      # Call `_init()` if configuration hasn't been initialized.
+      if [[ ! -e "${NB_DIR}"            ]] ||
+         [[ ! -e "${NB_NOTEBOOK_PATH}"  ]]
+      then
+        _init "${@:-}"
+
+        _ls || true # returns 0 due to empty repository.
+
+        return 0
+      fi
+
+      if [[ "${_SUBCOMMAND}" =~ ${_GIT_SUBCOMMANDS_PATTERN} ]]
+      then
+        if _git dirty "${NB_NOTEBOOK_PATH}"
+        then
+          _index reconcile
+
+          _git checkpoint "${NB_NOTEBOOK_PATH}" --spinner
+        elif _git autosyncable "${NB_NOTEBOOK_PATH}"
+        then
+          (_git checkpoint "${NB_NOTEBOOK_PATH}" &>/dev/null) &
+        fi
+      fi
+
+      if [[ "${_SUBCOMMAND}" == "ls" ]]
+      then
+        # Run `ls` on its own, exiting at the end in order to avoid running /
+        # loading the rest of the script.
+        "_${_SUBCOMMAND}" "${@}" --exit
+      else
+        # Defer subcommand call until the rest of the script has been loaded.
+        _defer "_${_SUBCOMMAND}" "${@:-}"
+
+        return 0
+      fi
+      ;;
+  esac
+}
+
+_main "${_ARGUMENTS[@]:-}"
+
+###############################################################################
+# Helpers: Group 2                                             Helpers: Group 2
+# ----------------                                             ----------------
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+# _build_related_list()
+#
+# Usage:
+#   _build_related_list (<url> | <selector>)...
+#
+# Description:
+#   Build a Markdown-formatted list of <url>s and <selector>s for bookmarks
+#   and todos.
+_build_related_list() {
+  local _list_content=
+  local _related_identifiers=("${@:-}")
+
+  local __identifier=
+  for   __identifier in "${_related_identifiers[@]:-}"
+  do
+    [[ -n "${__identifier:-}" ]] || continue
+
+    if _string_is_url "${__identifier:-}"
+    then
+      _list_content+="- <${__identifier:-}>${_NEWLINE}"
+    else
+      if [[ "${__identifier:-}" =~ \[\[.*\]\] ]]
+      then
+        __identifier="$(
+          sed -E -e "s/\[\[(.*)\]\]/\1/g" <<< "${__identifier:-}"
+        )"
+      fi
+
+      _list_content+="- [[${__identifier:-}]]${_NEWLINE}"
+    fi
+  done
+
+  printf "%s\\n" "${_list_content:-}"
+}
+
+# _decrypt_file()
+#
+# Usage:
+#   _decrypt_file <path> <password>
+_decrypt_file() {
+  local _encrypted_path="${1:-}"
+  local _password="${2:-}"
+
+  if [[ -z "${_encrypted_path}" ]]
+  then
+    return 1
+  fi
+
+  local _notebook_and_relative_path="${_encrypted_path#"${NB_DIR}"/}"
+
+  local _unencrypted_path=
+  _unencrypted_path="$(_temp file "${_notebook_and_relative_path%.enc}")"
+
+  local _file_command_response=
+  _file_command_response="$(file "${_encrypted_path}" 2>/dev/null || :)"
+
+  local _decryption_tool=
+  _decryption_tool="$(_get_decryption_tool "${_encrypted_path:-}")"
+
+  case "${_decryption_tool:-}" in
+    age)
+      if _command_exists "age"
+      then
+        age                                 \
+          --decrypt                         \
+          --output "${_unencrypted_path}"   \
+          "${_encrypted_path}"
+      else
+        _exit_1 printf                      \
+"This item was encrypted with \`age\`, but the \`age\` command was not found.\\n"
+      fi
+      ;;
+    gpg)
+      if _command_exists "gpg"
+      then
+        printf "%s\\n" "${_password}"       \
+          | gpg                             \
+            --batch                         \
+            --quiet                         \
+            --passphrase-fd 0               \
+            --output "${_unencrypted_path}" \
+            --decrypt "${_encrypted_path}"
+      else
+        _exit_1 printf                      \
+"This item was encrypted with GPG, but the GPG command was not found.\\n"
+      fi
+      ;;
+    openssl)
+      openssl enc                           \
+        -d                                  \
+        -aes-256-cbc                        \
+        -in   "${_encrypted_path}"          \
+        -md   sha256                        \
+        -out  "${_unencrypted_path}"        \
+        -pass file:<(printf "%s\\n" "${_password}") 2> /dev/null      || {
+          if [[ -f "${_unencrypted_path:?}" ]]
+          then
+            rm "${_unencrypted_path:?}"
+          fi
+
+          openssl enc                       \
+            -d                              \
+            -aes-256-cbc                    \
+            -in   "${_encrypted_path}"      \
+            -md   md5                       \
+            -out  "${_unencrypted_path}"    \
+            -pass file:<(printf "%s\\n" "${_password}") 2> /dev/null  ||
+              if [[ -f "${_unencrypted_path:?}" ]]
+              then
+                rm "${_unencrypted_path:?}"
+              fi
+        }
+      ;;
+    *)
+      _exit_1 printf "Unable to decrypt file.\\n"
+      ;;
+  esac
+
+  if [[ ! -e "${_unencrypted_path}" ]]
+  then
+    _exit_1 printf "Decryption error.\\n" 1>&2
+  fi
+
+  printf "%s\\n" "${_unencrypted_path}"
+}
+
+# _download_from()
+#
+# Usage:
+#   _download_from <url> [<outfile>]
+#
+# Description:
+#   Download the file at <url> and print to standard output or <outfile>, if
+#   present.
+_download_from() {
+  local _downloaded=0
+  local _timeout=15
+  local _url="${1:-}"
+
+  if [[ -z "${_url}" ]] ||
+     [[ !  "${_url}" =~ (^https\:|^http\:|^file\:|^ftp\:|^sftp\:) ]]
+  then
+    return 1
+  fi
+
+  local _target_path="${2:-}"
+
+  if _command_exists "curl"
+  then
+    local _curl_options=(
+      --silent
+      --location
+      --connect-timeout "${_timeout}"
+      "${_url}"
+    )
+
+    [[ -n "${NB_USER_AGENT:-}" ]]   &&
+      _curl_options+=(--user-agent "${NB_USER_AGENT}")
+
+    if [[ -n "${_target_path}" ]]
+    then
+      curl                          \
+        "${_curl_options[@]}"       \
+        --output "${_target_path}"  \
+        && _downloaded=1
+    else
+      curl                          \
+        "${_curl_options[@]}"       \
+        && _downloaded=1
+    fi
+  elif _command_exists "wget"
+  then
+    local _wget_options=(
+      --quiet
+      --connect-timeout="${_timeout}"
+      --dns-timeout="${_timeout}"
+      "${_url}"
+    )
+
+    [[ -n "${NB_USER_AGENT:-}" ]]   &&
+      _wget_options+=(--user-agent="${NB_USER_AGENT}")
+
+    if [[ -n "${_target_path}" ]]
+    then
+      wget                          \
+        "${_wget_options[@]}"       \
+        -O "${_target_path}"        \
+        2>/dev/null                 \
+        && _downloaded=1
+    else
+      wget                          \
+        "${_wget_options[@]}"       \
+        -O -                        \
+        2>/dev/null                 \
+        && _downloaded=1
+    fi
+  fi
+
+  if ! ((_downloaded))
+  then
+    return 1
+  fi
+}
+
+# _edit_file()
+#
+# Usage:
+#   _edit_file <path> [--no-wait]
+#
+# Description:
+#   Open the file in $EDITOR. Use the `-f` option in vim and `--wait` option in
+#   other GUI editors to wait until the file is closed in the editor before
+#   continuing, unless `--no-wait`.
+_edit_file() {
+  local _file_path="${1:-}"
+  local _wait=1
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      --no-wait)
+        _wait=0
+        ;;
+      *)
+        if [[ -z "${_file_path}"  ]]
+        then
+          _file_path="${__arg}"
+        fi
+        ;;
+    esac
+  done
+
+  if [[ -z "${_file_path}"        ]]
+  then
+    return 1
+  fi
+
+  local _current_notebook_path=
+  _current_notebook_path="$(_notebooks current --path)"
+
+  cd "${_current_notebook_path}"  ||  return 1
+
+  if [[ -e "${_file_path}"            ]]
+  then
+    if _file_is_encrypted "${_file_path}"
+    then
+      _exit_1 printf                  \
+"File must be decrypted before editing.\\n"
+    fi
+
+    if _file_is_archive "${_file_path}"   &&
+       [[ ! "${_file_path}" =~ docx$  ]]
+    then
+      _exit_1 printf                  \
+"Can't edit archives. Export archive and expand to edit.\\n"
+    fi
+
+    if ! _file_is_text "${_file_path}"    &&
+       [[ ! -d "${_file_path}"        ]]
+    then
+      if _open_in_gui_app "${_file_path:-}"
+      then
+        return 0
+      else
+        _exit_1 printf                                \
+          "%s doesn't know how to edit this file.\\n" \
+          "$(_color_primary "${_ME}")"
+      fi
+    fi
+  fi
+
+  local _editor_command="${EDITOR}"
+
+  # turn on case-insensitive matching
+  shopt -s nocasematch
+
+  if ((_wait))
+  then
+    case "${EDITOR}" in
+      *gvim*|*mvim*)
+        _editor_command="${_editor_command} -f"
+        ;;
+      *code*|*mate*|*subl*)
+        _editor_command="${_editor_command} --wait"
+        ;;
+    esac
+  fi
+
+  if [[ -d "${_file_path}" ]] &&
+     [[ "${EDITOR}" =~ vim ]]
+  then
+    cd "${_file_path}" && "${_editor_command:-}"
+  else
+    if [[ "${EDITOR}" =~ typora   ]] &&
+       [[ ! -f "${_file_path:-}"  ]]
+    then
+      touch "${_file_path:-}"
+    fi
+
+    eval "${_editor_command} \"${_file_path}\""
+
+    if [[ "${EDITOR}" =~ (typora|open\ -a) ]]
+    then
+      printf "Editing with %s\\n" "$(_color_primary "${EDITOR}")"
+
+      while true
+      do
+        read -n 1 -s -r -p "Press any key to save changes and exit$(_color_muted "...")"
+
+        printf "\\n"
+
+        break
+      done
+    fi
+  fi
+
+  # turn off case-insensitive matching
+  shopt -u nocasematch
+
+  return 0
+}
+
+# _encrypt_file()
+#
+# Usage:
+#   _encrypt_file <unencrypted-path> <encrypted-path>
+#                 [--password <password>] [--tool <tool>]
+_encrypt_file() {
+  local _encrypted_path="${2:-}"
+  local _password=
+  local _tool="${NB_ENCRYPTION_TOOL}"
+  local _unencrypted_path="${1:-}"
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --password)
+        if _option_value_is_present "${2:-}"
+        then
+          _password="${2:-}"
+
+          shift
+        fi
+        ;;
+      --tool)
+        if _option_value_is_present "${2:-}"
+        then
+          _tool="${2:-}"
+
+          shift
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  if [[ -z "${_password:-}"       ]]  &&
+     [[    "${_tool}" != "age"    ]]
+  then
+    _exit_1 printf "Password required.\\n"
+  fi
+
+  if [[ -z "${_unencrypted_path}" ]]  ||
+     [[ -z "${_encrypted_path}"   ]]
+  then
+    _exit_1 printf "Encrypted and unencrypted paths required.\\n"
+  fi
+
+  if [[   "${_tool}" == "age"         ]]
+  then
+    age                               \
+      --encrypt                       \
+      --output "${_encrypted_path}"   \
+      --passphrase                    \
+      "${_unencrypted_path}"
+  elif [[ "${_tool}" == "gpg"         ]]
+  then
+    printf "%s\\n" "${_password}"     \
+      | gpg                           \
+        --batch                       \
+        --cipher-algo AES256          \
+        --quiet                       \
+        --output "${_encrypted_path}" \
+        --passphrase-fd 0             \
+        --symmetric                   \
+        "${_unencrypted_path}"
+  elif [[ "${_tool}" == "openssl"     ]]
+  then
+    openssl enc                       \
+      -aes-256-cbc                    \
+      -in   "${_unencrypted_path}"    \
+      -md   sha256                    \
+      -out  "${_encrypted_path}"      \
+      -pass file:<(printf "%s\\n" "${_password}") 2>/dev/null
+  else
+    _exit_1 printf                    \
+      "\$NB_ENCRYPTION_TOOL must be set to 'gpg' or 'openssl'.\\n"
+  fi
+
+  if [[ ! -e "${_encrypted_path}"     ]]
+  then
+    _exit_1 printf "Encryption error.\\n"
+  fi
+}
+
+# _get_decryption_tool()
+#
+# Usage:
+#   _get_decryption_tool <path>
+#
+# Description:
+#   Print the name of the tool to use to decrypt the file at <path>.
+_get_decryption_tool() {
+  local _encrypted_path="${1:-}"
+
+  local _file_command_response=
+  _file_command_response="$(file "${_encrypted_path}" 2>/dev/null || :)"
+
+  local _decryption_tool=
+
+  if [[   "${_file_command_response}" =~ (GPG|PGP)  ]]
+  then
+    _decryption_tool="gpg"
+  elif [[ "${_file_command_response}" =~ openssl    ]]
+  then
+    _decryption_tool="openssl"
+  elif [[ "${_file_command_response}" =~ data       ]]
+  then
+    local         __first_line=
+    IFS=  read -r __first_line < "${_encrypted_path}"
+
+    if [[ "${__first_line:-}" =~ age-encryption     ]]
+    then
+      _decryption_tool="age"
+    fi
+  fi
+
+  printf "%s\\n" "${_decryption_tool:-}"
+}
+
+# _get_hash()
+#
+# Usage:
+#   _get_hash <path>
+#
+# Description:
+#   Generate a hash for the file or directory at <path>.
+_get_hash() {
+  # Usage: _get_hash_with_command <path> <command>
+  _get_hash_with_command() {
+    local _command=
+    IFS=' ' read -ra _command <<< "${2:-}"
+
+    local _path="${1:-}"
+
+    [[ -n "${_command[*]:-}" ]] && [[ -n "${_path}" ]] || return 1
+
+    if [[ -d "${_path}" ]]
+    then
+      tar -P -cf - "${_path}"     \
+        | "${_command[@]}"        \
+        | awk '{ print $1 }'
+    else
+      "${_command[@]}" "${_path}" \
+        | awk '{print $1}'
+    fi
+  }
+
+  local _path="${1:-}"
+  [[ -n "${_path:-}" ]] || return 1
+
+  if _command_exists "shasum"
+  then
+    _get_hash_with_command "${_path}" "shasum -a 256"
+  elif _command_exists "md5sum"
+  then
+    _get_hash_with_command "${_path}" "md5sum"
+  elif _command_exists "md5"
+  then
+    _get_hash_with_command "${_path}" "md5 -q"
+  else
+    _exit_1 printf "No hashing tool found.\\n"
+  fi
+}
+
+# _get_http_status()
+#
+# Usage:
+#   _get_http_status <url>
+#
+# Description:
+#   Print the http status response code for <url>.
+_get_http_status() {
+  local _url="${1:-}"
+  [[ -n "${_url:-}" ]] || return 1
+
+  if _command_exists "curl"
+  then
+    local _curl_options=(
+      --head
+      --silent
+      --output /dev/null
+      -w "%{http_code}\\n"
+    )
+
+    [[ -n "${NB_USER_AGENT:-}" ]] &&
+      _curl_options+=(--user-agent "${NB_USER_AGENT}")
+
+    curl "${_curl_options[@]}" "${_url}" || return 0
+  elif _command_exists "wget"
+  then
+    local _wget_options=(
+      --server-response
+    )
+
+    [[ -n "${NB_USER_AGENT:-}" ]] &&
+      _wget_options+=(--user-agent="${NB_USER_AGENT}")
+
+    wget "${_wget_options[@]}" "${_url}" 2>&1 \
+      | grep "HTTP/" | awk '{print $2}' || return 0
+  fi
+}
+
+# _get_unique_path()
+#
+# Usage:
+#   _get_unique_path <path>
+#
+# Description:
+#   Get a unique full path that doesn't conflict with any existing file.
+_get_unique_path() {
+  local _path="${1:-}"
+
+  local _dir_path=
+  _dir_path="$(dirname "${_path}")"
+
+  local _basename=
+  _basename="$(basename "${_path}")"
+
+  local _file_name="${_basename%%.*}"
+  local _file_extension="${_basename#*.}"
+
+  if [[ -n "${_file_extension:-}"               ]] &&
+     [[ "${_basename}"  =~ \.                   ]] &&
+     [[ "${_file_name}" != "${_file_extension}" ]]
+  then
+    _file_extension=".${_file_extension}"
+  else
+    _file_extension=
+  fi
+
+  local _unique_file_name="${_file_name}"
+  local _uniqueness_counter=0
+
+  while [[ -e "${_dir_path}/${_unique_file_name}${_file_extension}"     ]] ||
+        [[ -e "${_dir_path}/${_unique_file_name}${_file_extension}.enc" ]]
+  do
+    _uniqueness_counter="$((_uniqueness_counter+1))"
+
+    printf -v _unique_file_name -- "%s-%01d"  \
+      "${_file_name}"                         \
+      "${_uniqueness_counter}"
+  done
+
+  printf "%s\\n" "${_dir_path}/${_unique_file_name}${_file_extension}"
+}
+
+# _get_unique_relative_path()
+#
+# Usage:
+#   _get_unique_relative_path [<file-path>[<extension>] [<notebook-path>]
+#
+# Description:
+#   Get a unique basename that doesn't conflict with any existing file.
+_get_unique_relative_path() {
+  local _file_path="${1:-}"
+  local _notebook_path="${2:-"$(_notebooks current --path)"}"
+
+  local _file_basename="${_file_path##*/}" # strip ancestors
+  local _file_name="${_file_basename%%.*}" # strip extension
+  local _folder_path=
+  local _target_basename=
+  local _unique_path=
+
+  if [[ -z "${_file_name:-}"    ]]
+  then
+    _file_name="$(date "+%Y%m%d%H%M%S")"
+  fi
+
+  if [[ "${_file_path:-}" =~ /  ]]
+  then
+    _folder_path="${_file_path%\/*}"
+  fi
+
+  if [[ "${_file_basename:-}" =~ ^\.  ]]
+  then
+    local _file_type="${_file_basename#*.}"
+
+    _target_basename="${_file_name}.${_file_type}"
+  elif [[ -n "${_file_basename:-}"    ]]
+  then
+    _target_basename="${_file_basename}"
+  else
+    _target_basename="${_file_name}"
+  fi
+
+  _unique_path="$(
+    if [[ -n "${_folder_path:-}" ]]
+    then
+      _get_unique_path "${_notebook_path}/${_folder_path}/${_target_basename}"
+    else
+      _get_unique_path "${_notebook_path}/${_target_basename}"
+    fi
+  )"
+
+  printf "%s" "${_unique_path#"${_notebook_path}"/}"
+}
+
+# _get_uri()
+#
+# Usage:
+#   _get_uri [--encode | --decode] <string>
+#
+# Description:
+#   Encode or decode a URI.
+_get_uri() {
+  # Usage: _get_uri_decode <string>
+  _get_uri_decode() {
+    # https://unix.stackexchange.com/a/187256
+    local _input="${1:-}"
+
+    _input="${_input//+/ }"
+    _input="${_input//$'\r'}"
+
+    printf "%b" "${_input//%/\\x}"
+  }
+
+  # Usage: _get_uri_encode <string>
+  _get_uri_encode() {
+    local _encoding="${1//'%'/%25}"
+
+    _encoding="${_encoding//' '/%20}"
+    _encoding="${_encoding//'"'/%22}"
+    _encoding="${_encoding//'#'/%23}"
+    _encoding="${_encoding//'$'/%24}"
+    _encoding="${_encoding//'&'/%26}"
+    _encoding="${_encoding//'+'/%2B}"
+    _encoding="${_encoding//','/%2C}"
+    _encoding="${_encoding//${_SLASH}/%2F}"
+    _encoding="${_encoding//':'/%3A}"
+    _encoding="${_encoding//';'/%3B}"
+    _encoding="${_encoding//'='/%3D}"
+    _encoding="${_encoding//'?'/%3F}"
+    _encoding="${_encoding//'@'/%40}"
+    _encoding="${_encoding//'['/%5B}"
+    _encoding="${_encoding//'\n'/%0A}"
+
+    local _encoded="${_encoding//']'/%5D}"
+
+    printf "%s\\n" "${_encoded:-}"
+  }
+
+  case "${1:-}" in
+    --decode)                 _get_uri_decode "${2:-}"  ;;
+    --encode)                 _get_uri_encode "${2:-}"  ;;
+    http%3A%2F*|https%3A%2F*) _get_uri_decode "${1:-}"  ;;
+    http://*|https://*)       _get_uri_encode "${1:-}"  ;;
+  esac
+}
+
+# _option_get_tags()
+#
+# Usage:
+#   _option_get_tags <option> <comma,separated,tags>
+#
+# Description:
+#   Convert a comma-separated list of tags to a string of hashtags.
+_option_get_tags() {
+  local _tag_list=
+  _tag_list="$(_option_get_value "${1:-}" "${2:-}")" || return 1
+
+  local _tags=()
+  IFS=',' read -ra _tags <<< "${_tag_list}"
+
+  local _normalized_tags=()
+
+  local __tag=
+  for   __tag in "${_tags[@]:-}"
+  do
+    _normalized_tags+=("#${__tag#\#}")
+  done
+
+  local _tag_string=
+  _tag_string="$(_join " " "${_normalized_tags[@]-}")"
+
+  printf "%s\\n" "${_tag_string:-}"
+}
+
+# _render()
+#
+# Usage:
+#   [<input> |] _render [<path>] [--body] [--from] [--pandoc]
+#                       [--source-extension] [--title <title>]
+#                       [<pandoc-option>...]
+#
+# Options:
+#   --body              Only render body, without <head> and <body> opening
+#                       or closing tags.
+#   --from              The format to convert content from.
+#   --pandoc            Use pandoc to convert file.
+#   --source-extension  The extension of the original file. Used to select
+#                       syntax mode in Ace.
+#   --title             <title> content.
+_render() {
+  # Usage: _render_prepare_file <path> <pandoc-enabled>
+  _render_prepare_file() {
+    local _input_file_path="${1:?}"
+    local _prepared_file_path="${_input_file_path:-}"
+    local _use_pandoc="${2:-0}"
+
+    local _code_extensions=(
+      asm aspx awd awk bash bat bats bib c c++ cc cgi class cls cmake coffee
+      cpp cs cson cxx d diff "do" el f fs gcl go h hs haml hbs hx j jade java
+      jl js json jsp jsx kts ksh "less" lsp lua m matlab ml mk mm perl php pl
+      pm prl pug py rb r rh rs sass scala scpt scss sh sql styl swift tcl toml
+      tpl ts tsx vb vba vbscript vim xml xsl xslt yaml yml zsh
+    )
+
+    if ((_use_pandoc))
+    then
+      _code_extensions+=($(
+        pandoc --list-highlight-languages \
+          | sed -e "/html/d" -e "/latex/d" -e "/markdown/d"
+      ))
+    fi
+
+    local _source_extension="${_input_file_path##*\.}"
+
+    if _contains "${_source_extension}" "${_code_extensions[@]:-}"
+    then
+      if ((_use_pandoc))
+      then
+        local _code_block_temp_path=
+        _code_block_temp_path="$(_temp file ".md" --touch)"
+
+        printf "${_BT}${_BT}${_BT}%s\\n%s\\n${_BT}${_BT}${_BT}\\n"  \
+          "${_source_extension}"                                    \
+          "$(cat "${_input_file_path:-}")" >> "${_code_block_temp_path:-}"
+      else
+        local _code_block_temp_path=
+        _code_block_temp_path="$(_temp file ".html" --touch)"
+
+        printf "<code>\\n%s\\n</code>\\n" \
+          "$(cat "${_input_file_path:-}")" >> "${_code_block_temp_path:-}"
+      fi
+
+      _prepared_file_path="${_code_block_temp_path:-}"
+    fi
+
+    printf "%s\\n" "${_prepared_file_path:-}"
+  }
+
+  # Usage: _render_print_head [--title <title>]
+  _render_print_head() {
+    local _html_title="${_ME}"
+
+    if [[ "${1:-}" == "--title" ]] && [[ -n "${2:-}" ]]
+    then
+      _html_title="${2:-}"
+    fi
+
+    local _ansi_hex_values=(
+      '000000' '800000' '008000' '808000' '000080' '800080' '008080' 'c0c0c0'
+      '808080' 'ff0000' '00ff00' 'ffff00' '0000ff' 'ff00ff' '00ffff' 'ffffff'
+      '000000' '00005f' '000087' '0000af' '0000d7' '0000ff' '005f00' '005f5f'
+      '005f87' '005faf' '005fd7' '005fff' '008700' '00875f' '008787' '0087af'
+      '0087d7' '0087ff' '00af00' '00af5f' '00af87' '00afaf' '00afd7' '00afff'
+      '00d700' '00d75f' '00d787' '00d7af' '00d7d7' '00d7ff' '00ff00' '00ff5f'
+      '00ff87' '00ffaf' '00ffd7' '00ffff' '5f0000' '5f005f' '5f0087' '5f00af'
+      '5f00d7' '5f00ff' '5f5f00' '5f5f5f' '5f5f87' '5f5faf' '5f5fd7' '5f5fff'
+      '5f8700' '5f875f' '5f8787' '5f87af' '5f87d7' '5f87ff' '5faf00' '5faf5f'
+      '5faf87' '5fafaf' '5fafd7' '5fafff' '5fd700' '5fd75f' '5fd787' '5fd7af'
+      '5fd7d7' '5fd7ff' '5fff00' '5fff5f' '5fff87' '5fffaf' '5fffd7' '5fffff'
+      '870000' '87005f' '870087' '8700af' '8700d7' '8700ff' '875f00' '875f5f'
+      '875f87' '875faf' '875fd7' '875fff' '878700' '87875f' '878787' '8787af'
+      '8787d7' '8787ff' '87af00' '87af5f' '87af87' '87afaf' '87afd7' '87afff'
+      '87d700' '87d75f' '87d787' '87d7af' '87d7d7' '87d7ff' '87ff00' '87ff5f'
+      '87ff87' '87ffaf' '87ffd7' '87ffff' 'af0000' 'af005f' 'af0087' 'af00af'
+      'af00d7' 'af00ff' 'af5f00' 'af5f5f' 'af5f87' 'af5faf' 'af5fd7' 'af5fff'
+      'af8700' 'af875f' 'af8787' 'af87af' 'af87d7' 'af87ff' 'afaf00' 'afaf5f'
+      'afaf87' 'afafaf' 'afafd7' 'afafff' 'afd700' 'afd75f' 'afd787' 'afd7af'
+      'afd7d7' 'afd7ff' 'afff00' 'afff5f' 'afff87' 'afffaf' 'afffd7' 'afffff'
+      'd70000' 'd7005f' 'd70087' 'd700af' 'd700d7' 'd700ff' 'd75f00' 'd75f5f'
+      'd75f87' 'd75faf' 'd75fd7' 'd75fff' 'd78700' 'd7875f' 'd78787' 'd787af'
+      'd787d7' 'd787ff' 'd7af00' 'd7af5f' 'd7af87' 'd7afaf' 'd7afd7' 'd7afff'
+      'd7d700' 'd7d75f' 'd7d787' 'd7d7af' 'd7d7d7' 'd7d7ff' 'd7ff00' 'd7ff5f'
+      'd7ff87' 'd7ffaf' 'd7ffd7' 'd7ffff' 'ff0000' 'ff005f' 'ff0087' 'ff00af'
+      'ff00d7' 'ff00ff' 'ff5f00' 'ff5f5f' 'ff5f87' 'ff5faf' 'ff5fd7' 'ff5fff'
+      'ff8700' 'ff875f' 'ff8787' 'ff87af' 'ff87d7' 'ff87ff' 'ffaf00' 'ffaf5f'
+      'ffaf87' 'ffafaf' 'ffafd7' 'ffafff' 'ffd700' 'ffd75f' 'ffd787' 'ffd7af'
+      'ffd7d7' 'ffd7ff' 'ffff00' 'ffff5f' 'ffff87' 'ffffaf' 'ffffd7' 'ffffff'
+      '080808' '121212' '1c1c1c' '262626' '303030' '3a3a3a' '444444' '4e4e4e'
+      '585858' '626262' '6c6c6c' '767676' '808080' '8a8a8a' '949494' '9e9e9e'
+      'a8a8a8' 'b2b2b2' 'bcbcbc' 'c6c6c6' 'd0d0d0' 'dadada' 'e4e4e4' 'eeeeee'
+    )
+
+    # #1a1a1a #1b1b20 #17171c #19191f #18181c
+    local _color_background_hex="#141418"
+    local _color_background_alt_hex="#17171c" # #1b1b20 #1e1e25 #212121
+    local _color_muted_hex="#626480"
+    local _color_primary_hex="#7593eb"
+    # TODO: local _color_secondary_hex=
+    local _color_text_hex="#c5c4cc"           # #e6e6e6 #dedede
+
+    if [[ "${NB_COLOR_PRIMARY}" -lt 256 ]]
+    then
+      _color_primary_hex="#${_ansi_hex_values[${NB_COLOR_PRIMARY}]}"
+      # TODO: _color_secondary_hex="#${_ansi_hex_values[${NB_COLOR_SECONDARY}]}"
+
+      # desaturate select colors
+      case "${_color_primary_hex}" in
+        \#5f87ff) _color_primary_hex="#7593eb" ;;
+        \#ffff5f) _color_primary_hex="#ebeb75" ;;
+      esac
+    fi
+
+    cat <<HEREDOC
+<!DOCTYPE html>
+<html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang="">
+<head>
+<meta charset="UTF-8">
+<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
+
+<title>${_html_title}</title>
+
+<link rel="icon" type="image/x-icon" href="data:image/x-icon;base64,\
+AAABAAEAEBAAAAEAIABoBAAAFgAAACgAAAAQAAAAIAAAAAEAIAAAAAAAAAQAACQWAAAkFgAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAon8IB59/AlSegwFunYgCVJ+RBhGdlAFcnZkAbp2eAkqc\
+pwMxm6sBaJuxAzCbtwJim7wChZrAAlCaxgUHmsQEAKN+CQafgQJqnYUB2p6JA2WfkQYPnpYDdp2aAd\
+mengNXnKgEMZutAsCbsgHNm7cCiZu9AnGZwwG8mMcCbo6pAACehgIAnYYCIJ2HAbeeigMYnpUFAJ6c\
+BSednQK1nqAEE5irAACbsQKTm7MBlp++DwKZxgIAmccCPZjKAbuZzQQXnogCAJ2IAiCdigG8no0EHZ\
+6XBQCenwUnnZ8CtZ6iBBOZrgAAm7MCkZu1AmqatAAAmcsEAJnLAx2YzQG9mc8EKJ2LAgCdigIenY0B\
+152RAlqdlwAAnqEEL52iAbaepQQQmLAAAJu2ApObuAGbncQKBJjLAQCZzQJBmM8BupnRBBafiQUOnY\
+sBep2OAdOdlAKsnZoChZ2gAaidowKVoKwOA5a3AACbuAKQm7sC0ZrCApCYyAF8mM0Bv5jPAmeTxgAA\
+n4oGDJ6MA1WekANJnpcEIp2cAmudoAJsnaQDGp2jAgCVuwAAm7sCkJu9A3GZxAJUmcgCe5nNAkaa0Q\
+UGmdAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAKjBJwCZuwAAnLkFFZu9AqSbvwNkmr4AAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACowSYAl7sAAJu6A1iavQGym8EDQprAAQ\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAqcMpAJu9AACcvAUEnMAECJ3E\
+CAKcwwcAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA//8AAP//AAD//wAA//8AAAABAAAAAQAAiI\
+gAAIiYAACIiAAAAIEAAAGBAAD/HwAA/x8AAP8fAAD//wAA//8AAA==">
+
+<style>
+html {
+  background-color:   ${_color_background_hex};
+  color:              ${_color_text_hex};
+  font-size:          16px;
+  line-height:        1.5;
+}
+
+@media (min-width: 992px) {
+  html {
+    font-size:        17px;
+  }
+}
+
+html,
+input,
+textarea {
+  font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace;
+}
+
+body {
+  font-kerning:       normal;
+  hyphens:            none;
+  margin:             0;
+  text-rendering:     optimizeLegibility;
+  word-wrap:          break-word;
+}
+
+@media (max-width: 600px) {
+  body {
+    font-size:        0.9em;
+  }
+}
+
+@media print {
+  body {
+    background-color: transparent;
+    color:            black;
+    font-size:        12pt;
+  }
+
+  h2, h3, p {
+    orphans:          3;
+    widows:           3;
+  }
+
+  h2, h3, h4 {
+    page-break-after: avoid;
+  }
+}
+
+h1, h2, h3, h4, h5, h6 {
+  margin-bottom:      1rem;
+  margin-top:         1rem;
+}
+
+h1  { font-size:      1.5rem;   }
+h2  { font-size:      1.3rem;   }
+h3  { font-size:      1.17rem;  }
+
+h5, h6 {
+  font-size: 1em;
+  font-style: italic;
+}
+
+h6  {  font-weight:   normal; }
+
+p {
+  margin:             1em 0;
+  overflow:           hidden;
+}
+
+a         {  color:   ${_color_primary_hex}; text-decoration: none;       }
+a:hover   {  color:   ${_color_primary_hex}; text-decoration: underline;  }
+a:visited {  color:   ${_color_primary_hex}; text-decoration: none;       }
+
+:focus {
+  outline:            1px solid #2d2d2d;
+}
+
+body.using-mouse a:focus,
+body.using-mouse input:focus {
+  outline:            none;
+}
+
+h1 a,
+h1 a:hover,
+h1 a:visited,
+nav a,
+nav a:hover,
+nav a:visited,
+a.list-item,
+a.list-item:hover,
+a.list-item:visited {
+  color:              ${_color_text_hex};
+  text-decoration:    none;
+}
+
+blockquote {
+  border-left:        2px solid #4d4d4d;
+  color:              #878787;            /* #606060 */
+  margin:             1em 0 1em 1.7em;
+  padding-left:       1em;
+}
+
+code {
+  font-family: Menlo, Monaco, 'Lucida Console', Consolas, monospace;
+  font-size:          85%;
+  margin:             0;
+  white-space:        pre-wrap;
+}
+
+pre {
+  background-color:   ${_color_background_alt_hex};
+  border:             1px solid ${_color_background_alt_hex};
+  border-radius:      1px;
+  margin:             1rem 0;
+  overflow:           auto;
+  padding:            1rem;
+}
+
+pre.sourceCode {
+  padding:            1rem;
+}
+
+pre code {
+  overflow:           visible;
+}
+
+hr  {
+  background-color:   #4d4d4d;
+  border:             none;
+  height:             1px;
+  margin:             1em 0;
+}
+
+img {
+  border-radius:      1px;
+  max-width:          100%;
+}
+
+ol, ul {
+  padding-left:       1.7em;
+  margin-top:         1em;
+}
+
+li > ol, li > ul {
+  margin-top:         0;
+}
+
+table {
+  border-collapse:    collapse;
+  border-color:       transparent;
+  display:            block;
+  font-variant-numeric: lining-nums tabular-nums;
+  margin:             1em 0;
+  overflow-x:         auto;
+  width:              100%;
+}
+
+th {
+  border-top:         1px solid #4d4d4d;
+  padding:            0.25em 0.5em 0.25em 0.5em;
+}
+
+tbody {
+  border: none;
+  border-bottom:      1px solid #4d4d4d;
+  margin-top:         0.5em;
+}
+
+td {
+  padding:            0 0 1rem 0;
+}
+
+td > table {
+  margin:             0;
+}
+
+table caption {
+  margin-bottom:      0.75em;
+}
+
+col {
+  width:              auto !important;
+}
+
+audio {
+  padding:            1rem 0;
+}
+
+audio,
+video {
+  margin:             0 auto;
+  width:              100%;
+}
+
+audio:focus,
+video:focus {
+  outline:            ${_color_background_hex};
+}
+
+video {
+  height:             auto;
+  max-height:         50rem;
+}
+
+.media-item {
+  padding:            2rem 0 1rem;
+}
+
+header {
+  margin-bottom:      4em;
+  text-align:         center;
+}
+
+.center {
+  text-align:         center;
+}
+
+.header-crumbs {
+  font-size:          1rem;
+  font-weight:        normal;
+  line-height:        2;
+  margin:             0 auto;
+  max-width:          45rem;
+  padding:            1.75rem 2rem 0rem;
+  text-align:         left;
+}
+
+/* <strong> for bold in terminal browsers only */
+.header-crumbs strong {
+  font-weight:        normal;
+}
+
+.header-crumbs-spacer {
+  display:            none;
+}
+
+.main {
+  margin:             0 auto;
+  max-width:          45rem;
+  padding:            0rem 2rem 2rem;
+}
+
+.main h1:first-child {
+  padding-top:        0.35rem;
+}
+
+.main p:first-child,
+.main .sourceCode:first-child {
+  padding-top:        0.5rem;
+}
+
+.item-list {
+  margin-top:         0;
+}
+
+.list-item  {
+  display:            inline-block;
+  max-width:          45rem;
+  overflow:           hidden;
+  text-overflow:      ellipsis;
+  white-space:        nowrap;
+  vertical-align:     top;
+}
+
+.identifier {         color: ${_color_primary_hex}; }
+.muted      {         color: ${_color_muted_hex};   }
+
+form {
+  padding-top:        1rem;
+}
+
+#search {
+  position:           relative;
+}
+
+label[for=search-input] {
+  display:            none;
+}
+
+#search-input {
+  background-color:   ${_color_background_hex};
+  border:             none;
+  border-bottom:      1px solid #4d4d4d;
+  color:              ${_color_text_hex};
+  font-size:          1rem;
+  padding:            0.5rem 0;
+  width:              100%;
+}
+
+#search-input:focus {
+  outline:            0;
+}
+
+.search-spacer {
+  display:            none;
+}
+
+#search	i {
+  animation-name:     blink;
+  animation-duration: 3000ms;
+  animation-iteration-count: infinite;
+  background-color:   #a6a659;
+  display:            none;
+  height:             80%;
+  left:               5px;
+  opacity:            0.5;
+  position:           absolute;
+  top:                10%;
+  width:              1em;
+}
+
+#search input:focus + i {
+  display:            none;
+}
+
+@keyframes blink {
+  from  { opacity:    1; }
+  to    { opacity:    0; }
+}
+
+form br {
+  display:            none;
+}
+
+input[type="submit"] {
+  background:         none;
+  border:             none;
+  color:              ${_color_primary_hex};
+  font-size:          1rem;
+  outline:            0 solid ${_color_background_hex};
+  padding:            1rem;
+}
+
+input[type="submit"]:active {
+  border-bottom:      1px solid #bae7ff;
+  color:              #bae7ff;
+}
+
+input[type="submit"]:focus {
+  outline:            1px solid #2d2d2d;
+}
+
+input[type="submit"]:hover {
+  border-bottom:      1px solid ${_color_primary_hex};
+}
+
+.last-saved {
+  padding-left:       1rem;
+}
+
+textarea,
+.ace_editor {
+  background-color:   ${_color_background_alt_hex};
+  border:             none;
+  box-sizing:         border-box;
+  color:              #dddddd;
+  font-size:          0.875rem;
+  line-height:        1.5;
+  margin-bottom:      1rem;
+  margin-top:         1rem;
+  outline:            1px solid ${_color_background_hex};
+  padding:            0;
+  vertical-align:     top;
+  width:              100%;
+}
+
+textarea {
+  padding:            1rem;
+}
+
+#TOC li {
+  list-style:         none;
+}
+
+#TOC a:not(:hover) {
+  text-decoration:    none;
+}
+
+div.column {
+  display:            inline-block;
+  vertical-align:     top;
+  width:              50%;
+}
+
+div.hanging-indent {
+  margin-left:        1.5em;
+  text-indent:        -1.5em;
+}
+
+.display.math {
+  display:            block;
+  margin:             0.5rem auto;
+  text-align:         center;
+}
+
+span.smallcaps {
+  font-variant:       small-caps;
+}
+
+span.underline {
+  text-decoration:    underline;
+}
+
+ul.task-list {
+  list-style:         none;
+}
+
+ul.task-list input[type="checkbox"] {
+  -webkit-appearance: none;
+  -moz-appearance:    none;
+  background-color:   #2d2d2d;
+  border-radius:      3px;
+  font-size:          1.2rem;
+  padding:            0 0.3rem;
+}
+
+ul.task-list input[type="checkbox"]:before {
+  color:              transparent;
+  content:            "\0000A0";
+}
+
+ul.task-list input[type="checkbox"]:checked:before {
+  color:              ${_color_primary_hex};
+  content:            "x";
+}
+
+/*
+ * #93a5cc #ffcfaf #7f9f7f #dca3a3 #f0dfaf #dfdfbf #dcdccc #c3bf9f #c0bed1
+ * #efef8f #b7bcd8 #cccc96 #7290b1
+ * /
+
+/* Ace Editor & Syntax */
+
+.ace_editor {
+  /* border:             1rem solid ${_color_background_alt_hex}; */
+}
+
+.ace_gutter {
+  padding:            1rem 0;
+}
+
+.ace_gutter-cell {
+  padding:            0 0.5rem;
+}
+
+.ace_content {
+  padding:            1rem 0.5rem;
+}
+
+.ace_scroller.ace_scroll-left {
+  box-shadow:         initial !important;
+}
+
+.ace-twilight .ace_constant,
+.ace-twilight .ace_constant.ace_character,
+.ace-twilight .ace_constant.ace_character.ace_escape,
+.ace-twilight .ace_constant.ace_other,
+.ace-twilight .ace_heading,
+.ace-twilight .ace_markup.ace_heading,
+.ace-twilight .ace_support.ace_constant {
+  color:              #9191a1;
+}
+
+.ace-twilight .ace_gutter {
+  background-color:   ${_color_background_hex};
+}
+
+.ace-twilight .ace_indent-guide-active {
+  filter: invert(1) grayscale(100%) brightness(0.75);
+}
+
+.ace-twilight .ace_invisible {
+  color:              #333333;
+}
+
+.ace-twilight .ace_list,
+.ace-twilight .ace_markup.ace_list,
+.ace-twilight .ace_storage,
+.ace-twilight .ace_string.ace_strong {
+  color:              #cccc96;
+}
+
+.ace-twilight .ace_print-margin {
+  background:         none;
+}
+
+.ace_separator {
+  color:              #7290b1;
+}
+
+.ace-twilight .ace_keyword,
+.ace-twilight .ace_meta {
+  color:              #7290b1;
+}
+
+.ace-twilight .ace_string {
+  color:              ${_color_primary_hex};
+}
+
+.normal-mode .ace_cursor {
+  background-color:   rgba(255,255,0,0.5);
+}
+
+.normal-mode .ace_hidden-cursors .ace_cursor {
+  border:             1px solid yellow;
+}
+
+/* Pandoc Syntax */
+
+pre > code.sourceCode {
+  position:           relative;
+  white-space:        pre;
+}
+
+pre > code.sourceCode > span  {
+  display:            inline-block;
+  line-height:        1.25;
+}
+
+pre > code.sourceCode > span:empty {
+  height:             1.2em;
+}
+
+code.sourceCode > span {
+  color:              inherit;
+  text-decoration:    inherit;
+}
+
+@media screen {
+  div.sourceCode {
+    overflow:         auto;
+  }
+}
+
+@media print {
+  pre > code.sourceCode {
+    white-space:      pre-wrap;
+  }
+
+  pre > code.sourceCode > span {
+    padding-left:     5em;
+    text-indent:      -5em;
+  }
+}
+
+pre.numberSource code {
+  counter-reset:      source-line 0;
+}
+
+pre.numberSource code > span {
+  counter-increment:  source-line;
+  left:               -4em;
+  position:           relative;
+}
+
+pre.numberSource code > span > a:first-child::before {
+  border:             none;
+  content:            counter(source-line);
+  display:            inline-block;
+  left:               -1em;
+  padding:            0 4px;
+  position:           relative;
+  text-align:         right;
+  -webkit-touch-callout: none;
+  -webkit-user-select: none;
+  -khtml-user-select: none;
+  -moz-user-select:   none;
+  -ms-user-select:    none;
+  user-select:        none;
+  vertical-align:     baseline;
+  width:              4em;
+}
+
+pre.numberSource {
+  margin-left:        3em;
+  padding-left:       4px;
+}
+
+div.sourceCode {
+  color:              #cccccc;
+}
+
+@media screen {
+  pre > code.sourceCode > span > a:first-child::before {
+    text-decoration:  underline;
+  }
+}
+
+code span.al { color: #ffcfaf;                          } /*     Alert      */
+code span.an { color: #7f9f7f;      font-weight: bold;  } /*   Annotation   */
+code span.at {                                          } /*   Attribute    */
+code span.bn { color: #dca3a3;                          } /*     BaseN      */
+code span.bu {                                          } /*    BuiltIn     */
+code span.cf { color: #7290b1;                          } /*  ControlFlow   */
+code span.ch { color: #8987a0;                          } /*      Char      */
+code span.cn { color: #8987a0;      font-weight: bold;  } /*    Constant    */
+code span.co { color: ${_color_muted_hex};              } /*    Comment     */
+code span.cv { color: #7f9f7f;      font-weight: bold;  } /*   CommentVar   */
+code span.do { color: ${_color_muted_hex};              } /* Documentation  */
+code span.dt { color: #cccc96;                          } /*    DataType    */
+code span.dv { color: #cccc96;                          } /*     DecVal     */
+code span.er { color: #cccc96;                          } /*     Error      */
+code span.ex {                                          } /*   Extension    */
+code span.fl { color: #c0bed1;                          } /*     Float      */
+code span.fu { color: #7290b1;                          } /*    Function    */
+code span.im {                                          } /*     Import     */
+code span.in { color: #7f9f7f;      font-weight: bold;  } /*  Information   */
+code span.kw { color: #7290b1;                          } /*    Keyword     */
+code span.op { color: #f0efd0;                          } /*   Operator     */
+code span.ot { color: #cccc96;                          } /*     Other      */
+code span.pp { color: #ffcfaf;      font-weight: bold;  } /*  Preprocessor  */
+code span.sc { color: #8987a0;                          } /*  SpecialChar   */
+code span.ss { color: ${_color_primary_hex};            } /* SpecialString  */
+code span.st { color: ${_color_primary_hex};            } /*     String     */
+code span.va {                                          } /*    Variable    */
+code span.vs { color: ${_color_primary_hex};            } /* VerbatimString */
+code span.wa { color: #93a5cc;      font-weight: bold;  } /*    Warning     */
+</style>
+
+<script>
+// hide broken images
+document.addEventListener("DOMContentLoaded", function(event) {
+  document.querySelectorAll('img').forEach(function(img) {
+    img.onerror = function() { this.style.display = 'none'; };
+  })
+});
+
+// let the document know when the mouse is being used
+document.addEventListener('mousedown', function() {
+  document.body.classList.add('using-mouse');
+});
+
+// re-enable focus styling when <tab> is pressed
+document.addEventListener('keydown', function(event) {
+  if (event.keyCode === 9) {
+    document.body.classList.remove('using-mouse');
+  }
+});
+</script>
+<meta name="referrer" content="no-referrer" />
+</head>
+<body>
+HEREDOC
+  }
+
+  local _from=
+  local _html_title=
+  local _input_file_path=
+  local _input_string=
+  local _only_body=0
+  local _pandoc_arguments=("--highlight-style=zenburn")
+  local _source_extension="${NB_DEFAULT_EXTENSION:-md}"
+  local _filter_bookmark_content=0
+  local _use_pandoc=0
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      "")         :                                           ;;
+      --body)     _only_body=1                                ;;
+      --bookmark) _filter_bookmark_content=1                  ;;
+      --from)     _from="${2:?}" && _use_pandoc=1   && shift  ;;
+      --*pandoc)  _use_pandoc=1                               ;;
+      --source*)  _source_extension="${2:?}"        && shift  ;;
+      --title)    _html_title="${2:?}"              && shift  ;;
+      -*)         _pandoc_arguments+=("${1:-}")               ;;
+      *)
+        if [[ -z "${_input_file_path:-}"  ]] &&
+           [[ -f "${1:-}"                 ]]
+        then
+          _input_file_path="${1:-}"
+        elif [[ -z "${_input_string:-}"   ]]
+        then
+          _input_string="${1:-}"
+        else
+          _pandoc_arguments+=("${1:-}")
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  local _prepared_file_path="${_input_file_path:-}"
+
+  if ! _command_exists "pandoc"
+  then
+    _use_pandoc=0
+  fi
+
+  if [[ -n "${_input_file_path:-}"  ]]
+  then
+    _prepared_file_path="$(
+      _render_prepare_file "${_input_file_path:-}" "${_use_pandoc:-0}"
+    )"
+  fi
+
+  {
+    # body
+    if ((_use_pandoc))
+    then
+      if [[ -n "${_from:-}"                   ]]
+      then
+        _pandoc_arguments+=("--from=${_from:-}")
+      elif [[ -z "${_prepared_file_path:-}"   ]]
+      then
+        _pandoc_arguments+=("--from=markdown+raw_html")
+      fi
+
+      {
+        if _piped_input
+        then
+          _pandoc                             \
+            --standard-input                  \
+            "${_pandoc_arguments[@]:-}"       \
+            2>/dev/null
+        fi
+
+        if [[ -n "${_prepared_file_path:-}"   ]]
+        then
+          _pandoc                             \
+            "${_prepared_file_path:-}"        \
+            "${_pandoc_arguments[@]:-}"       \
+            2>/dev/null
+        fi
+      } | {
+        if [[ -n "${_input_string}"           ]]
+        then
+          printf "%s\\n" "${_input_string}"   \
+            | _pandoc                         \
+                --standard-input              \
+                "${_pandoc_arguments[@]:-}"   \
+                2>/dev/null
+        fi
+
+        cat
+      }
+    else
+      {
+        if _piped_input
+        then
+          cat
+        fi
+
+        if [[ -n "${_prepared_file_path:-}"   ]]
+        then
+          if _file_is_text "${_prepared_file_path}"
+          then
+            cat "${_prepared_file_path}"
+          else
+            cat <<HEREDOC
+File type not yet supported: ${_prepared_file_path##*.}
+HEREDOC
+          fi
+        fi
+      } | {
+        if [[ -n "${_input_string}"           ]]
+        then
+          printf "%s\\n" "${_input_string}"
+        fi
+
+        cat
+      }
+    fi
+  } | {
+    # head
+    if ! ((_only_body))
+    then
+      _render_print_head --title "${_html_title}"
+    fi
+
+    cat
+  } | {
+    # footer / tail
+    cat
+
+    if ! ((_only_body))
+    then
+      if ((${NB_ACE_ENABLED:-0}))
+      then
+        if [[ ! -e "${NB_DIR}/.assets/ace-builds" ]] && ! ((${NB_TESTING:-0}))
+        then
+          _env install --ace
+        fi
+
+        cat <<HEREDOC
+<script src="/--ace/ace.js"></script>
+<script src="/--ace/ext-modelist.js"></script>
+<script>
+  function initializeAceEditor() {
+    var aceModeList = ace.require("ace/ext/modelist");
+
+    var textarea    = document.querySelector('textarea');
+
+    if (!textarea) return;
+
+    var editDiv = document.createElement('div');
+
+    editDiv.setAttribute(
+      'style',
+      'height:' + textarea.offsetHeight + 'px;' +
+      'width:'  + textarea.offsetWidth  + 'px;'
+    )
+
+    editDiv.style.height    = textarea.offsetHeight + 'px';
+    editDiv.style.width     = textarea.offsetWidth  + 'px';
+    editDiv.classList.add(textarea.classList[0]);
+
+    textarea.parentNode.insertBefore(editDiv, textarea);
+
+    textarea.style.display  = 'none';
+
+    var editor = ace.edit(editDiv);
+
+    editor.getSession().setValue(textarea.value);
+
+    var mode = aceModeList.getModeForPath('example.${_source_extension:-md}').mode;
+    editor.getSession().setMode(mode);
+
+    editor.setOptions({
+      autoScrollEditorIntoView: true,
+      copyWithEmptySelection:   true,
+      displayIndentGuides:      true,
+      fadeFoldWidgets:          true,
+      fixedWidthGutter:         true,
+      highlightActiveLine:      true,
+      navigateWithinSoftTabs:   true,
+      newLineMode:              'unix',
+      printMargin:              false,
+      scrollPastEnd:            0.5,
+      showFoldWidgets:          true,
+      showGutter:               true,
+      showInvisibles:           true,
+      showLineNumbers:          true,
+      tabSize:                  2,
+      useSoftTabs:              true,
+      wrap:                     false
+    });
+
+    if ('${_source_extension:-md}' === 'md') {
+      if ('${NB_ACE_MD_GUTTER:-1}' === '1') {
+        editor.setOptions({
+          wrap:                 true
+        });
+      } else {
+        editor.setOptions({
+          wrap:                 true,
+          showFoldWidgets:      false,
+          showLineNumbers:      false,
+          showGutter:           false
+        });
+      }
+    }
+
+    if ('${NB_ACE_SOFT_TABS:-0}' === '0') {
+      editor.setOptions({
+        useSoftTabs:            false
+      })
+    }
+
+    var keyboard = '${NB_ACE_KEYBOARD:-ace}';
+
+    if (['emacs', 'sublime', 'vim', 'vscode'].indexOf(keyboard) !== -1) {
+      editor.setKeyboardHandler('ace/keyboard/' + keyboard);
+    }
+
+    editor.setTheme('ace/theme/${NB_ACE_THEME:-twilight}');
+
+    textarea.form.addEventListener('submit', function() {
+      textarea.value = editor.getSession().getValue();
+    });
+  }
+
+  (function() {
+    if (document.readyState !== 'loading') {
+      setTimeout(initializeAceEditor, 0);
+    } else {
+      document.addEventListener('DOMContentLoaded', initializeAceEditor);
+    }
+  }());
+</script>
+HEREDOC
+      fi
+
+      cat <<HEREDOC
+</body>
+</html>
+HEREDOC
+    fi
+  } | {
+    if ((_filter_bookmark_content))
+    then
+      local _in_content=0
+
+      {
+        local               __line=
+        while IFS= read -r  __line
+        do
+          if ! ((_in_content))  &&
+             [[ "${__line:-}" =~  (^\<h2\ id=\"content\"|^\<h2\ id=\"page-content\") ]]
+          then
+            _in_content=1
+          fi
+
+          if ((_in_content))
+          then
+            # add line marker
+            printf "%s-content-%s%s\\n" "${_ME}" "${_ME}" "${__line:-}"
+          else
+            printf "%s\\n" "${__line:-}"
+          fi
+        done
+      } | {
+        # strip bookmark <img> images
+        LC_ALL=C sed -E -e "/^${_ME}-content-${_ME}/ s/<img[^>]*>//g"
+      } | {
+        # remove empty <p> paragraph elements
+        LC_ALL=C sed -E -e "/^${_ME}-content-${_ME}/ s/.*<p>[ ]*<\/p>$//g"
+      } | {
+        # remove line marker
+        LC_ALL=C sed -E -e "s/^${_ME}-content-${_ME}//g"
+      }
+    else
+      cat
+    fi
+  } | {
+    LC_ALL=C sed -e "s/<a\ /<a\ rel=\"noopener\ noreferrer\"\ /g"
+  } | {
+    # mark up checkboxes
+    local _checkbox_pattern_open="<span class=\"muted\">[<\/span><span class=\"identifier\">"
+    local _checkbox_pattern_close="<\/span><span class=\"muted\">\]<\/span>"
+
+    LC_ALL=C sed -E                                                                       \
+-e "1, /<textarea/ s/\[x\]/${_checkbox_pattern_open}x${_checkbox_pattern_close}/g"        \
+-e "1, /<textarea/ s/\[ \]/${_checkbox_pattern_open}${_NBSP}${_checkbox_pattern_close}/g" \
+-e "1, /<textarea/ s/\[\]/${_checkbox_pattern_open}${_NBSP}${_checkbox_pattern_close}/g"
+  }
+}
+
+# _resolve_links()
+#
+# Usage:
+#   <input> | _resolve_links <notebook-path> [--browse] [--limit <limit>]
+#                            [--terminal] [--type <type>]
+#
+# Options:
+#   --browse  Link to web server, link #tags, and redirect outbound links.
+#
+# Description:
+#   Read standard input, resolve all [[wiki-style links]] and wrap each
+#   one in a link to the target item, then print the updated file contents.
+#   When the --browse option is specified, #tags are linked to the search
+#   page for each tag and outbound links are updated to redirect through the
+#   root level of the app to avoid leaking information via the referer header.
+#
+#   By default, links are created with file:// URLs to the item on the
+#   local filesystem. With --browse, links are created with internal web
+#   server URLs.
+_resolve_links() {
+  # Usage: <input> | _resolve_links_get_matches <pattern> [<path>]
+  _resolve_links_get_matches() {
+    local _arguments=()
+
+    case "${1:-}" in
+      '') return 1 ;;
+      *)
+        _arguments+=("-e" "${1:?}")
+        [[ -n "${2:-}" ]] && _arguments+=("${2:-}")
+        ;;
+    esac
+
+    if _command_exists "rg"
+    then
+      rg                      \
+        --color=never         \
+        --no-filename         \
+        --only-matching       \
+        --text                \
+        "${_arguments[@]:-}"  \
+        2>/dev/null || :
+    else
+      grep                    \
+        --color=never         \
+        --extended-regexp     \
+        -h                    \
+        --only-matching       \
+        --text                \
+        "${_arguments[@]:-}"  \
+        2>/dev/null || :
+    fi
+  }
+
+  local _columns="${NB_BROWSE_COLUMNS:-70}"
+  local _for_browsing=0
+  local _input_type="html"
+  local _limit=
+  local _terminal=0
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --browse)   _for_browsing=1                             ;;
+      --col*)     _columns="${2:?}"                 && shift  ;;
+      --limit|-n|--num|--number|--per*)
+        _limit="${2:?}"
+
+        shift
+        ;;
+      --page)     _option_value_is_present "${2:-}" && shift  ;;
+      --terminal) _terminal=1                                 ;;
+      --type)     _input_type="${2:?}"              && shift  ;;
+      *)
+        if [[ -z "${_notebook_path:-}"  ]]
+        then
+          _notebook_path="${1:-}"
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  [[ ! -d "${_notebook_path:-}" ]] && return 1
+
+  local _url_params_pattern=
+
+  if ((_terminal))
+  then
+    _url_params_pattern="?--columns=${_columns:-}\&--limit=${_limit:-}"
+  fi
+
+  local _notebook_name="${_notebook_path##*/}"
+
+  if [[ ! "${_notebook_path:-}" =~ ^${NB_DIR} ]]
+  then
+    _notebook_name="local"
+
+    local _encoded_local_notebook_path=
+    _encoded_local_notebook_path="$(
+      _get_uri --encode "${_notebook_path:-}"
+    )"
+
+    case "${_url_params_pattern:-}" in
+      '') _url_params_pattern+="?--local=${_encoded_local_notebook_path:-}"   ;;
+      *)  _url_params_pattern+="\&--local=${_encoded_local_notebook_path:-}"  ;;
+    esac
+  fi
+
+  local _input_temp_file_path=
+  _input_temp_file_path="$(_temp file ".${_input_type}" --touch)"
+
+  cat >> "${_input_temp_file_path}"
+
+  {
+    cat "${_input_temp_file_path}"
+  } | {
+    # link #hashtags to internal search URLs
+
+    if ! ((_for_browsing))
+    then
+      cat
+    else
+      local _replacement_url="\/\/${NB_SERVER_HOST}:${NB_SERVER_PORT}\/${_notebook_name}:"
+
+      case "${_url_params_pattern:-}" in
+        '') _replacement_url+="?--query=%23\\2"                         ;;
+        *)  _replacement_url+="${_url_params_pattern}\&--query=%23\\2"  ;;
+      esac
+
+      local _pattern=
+
+      case "${_input_type:-}" in
+        html) _pattern="<a\ href=\"${_replacement_url//' '/%20}\">\#\\2<\/a>" ;;
+        org)  _pattern="[[${_replacement_url//' '/%20}][\#\\2]]"              ;;
+        *)    _pattern="\#\\2"                                                ;;
+      esac
+
+      if [[ "${_input_type:-}" == "html" ]] &&
+         grep -q "<\/body>" "${_input_temp_file_path}"
+      then
+        LC_ALL=C sed -E \
+          -e "/<body>/,/<\/body>/ s/(^|[>|\ ])\#([A-Za-z0-9_\-]+)/\1${_pattern}/g"
+      else
+        LC_ALL=C sed -E -e "s/(^|[>|\ ])\#([A-Za-z0-9_\-]+)/\1${_pattern}/g"
+      fi
+    fi
+  } | {
+    # resolve and link [[wiki-style links]]
+    # TODO: HTML uses `sed` streaming replacement. The current Org
+    # implementation uses querying to ensure link is not an
+    # outbound URL, which requires a separate matching operation. The
+    # match replacement code supports both HTML and Org, with HTML unused.
+
+    if ((_for_browsing)) && [[ "${_input_type:-}" == "html" ]]
+    then
+      # patterns for wrapping [[wiki-style links]] in HTML links
+      local _host_port_pattern="${NB_SERVER_HOST}:${NB_SERVER_PORT}"
+      local _link_match_pattern="\[\[([^#|][^]|]*)\]\]"
+      local _url_pattern="\/\/${_host_port_pattern}\/\1${_url_params_pattern:-}"
+      local _replacement_pattern="<a\ href=\"${_url_pattern}\">[[\1]]<\/a>"
+
+      local _labeled_link_match_pattern="\[\[([^#][^]|]+)\|([^]]+)\]\]"
+      local _labeled_url_pattern="\/\/${_host_port_pattern}\/\1${_url_params_pattern:-}"
+      local _labeled_replacement_pattern="<a\ href=\"${_labeled_url_pattern}\">[[\2]]<\/a>"
+
+      # patterns for adding notebook prefixes to just-linked URLs
+      local _notebookless_pattern="${_host_port_pattern}\/([^:?\"-]+[\?\"])"
+      local _notebookless_replacement_pattern="${_host_port_pattern}\/${_notebook_name}:\1"
+
+      local _linkable=1
+
+      {
+        local               __line=
+        while IFS= read -r  __line
+        do
+          if [[ "${__line:-}" =~ (\<nav|\<code)     ]]
+          then
+            _linkable=0
+          fi
+
+          if ((_linkable))
+          then
+            printf "%s-linkable-%s%s\\n" "${_ME}" "${_ME}" "${__line:-}"
+          else
+            printf "%s\\n" "${__line:-}"
+          fi
+
+          if [[ "${__line:-}" =~ (\<\/nav|\<\/code) ]]
+          then
+            _linkable=1
+          fi
+        done
+      } | {
+        # wrap [[wiki-style links]] in HTML links and add missing notebooks
+        sed -E                                                                                    \
+-e "/^${_ME}-linkable-${_ME}/ s/${_link_match_pattern}/${_replacement_pattern}/g"                 \
+-e "/^${_ME}-linkable-${_ME}/ s/${_labeled_link_match_pattern}/${_labeled_replacement_pattern}/g" \
+-e "/^${_ME}-linkable-${_ME}/ s/${_notebookless_pattern}/${_notebookless_replacement_pattern}/g"
+      } | {
+        LC_ALL=C sed -E -e "s/^${_ME}-linkable-${_ME}//g"
+      }
+    else
+      local __match=
+      for   __match in  $(_resolve_links_get_matches  \
+                          "\[\[[^\[]+\]\]"            \
+                          "${_input_temp_file_path}")
+      do
+        local _link=
+        local _link_label=
+
+        [[ -z "${__match:-}" ]] && continue
+
+        local _selector="${__match#[[}"
+
+        if [[ "${__match}" =~ \| ]]
+        then
+          _selector="${_selector%%|*}"
+
+          _link_label="${__match##*|}"
+          _link_label="${_link_label%]]}"
+        else
+          _selector="${_selector%]]}"
+          _link_label="${_selector}"
+        fi
+
+        if ((_for_browsing))
+        then
+          if [[ -z "${_selector:-}" ]]
+          then
+            _link="${__match}"
+          else
+            local _link_notebook_name=
+            local _query_selector=
+
+            if [[ "${_selector:-}" =~ : ]] && [[ ! "${_selector:-}" =~ :// ]]
+            then
+              _link_notebook_name="${_selector%%:*}"
+              _query_selector="${_selector}"
+            else
+              _link_notebook_name="${_notebook_name}"
+              _query_selector="${_link_notebook_name}:${_selector}"
+            fi
+
+            local _selector_path=
+            _selector_path="$(_selector_resolve_path "${_query_selector:-}")"
+
+            local _id_selector=
+            _id_selector="$(
+              _get_id_selector "${_link_notebook_name}:${_selector_path}" 2>/dev/null || :
+            )"
+
+            if [[ -n "${_selector#*:}" ]] && [[ -z "${_selector_path:-}" ]]
+            then
+              _link="[[${_selector:-}]]"
+            else
+              local _target_url="//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_id_selector}${_url_params_pattern:-}"
+
+              case "${_input_type:-}" in
+                html)
+                  _link="<a href=\"${_target_url//' '/%20}\">[[${_link_label:-}]]</a>"
+                  ;;
+                org)
+                  _link="[[${_target_url:-}][[[${_link_label:-}]]]]"
+                  ;;
+                *)
+                  _link="[[${_selector:-}]]"
+                  ;;
+              esac
+            fi
+          fi
+        else
+          local _link_path=
+          _link_path="$(_show "${_selector}" --path 2>/dev/null || :)"
+
+          if [[ -z "${_link_path:-}" ]]
+          then
+            _link="[[${_selector}]]"
+          else
+            case "${_input_type:-}" in
+              html)
+                _link="<a href=\"file://${_link_path//' '/%20}\">[[${_link_label:-}]]</a>"
+                ;;
+              org)
+                _link="[[file://${_link_path//' '/%20}][[[${_link_label:-}]]]]"
+                ;;
+              *)
+                _link="[[${_selector:-}]]"
+                ;;
+            esac
+          fi
+        fi
+
+        local _escaped_match="${__match//${_SLASH}/\\/}"
+        _escaped_match="${_escaped_match//\[/\\[}"
+        _escaped_match="${_escaped_match//\]/\\]}"
+        _escaped_match="${_escaped_match//\(/\(}"
+        _escaped_match="${_escaped_match//\)/\)}"
+
+        local _escaped_replacement="${_link//${_SLASH}/\\/}"
+        _escaped_replacement="${_escaped_replacement//\[/\\[}"
+        _escaped_replacement="${_escaped_replacement//\]/\\]}"
+        _escaped_replacement="${_escaped_replacement//\(/\(}"
+        _escaped_replacement="${_escaped_replacement//\)/\)}"
+
+        if [[ -n "${_escaped_match:-}"        ]] &&
+           [[ -n "${_escaped_replacement:-}"  ]] &&
+           ! _contains "${_escaped_match}" "${_seen_matches[@]:-}"
+        then
+          _sed_arguments+=("-e" "s/${_escaped_match}/${_escaped_replacement}/g")
+          _seen_matches+=("${_escaped_match}")
+        fi
+      done
+
+      LC_ALL=C sed "${_sed_arguments[@]:-}"
+    fi
+  } | {
+    # rewrite outbound links to use an exit page
+
+    if ! ((_for_browsing))
+    then
+      cat
+    else
+      local _outbound_url_pattern=
+
+      case "${_input_type:-}" in
+        org)  _outbound_url_pattern="\[\[https?://[^]]+"      ;;
+        html) _outbound_url_pattern="href=\"https?://[^\"]+"  ;;
+      esac
+
+      local _sed_arguments=()
+      local _seen_matches=()
+
+      local __match=
+      for   __match in  $(_resolve_links_get_matches    \
+                          "${_outbound_url_pattern:-}"  \
+                          "${_input_temp_file_path}")
+      do
+        [[ -z "${__match:-}" ]] && continue
+
+        if [[ "${__match}" =~ https?://${NB_SERVER_HOST} ]]
+        then
+          continue
+        fi
+
+        case "${_input_type:-}" in
+          org)  local _target_url="${__match#\[\[}"     ;;
+          html) local _target_url="${__match#href=\"}"  ;;
+        esac
+
+        # NOTE: skip _get_uri() for performance
+        # use ${_SLASH} for macOS bash support
+
+        local _encoding="${_target_url//'%'/%25}"
+        _encoding="${_encoding//' '/%20}"
+        _encoding="${_encoding//'"'/%22}"
+        _encoding="${_encoding//'#'/%23}"
+        _encoding="${_encoding//'$'/%24}"
+        _encoding="${_encoding//'&'/%26}"
+        _encoding="${_encoding//'+'/%2B}"
+        _encoding="${_encoding//','/%2C}"
+        _encoding="${_encoding//${_SLASH}/%2F}"
+        _encoding="${_encoding//':'/%3A}"
+        _encoding="${_encoding//';'/%3B}"
+        _encoding="${_encoding//'='/%3D}"
+        _encoding="${_encoding//'?'/%3F}"
+        _encoding="${_encoding//'@'/%40}"
+        _encoding="${_encoding//'['/%5B}"
+        local _encoded_url="${_encoding//']'/%5D}"
+
+        local _replacement_url="//${NB_SERVER_HOST}:${NB_SERVER_PORT}?url=${_encoded_url}"
+        local _replacement="${_replacement_url}"
+
+        case "${_input_type:-}" in
+          org)
+            if [[ "${__match:-}" =~ ^\[\[ ]]
+            then
+              _replacement="[[${_replacement}"
+            fi
+            ;;
+          html)
+            _replacement="href=\"${_replacement}"
+            ;;
+        esac
+
+        local _escaped_match="${__match//${_SLASH}/\\/}"
+        _escaped_match="${_escaped_match//\[/\\[}"
+        _escaped_match="${_escaped_match//\]/\\]}"
+        _escaped_match="${_escaped_match//\(/\(}"
+        _escaped_match="${_escaped_match//\)/\)}"
+
+        local _escaped_replacement="${_replacement//${_SLASH}/\\/}"
+        _escaped_replacement="${_escaped_replacement//\[/\\[}"
+        _escaped_replacement="${_escaped_replacement//\]/\\]}"
+        _escaped_replacement="${_escaped_replacement//\(/\(}"
+        _escaped_replacement="${_escaped_replacement//\)/\)}"
+
+        if [[ -n "${_escaped_match:-}"        ]] &&
+           [[ -n "${_escaped_replacement:-}"  ]] &&
+           ! _contains "${_escaped_match}" "${_seen_matches[@]:-}"
+        then
+          _sed_arguments+=("-e" "s/${_escaped_match}/${_escaped_replacement}/g")
+          _seen_matches+=("${_escaped_match}")
+        fi
+      done
+
+      LC_ALL=C sed "${_sed_arguments[@]:-}"
+    fi
+  }
+}
+
+# _web_browser()
+#
+# Usage:
+#   _web_browser [[<url>] [--dump] | --check]
+#
+# Options:
+#   --check   Return with status 0 if a browser is available, or 1 if not.
+#   --dump    Print the page to standard output.
+#
+# Description:
+#   Interact with the preferred or available terminal web browser. When called
+#   with no input or arguments, or with only the --check option, test if a
+#   terminal web browser is available. With <url> or standard input, view in
+#   the preferred or available browser.
+#
+# Exit / Error / Return Status:
+#   0 (success, true)  If a terminal browser is available.
+#   1 (error,  false)  if not.
+_web_browser() {
+  local _arguments=()
+  local _check=0
+  local _check_gui=0
+  local _dump=0
+  local _url=
+  local _web_browser_command=()
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      --check)
+        _check=1
+        ;;
+      --dump|--print)
+        _dump=1
+        ;;
+      --gui)
+        _check_gui=1
+        ;;
+      *)
+        [[ -z "${_url:-}" ]] && _url="${__arg}"
+        ;;
+    esac
+  done
+
+  if [[ -n "${BROWSER:-}" ]]
+  then
+    _web_browser_command=("${BROWSER}")
+  else
+    if _command_exists "w3m"
+    then
+      _web_browser_command+=("w3m")
+    elif _command_exists "links"
+    then
+      _web_browser_command+=("links")
+    fi
+  fi
+
+  # checks
+
+  if [[ -z "${_web_browser_command[*]:-}" ]]
+  then
+    _warn cat <<HEREDOC
+Web browser not found. Try \`w3m\`: $(_color_primary "http://w3m.sourceforge.net")
+HEREDOC
+    exit 1
+  fi
+
+  if ((_check_gui))
+  then
+    shopt -s nocasematch
+
+    if [[ "${_web_browser_command[*]}" =~ (firefox|chrom|brave|edg) ]]
+    then
+      return 0
+    else
+      return 1
+    fi
+
+    shopt -u nocasematch
+  fi
+
+  if ((_check))
+  then
+    if ((_dump)) && [[ -n "${_web_browser_command[*]:-}" ]]
+    then
+      printf "%s\\n" "${_web_browser_command[*]:-}"
+    fi
+
+    return 0
+  fi
+
+  # behaviors
+
+  if ! _piped_input && [[ -z "${_url:-}"        ]]
+  then
+    return 0
+  else
+    if [[ "${_web_browser_command[*]:-}" =~ w3m ]]
+    then
+      _web_browser_command+=("-I" "UTF-8")
+      _web_browser_command+=("-O" "UTF-8")
+
+      if [[ -n "${_url:-}" ]]
+      then
+        _web_browser_command+=("${_url:-}")
+      fi
+
+      if ((_dump))
+      then
+        "${_web_browser_command[@]:-}" -T text/html -dump
+      else
+        "${_web_browser_command[@]:-}" -T text/html
+      fi
+
+      return 0
+    elif [[ "${_web_browser_command[*]:-}" =~ lynx    ]]
+    then
+      ((_dump)) && _arguments+=("-dump")
+
+      if [[ -n "${_url:-}" ]]
+      then
+        _arguments+=("${_url:-}")
+      else
+        _arguments+=("-stdin")
+      fi
+
+      _arguments+=("-nomargins")
+      _arguments+=("-noreferer")
+      _arguments+=("-notitle")
+
+      "${_web_browser_command[@]:-}" "${_arguments[@]:-}"
+
+      return 0
+    elif [[ "${_web_browser_command[*]:-}" =~ links   ]]
+    then
+      ((_dump)) && _arguments+=("-dump")
+
+      if [[ ! "${_web_browser_command[*]}" =~ elinks  ]]
+      then # links
+        _arguments+=("-html-assume-codepage" "Unicode UTF-8")
+      fi
+
+      if [[ -n "${_url:-}" ]]
+      then
+        _arguments+=("${_url:-}")
+      fi
+
+      "${_web_browser_command[@]:-}" "${_arguments[@]:-}"
+    else
+      if [[ -n "${_url:-}" ]]
+      then
+        _web_browser_command+=("${_url:-}")
+      fi
+
+      "${_web_browser_command[@]}"
+
+      return 0
+    fi
+  fi
+}
+
+###############################################################################
+# Subcommands: Group 2                                     Subcommands: Group 2
+# --------------------                                     --------------------
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+# add ##################################################################### add
+
+_describe_add() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} add [<notebook>:][<folder-path>/][<filename>] [<content>]
+         [-b | --browse] [-c <content> | --content <content>] [--edit]
+         [-e | --encrypt] [-f <filename> | --filename <filename>]
+         [--folder <folder-path>] [--tags <tag1>,<tag2>...]
+         [-t <title> | --title <title>] [--type <type>]
+  ${_ME} add bookmark [<bookmark-options>...]
+  ${_ME} add folder [<name>]
+  ${_ME} add todo [<todo-options>...]
+
+$(_color_primary "Options"):
+  -b, --browse                Add using a terminal or GUI web browser.
+  -c, --content <content>     The content for the new note.
+  --edit                      Open the note in the editor before saving when
+                              content is piped or passed as an argument.
+  -e, --encrypt               Encrypt the note with a password.
+  -f, --filename <filename>   The filename for the new note.
+  --folder <folder-path>      Add within the folder located at <folder-path>.
+  --tags <tag1>,<tag2>...     A comma-separated list of tags.
+  -t, --title <title>         The title for a new note. If \`--title\` is
+                              present, the filename is derived from the
+                              title, unless \`--filename\` is specified.
+  --type <type>               The file type for the new note, as a file
+                              extension.
+
+$(_color_primary "Description"):
+  Create a new note or folder.
+
+  If no arguments are passed, a new blank note file is opened with \`\$EDITOR\`,
+  currently set to: ${EDITOR}
+
+  If a non-option argument is passed, \`${_ME}\` will treat it as a <filename≥
+  if a file extension is found. If no file extension is found,  \`${_ME}\` will
+  treat the string as <content> and will create a new note without opening the
+  editor. \`${_ME} add\` can also create a new note with piped content.
+
+  \`${_ME}\` creates Markdown files by default. To create a note with a
+  different file type, use the extension in the filename or use the \`--type\`
+  option. To change the default file type, use \`${_ME} set default_extension\`.
+
+  When the \`-e\` / \`--encrypt\` option is used, \`${_ME}\` will encrypt the
+  note with AES-256 using OpenSSL by default, or GPG, if configured in
+  \`${_ME} set encryption_tool\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#adding
+
+$(_color_primary "See Also"):
+  ${_ME} help bookmark
+  ${_ME} help browse
+  ${_ME} help delete
+  ${_ME} help edit
+  ${_ME} help folders
+  ${_ME} help import
+  ${_ME} help show
+  ${_ME} help todo
+
+$(_color_primary "Examples"):
+  ${_ME} add
+  ${_ME} add example.md
+  ${_ME} add "Note content."
+  ${_ME} add example.md --title "Example Title" --content "Example content."
+  echo "Note content." | ${_ME} add
+  ${_ME} add -t "Secret Document" --encrypt
+  ${_ME} add example/document.md
+  ${_ME} add folder sample/demo
+  ${_ME} example:add
+  ${_ME} example:add -t "Title"
+  ${_ME} a
+  ${_ME} a "Note content."
+  ${_ME} example:a
+  ${_ME} example:a -t "Title"
+
+$(_color_primary "Aliases"):
+  ${_ME} create
+  ${_ME} new
+
+$(_color_primary "Shortcut Aliases"):
+  ${_ME} a
+  ${_ME} +
+HEREDOC
+}
+_add() {
+  local _add_type=
+  local _arguments=()
+  local _browse=0
+  local _defer_arguments=()
+  local _edit_before_commit=0
+  local _encrypt=0
+  local _file_type="${NB_DEFAULT_EXTENSION}"
+  local _folder_prompt=0
+  local _option_content=
+  local _option_folder_relative_path=
+  local _option_relative_path=
+  local _password=
+  local _skip_standard_input=0
+  local _tag_list=
+  local _title=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -b|-br|--browse)
+        _browse=1
+        ;;
+      -c|--content)
+        if [[ -z "${2:-}"                   ]]
+        then
+          _exit_1 printf                          \
+            "%s requires a valid argument.\\n"    \
+            "$(_color_primary "${1:-}")"
+        else
+          if [[ -n "${_option_content:-}"   ]]
+          then
+            _option_content+="${_NEWLINE}${_NEWLINE}"
+          fi
+
+          _option_content+="$(printf "%s\\n" "${2:-}")"
+          _defer_arguments+=("${1}" "${2:-}")
+
+          shift
+        fi
+        ;;
+      --edit)
+        _edit_before_commit=1
+        ;;
+      -e|--encrypt*)
+        if [[ -z "${NB_ENCRYPTION_TOOL:-}"  ]]  ||
+           ! _command_exists "${NB_ENCRYPTION_TOOL:-}"
+        then
+          _exit_1 printf                        \
+            "Encryption tool not found: %s\\n"  \
+            "$(_color_primary "${NB_ENCRYPTION_TOOL:-}")"
+        else
+          _encrypt=1
+        fi
+        ;;
+      -f|--file*|--*path|--target*)
+        _option_relative_path="$(_option_get_value "${1}" "${2:-}")"
+        _defer_arguments+=("${1}" "${2:-}")
+
+        shift
+        ;;
+      --folder)
+        _option_folder_relative_path="$(
+          _option_get_value "${1}" "${2:-}" | sed -e 's/\/$//'
+        )"
+        _defer_arguments+=("${1}" "${_option_folder_relative_path:-}")
+
+        shift
+        ;;
+      --folder*prompt)
+        _folder_prompt=1
+        ;;
+      --no*color)
+        _COLOR_ENABLED=0
+        ;;
+      --password)
+        _password="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --skip*standard*input)
+        _skip_standard_input=1
+        ;;
+      --tag*)
+        [[ -n "${_tag_list:-}" ]] && _tag_list+=" "
+        _tag_list+="$(_option_get_tags "${1}" "${2:-}")"
+        _defer_arguments+=("${1}" "${2:-}")
+
+        shift
+        ;;
+      -t|--title|--name)
+        # TODO: Detect tag list for dynamic -t for --titles and --tags?
+        _title="$(_option_get_value "${1}" "${2:-}")"
+        _defer_arguments+=("${1}" "${2:-}")
+
+        shift
+        ;;
+      --type)
+        _file_type="$(_option_get_value "${1}" "${2:-}")"
+        _defer_arguments+=("${1}" "${2:-}")
+
+        shift
+        ;;
+      bookmark)
+        _add_type="bookmark"
+        ;;
+      folder|folders|directory)
+        _file_type="folder"
+        _defer_arguments+=("${1}")
+        ;;
+      todo)
+        _add_type="todo"
+        ;;
+      *)
+        _arguments+=("${1:-}")
+        ;;
+    esac
+
+    shift
+  done
+
+  case "${_add_type:-}" in
+    bookmark)
+      _defer "_bookmark"    "${_arguments[@]:-}" "${_defer_arguments[@]:-}"
+
+      return 0
+      ;;
+    todo)
+      _defer "_todo" "add"  "${_arguments[@]:-}" "${_defer_arguments[@]:-}"
+
+      return 0
+      ;;
+  esac
+
+  if ((_browse))
+  then
+    _defer "_browse" "add"  "${_arguments[@]:-}" "${_defer_arguments[@]:-}"
+
+    return 0
+  fi
+
+  local _common_tlds_excluding_text_file_extensions=(
+    app agency au com company biz blog buzz ca cloud club de design dev cf ch
+    cn edu email es fr fun ga gov guru icu info it jp link life live ly media
+    mil net new nl no online nyc page rocks ru se shop site solutions space
+    store tech top tk tv uk us vip wang website work xyz
+  )
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  local _selector_content=
+  local _selector_filename=
+  local _selector_folder_relative_path=
+
+  local i=
+  for ((i=0; i < ${#_arguments[@]}; i++))
+  do
+    local _argument_content=
+
+    if [[ -n "${_arguments[i]:-}"         ]]
+    then # argument is not blank
+      if [[ -z "${_selector_content:-}"   ]]  &&
+         [[ -n "${_selector_filename:-}"  ]]
+      then # argument #2 and the first argument was a selector with filename
+        _argument_content+="${_arguments[i]:-}"
+      else
+        local _content_or_filename_extension=
+        local _selector_notebook_path=
+        local _selector_relative_path="${_arguments[i]}"
+
+        if [[ "${_arguments[i]:-}" =~ \.[A-Za-z0-9]+$ ]]
+        then # argument appears to be a file extension
+          _content_or_filename_extension="${_arguments[i]##*\.}"
+        fi
+
+        if _string_is_url    "${_arguments[i]:-}"           ||
+           _string_is_email  "${_arguments[i]:-}"           ||
+           _contains "${_content_or_filename_extension:-}"  \
+                     "${_common_tlds_excluding_text_file_extensions[@]}"
+        then # argument contains content
+          _argument_content+="${_arguments[i]:-} "
+        else
+          if [[ "${_arguments[i]}" =~ (:|^/)                ]]
+          then
+            if [[ -n "${_selector_filename:-}"              ]] ||
+               [[ -n "${_selector_folder_relative_path:-}"  ]]
+            then
+              _argument_content+="${_arguments[i]:-} "
+            else
+              _selector_notebook_path="$(
+                _notebook show "${_arguments[i]%%:*}" --path 2>/dev/null || :
+              )"
+
+              if [[ -n "${_selector_notebook_path}"         ]]
+              then # argument is a selector with a valid notebook
+                _notebook_path="${_selector_notebook_path}"
+
+                if [[ "${_arguments[i]:-}" =~ ^/            ]]
+                then
+                  _selector_relative_path="${_arguments[i]#${_notebook_path}/}"
+                else
+                  _selector_relative_path="${_arguments[i]#*:}"
+                fi
+              else # argument is not a selector
+                _argument_content+="${_arguments[i]:-} "
+              fi
+            fi
+          fi
+
+          if [[ -z "${_argument_content:-}"                 ]]
+          then # still a candidate selector
+            if [[ "${_selector_relative_path:-}" =~ /       ]] &&
+               [[ -z "${_selector_folder_relative_path:-}"  ]]
+            then # argument appears to contain a relative path
+              _selector_folder_relative_path="${_selector_relative_path%\/*}"
+            fi
+
+            if [[ -z "${_option_relative_path}"                     ]]  &&
+               [[ -z "${_selector_filename}"                        ]]  &&
+               {
+                 _contains "${_file_type:-}" "folder" "directory"       ||
+                 [[ "${_arguments[i]:-}" =~ (\.[A-Za-z0-9]+$|/|:)   ]]
+               }
+            then
+              _selector_filename="${_selector_relative_path##*\/}"
+            elif [[ -n "${_selector_content:-}"             ]]
+            then
+              _argument_content+="${_arguments[i]:-} "
+            elif [[ !   "${_selector_relative_path}" =~ /$  ]] &&
+                 [[ -z  "${_selector_notebook_path:-}"      ]]
+            then
+              _selector_folder_relative_path=""
+              _argument_content+="${_arguments[i]:-} "
+            fi
+          fi
+        fi
+      fi
+    fi
+
+    if [[ -n "${_argument_content:-}" ]]
+    then
+      _selector_content+="${_argument_content}"
+    fi
+  done
+
+  if [[ -n "${_selector_content:-}"   ]]
+  then
+    _selector_content="${_selector_content%\ }"
+  fi
+
+  # Filename
+  # --------
+
+  local _target_filename=
+
+  if [[ -n "${_option_relative_path:-}"   ]]
+  then
+    _target_filename="${_option_relative_path##*\/}"
+  elif [[ -n "${_selector_filename:-}"    ]]
+  then
+    _target_filename="${_selector_filename:-}"
+  fi
+
+  if [[ -z "${_target_filename:-}"        ]] &&
+     [[ -z "${_option_relative_path:-}"   ]]
+  then
+    if [[ -n "${_title:-}" ]] &&
+       ! _contains "${_file_type:-}" "folder" "directory"
+    then
+      _target_filename="$(
+        printf "%s" "${_title}"           \
+          | tr '[:upper:]' '[:lower:]'    \
+          | tr '[:space:]:*/\\<>?|' '_'   \
+          | tr "\"" '_'
+      )"
+    fi
+
+    if [[ -n "${_file_type}"              ]] &&
+       [[ "${_file_type:-}" != "folder"   ]]
+    then
+      # NOTE: ${_target_filename} can be blank, resulting in '.type'
+      _target_filename="${_target_filename:-}.${_file_type}"
+    elif [[ "${_file_type:-}" == "folder" ]] &&
+         [[ -z "${_target_filename:-}"    ]]
+    then
+      _target_filename="folder"
+    fi
+  fi
+
+  # Folder
+  # ------
+
+  local _target_folder_relative_path=
+
+  if [[ "${_option_relative_path}" =~ /           ]]
+  then
+    _target_folder_relative_path="${_option_relative_path%%\/*}"
+  fi
+
+  if [[ -n "${_option_folder_relative_path:-}"    ]]
+  then
+    _target_folder_relative_path="${_option_folder_relative_path}/${_target_folder_relative_path:-}"
+  fi
+
+  if [[ -n "${_selector_folder_relative_path:-}"  ]]
+  then
+    _resolved_selector_folder_relative_path="$(
+      _selector_resolve_folders               \
+        "${_selector_folder_relative_path}/"  \
+        --build || :
+    )"
+
+    if [[ -n "${_resolved_selector_folder_relative_path:-}" ]]
+    then
+      _target_folder_relative_path="${_resolved_selector_folder_relative_path:-}/${_target_folder_relative_path}"
+    fi
+  fi
+
+  _target_folder_relative_path="${_target_folder_relative_path%/}"
+
+  # Target
+  # ------
+
+  local _target_relative_path="${_target_folder_relative_path:-}/${_target_filename:-}"
+  _target_relative_path="${_target_relative_path#/}"
+
+  local _target_unique_relative_path=
+
+  if [[     "${_target_relative_path}" =~ ^\..* ]] &&
+     [[ -n  "${_option_relative_path:-}"        ]]
+  then
+    local _target_unique_path=
+    _target_unique_path="$(
+      _get_unique_path "${_notebook_path}/${_target_relative_path}"
+    )"
+
+    _target_unique_relative_path="${_target_unique_path#"${_notebook_path}"/}"
+  else
+    _target_unique_relative_path="$(
+      _notebooks current --filename "${_target_relative_path}"
+    )"
+  fi
+
+  local _target_basename=
+  _target_basename="$(basename "${_target_unique_relative_path}")"
+
+  local _target_path="${_notebook_path}/${_target_unique_relative_path}"
+
+  if _contains "${_file_type:-}" "folder" "directory"
+  then
+    if ! mkdir -p "${_target_path:?}" 2>/dev/null
+    then
+      _exit_1 printf "Unable to create folder: %s\\n"       \
+        "$(_color_primary "${_target_unique_relative_path}")"
+    fi
+
+    touch "${_target_path:?}/.index"
+
+    if [[ -n "${_target_folder_relative_path:-}" ]]
+    then
+      _index reconcile                                      \
+        "${_notebook_path}/${_target_folder_relative_path}" \
+        --ancestors
+    fi
+  else
+    if ((_encrypt))
+    then
+      if [[ -z "${_password}"                   ]] &&
+         [[ "${NB_ENCRYPTION_TOOL:-}" != "age"  ]]
+      then
+        # request password without displaying it
+        printf "%s: " "$(_color_primary "Password")"
+
+        local _password=
+        IFS='' read -r -e -d $'\n' -s _password </dev/tty
+        printf "\\n" # print newline to stop `read`
+
+        if [[ -z "${_password:-}"               ]]
+        then
+          _exit_1 printf "Password required.\\n"
+        fi
+
+        local _password_confirmation=
+
+        # request password without displaying it
+        printf "%s: " "$(_color_primary "Confirm Password")"
+
+        local _password_confirmation=
+        IFS='' read -r -e -d $'\n' -s _password_confirmation </dev/tty
+        printf "\\n" # print newline to stop `read`
+
+        if [[ "${_password}" != "${_password_confirmation}" ]]
+        then
+          _exit_1 printf "Password mismatch.\\n"
+        fi
+      fi
+
+      if [[ -n "${_target_folder_relative_path:-}"  ]]
+      then
+        if ! mkdir -p "$(_temp directory)/${_target_folder_relative_path}" 2>/dev/null
+        then
+          _exit_1 printf "Unable to create temporary folder: %s\\n" \
+            "$(_color_primary "$(_temp directory)/${_target_folder_relative_path}")"
+        fi
+      fi
+
+      _target_path="$(_temp directory)/${_target_unique_relative_path}"
+    fi
+
+    if [[ -n "${_target_folder_relative_path:-}"                      ]] &&
+       [[ ! -d "${_notebook_path}/${_target_folder_relative_path:-}"  ]]
+    then
+      if [[ -e "${_notebook_path}/${_target_folder_relative_path:-}"  ]]
+      then
+        _exit_1 printf "File exists at: %s\\n"  \
+          "$(_color_primary "${_target_folder_relative_path:-}")"
+      else
+        if ((_folder_prompt))
+        then
+          local _target_folder_selector="${_target_folder_relative_path:-}/"
+
+          if _notebooks current --selected
+          then
+            _target_folder_selector="$(_notebooks current --name):${_target_folder_selector}"
+          fi
+
+          printf "Creating new folder: %s\\n"   \
+            "$(_color_primary "${_target_folder_selector}")"
+
+          while true
+          do
+            local __yn=
+            IFS='' read -r -e -d $'\n' -p       \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+            case "${__yn}" in
+              [Yy]*)
+                break
+                ;;
+              *)
+                printf "Exiting...\\n"
+
+                exit 0
+                ;;
+            esac
+          done
+        fi
+
+        if ! mkdir -p "${_notebook_path:?}/${_target_folder_relative_path}" 2>/dev/null
+        then
+          _exit_1 printf "Unable to create folder: %s\\n" \
+            "$(_color_primary "${_target_folder_relative_path}")"
+        fi
+      fi
+    fi
+
+    if [[ -n "${_title}"                  ]]
+    then
+      if [[ "${_target_path:-}" =~ .org$  ]]
+      then
+        local _title_prefix="#+TITLE:"
+      else
+        local _title_prefix="#"
+      fi
+
+      printf "%s\\n\\n" "${_title_prefix} ${_title}" >> "${_target_path}"
+    fi
+
+    local _print_spacing=0
+
+    if [[ -n "${_tag_list:-}"             ]]
+    then
+      printf "%s\\n" "${_tag_list}" >> "${_target_path}"
+      _print_spacing=1
+    fi
+
+    if [[ -n "${_selector_content:-}"     ]]
+    then # argument content
+      ((_print_spacing)) && printf "\\n"    >> "${_target_path}"
+
+      printf "%s\\n" "${_selector_content}" >> "${_target_path}"
+      _print_spacing=1
+    fi
+
+    if [[ -n "${_option_content:-}"       ]]
+    then # argument content
+      ((_print_spacing)) && printf "\\n"  >> "${_target_path}"
+
+      printf "%s\\n" "${_option_content}" >> "${_target_path}"
+      _print_spacing=1
+    fi
+
+    if _piped_input && ! ((_skip_standard_input))
+    then # piped input
+      ((_print_spacing)) &&
+        printf "\\n"  >> "${_target_path}"
+
+      cat             >> "${_target_path}"
+    fi
+
+    if ((_edit_before_commit))                ||
+       {
+         ! _piped_input                       &&
+         [[ -z "${_selector_content:-}"   ]]  &&
+         [[ -z "${_option_content:-}"     ]]
+       }
+    then
+      _edit_file "${_target_path}"
+    fi
+
+    # walk up and delete empty directories when file not created
+    if [[ ! -e "${_target_path:?}"                                    ]] &&
+       [[   -n "${_target_folder_relative_path:-}"                    ]] &&
+       [[   -e "${_notebook_path:?}/${_target_folder_relative_path}"  ]]
+    then
+      cd "${_notebook_path:?}/${_target_folder_relative_path:?}"
+
+      while [[ "${PWD:?}" =~ ^${_notebook_path:?}       ]] &&
+            [[ "${PWD:?}" != "${_notebook_path:?}"      ]] &&
+            [[ -z "$(find "${PWD}/." ! -name . -prune)" ]]
+      do
+        local _empty_directory_path="${PWD:?}"
+
+        cd ..
+
+        if [[ -d "${_empty_directory_path:?}"                             ]] &&
+           [[ -z "$(find "${_empty_directory_path}/." ! -name . -prune)"  ]]
+        then
+          rm -r "${_empty_directory_path:?}"
+        fi
+      done
+    fi
+
+    if ((_encrypt)) && [[ -e "${_target_path}" ]]
+    then
+      _target_basename="${_target_basename}.enc"
+
+      local _decrypted_path="${_target_path}"
+      local _encrypted_path="${_notebook_path}/${_target_unique_relative_path}.enc"
+
+      _encrypt_file           \
+        "${_decrypted_path}"  \
+        "${_encrypted_path}"  \
+        --password "${_password}"
+
+      if [[ -n "${_decrypted_path}" ]] && [[ -e "${_decrypted_path}" ]]
+      then
+        rm "${_decrypted_path:?}"
+      fi
+
+      _target_unique_relative_path="${_target_unique_relative_path}.enc"
+      _target_path="${_encrypted_path}"
+    fi
+  fi
+
+  if [[ -e "${_target_path}"              ]]
+  then
+    if [[ ! "${_target_path##*/}" =~ ^\.  ]]
+    then
+      _index add                          \
+        "${_target_basename}"             \
+        "${_notebook_path:?}/${_target_folder_relative_path:-}"
+    fi && _git checkpoint                 \
+      "${_notebook_path}"                 \
+      "[${_ME}] Add: ${_target_unique_relative_path}"
+
+    local _info=
+    _info="$(
+      _show "${_notebook_path:?}/${_target_unique_relative_path:?}" --info-line
+    )"
+
+    printf "Added: %s\\n" "${_info}"
+  fi
+}
+_alias_subcommand "add" "+"
+_alias_subcommand "add" "a"
+_alias_subcommand "add" "create"
+_alias_subcommand "add" "new"
+
+# bookmark ########################################################### bookmark
+
+_describe_bookmark() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} bookmark [<ls-options>...]
+  ${_ME} bookmark [<notebook>:][<folder-path>/] <url>
+              [-c <comment> | --comment <comment>] [--edit] [-e | --encrypt]
+              [-f <filename> | --filename <filename>] [--no-request]
+              [-q <quote> | --quote <quote>] [--save-source]
+              [-r (<url> | <selector>) | --related (<url> | <selector>)]...
+              [-t <tag1>,<tag2>... | --tags <tag1>,<tag2>...] [--title <title>]
+  ${_ME} bookmark list [<list-options>...]
+  ${_ME} bookmark (edit | delete | open | peek | url)
+              ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} bookmark search <query>
+
+$(_color_primary "Options"):
+  -c, --comment <comment>      A comment or description for this bookmark.
+  --edit                       Open the bookmark in your editor before saving.
+  -e, --encrypt                Encrypt the bookmark with a password.
+  -f, --filename <filename>    The filename for the bookmark. It is
+                               recommended to omit the extension so the
+                               default bookmark extension is used.
+  --no-request                 Don't request or download the target page.
+  -q, --quote <quote>          A quote or excerpt from the saved page.
+                               Alias: \`--excerpt\`
+  -r, --related <selector>     A selector for an item related to the
+                               bookmarked page.
+  -r, --related <url>          A URL for a page related to the bookmarked page.
+                               Multiple \`--related\` flags can be used in a
+                               command to save multiple related URLs and
+                               selectors.
+  --save-source                Save the page source as HTML.
+  -t, --tags <tag1>,<tag2>...  A comma-separated list of tags.
+  --title <title>              The bookmark title. When not specified,
+                               \`${_ME}\` will use the html <title> tag.
+
+$(_color_primary "Subcommands"):
+  (default)  Add a new bookmark for <url>, or list bookmarks.
+             Bookmarks can also be added with \`${_ME} <url>\`
+  delete     Delete a bookmark.
+  edit       Edit a bookmark.
+  list       List bookmarks in the current notebook.
+             Shortcut Alias: \`ls\`
+  open       Open the bookmarked page in your system's primary web browser.
+             Shortcut Alias: \`o\`
+  peek       Open the bookmarked page in your terminal web browser.
+             Alias: \`preview\`
+             Shortcut Alias: \`p\`
+  search     Search bookmarks for <query>.
+             Shortcut Alias: \`q\`
+  url        Print the URL for the specified bookmark.
+
+$(_color_primary "Description"):
+  Create, view, search, edit, and delete bookmarks.
+
+  By default, the html page content is saved within the bookmark, making the
+  bookmarked page available for full-text search. When Pandoc [1] is
+  installed, the HTML content is converted to Markdown before saving.
+  When readability-cli [2] is install, markup is cleaned up to focus on
+  content.
+
+  \`peek\` opens the page in \`w3m\` [3] or \`links\` [4] when available.
+  To specify a preferred browser, set the \`\$BROWSER\` environment variable
+  in your .bashrc, .zshrc, or equivalent, e.g.: export BROWSER="links"
+
+  Bookmarks are identified by the \`.bookmark.md\` file extension. The
+  bookmark URL is the first URL in the file within "<" and ">" characters:
+
+    <https://www.example.com>
+
+    1. https://pandoc.org/
+    2. https://gitlab.com/gardenappl/readability-cli
+    3. https://en.wikipedia.org/wiki/W3m
+    4. https://en.wikipedia.org/wiki/Links_(web_browser)
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-bookmark
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help open
+  ${_ME} help peek
+  ${_ME} help show
+
+$(_color_primary "Examples"):
+  ${_ME} https://example.com
+  ${_ME} example: https://example.com
+  ${_ME} https://example.com --encrypt
+  ${_ME} https://example.com --tags example,sample,demo
+  ${_ME} https://example.com/about -c "Example comment."
+  ${_ME} https://example.com/faqs -f example-filename
+  ${_ME} https://example.com --quote "Example quote or excerpt."
+  ${_ME} bookmark list
+  ${_ME} bookmark search "example query"
+  ${_ME} bookmark open 5
+  ${_ME} bk
+
+$(_color_primary "Shortcut Aliases"):
+  ${_ME} bk
+  ${_ME} bm
+HEREDOC
+}
+_bookmark() {
+    # Usage: _bookmark_cleanup_tag_content <string>
+  _bookmark_cleanup_tag_content() {
+    local _character_removal_pattern=
+    _character_removal_pattern="$(
+      printf "\xE2\x80\xAA|\xE2\x80\xAB|\xE2\x80\xAC"
+    )"
+
+    # `awk` condenses and trims whitespace
+    # `sed` removes select unicode characters
+    # `w3m` converts HTML entities
+    printf "%s\\n" "${1:-}"                             \
+      | awk '$1=$1'                                     \
+      | sed -E -e "s/${_character_removal_pattern}//g"  \
+      | if _command_exists "w3m"
+        then
+           w3m -dump -T text/html -cols 99999
+         else
+           cat
+        fi
+  }
+
+  # Usage: _bookmark_view_in_terminal_browser (<url>)
+  _bookmark_view_in_terminal_browser() {
+    local _target_url="${1:-}"
+
+    if _web_browser --check
+    then
+      _web_browser "${_target_url}"
+
+      return 0
+    elif _command_exists "curl" || _command_exists "wget"
+    then
+      _download_from "${_target_url}"               \
+        | if _command_exists "pandoc"
+          then
+            _pandoc                                 \
+              --standard-input                      \
+              --from  html-native_divs-native_spans \
+              --to    markdown                      \
+              | _highlight_syntax_if_available "md"
+          else
+            cat
+          fi | _pager
+
+      return 0
+    else
+      _exit_1 printf "Terminal web browser not detected.\\n"
+    fi
+  }
+
+  local _arguments=()
+  local _bookmark_content=
+  local _comment=
+  local _edit_before_commit=0
+  local _encrypt=0
+  local _password=
+  local _quote=
+  local _readability_enabled=1
+  local _related_identifiers=()
+  local _request_page=1
+  local _save_source=0
+  local _selector=
+  local _skip_content=0
+  local _skip_folder_prompt=0
+  local _subcommand=
+  local _tag_list=
+  local _target_filename=
+  local _title=
+  local _url=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -c|--comment*)
+        _comment="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --download|--fetch|--online|--request)
+        _request_page=1
+        ;;
+      --edit)
+        _edit_before_commit=1
+        ;;
+      -e|--encrypt*)
+        _encrypt=1
+        ;;
+      -f|--filename)
+        _target_filename="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --no*download|--no*fetch|--no*request|--offline)
+        _request_page=0
+        ;;
+      --no*readab*|--skip*readab*)
+        _readability_enabled=0
+        ;;
+      --password)
+        _password="$(_option_get_value "${1}" "${2:-}")"
+        _arguments+=("${1:-}" "${2:-}")
+
+        shift
+        ;;
+      -q|--quote|--excerpt)
+        _quote="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      -r|--via|--also|--related)
+        _related_identifiers+=("$(_option_get_value "${1}" "${2:-}")")
+
+        shift
+        ;;
+      --save*source|--source|--save*html|--html|--raw*content|--raw*html)
+        _save_source=1
+        ;;
+      --skip*content|--no*content)
+        _skip_content=1
+        ;;
+      --skip*folder*prompt)
+        _skip_folder_prompt=1
+        ;;
+      -t|--tag*)
+        _tag_list="$(_option_get_tags "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --title)
+        _title="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      delete)
+        _delete "${2:-}" "${3:-}"
+
+        return 0
+        ;;
+      edit)
+        _edit "${2:-}"
+
+        return 0
+        ;;
+      help)
+        _help "bookmark"
+
+        return 0
+        ;;
+      ls|list)
+        _subcommand="list"
+        ;;
+      search|q)
+        _subcommand="search"
+        ;;
+      open|o|peek|p|preview|url)
+        if _option_value_is_present "${2:-}"
+        then
+          if [[ "${1}" =~ (^open$|^o$)  ]]
+          then
+            _subcommand="open"
+          elif [[ "${1}" =~ (^peek$|^p$|^preview$) ]]
+          then
+            _subcommand="peek"
+          elif [[ "${1}" == "url"       ]]
+          then
+            _subcommand="url"
+          fi
+
+          _selector="${2:-}"
+
+          shift
+        else
+          _exit_1                                     \
+            printf "%s requires a valid argument.\\n" \
+            "$(_color_primary "bookmark ${1}")"
+        fi
+        ;;
+      *)
+        if [[ ! "${_subcommand:-}"  =~ (^list$|^search$)  ]] &&
+           [[ -z "${_url:-}"                              ]] &&
+           _string_is_url "${1}"
+        then
+          _url="${1}"
+        elif [[ -z "${_subcommand:-}"                     ]] ||
+             [[ "${_subcommand}"    =~ (^list$|^search$)  ]]
+        then
+          _arguments+=("${1}")
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  # `bookmark list`
+
+  if [[ "${_subcommand}" == "list"  ]]
+  then
+    if [[ -n "${_arguments[*]:-}"   ]]
+    then
+      _list --bookmarks "${_arguments[@]}"
+
+      return 0
+    else
+      _list --bookmarks
+
+      return 0
+    fi
+  fi
+
+  # `bookmark search`
+
+  if [[ "${_subcommand}" == "search" ]]
+  then
+    _search --bookmarks "${_arguments[@]}"
+
+    return 0
+  fi
+
+  # `bookmark open`, `bookmark peek`, `bookmark url`
+
+  {
+    if [[ "${_subcommand}" =~ (^open$|^peek$|^url$) ]]
+    then
+      local _relative_path=
+      _relative_path="$(_show "${_selector}" --relative-path)"
+
+      local _notebook_path=
+      _notebook_path="$(_notebooks current --path)"
+
+      if [[ -z "${_relative_path}"                  ]]
+      then
+        if [[ "${_subcommand}" =~ (^open$|^peek$)   ]]
+        then
+          local _maybe_notebook="${_selector:-}"
+          _maybe_notebook="$(printf "%s\\n" "${_maybe_notebook}" | sed 's/\:$//')"
+
+          if [[ -d "${NB_DIR}/${_maybe_notebook}/.git" ]]
+          then
+            _notebooks "${_subcommand}" "${_maybe_notebook}" && return 0
+          fi
+        fi
+        _exit_1 printf "Not found: %s\\n" "$(_color_primary "${_selector}")"
+      fi
+
+      local _target_path="${_notebook_path}/${_relative_path}"
+
+      # handle non-bookmarks
+      if [[ "${_subcommand}" =~ (^open$|^peek$) ]]
+      then
+        if [[ "${_relative_path}" =~ \.html$  ]]
+        then
+          if [[ "${_subcommand}" == "open"  ]]
+          then
+            _open_in_gui_app "${_target_path:-}" && return 0
+          elif [[ "${_subcommand}" == "peek"  ]]
+          then
+            _bookmark_view_in_terminal_browser "file://${_target_path}"
+
+            return 0
+          fi
+        elif [[ ! "${_relative_path}" =~ .bookmark\.md$       ]] &&
+             [[ ! "${_relative_path}" =~ .bookmark\.md\.enc$  ]]
+        then
+          if [[ "${_subcommand}" == "open"    ]]
+          then
+            if [[ -d "${_target_path:-}"      ]] &&
+               _open_in_gui_app "${_target_path:-}"
+            then
+              return 0
+            elif [[ -n "${_password}"         ]]
+            then
+              _edit "${_selector}" --password "${_password}"
+            else
+              _edit "${_selector}"
+            fi
+          elif [[ "${_subcommand}" == "peek"  ]]
+          then
+            if [[ -n "${_password}"           ]]
+            then
+              _show "${_selector}" --password "${_password}"
+            else
+              _show "${_selector}"
+            fi
+          fi
+
+          return 0
+        fi
+      fi
+
+      local _target_url=
+      _target_url="$(_show "${_target_path}" --url "${_arguments[@]:-}")"
+
+      if [[ "${_subcommand}" == "url"           ]]
+      then
+        printf "%s\\n" "${_target_url}"
+
+        return 0
+      fi
+
+      if [[ "${_subcommand}" =~ (^open$|^peek$) ]]
+      then
+        local _check_wayback=0
+        local _http_error_codes=(
+          404 408 410 451 500 502 503 504 509 520 521 523 524 525 526
+        )
+        local _http_status=
+        _http_status="$(_get_http_status "${_target_url}")"
+
+        if _contains "${_http_status}" "${_http_error_codes[@]}"
+        then
+          printf "Page no longer available: %s\\n" \
+            "$(_color_primary "${_target_url}")"
+
+          while true
+          do
+            local __yn=
+            IFS='' read -r -e -d $'\n' -p \
+"Check the Wayback Machine for an archived version instead? $(_color_brackets "y/N") " __yn
+
+            case "${__yn}" in
+              [Yy]*)
+                _check_wayback=1
+
+                break
+                ;;
+              *)
+                break
+                ;;
+            esac
+          done
+        fi
+
+        if ((_check_wayback))
+        then
+          local _wayback_response=
+          _wayback_response="$(
+            _download_from                                                \
+              "https://archive.org/wayback/available?url=${_target_url}"  \
+              | grep --color=never 'closest'                              \
+              | sed -E "s/.*\"closest\": {([^}]+)}.*/\1/g"                \
+              | sed -E "s/.*\"url\": \"([^\"]+)\".*/\1/g" || printf ""
+          )"
+
+          if [[ -n "${_wayback_response:-}" ]]
+          then
+            _target_url="${_wayback_response}"
+          else
+            _exit_1 printf                  \
+              "No archived version available from the Wayback Machine.\\n"
+          fi
+        fi
+      fi
+
+      # `bookmark peek`
+      if [[   "${_subcommand}" == "peek"    ]]
+      then
+        _bookmark_view_in_terminal_browser "${_target_url}"
+
+        return 0
+      # `bookmark open`
+      elif [[ "${_subcommand}" == "open"    ]]
+      then
+        if _open_in_gui_app "${_target_url:-}"
+        then
+          return 0
+        else
+          _exit_1 printf                                          \
+            "%s doesn't know how to open URLs on this system.\\n" \
+            "$(_color_primary "${_ME}")"
+        fi
+      fi
+    fi
+  }
+
+  # `bookmark`
+
+  if [[   -z "${_url:-}"          ]]
+  then
+    if [[ -z "${_arguments[*]:-}" ]]
+    then
+      local _line_length=36
+      local _maybe_header_selector=
+
+      if _notebooks current --selected
+      then
+        _maybe_header_selector="$(
+          _notebooks show "$(_notebooks current)" --no-color --escaped
+        ): "
+
+        local _padded_header_selector_length=
+        _padded_header_selector_length="$(
+          _get_visible_length "${_maybe_header_selector}"
+        )"
+
+        _line_length="$((_line_length + _padded_header_selector_length))"
+      fi
+
+      local _header=
+      _header="Add: $(_color_primary "${_ME} ${_maybe_header_selector}<url>")"
+      _header="${_header} Help: $(_color_primary "${_ME} help bookmark")"
+
+      printf "%s\\n" "${_header}"
+      _print_line "$(printf "%-${_line_length}s" '.')"
+    fi
+
+    _bookmark list "${_arguments[@]:-}"
+
+    return 0
+  fi
+
+  # `bookmark <url>`
+
+  local _temp_file=
+  _temp_file="$(_temp file)"
+
+  local _download_url="${_url}"
+  _download_url="$(
+    printf "%s\\n" "${_download_url}"       \
+      | sed 's/https:\/\/twitter.com/https:\/\/mobile.twitter.com/g'
+  )"
+
+  local _relative_folder_path=
+  local _relative_path=
+
+  _relative_folder_path="$(
+    _selector_resolve_folders "${_arguments[0]:-}" --build || :
+  )"
+
+  if [[ -n "${_relative_folder_path:-}"     ]]
+  then
+    _relative_folder_path="${_relative_folder_path}/"
+  fi
+
+  if [[ -z "${_target_filename:-}"          ]]
+  then
+    _relative_path="$(
+      _notebooks current --filename         \
+        "${_relative_folder_path}$(date '+%Y%m%d%H%M%S').bookmark.md"
+    )"
+  else
+    if [[ "${_target_filename}" =~ \.       ]]
+    then
+      _relative_path="$(
+        _notebooks current --filename       \
+          "${_relative_folder_path}${_target_filename}")"
+    else
+      _relative_path="$(
+        _notebooks current --filename       \
+          "${_relative_folder_path}${_target_filename}.bookmark.md"
+      )"
+    fi
+  fi
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  local _duplicate_search_path="${_notebook_path}"
+
+  if [[ -n "${_relative_folder_path:-}"     ]]
+  then
+    _duplicate_search_path="${_notebook_path}/${_relative_folder_path}"
+  fi
+
+  if [[ -d "${_duplicate_search_path:-}"    ]]
+  then
+    local _grep_command=(
+      grep -s                         \
+        -e "^<${_download_url}>"      \
+        -e "^##"
+    )
+
+    if ((_GIT_ENABLED))
+    then
+      _grep_command=(
+        git -C "${_notebook_path:-}"  \
+          grep                        \
+          -e "^<${_download_url}>"    \
+          -e "^##"                    \
+          --no-heading                \
+          --color=never
+      )
+    elif _command_exists "rg"
+    then
+      _grep_command=(
+        rg                            \
+          --color never               \
+          --no-heading                \
+          --with-filename             \
+          -e "^##"                    \
+          -e "^<${_download_url}>"
+      )
+    fi
+
+    local _candidate_matches=()
+    _candidate_matches=($(
+      set +o noglob
+
+      "${_grep_command[@]:-}"                     \
+        "${_duplicate_search_path}/"*.bookmark.md \
+        2>/dev/null || :
+
+      set -o noglob
+    ))
+
+    local _duplicate_matches=()
+
+    if ((${#_candidate_matches[@]}))
+    then
+      local _current_filename=
+      local _include_match=1
+
+      local __candidate_match=
+      for   __candidate_match in "${_candidate_matches[@]:-}"
+      do
+        if [[ "${_current_filename:-}" != "${__candidate_match%%:*}"  ]]
+        then
+          _current_filename="${__candidate_match%%:*}"
+          _include_match=1
+        fi
+
+        if [[ "${__candidate_match#*:}" =~ ^##                        ]]
+        then
+          _include_match=0
+        fi
+
+        if ((_include_match))
+        then
+          _duplicate_matches+=("${_current_filename:-}")
+
+          _include_match=0
+        fi
+      done
+    fi
+
+    if ((${#_duplicate_matches[@]}))
+    then
+      if [[ "${#_duplicate_matches[@]}" == "1" ]]
+      then
+        printf      \
+"1 bookmark for this URL exists in this folder:\\n"
+      _print_line   \
+"----------------------------------------------"
+      else
+        printf      \
+"%s bookmarks for this URL exist in this folder:\\n" "${#_duplicate_matches[@]}"
+        _print_line \
+"${#_duplicate_matches[@]}----------------------------------------------"
+      fi
+
+      local __duplicate_match=
+      for   __duplicate_match in "${_duplicate_matches[@]:-}"
+      do
+        _show --info-line "${__duplicate_match%%:*}"
+      done
+
+      _print_line "------------------------------"
+
+      while true
+      do
+        local __yn=
+        IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Create another bookmark?") $(_color_brackets "y/N") " __yn
+
+        case "${__yn}" in
+          [Yy]*)
+            break
+            ;;
+          *)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            exit 0
+            ;;
+        esac
+      done
+    fi
+  fi 1>&2
+
+  if ((_request_page))
+  then
+    if ! _download_from "${_download_url}" "${_temp_file}" ||
+       [[ ! -e "${_temp_file}"                          ]] ||
+       [[ "$(wc -c <"${_temp_file}")" == 0              ]]
+    then
+      _warn printf                            \
+        "Unable to download page at %s\\n"    \
+        "$(_color_primary "${_url}")"
+    fi
+  fi
+
+  if _file_is_text "${_temp_file}"
+  then
+    if [[ -z "${_title}"    ]]
+    then
+      _title="$(
+        cat "${_temp_file}"                   \
+          | awk '/<title[^>]*>/,/<\/title>/'  \
+          | LC_ALL=C sed -e '/<\/title>/ q'   \
+          | LC_ALL=C sed -e 's/<\/title>.*//' \
+          | LC_ALL=C sed                      \
+            -e 's/.*<title[^>]*>//'           \
+            -e 's/.*<TITLE[^>]*>//'           \
+            -e 's/<\/title>.*//'              \
+            -e 's/<\/TITLE>.*//'              \
+          | awk '$1=$1'     ||  :
+      )"
+    fi
+
+    if [[ -z "${_title:-}"  ]]
+    then
+      _title="$(
+        cat "${_temp_file}"     \
+          | LC_ALL=C sed -E -n  \
+            "s/.*<meta .*property=.og:title[^>]*content=\"([^\"]+)\".*/\1/p" \
+            2>/dev/null     ||  :
+      )"
+    fi
+  fi
+
+  local _domain=
+  _domain="$(printf "%s\\n" "${_url}" | awk -F[/:] '{print $4}')"
+
+  if [[ -n "${_domain:-}"   ]]
+  then
+    [[ -n "${_title:-}"     ]]  && _title+=" "
+    _title+="(${_domain})"
+  fi
+
+  if [[ -n "${_title:-}"    ]]
+  then
+    _title="$(_bookmark_cleanup_tag_content "${_title}")"
+
+    _bookmark_content="# ${_title}${_NEWLINE}${_NEWLINE}"
+  fi
+
+  _bookmark_content+="<${_url}>${_NEWLINE}"
+
+  if _file_is_text "${_temp_file}"
+  then
+    local _description=
+    _description="$(
+      cat "${_temp_file}"       \
+        | LC_ALL=C sed -E -n    \
+            "s/.*<meta .*name=.description.[^>]*content=\"([^\"]+)\".*/\1/p" \
+            2>/dev/null     ||  :
+    )"
+
+    if [[ -z "${_description:-}"    ]]
+    then
+      _description="$(
+        cat "${_temp_file}"     \
+          | LC_ALL=C sed -E -n  \
+              "s/.*<meta .*property=.og:description[^>]*content=\"([^\"]+)\".*/\1/p" \
+              2>/dev/null   ||  :
+      )"
+    fi
+
+    if [[ -n "${_description:-}"    ]]
+    then
+      _description="$(_bookmark_cleanup_tag_content "${_description}")"
+
+      _bookmark_content+="${_NEWLINE}## Description${_NEWLINE}"
+      _bookmark_content+="${_NEWLINE}${_description}${_NEWLINE}"
+    fi
+  fi
+
+  if [[ -n "${_quote:-}"            ]]
+  then
+    _bookmark_content+="${_NEWLINE}## Quote${_NEWLINE}"
+
+    local _counter=0
+
+    local               __line=
+    while IFS= read -r  __line
+    do
+      if ! ((_counter))
+      then
+        _bookmark_content+="${_NEWLINE}> ${__line}${_NEWLINE}"
+      elif [[ -z "${__line:-}"      ]]
+      then
+        _bookmark_content+=">${_NEWLINE}"
+      else
+        _bookmark_content+="> ${__line}${_NEWLINE}"
+      fi
+
+      _counter="$((_counter+1))"
+    done <<< "${_quote}"
+  fi
+
+  if [[ -n "${_comment:-}"          ]]
+  then
+    _bookmark_content+="${_NEWLINE}## Comment${_NEWLINE}"
+    _bookmark_content+="${_NEWLINE}${_comment}${_NEWLINE}"
+  fi
+
+  if [[ -n "${_related_identifiers[*]:-}" ]]
+  then
+    _bookmark_content+="${_NEWLINE}## Related${_NEWLINE}${_NEWLINE}"
+    _bookmark_content+="$(_build_related_list "${_related_identifiers[@]:-}")"
+    _bookmark_content+="${_NEWLINE}"
+  fi
+
+  if [[ -n "${_tag_list:-}"         ]]
+  then
+    _bookmark_content+="${_NEWLINE}## Tags${_NEWLINE}"
+    _bookmark_content+="${_NEWLINE}${_tag_list}${_NEWLINE}"
+  fi
+
+  if _file_is_text "${_temp_file}"
+  then
+    if ! ((_skip_content))
+    then
+      local _processed_content=
+
+      if _command_exists "pandoc"   || _command_exists "readable"
+      then
+        _processed_content="$(
+          {
+            cat "${_temp_file}"
+          } | {
+            if _command_exists "readable" && ((_readability_enabled))
+            then
+              readable --base "${_url}" 2>/dev/null || cat
+            else
+              cat
+            fi
+          } | {
+            if _command_exists "pandoc"
+            then
+              {
+                _pandoc                                 \
+                  --standard-input                      \
+                  --from  html-native_divs-native_spans \
+                  --to    markdown-grid_tables          \
+                  --wrap=none                           \
+                  2>/dev/null || cat
+              } | {
+                # strip empty list items
+                LC_ALL=C sed -E -e 's/^-[[:space:]]*$//g'
+              }
+            else
+              cat
+            fi
+          }
+        )"
+
+        if [[ -n "${_processed_content}"  ]]
+        then
+          _bookmark_content+="${_NEWLINE}## Content${_NEWLINE}"
+          _bookmark_content+="${_NEWLINE}${_processed_content}${_NEWLINE}"
+        fi
+      else
+        _save_source=1
+      fi
+    fi
+
+    if ((_save_source))
+    then
+      _bookmark_content+="${_NEWLINE}## Source${_NEWLINE}"
+      _bookmark_content+="${_NEWLINE}${_BT}${_BT}${_BT}html${_NEWLINE}"
+      _bookmark_content+="$(cat "${_temp_file}")"
+      _bookmark_content+="${_NEWLINE}${_BT}${_BT}${_BT}${_NEWLINE}"
+    fi
+  fi
+
+  if [[ -n "${_bookmark_content}"         ]]
+  then
+
+    local _add_options=(
+      "${_relative_path}"
+      --content "${_bookmark_content}"
+      --skip-standard-input
+    )
+
+    ((_encrypt))                &&  _add_options+=("--encrypt")
+    ((_edit_before_commit))     &&  _add_options+=("--edit")
+    [[ -n "${_password:-}"  ]]  &&  _add_options+=("--password" "${_password}")
+
+    if ! ((_skip_folder_prompt))
+    then
+      _add_options+=("--folder-prompt")
+    fi
+
+    _add "${_add_options[@]}"
+
+    [[ -f "${_temp_file:-}" ]]  &&  rm -f "${_temp_file:?}"
+
+    return 0
+  fi
+}
+_alias_subcommand "bookmark" "bk"
+_alias_subcommand "bookmark" "bm"
+_alias_subcommand "bookmark" "bookmarks"
+
+# completions ##################################################### completions
+
+_describe_completions() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} completions (check | install [-d | --download] | uninstall)
+
+$(_color_primary "Options"):
+  -d, --download  Download the completion scripts and install.
+
+$(_color_primary "Description"):
+  Manage completion scripts.
+
+$(_color_primary "Read More"):
+  https://github.com/${_REPO}/blob/${_REPO_MAIN_BRANCH}/etc/README.md
+
+$(_color_primary "See Also"):
+  ${_ME} help env
+HEREDOC
+}
+_completions() {
+  local _BASH_COMP_NAME="${_ME}"
+  local _FISH_COMP_NAME="${_ME}.fish"
+  local _ZSH_COMP_NAME="_${_ME}"
+
+  # Usage: _completions_check
+  _completions_check() {
+    local _exists=0
+
+    local __shell=
+    for   __shell in bash fish zsh
+    do
+      local _completion_path=
+      local _completion_target=
+
+      case "${__shell}" in
+        bash)
+          _completion_path="$(_get_bash_completion_path)"
+          _completion_target="${_completion_path}/${_BASH_COMP_NAME}"
+          ;;
+        fish)
+          _completion_path="$(_get_fish_completion_path)"
+          _completion_target="${_completion_path}/${_FISH_COMP_NAME}"
+          ;;
+        zsh)
+          _completion_path="/usr/local/share/zsh/site-functions"
+          _completion_target="${_completion_path}/${_ZSH_COMP_NAME}"
+          ;;
+      esac
+
+      if [[ -d "${_completion_path}"        ]]
+      then
+        if [[ -w "${_completion_path}"      ]]
+        then
+          if [[ -e "${_completion_target}"  ]]
+          then
+            _exists=1
+
+            printf "Exists: %s\\n" "${_completion_target}"
+          fi
+        else
+          _warn printf "Permission denied: %s\\n" "${_completion_path}"
+        fi
+      fi
+    done
+
+    if ! ((_exists))
+    then
+      _exit_1 printf "Completion scripts not found.\\n"
+    fi
+  }
+
+  # Usage: _get_bash_completion_path
+  _get_bash_completion_path() {
+    local _bash_completion_path=
+
+    if [[ -n "${BASH_COMPLETION_COMPAT_DIR:-}"  ]]
+    then
+      _bash_completion_path="${BASH_COMPLETION_COMPAT_DIR}"
+    fi
+
+    if [[ -z "${_bash_completion_path:-}"       ]]
+    then
+      local _maybe_path=
+      _maybe_path="$(
+        pkg-config --variable=completionsdir bash-completion 2>/dev/null || :
+      )"
+
+      if [[ -n "${_maybe_path:-}"               ]]
+      then
+        _bash_completion_path="${_maybe_path}"
+      fi
+    fi
+
+    if [[ -z "${_bash_completion_path:-}"       ]] &&
+       [[ -d "/usr/local/etc/bash_completion.d" ]]
+    then
+      _bash_completion_path="/usr/local/etc/bash_completion.d"
+    fi
+
+    if [[ -z "${_bash_completion_path:-}"       ]] &&
+       [[ -d "/etc/bash_completion.d"           ]]
+    then
+      _bash_completion_path="/etc/bash_completion.d"
+    fi
+
+    printf "%s\\n" "${_bash_completion_path:-}"
+  }
+
+  # Usage: _get_fish_completion_path
+  _get_fish_completion_path() {
+    local _fish_completion_path=
+
+    if [[ -z "${_fish_completion_path:-}"                 ]] &&
+       [[ -d "/usr/local/share/fish/vendor_completions.d" ]]
+    then
+      _fish_completion_path="/usr/local/share/fish/vendor_completions.d"
+    fi
+
+    if [[ -z "${_fish_completion_path:-}"       ]]
+    then
+      local _maybe_path=
+      _maybe_path="$(
+        pkg-config --variable=completionsdir fish 2>/dev/null || :
+      )"
+
+      if [[ -n "${_maybe_path:-}"               ]]
+      then
+        _fish_completion_path="${_maybe_path}"
+      fi
+    fi
+
+    if [[ -z "${_fish_completion_path:-}"                 ]] &&
+       [[ -d "/usr/share/fish/vendor_completions.d"       ]]
+    then
+      _fish_completion_path="/usr/share/fish/vendor_completions.d"
+    fi
+
+    printf "%s\\n" "${_fish_completion_path:-}"
+  }
+
+  _get_zsh_completion_path() {
+      local _zsh_completion_path=
+
+      if [[ -z "${_zsh_completion_path:-}"                 ]] &&
+         [[ -d "/usr/local/share/zsh/site-functions" ]]
+      then
+        _zsh_completion_path="/usr/local/share/zsh/site-functions"
+      fi
+
+      if [[ -z "${_zsh_completion_path:-}"                 ]] &&
+         [[ -d "/usr/share/zsh/site-functions"       ]]
+      then
+        _zsh_completion_path="/usr/share/zsh/site-functions"
+      fi
+
+      printf "%s\\n" "${_zsh_completion_path:-}"
+  }
+
+  # Usage: _completions_install [--download]
+  _completions_install() {
+    local _download=0
+    if [[ "${1:-}" == "--download"  ]]
+    then
+      _download=1
+    fi
+
+    local _my_path="${0}"
+
+    if [[ -L "${_my_path}"          ]]
+    then
+      _my_path="$(_resolve_symlink "${_my_path}")"
+    fi
+
+    local _my_dir=
+    _my_dir="$(cd "$(dirname "${_my_path}")"; pwd)"
+    if [[ -z "${_my_dir}"   ]]  ||  [[ ! -d "${_my_dir}"        ]]
+    then
+      exit 1
+    fi
+
+    if [[ -z "${_REPO:-}"   ]]  ||  [[ -z "${_REPO_RAW_URL:-}"  ]]
+    then
+      _exit_1 printf "Source Git repository not configured.\\n"
+    fi
+
+    local __shell=
+    for   __shell in bash fish zsh
+    do
+      local _completion_source="${_my_dir}/etc/${_ME}-completion.${__shell}"
+
+      if ((_download))
+      then
+        if [[ ! -f "${_completion_source}"  ]]
+        then
+          _completion_source="$(_temp file)"
+          local _completion_url="${_REPO_RAW_URL}/etc/${_ME}-completion.${__shell}"
+
+          if ! _download_from "${_completion_url}" "${_completion_source}"
+          then
+            _exit_1 printf "Unable to download completion script from %s\\n" \
+              "${_completion_source}"
+          fi
+        fi
+      fi
+
+      if [[ ! -f "${_completion_source}"    ]]
+      then
+        cat <<HEREDOC
+Unable to find source ${__shell} completion script. You can try downloading
+and installing the latest version with the following command (\`sudo\` might
+be necessary):
+  ${_ME} completions install --download
+
+More Information: ${__shell}
+  https://github.com/${_REPO}/blob/${_REPO_MAIN_BRANCH}/etc/README.md
+HEREDOC
+      else
+        local _completion_path=
+        local _completion_target=
+
+        case "${__shell}" in
+          bash)
+            _completion_path="$(_get_bash_completion_path)"
+            _completion_target="${_completion_path}/${_BASH_COMP_NAME}"
+            ;;
+          fish)
+            _completion_path="$(_get_fish_completion_path)"
+            _completion_target="${_completion_path}/${_FISH_COMP_NAME}"
+            ;;
+          zsh)
+            _completion_path="$(_get_zsh_completion_path)"
+            _completion_target="${_completion_path}/${_ZSH_COMP_NAME}"
+            ;;
+        esac
+
+        if [[ -n "${_completion_path:-}"        ]] &&
+           [[ -d "${_completion_path}"          ]]
+        then
+          if [[ -w "${_completion_path}"        ]]
+          then
+            if [[ ! -e "${_completion_target}"  ]]
+            then
+              cp                                \
+                "${_completion_source}"         \
+                "${_completion_target}"
+
+              chmod +r "${_completion_target}"
+
+              printf "Completion script installed: %s\\n" \
+                "${_completion_target}"
+            else
+              _warn printf "Exists: %s\\n" "${_completion_target}"
+            fi
+          else
+            _warn printf "Permission denied: %s\\n" "${_completion_path}"
+          fi
+        fi
+      fi
+    done
+  }
+
+  # Usage: _completions_uninstall
+  _completions_uninstall() {
+    local _completion_path=
+    local _completion_target=
+
+    local __shell=
+    for   __shell in bash fish zsh
+    do
+      case "${__shell}" in
+        bash)
+          _completion_path="$(_get_bash_completion_path)"
+          _completion_target="${_completion_path}/${_BASH_COMP_NAME}"
+          ;;
+        fish)
+          _completion_path="$(_get_fish_completion_path)"
+          _completion_target="${_completion_path}/${_FISH_COMP_NAME}"
+          ;;
+        zsh)
+          _completion_path="/usr/local/share/zsh/site-functions"
+          _completion_target="${_completion_path}/${_ZSH_COMP_NAME}"
+          ;;
+      esac
+
+      if [[ -n "${_completion_path:-}"  ]] &&
+         [[ -d "${_completion_path}"    ]]
+      then
+        if [[ -w "${_completion_path}"    ]] &&
+           [[ -w "${_completion_target}"  ]]
+        then
+          if [[ -f "${_completion_target}"  ]]
+          then
+            rm "${_completion_target:?}"
+
+            printf "Completion script removed: %s\\n" \
+              "${_completion_target}"
+          fi
+        else
+          _warn printf "Permission denied: %s\\n" "${_completion_path}"
+        fi
+      fi
+    done
+  }
+
+  local _subcommand="${1:-}"
+
+  case "${_subcommand}" in
+    check)
+      _completions_check
+      ;;
+    install)
+      if [[ "${2:-}" =~ (^-d|--download$)   ]]
+      then
+        _completions_install --download
+      else
+        _completions_install
+      fi
+      ;;
+    uninstall)
+      _completions_uninstall
+      ;;
+    *)
+      _help "completions"
+
+      return 0
+      ;;
+  esac
+}
+
+# delete ############################################################### delete
+
+_describe_delete() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} delete ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])...
+            [-f | --force]
+
+$(_color_primary "Options"):
+  -f, --force   Skip the confirmation prompt.
+
+$(_color_primary "Description"):
+  Delete one or more items.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#deleting
+
+$(_color_primary "See Also"):
+  ${_ME} help add
+  ${_ME} help browse
+  ${_ME} help edit
+  ${_ME} help move
+  ${_ME} help show
+
+$(_color_primary "Examples"):
+  ${_ME} delete 3
+  ${_ME} delete example.md
+  ${_ME} delete "A Document Title"
+  ${_ME} 3 delete --force
+  ${_ME} example:delete 12
+  ${_ME} delete example:12
+  ${_ME} example:12 delete
+  ${_ME} d 3
+  ${_ME} 3 d
+  ${_ME} d example:12
+  ${_ME} example:12 d
+
+$(_color_primary "Aliases"):
+  ${_ME} rm
+  ${_ME} trash
+
+$(_color_primary "Shortcut Aliases"):
+  ${_ME} d
+  ${_ME} -
+HEREDOC
+}
+_delete() {
+  local _force=0
+  local _print_prompt_list=0
+  local _selectors=()
+  local _title=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      -f|--force|--skip*|-y|--yes)
+        _force=1
+        ;;
+      --prompt-list)
+        _print_prompt_list=1
+        ;;
+      *)
+        [[ -n "${__arg:-}"  ]]  && _selectors+=("${__arg:-}")
+        ;;
+    esac
+  done
+
+  if ! ((${#_selectors[@]}))
+  then
+    _exit_1 _help "delete"
+  fi
+
+  local _target_paths=()
+
+  local __selector=
+  for   __selector in "${_selectors[@]:-}"
+  do
+    [[ -z "${__selector:-}" ]]  && continue
+
+    local _selector_path=
+    _selector_path="$(_show "${__selector:-}" --path)"
+
+    if [[ -n "${_selector_path:-}"    ]]
+    then
+      _target_paths+=("${_selector_path:-}")
+    else
+      _exit_1 printf "Not found: %s\\n" "$(_color_primary "${__selector}")"
+    fi
+  done
+
+  if ((_print_prompt_list))     || ! ((_force))
+  then
+    if [[ "${#_selectors[@]}"   == 1  ]]
+    then
+      printf "Deleting: %s\\n" "$(_show "${_selectors[0]:-}" --info-line)"
+    else
+      printf "Deleting:\\n"
+
+      local __prompt_selector=
+      for   __prompt_selector in "${_target_paths[@]:-}"
+      do
+        printf "%s\\n" "$(_show "${__prompt_selector:-}" --info-line)"
+      done
+
+    fi
+  fi
+
+  if ! ((_force))
+  then
+    while true
+    do
+      local __yn=
+      IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Proceed?")  $(_color_brackets "y/N") " __yn
+
+      case "${__yn}" in
+        [Yy]*)
+          break
+          ;;
+        *)
+          printf "Exiting...\\n"
+
+          exit 0
+          ;;
+      esac
+    done
+  fi
+
+  local __delete_selector=
+  for   __delete_selector in "${_target_paths[@]:-}"
+  do
+    local _info_line=
+    _info_line="$(_show "${__delete_selector:-}" --info-line)"
+
+    local _relative_path=
+    _relative_path="$(_show "${__delete_selector}" --relative-path)"
+
+    local _notebook_path=
+    _notebook_path="$(
+      _notebooks show "${__delete_selector:-}" --path ||
+        _notebooks current --path
+    )"
+
+    local _basename="${_relative_path##*\/}"
+    local _folder_path="${_notebook_path}"
+
+    if [[ "${_relative_path:-}" =~ / ]]
+    then
+      _folder_path="${_notebook_path}/${_relative_path%\/*}"
+    fi
+
+    if [[ -n "${_basename}" ]] && [[ -e "${_notebook_path}/${_relative_path}" ]]
+    then
+      _pin unpin "${_notebook_path}/${_relative_path}" &> /dev/null || :
+
+      if [[ -d "${_notebook_path}/${_relative_path}"            ]]  &&
+         [[ -z "$(ls -A "${_notebook_path}/${_relative_path}")" ]]
+      then
+        rm -r "${_notebook_path:?}/${_relative_path:?}"
+      else
+        if git -C "${_notebook_path:?}" check-ignore    \
+             "${_notebook_path:?}/${_relative_path:?}" 1>/dev/null
+        then
+          rm -r "${_notebook_path:?}/${_relative_path:?}"
+        else
+          git -C "${_notebook_path:?}" rm -r            \
+            "${_notebook_path:?}/${_relative_path:?}" 1>/dev/null
+        fi
+      fi
+
+      if [[ ! -e "${_notebook_path}/${_relative_path}"  ]]
+      then
+        _index delete "${_basename}" "${_folder_path}"
+
+        _git checkpoint "${_notebook_path}" "[${_ME}] Delete: ${_relative_path}"
+
+        printf "Deleted:  %s\\n" "${_info_line}"
+      fi
+    else
+      _exit_1 printf "Selection not found.\\n"
+    fi
+  done
+}
+_alias_subcommand "delete" "-"
+_alias_subcommand "delete" "d"
+_alias_subcommand "delete" "rm"
+_alias_subcommand "delete" "trash"
+
+# edit ################################################################### edit
+
+_describe_edit() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} edit ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [-c <content> | --content <content>] [--edit]
+          [-e <editor> | --editor <editor>] [--overwrite] [--prepend]
+
+$(_color_primary "Options"):
+  -c, --content <content>  Content to add to the item.
+  --edit                   Open the note in the editor before saving when
+                           content is piped or passed as an argument.
+  -e, --editor <editor>    Edit the note with <editor>, overriding the editor
+                           specified in the \`\$EDITOR\` environment variable.
+  --overwrite              Overwrite existing content with <content> and
+                           standard input.
+  --prepend                Prepend <content> and standard input before
+                           existing content.
+
+$(_color_primary "Description"):
+  Open the specified note in \`\$EDITOR\`, currently set to: ${EDITOR}
+
+  Content piped to \`${_ME} edit\` or passed using the \`--content\` option
+  is appended to the file without opening it in the editor, unless the
+  \`--edit\` flag is specified.
+
+  Non-text files are opened in your system's preferred app or program for
+  that file type.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#editing
+
+$(_color_primary "See Also"):
+  ${_ME} help add
+  ${_ME} help browse
+  ${_ME} help delete
+  ${_ME} help move
+  ${_ME} help show
+
+$(_color_primary "Examples"):
+  ${_ME} edit 3
+  ${_ME} edit example.md
+  ${_ME} edit "A Document Title"
+  echo "Content to append." | ${_ME} edit 1
+  ${_ME} 3 edit
+  ${_ME} example:edit 12
+  ${_ME} edit example:12
+  ${_ME} example:12 edit
+  ${_ME} e 12
+  ${_ME} 12 e
+  ${_ME} e example:12
+  ${_ME} example:12 e
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} e
+HEREDOC
+}
+_edit() {
+  local _content=
+  local _edit_before_commit=0
+  local _edit_type="append"
+  local _local_editor=
+  local _password=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -c|--content)
+        _content="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --edit)
+        _edit_before_commit=1
+        ;;
+      -e|--editor)
+        _local_editor="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --overwrite)
+        _edit_type="overwrite"
+        ;;
+      --password)
+        _password="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --prepend)
+        _edit_type="prepend"
+        ;;
+      *)
+        if [[ -z "${_selector:-}" ]]
+        then
+          _selector="${1:-}"
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  [[ -z "${_selector:-}" ]] && _exit_1 _help "edit"
+
+  local _relative_path=
+  _relative_path="$(_show "${_selector:-}" --relative-path)"
+
+  local _basename="${_relative_path##*\/}"
+  local _folder_path="${_relative_path%\/*}"
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  if [[ -z "${_relative_path:-}"  ]]
+  then
+    _exit_1 printf "Not found: %s\\n" "$(_color_primary "${_relative_path}")"
+  fi
+
+  if [[ -n "${_relative_path}"                    ]] &&
+     [[ -e "${_notebook_path}/${_relative_path}"  ]]
+  then
+    local _before=
+    _before="$(_get_hash "${_notebook_path}/${_relative_path}")"
+
+    local _decrypted_path=
+    local _encrypted_path=
+    local _encryption_tool=
+    local _target_file="${_notebook_path}/${_relative_path}"
+
+    if _file_is_encrypted "${_target_file}"
+    then
+      _encrypted_path="${_target_file}"
+      _encryption_tool="$(_get_decryption_tool "${_encrypted_path:-}")"
+
+      if [[    "${_encryption_tool:-}" != "age"   ]] &&
+         [[ -z "${_password}"                     ]]
+      then
+        # request password without displaying it
+        printf "%s: " "$(_color_primary "Password")"
+
+        IFS='' read -r -e -d $'\n' -s _password </dev/tty
+
+        printf "\\n" # print newline to stop `read`
+
+        if [[ -z "${_password}"                   ]]
+        then
+          _exit_1 printf "Password required.\\n"
+        fi
+      fi
+
+      _decrypted_path="$(_decrypt_file "${_target_file}" "${_password:-}")"
+
+      _target_file="${_decrypted_path}"
+
+      _before="$(_get_hash "${_decrypted_path}")"
+    fi
+
+    if [[ -n "${_content:-}"      ]] || _piped_input
+    then
+      {
+        if [[ -n "${_content}"    ]]
+        then
+          printf "%s\\n" "${_content}"
+        fi
+
+        if _piped_input
+        then
+          cat
+        fi
+      } | {
+        if [[   "${_edit_type:-}" == "overwrite"  ]]
+        then
+          cat > "${_target_file}"
+        elif [[ "${_edit_type:-}" == "prepend"    ]]
+        then
+          local _prepend_temp=
+          _prepend_temp="$(_temp file)"
+
+          cat                       >   "${_prepend_temp:?}"
+          printf "\\n"              >>  "${_prepend_temp:?}"
+          cat "${_target_file}"     >>  "${_prepend_temp:?}"
+
+          cat "${_prepend_temp:?}"  >   "${_target_file}"
+
+          if [[ -f "${_prepend_temp:?}" ]]
+          then
+            rm  "${_prepend_temp:?}"
+          fi
+        else
+          printf "\\n"  >>  "${_target_file}"
+          cat           >>  "${_target_file}"
+        fi
+      }
+    fi
+
+    if ((_edit_before_commit)) || {
+       ! _piped_input && [[ -z "${_content:-}"    ]]
+    }
+    then
+      if [[ -n "${_local_editor}"   ]]
+      then
+        EDITOR="${_local_editor}" _edit_file "${_target_file}"
+      else
+        _edit_file "${_target_file}"
+      fi
+    fi
+
+    local _after=
+    _after="$(_get_hash "${_notebook_path}/${_relative_path}")"
+
+    if [[ -n "${_encrypted_path:-}" ]]  &&  [[ -e "${_decrypted_path:-}" ]]
+    then
+      _after="$(_get_hash "${_decrypted_path}")"
+
+      if [[ "${_before}" != "${_after}" ]]
+      then
+        local _temp_encrypted_path=
+        _temp_encrypted_path="$(_temp file "${_relative_path}").tmp"
+
+        mv "${_encrypted_path}" "${_temp_encrypted_path}"
+
+        _encrypt_file                   \
+          "${_decrypted_path}"          \
+          "${_encrypted_path}"          \
+          --password "${_password:-}"   \
+          --tool "${_encryption_tool:-}"
+
+        if [[ -e "${_temp_encrypted_path:-}"  ]]
+        then
+          if [[ -e "${_encrypted_path:?}"     ]]
+          then
+            rm "${_temp_encrypted_path:?}"
+          else
+            mv "${_temp_encrypted_path}" "${_encrypted_path}"
+          fi
+        fi
+      fi
+
+      rm "${_decrypted_path:?}"
+    fi
+
+    _git checkpoint "${_notebook_path}" "[${_ME}] Edit: ${_relative_path}"
+
+    if [[ "${_before}" != "${_after}"   ]]
+    then
+      local _info=
+      _info="$(_show "${_relative_path}" --info-line)"
+
+      printf "Updated: %s\\n" "${_info}"
+    fi
+  else
+    _exit_1 printf "Selection not found.\\n"
+  fi
+}
+_alias_subcommand "edit" "e"
+
+# env ##################################################################### env
+
+_describe_env() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} env [install]
+
+$(_color_primary "Subcommands"):
+  install  Install dependencies on supported systems.
+
+$(_color_primary "Description"):
+  Print program environment and configuration information, or install
+  dependencies.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#installation
+
+$(_color_primary "See Also"):
+  ${_ME} help completions
+  ${_ME} help init
+  ${_ME} help update
+  ${_ME} help version
+HEREDOC
+}
+_env() {
+  # Usage: _env_install_deb <name> <version> <repo>
+  _env_install_deb() {
+    local _deb_filename=
+    local _name="${1:?}"
+    local _repo="${3:?}"
+    local _version="${2:?}"
+    local _x86_64_bit=1
+
+    local _arch=
+    _arch="$(uname -m)"
+
+    case "${_arch:-}" in
+      x86_64)
+        _deb_filename="${_name}_${_version}_amd64.deb"
+        ;;
+      aarch64)
+        _x86_64_bit=0
+        _deb_filename="${_name}_${_version}_arm64.deb"
+        ;;
+      arm*)
+        _x86_64_bit=0
+        _deb_filename="${_name}_${_version}_armhf.deb"
+        ;;
+    esac
+
+    if [[ -z "${_deb_filename:-}"   ]]  || {
+         [[ "${_name}" == "ripgrep" ]]  && ! ((_x86_64_bit))
+       }
+    then
+      _warn printf                                                      \
+        "Please install %s manually. No .deb package available for %s." \
+        "$(_color_primary "${_name}")"                                  \
+        "$(_color_primary "${_arch}")"
+      return 0
+    fi
+
+    local _deb_path="${HOME}/${_deb_filename}"
+
+    # handle bat version prefix in URL
+    [[ "${_name}" == "bat"  ]] && _version="v${_version}"
+
+    wget                    \
+      -O "${_deb_path}"     \
+      "https://github.com/${_repo}/releases/download/${_version}/${_deb_filename}"
+
+    if [[ -e "${_deb_path}" ]]
+    then
+      dpkg -i "${_deb_path}"
+      rm "${_deb_path:?}"
+    fi
+  }
+
+  # Usage: _env_max_version <version> <version>
+  _env_max_version() {
+    printf "%s\\n" "${@:?}"                           \
+      | sort -r -t '.' -k 1,1 -k 2,2 -k 3,3 -k 4,4 -g \
+      | head -n 1
+  }
+
+  local _subcommand="${1:-}"
+
+  case "${_subcommand}" in
+    install)
+      if [[ ! "${2:-}" == "--ace"     ]]
+      then # skip to next section if `_env install --ace`
+        # packages: curl pandoc pygments w3m ripgrep tig
+        if [[ -x "$(command -v apk)"  ]]
+        then
+          _completions install --download
+
+          apk add --no-cache  \
+            bash-completion   \
+            curl              \
+            pandoc            \
+            py3-pygments      \
+            ripgrep           \
+            tig               \
+            w3m
+        elif [[ -x "$(command -v apt-get)" ]]
+        then
+          _completions install --download
+
+          local _apt_packages=()
+          local _deb_packages=()
+          local _dependencies=(
+            bash-completion
+            bat
+            curl
+            ncat
+            pandoc
+            python3-pygments
+            ripgrep
+            tig
+            w3m
+          )
+
+          [[ "$(cat /etc/os-release)" =~ (ubuntu|debian) ]] || return 1
+
+          apt-get update
+
+          local __package=
+          for   __package in "${_dependencies[@]}"
+          do
+            if ! _command_exists "${__package}" &&
+               apt-cache show "${__package}" | grep -q "Package: ${__package}"
+            then
+              _apt_packages+=("${__package}")
+            fi
+          done
+
+          apt-get install -y "${_apt_packages[@]:-}"
+
+          # force install of bat
+          apt-get install -y bat -o Dpkg::Options::="--force-overwrite"
+
+          if ! _command_exists "rg"
+          then
+            _deb_packages+=("ripgrep 12.1.1 BurntSushi/ripgrep")
+          fi
+
+          if ! _command_exists "bat" || ! _command_exists "batcat"
+          then
+            _deb_packages+=("bat 0.22.1 sharkdp/bat")
+          fi
+
+          local __package=
+          for   __package in "${_deb_packages[@]}"
+          do
+            local _arguments=()
+            IFS=' ' read -ra _arguments <<< "${__package:-}"
+
+            _env_install_deb "${_arguments[@]:-}"
+          done
+        elif [[ -x "$(command -v dnf)"    ]]
+        then
+          : # TODO: dnf install
+          _completions install --download
+        elif [[ -x "$(command -v zypper)" ]]
+        then
+          : # TODO: zypper install
+          _completions install --download
+        else
+          _completions install --download
+        fi
+      fi
+
+      # install ace editor
+
+      if ((${NB_ACE_ENABLED:-0})) && [[ ! -e "${NB_DIR}/.assets/ace-builds" ]]
+      then
+        if [[ ! -e "${NB_DIR}/.assets" ]]
+        then
+          mkdir "${NB_DIR}/.assets"
+        fi
+
+        cd "${NB_DIR}/.assets" ||
+          _exit_1 printf "Unable to \`cd\` to %s\\n" "${NB_DIR}/.assets"
+
+        git clone https://github.com/ajaxorg/ace-builds.git
+      fi
+
+      ;;
+    uninstall)
+      _completions uninstall
+      ;;
+    *)
+      printf "_ME=%s\\n" "${_ME:-}"
+      printf "_MY_PATH=%s\\n" "${_MY_PATH:-}"
+      printf "NB_NOTEBOOK_PATH=%s\\n" "${NB_NOTEBOOK_PATH:-}"
+      printf "BROWSER=%s\\n" "${BROWSER:-}"
+      printf "EDITOR=%s\\n" "${EDITOR:-}"
+      printf "PAGER=%s\\n" "${PAGER:-}"
+      printf "NB_AUTO_SYNC=%s\\n" "${NB_AUTO_SYNC:-}"
+      printf "NB_DIR=%s\\n" "${NB_DIR:-}"
+      printf "NB_DEFAULT_EXTENSION=%s\\n" "${NB_DEFAULT_EXTENSION:-}"
+      printf "NB_ENCRYPTION_TOOL=%s\\n" "${NB_ENCRYPTION_TOOL:-}"
+      printf "NB_COLOR_PRIMARY=%s\\n" "${NB_COLOR_PRIMARY:-}"
+      printf "NB_COLOR_SECONDARY=%s\\n" "${NB_COLOR_SECONDARY:-}"
+      printf "NB_COLOR_THEME=%s\\n" "${NB_COLOR_THEME:-}"
+      printf "NB_FOOTER=%s\\n" "${NB_FOOTER:-}"
+      printf "NB_HEADER=%s\\n" "${NB_HEADER:-}"
+      printf "NB_LIMIT=%s\\n"  "${NB_LIMIT:-}"
+      printf "NB_SYNTAX_THEME=%s\\n"  "${NB_SYNTAX_THEME:-}"
+      printf "NBRC_PATH=%s\\n" "${NBRC_PATH:-}"
+      printf "ack:        %s\\n" "$(command -v ack)"
+      printf "ag:         %s\\n" "$(command -v ag)"
+      printf "bat:        %s\\n" "$(command -v bat)"
+      printf "code:       %s\\n" "$(command -v code)"
+      printf "curl:       %s\\n" "$(command -v curl)"
+      printf "emacs:      %s\\n" "$(command -v emacs)"
+      printf "git:        %s\\n" "$(command -v git)"
+      printf "gvim:       %s\\n" "$(command -v gvim)"
+      printf "gpg:        %s\\n" "$(command -v gpg)"
+      printf "highlight:  %s\\n" "$(command -v highlight)"
+      printf "less:       %s\\n" "$(command -v less)"
+      printf "lynx:       %s\\n" "$(command -v lynx)"
+      printf "macdown:    %s\\n" "$(command -v macdown)"
+      printf "mate:       %s\\n" "$(command -v mate)"
+      printf "mvim:       %s\\n" "$(command -v mvim)"
+      printf "nano:       %s\\n" "$(command -v nano)"
+      printf "nvim:       %s\\n" "$(command -v nvim)"
+      printf "openssl:    %s\\n" "$(command -v openssl)"
+      printf "pandoc:     %s\\n" "$(command -v pandoc)"
+      printf "pygments:   %s\\n" "$(command -v pygmentize)"
+      printf "readable:   %s\\n" "$(command -v readable)"
+      printf "rg:         %s\\n" "$(command -v rg)"
+      printf "subl:       %s\\n" "$(command -v subl)"
+      printf "tig:        %s\\n" "$(command -v tig)"
+      printf "w3m:        %s\\n" "$(command -v w3m)"
+      printf "vim:        %s\\n" "$(command -v vim)"
+      printf "bash --version: %s\\n" "$(bash --version | head -1)"
+      printf "uname -a: %s\\n" "$(uname -a)"
+      ;;
+  esac
+}
+
+# export ############################################################### export
+
+_describe_export() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} export ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            <path> [-f | --force] [<pandoc options>...]
+  ${_ME} export notebook <name> [<path>]
+  ${_ME} export pandoc ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            [<pandoc options>...]
+
+$(_color_primary "Options"):
+  -f, --force   Skip the confirmation prompt when overwriting an existing file.
+
+$(_color_primary "Subcommands"):
+  (default)     Export a file to <path>. If <path> has a different extension
+                than the source note, convert the note using \`pandoc\`.
+  notebook      Export the notebook <name> to the current directory or <path>.
+                Alias for \`${_ME} notebooks export\`.
+  pandoc        Export the file to standard output or a file using \`pandoc\`.
+                \`export pandoc\` prints to standard output by default.
+
+$(_color_primary "Description"):
+  Export a file or notebook.
+
+  If Pandoc [1] is available, convert the note from its current format
+  to the format of the output file as indicated by the file extension
+  in <path>. Any additional arguments are passed directly to Pandoc.
+  See the Pandoc help information for available options.
+
+    1. https://pandoc.org/
+
+$(_color_primary "Read More"):
+  ${_README_URL}#%EF%B8%8F-import--export
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help import
+
+$(_color_primary "Examples"):
+  # Export an Emacs Org mode note
+  ${_ME} export example.org /path/to/example.org
+
+  # Export a Markdown note to HTML and print to standard output
+  ${_ME} export pandoc example.md --from=markdown_strict --to=html
+
+  # Export a Markdown note to a .docx Microsoft Office Word document
+  ${_ME} export example.md /path/to/example.docx
+
+  # Export note 12 in the "sample" notebook to HTML
+  ${_ME} export sample:12 /path/to/example.html
+HEREDOC
+}
+_export() {
+  local _args=()
+  local _force=0
+  local _notebook_export=0
+  local _pandoc_only=0
+  local _selector=
+  local _target_path=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      -f|--force|--skip*|-y|--yes)
+        _force=1
+        ;;
+      notebook*)
+        _notebook_export=1
+        ;;
+      pandoc)
+        _pandoc_only=1
+        ;;
+      *)
+        if [[ -z "${_selector:-}"   ]]
+        then
+          _selector="${__arg}"
+        elif ! ((_pandoc_only)) &&  [[ -z "${_target_path:-}" ]]
+        then
+          _target_path="${__arg}"
+        else
+          _args+=("${__arg}")
+        fi
+        ;;
+    esac
+  done
+
+  if [[ -z "${_selector:-}" ]]
+  then
+    _exit_1 _help "export"
+  fi
+
+  if ((_notebook_export))
+  then
+    _notebooks export "${_selector:-}" "${_target_path:-}"
+
+    return 0
+  fi
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  local _relative_path=
+  _relative_path="$(_show "${_selector}" --relative-path)"
+
+  local _basename="${_relative_path##*\/}"
+
+  if [[ -z "${_relative_path:-}"                      ]] ||
+     [[ ! -e "${_notebook_path}/${_relative_path:-}"  ]]
+  then
+    _exit_1 printf "Not found: %s\\n" "$(_color_primary "${_selector}")"
+  fi
+
+  if ((_pandoc_only))
+  then
+    if _command_exists "pandoc"
+    then
+      if [[ -n "${_args[*]:-}"    ]]
+      then
+        pandoc "${_notebook_path}/${_relative_path}" "${_args[@]:-}"
+      else
+        pandoc "${_notebook_path}/${_relative_path}"
+      fi
+    else
+      _exit_1 printf "Pandoc required. https://pandoc.org/\\n"
+    fi
+  else
+    if [[ -z "${_target_path:-}"  ]]
+    then
+      _exit_1 _help "export"
+    fi
+
+    if [[ -d "${_target_path:-}"  ]]
+    then
+      _target_path="${_target_path%/}/${_basename}"
+    fi
+
+    if [[ -e "${_target_path:-}"  ]]
+    then
+      if ! ((_force))
+      then
+        printf "File exists at %s\\n" "$(_color_primary "${_target_path}")"
+
+        while true
+        do
+          local __yn=
+          IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Overwrite existing file?") $(_color_brackets "y/N") " __yn
+
+          case "${__yn}" in
+            [Yy]*)
+              break
+              ;;
+            *)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+          esac
+        done
+      fi
+    fi
+
+    local _source_file_type="${_basename##*.}"
+    local _target_file_type="${_target_path##*.}"
+
+    if _command_exists "pandoc"   &&
+       [[ "${_source_file_type}"  != "${_target_file_type}" ]]
+    then
+      if [[ -n "${_args[*]:-}"    ]]
+      then
+        pandoc                                    \
+          -o "${_target_path}"                    \
+          --standalone                            \
+          "${_notebook_path}/${_relative_path}"   \
+          "${_args[@]:-}"
+      else
+        pandoc                    \
+          -o "${_target_path}"    \
+          --standalone            \
+          "${_notebook_path}/${_relative_path}"
+      fi
+    else
+      cp "${_notebook_path}/${_relative_path}" "${_target_path}"
+    fi &&
+      printf "Exported: %s\\n"  "$(_show "${_relative_path}" --info-line)"
+      printf "To:        %s\\n" "$(_color_primary "${_target_path}")"
+  fi
+}
+
+# history ############################################################# history
+
+_describe_history() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} history [<notebook>:][<folder-path>/][<id> | <filename> | <title>]
+
+$(_color_primary "Description"):
+  Display notebook history using \`tig\` [1] (if available) or \`git log\`.
+  When a note is specified, the history for that note is displayed.
+
+    1. https://github.com/jonas/tig
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-revision-history
+  ${_README_URL}#-git-sync
+
+$(_color_primary "See Also"):
+  ${_ME} help git
+  ${_ME} help remote
+  ${_ME} help status
+  ${_ME} help sync
+
+$(_color_primary "Examples"):
+  ${_ME} history
+  ${_ME} history example.md
+  ${_ME} 3 history
+  ${_ME} example:history
+  ${_ME} history example:
+  ${_ME} example:history 12
+  ${_ME} history example:12
+  ${_ME} example:12 history
+HEREDOC
+}
+_history() {
+  local _basename=
+  local _force_git_log=0
+  local _notebook_path=
+  local _selector=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      --*log*|--*git*)
+        _force_git_log=1
+        ;;
+      *)
+        if [[ -z "${_selector:-}" ]]
+        then
+          _selector="${__arg}"
+        fi
+        ;;
+    esac
+  done
+
+  if [[ -n "${_selector:-}"       ]]
+  then
+    if [[  "${_selector}" =~ :$   ]] ||
+       ! _relative_path="$(_show "${_selector}" --relative-path 2>/dev/null)"
+    then
+      if ! _notebook_path="$(_notebooks show "${_selector}" --path 2>/dev/null)"
+      then
+        _exit_1 printf "Not found: %s\\n" "$(_color_primary "${_selector:-}")"
+      fi
+    fi
+  fi
+
+  if [[ -z "${_notebook_path:-}"  ]]
+  then
+    _notebook_path="$(_notebooks current --path)"
+  fi
+
+  cd "${_notebook_path}" || _exit_1 printf "_history() \`cd\` failed.\\n"
+
+  local _log_command="git log"
+
+  if _command_exists "tig" && ! ((_force_git_log))
+  then
+    _log_command="tig --all"
+  fi
+
+  if [[ -n "${_relative_path:-}"  ]] && [[ -e "${_notebook_path}/${_relative_path}" ]]
+  then
+    eval "${_log_command} -- \"${_relative_path}\""
+  else
+    eval "${_log_command}"
+  fi
+}
+
+# import ############################################################### import
+
+_describe_import() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} import [copy | download | move] (<path>... | <url>) [--convert]
+            [<notebook>:][<folder-path>/][<filename>]
+  ${_ME} import notebook <path> [<name>]
+
+$(_color_primary "Options"):
+  --convert  Convert HTML content to Markdown.
+
+$(_color_primary "Subcommands"):
+  (default) Copy or download the file(s) at <path> or <url>.
+  copy      Copy the file(s) at <path> into the current notebook.
+  download  Download the file at <url> into the current notebook.
+  move      Move the file(s) at <path> into the current notebook.
+  notebook  Import the local notebook at <path> to make it global.
+
+$(_color_primary "Description"):
+  Copy, move, or download files into the current notebook or import
+  a local notebook to make it global.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#%EF%B8%8F-import--export
+
+$(_color_primary "See Also"):
+  ${_ME} help add
+  ${_ME} help export
+
+$(_color_primary "Examples"):
+  ${_ME} import ~/Pictures/example.png
+  ${_ME} import ~/Documents/example.docx
+  ${_ME} import https://example.com/example.pdf
+  ${_ME} example:import https://example.com/example.jpg
+  ${_ME} import ./*
+  ${_ME} import ./*.md
+  ${_ME} import ~/Pictures/example.png example-notebook:
+  ${_ME} import ~/Documents/example.docx example-folder/
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} i
+HEREDOC
+}
+_import() {
+  # _import_create_bookmark()
+  #
+  # Usage:
+  #   _import_create_bookmark <target-selector> <line>
+  _import_create_bookmark() {
+    local _line="${2:?}"
+    local _target_selector="${1:-}"
+
+    local _bookmark_options=(--skip-folder-prompt)
+
+    local _add_timestamp=
+    _add_timestamp="$(
+      sed -E -e 's/.*ADD_DATE=\"([[:digit:]]+)\".*/\1/g'  <<< "${_line}"
+    )"
+
+    local _target_filename=
+    _target_filename="$(
+      if hash "gdate" 2>/dev/null
+      then # GNU prefixed
+        gdate -u -d "@${_add_timestamp}"  "+%Y%m%d%H%M%S"
+      elif date --version >/dev/null 2>&1
+      then # GNU
+        date  -u -d "@${_add_timestamp}"  "+%Y%m%d%H%M%S"
+      else # BSD
+        date  -u -r "${_add_timestamp}"   "+%Y%m%d%H%M%S"
+      fi
+    )"
+
+    if [[ -n "${_target_filename:-}"  ]]
+    then
+      _bookmark_options+=(--filename "${_target_filename}")
+    fi
+
+    local _tag_list=
+    _tag_list="$(
+      grep -q 'TAGS=\"'                             <<< "${_line}" &&
+        sed -E -e 's/.*TAGS=\"([^\"]+)\".*/\1/g'    <<< "${_line}" || :
+    )"
+
+    if [[ -n "${_tag_list:-}"         ]]
+    then
+      _bookmark_options+=(--tags "${_tag_list}")
+    fi
+
+    local _title=
+    _title="$(
+      sed -E -e 's/.*>(.*)<\/A>/\1/g'               <<< "${_line}"
+    )"
+
+    if [[ -n "${_title:-}"            ]]
+    then
+      _bookmark_options+=(--title "${_title}")
+    fi
+
+    local _url=
+    _url="$(
+      sed -E -e 's/.*HREF=\"(.*)\" ADD_DATE.*/\1/g' <<< "${_line}"
+    )"
+
+    _notebooks select "${_target_selector%%:*}"
+
+    _bookmark                         \
+      "${_target_selector}"           \
+      "${_url}"                       \
+      "${_bookmark_options[@]}"
+  }
+
+  # _import_init_target_relative_path()
+  #
+  # Usage:
+  #   _import_init_target_relative_path <notebook-path> <source-basename> <selector-path>
+  _import_init_target_relative_path() {
+    local _notebook_path="${1:?}"
+    local _source_basename="${2:?}"
+    local _selector_path="${3:-}"
+    local _target_folder_relative_path=
+    local _target_relative_path=
+
+    if [[ -n "${_selector_path:-}"          ]]
+    then
+      if [[ "${_selector_path}" =~ /$                 ]] ||
+         [[ -d "${_notebook_path}/${_selector_path}"  ]]
+      then
+        if [[ ! "${_selector_path}" =~ /$   ]]
+        then
+          _selector_path="${_selector_path}/"
+        fi
+
+        _target_folder_relative_path="$(
+          _selector_resolve_folders "${_selector_path}" --build || :
+        )"
+
+        _target_relative_path="${_target_folder_relative_path}/${_source_basename}"
+      elif [[ "${_selector_path}" =~ /      ]]
+      then
+        _target_folder_relative_path="$(
+          _selector_resolve_folders "${_selector_path}" --build || :
+        )"
+
+        _target_relative_path="${_target_folder_relative_path}/${_selector_path##*\/}"
+      else
+        _target_relative_path="${_selector_path}"
+      fi
+    else
+      _target_relative_path="${_source_basename}"
+    fi
+
+    if [[ "${_target_relative_path:-}" =~ / ]]
+    then
+      _target_folder_relative_path="${_target_relative_path%\/*}"
+
+      if [[ ! -e "${_notebook_path}/${_target_folder_relative_path}" ]]
+      then
+        mkdir -p "${_notebook_path}/${_target_folder_relative_path}"
+      fi
+    fi
+
+    printf "%s\\n" "$(
+      _notebooks show "${_notebook_path}" --filename "${_target_relative_path}"
+    )"
+  }
+
+  # _import_validate_path()
+  #
+  # Usage:
+  #   _import_validate_path <path>
+  _import_validate_path() {
+    if [[     -z "${1:-}" ]]
+    then
+      _exit_1 _help "import"
+    elif [[ ! -e "${1:-}" ]]
+    then
+      _exit_1 printf "File not found: %s\\n" "$(_color_primary "${1:-}")"
+    fi
+  }
+
+  local _convert=0
+  local _paths=()
+  local _selector=
+  local _source_and_target_identifiers=()
+  local _subcommand=
+  local _target_notebook_name=
+  local _url=
+
+  local _local_notebook_path=
+  _local_notebook_path="$(_notebooks --local --path || :)"
+
+  if _piped_input
+  then
+    IFS=$' \n' _paths+=($(cat))
+  fi
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      bookmark|bookmarks)
+        _subcommand="bookmarks"
+        ;;
+      copy|download|move)
+        _subcommand="${__arg}"
+        ;;
+      notebook*)
+        _subcommand="notebook"
+        ;;
+      --convert)
+        _convert=1
+        ;;
+      *)
+        if _string_is_url "${__arg:-}"
+        then
+          _url="${__arg:-}"
+          _subcommand="download"
+        else
+          _source_and_target_identifiers+=("${__arg:-}")
+        fi
+        ;;
+    esac
+  done
+
+  [[ -n "${_subcommand:-}" ]] || _subcommand="copy"
+
+  local __source_and_target_identifier=
+  for   __source_and_target_identifier in "${_source_and_target_identifiers[@]:-}"
+  do
+    if [[    "${_subcommand:-}" == "download" ]] &&
+       [[ -n "${_url:-}"                      ]]
+    then
+      _selector="${__source_and_target_identifier:-}"
+    elif [[ "${_subcommand}" == bookmarks                     ]] &&
+         [[ ! "${__source_and_target_identifier}" =~ ^/       ]] &&
+         [[ "${__source_and_target_identifier}"   =~ (:$|/$)  ]]
+    then
+      _selector="${__source_and_target_identifier}"
+    elif [[ "${_subcommand}" =~ (^copy$|^move$)               ]] &&
+         [[ ! "${__source_and_target_identifier}" =~ ^/       ]] &&
+         {
+           [[ -n "${_local_notebook_path}"                    ]] ||
+           [[ ! -e "${PWD}/${__source_and_target_identifier}" ]]
+         }
+    then
+      _selector="${__source_and_target_identifier}"
+    elif [[ "${_subcommand}" == "notebook"    ]] &&
+         [[ -n "${_paths[*]:-}"               ]]
+    then
+      _target_notebook_name="${__source_and_target_identifier:-}"
+    else
+      _paths+=("${__source_and_target_identifier:-}")
+    fi
+  done
+
+  local _notebook_name=
+  local _notebook_path=
+  local _selector_path=
+
+  if [[ "${_selector:-}" =~ :     ]]
+  then
+    _notebook_name="$(
+      _notebooks show "${_selector%%:*}" --name 2>/dev/null \
+        || _notebooks current --name
+    )"
+    _notebook_path="$(
+      _notebooks show "${_selector%%:*}" --path 2>/dev/null \
+        || _notebooks current --path
+      )"
+    _selector_path="${_selector#*:}"
+  else
+    _notebook_name="$(_notebooks current --name)"
+    _notebook_path="$(_notebooks current --path)"
+    _selector_path="${_selector:-}"
+  fi
+
+  local _source_basename=
+  local _target_basename=
+  local _target_folder_relative_path=
+  local _target_relative_path=
+
+  case "${_subcommand}" in
+    bookmarks)
+      local _target_folder_relative_path=
+      _target_folder_relative_path="$(
+        _selector_resolve_folders "${_selector_path}" --build || :
+      )"
+
+      if [[ -n  "${_target_folder_relative_path:-}"     ]] &&
+         [[ !   "${_target_folder_relative_path}" =~ /$ ]]
+      then
+        _target_folder_relative_path="${_target_folder_relative_path}/"
+      fi
+
+      local __path=
+      for   __path in "${_paths[@]:-}"
+      do
+        _import_validate_path "${__path:-}"
+
+        local               __line=
+        while IFS= read -r  __line || [[ -n "${__line:-}"           ]]
+        do
+          if [[ "${__line}" =~ ^[[:space:]]*\<DT\>                  ]]
+          then
+            if [[ "${__line}" =~ PERSONAL_TOOLBAR_FOLDER=\"true\"   ]]
+            then
+              _target_folder_relative_path="${_target_folder_relative_path}toolbar/"
+            elif [[ "${__line}" =~ \<DT\>\<A.*\>.*\</A\>            ]]
+            then
+              _import_create_bookmark                               \
+                "${_notebook_name}:${_target_folder_relative_path}" \
+                "${__line}" || :
+            elif [[ "${__line}" =~ \<DT\>\<H3.*\>.*\</H3\>          ]]
+            then
+              local _parent_folder_name=
+              _parent_folder_name="$(
+                sed -E -e 's/.*>(.*)<\/H3>.*/\1/g' <<< "${__line}"
+              )"
+
+              _target_folder_relative_path="${_target_folder_relative_path}${_parent_folder_name}/"
+            fi
+          elif [[ "${__line}" =~ \</DL\>\<p\>                       ]]
+          then
+            _target_folder_relative_path="${_target_folder_relative_path%/}"
+
+            if [[ "${_target_folder_relative_path:-}" =~ \/         ]]
+            then
+              _target_folder_relative_path="${_target_folder_relative_path%/*}/"
+            else
+              _target_folder_relative_path=
+            fi
+          fi
+        done < "${__path}"
+      done
+      ;;
+    copy)
+      local __path=
+      for   __path in "${_paths[@]:-}"
+      do
+        _import_validate_path "${__path:-}"
+
+        _source_basename="$(basename -- "${__path}")"
+
+        _target_relative_path="$(
+          _import_init_target_relative_path \
+            "${_notebook_path}"             \
+            "${_source_basename}"           \
+            "${_selector_path}"
+        )"
+
+        if [[ "${_target_relative_path}" =~ / ]]
+        then
+          _target_folder_relative_path="${_target_relative_path%\/*}"
+        fi
+
+        _target_basename="${_target_relative_path##*\/}"
+
+        if [[ -d "${__path}"      ]]
+        then
+          cp -R "${__path}" "${_notebook_path}/${_target_relative_path}"
+        else
+          cp "${__path}" "${_notebook_path}/${_target_relative_path}"
+        fi &&
+          _index add              \
+            "${_target_basename}" \
+            "${_notebook_path}/${_target_folder_relative_path}" &&
+              _git checkpoint "${_notebook_path}" "[${_ME}] Import: ${_target_relative_path}"
+
+        printf "Imported %s from %s\\n"                                       \
+          "$(_show "${_notebook_path}/${_target_relative_path}" --info-line)" \
+          "$(_color_primary "${__path}")"
+      done
+      ;;
+    download)
+      _source_basename="$(basename -- "${_url}" | tr -d '[:space:]')"
+
+      if [[ "${_url}" =~ \/$ ]]
+      then
+        _source_basename="${_source_basename}.html"
+      fi
+
+      _target_relative_path="$(
+        _import_init_target_relative_path \
+          "${_notebook_path}"             \
+          "${_source_basename}"           \
+          "${_selector_path}"
+      )"
+
+      if [[ "${_target_relative_path}" =~ / ]]
+      then
+        _target_folder_relative_path="${_target_relative_path%\/*}"
+      fi
+
+      _target_basename="${_target_relative_path##*\/}"
+
+      if ((_convert))
+      then
+        if ! _download_from "${_url}" \
+            | _pandoc                 \
+              --standard-input        \
+              --from html             \
+              --to markdown           \
+              -o "${_notebook_path}/${_target_relative_path}"
+        then
+          _exit_1 printf "Unable to download and convert: %s\\n" "${_url}"
+        fi
+      else
+        if ! _download_from "${_url}" "${_notebook_path}/${_target_relative_path}"
+        then
+          _exit_1 printf "Unable to download: %s\\n" "${_url}"
+        fi
+      fi &&
+        _index add              \
+          "${_target_basename}" \
+          "${_notebook_path}/${_target_folder_relative_path:-}" &&
+            _git checkpoint "${_notebook_path}" "\
+[${_ME}] Import: ${_target_relative_path}
+
+Source:
+${_url}
+"
+      printf "Imported %s from %s\\n"                     \
+        "$(_show "${_target_relative_path}" --info-line)" \
+        "$(_color_primary "${_url}")"
+      ;;
+    move)
+      local __path=
+      for   __path in "${_paths[@]:-}"
+      do
+        _import_validate_path "${__path:-}"
+
+        _source_basename="$(basename -- "${__path}")"
+
+        _target_relative_path="$(
+          _import_init_target_relative_path   \
+            "${_notebook_path}"               \
+            "${_source_basename}"             \
+            "${_selector_path}"
+        )"
+
+        if [[ "${_target_relative_path}" =~ / ]]
+        then
+          _target_folder_relative_path="${_target_relative_path%\/*}"
+        fi
+
+        _target_basename="${_target_relative_path##*\/}"
+
+        mv "${__path}" "${_notebook_path}/${_target_relative_path}" &&
+          _index add              \
+            "${_target_basename}" \
+            "${_notebook_path}/${_target_folder_relative_path:-}"   &&
+              _git checkpoint "${_notebook_path}" "[${_ME}] Import: ${_target_relative_path}"
+
+        printf "Imported %s from %s\\n"                     \
+          "$(_show "${_target_relative_path}" --info-line)" \
+          "$(_color_primary "${__path}")"
+      done
+      ;;
+    notebook)
+      _notebooks import "${_paths[0]:-}" "${_target_notebook_name:-}"
+
+      return 0
+      ;;
+    *)
+      _exit_1 _help "import"
+      ;;
+  esac
+}
+_alias_subcommand "import" "i"
+
+# move ################################################################### move
+
+_describe_move() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} move ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          ([<notebook>:][<path>] | --reset | --to-bookmark | --to-note |
+          --to-title | --to-todo) [-f | --force]
+
+$(_color_primary "Options"):
+  -f, --force     Skip the confirmation prompt.
+  --reset         Reset the filename to the last modified timestamp.
+  --to-bookmark   Preserve the existing filename and replace the extension
+                  with ".bookmark.md" to convert the note to a bookmark.
+  --to-note       Preserve the existing filename and replace the bookmark's
+                  ".bookmark.md" extension with ".md" to convert the bookmark
+                  to a Markdown note.
+  --to-title      Set the filename to the note title, lowercased with spaces
+                  and disallowed filename characters replaced with underscores.
+  --to-todo       Preserve the existing filename and replace the extension
+                  with ".todo.md" to convert the note to a todo.
+
+$(_color_primary "Description"):
+  Move or rename a note. Move the note to <path> or change the file type.
+  When the file extension is omitted, the existing extension is used.
+  When only a file extension is specified, only the extension will be updated.
+
+  \`move\` and \`rename\` are aliases and can be used interchangeably.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-moving--renaming
+
+$(_color_primary "See Also"):
+  ${_ME} help copy
+  ${_ME} help delete
+  ${_ME} help edit
+
+$(_color_primary "Examples"):
+  # move "example.md" to "sample.org"
+  ${_ME} move example.md sample.org
+
+  # rename note 3 ("example.md") to "New Name.md"
+  ${_ME} rename 3 "New Name"
+
+  # rename "example.bookmark.md" to "New Name.bookmark.md"
+  ${_ME} move example.bookmark.md "New Name"
+
+  # rename note 3 ("example.md") to a bookmark named "example.bookmark.md"
+  ${_ME} rename 3 --to-bookmark
+
+  # move note 12 into "Sample Folder" in the "demo" notebook
+  ${_ME} move example:12 demo:Sample\ Folder/
+
+  # rename note 12 in the "example" notebook to "sample.md"
+  ${_ME} rename example:12 "sample.md"
+
+  # change the file extension of note 5 to .org
+  ${_ME} rename 5 .org
+
+$(_color_primary "Alias"):
+  ${_ME} rename
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} mv
+HEREDOC
+}
+_move() {
+  local _force=0
+  local _reset=0
+  local _selectors=()
+  local _to_target_type=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -f|--force|--skip*|-y|--yes)
+        _force=1
+        ;;
+      --reset)
+        _reset=1
+        ;;
+      --to*bookmark)
+        _to_target_type="bookmark"
+        ;;
+      --to*note)
+        _to_target_type="note"
+        ;;
+      --to*title)
+        _to_target_type="title"
+        ;;
+      --to*todo)
+        _to_target_type="todo"
+        ;;
+      --to)
+        _to_target_type="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      -*)
+        :
+        ;;
+      *)
+        _selectors+=("${1:-}")
+        ;;
+    esac
+
+    shift
+  done
+
+  local _source_selectors=()
+  local _target_selector=
+
+  if ((${#_selectors[@]}))
+  then
+    local i=
+    for ((i=0; i < ${#_selectors[@]}; i++))
+    do
+      _source_selectors+=("${_selectors[i]}")
+    done
+
+    if ((${#_selectors[@]} - 1))
+    then
+      _target_selector="${_selectors[${#_selectors[@]}-1]}"
+    fi
+  fi
+
+  if ! ((${#_source_selectors[@]}))
+  then
+    _exit_1 _help "move"
+  fi
+
+  local _source_relative_path=
+  _source_relative_path="$(_show "${_source_selectors[0]}" --relative-path)"
+
+  if [[ -z "${_source_relative_path:-}"     ]]
+  then
+    _exit_1 _help "move"
+  fi
+
+  local _source_notebook_path=
+  if [[ "${_source_selectors[0]:-}" =~ :    ]]
+  then
+    _source_notebook_path="$(
+      _notebooks show "${_source_selectors[0]}" --path 2>/dev/null || :
+    )"
+  fi
+
+  if [[ -z "${_source_notebook_path:-}"     ]]
+  then
+    _source_notebook_path="$(_notebooks current --path)"
+  fi
+
+  local _source_basename="${_source_relative_path##*\/}"
+  local _source_folder_path="${_source_notebook_path}"
+  local _source_path="${_source_notebook_path}/${_source_relative_path}"
+
+  if [[ "${_source_relative_path:-}" =~ /   ]]
+  then
+    _source_folder_path="${_source_notebook_path}/${_source_relative_path%\/*}"
+  fi
+
+  local _source_file_name="${_source_basename%%.*}"
+  local _source_file_type="${_source_basename#*.}"
+
+  if [[ -z "${_source_file_type:-}"                     ]] ||
+     [[ "${_source_file_type}" == "${_source_basename}" ]]
+  then
+    _source_file_type=
+  fi
+
+  local _target_selector_relative_path=
+
+  if ((_reset))
+  then
+    local _target_file_name=
+    _target_file_name="$(
+      date -r "${_source_notebook_path}/${_source_relative_path}" "+%Y%m%d%H%M%S"
+    )"
+
+    local _target_file_type="${_source_file_type:-"${NB_DEFAULT_EXTENSION}"}"
+
+    _target_basename="${_target_file_name}.${_target_file_type}"
+  elif [[ "${_to_target_type:-}" == "title" ]]
+  then
+    if ! _file_is_text "${_source_path:-}"
+    then
+      _exit_1 printf "Must be a text file.\\n"
+    fi
+
+    local _source_title=
+    _source_title="$(_get_content "${_source_path:-}" --title)"
+
+    if [[ -z "${_source_title:-}"           ]]
+    then
+      _exit_1 printf "Title not found.\\n"
+    fi
+
+    local _processed_title=
+    _processed_title="$(
+      printf "%s" "${_source_title}"        \
+        | tr '[:upper:]' '[:lower:]'        \
+        | tr '[:space:]:*/\\<>?|' '_'       \
+        | tr "\"" '_'
+    )"
+
+    local _target_file_type="${_source_file_type:-"${NB_DEFAULT_EXTENSION}"}"
+
+    _target_basename="${_processed_title}.${_target_file_type}"
+  elif [[ -n "${_target_selector:-}"        ]] ||
+       [[ -n "${_to_target_type:-}"         ]]
+  then
+    _target_selector_relative_path="${_target_selector#*:}"
+
+    local _target_basename="${_target_selector_relative_path##*\/}"
+    local _target_file_name="${_target_basename%%.*}"
+    local _target_file_type="${_target_basename#*.}"
+
+    if [[   -n "${_target_file_type:-}"                         ]] &&
+       [[   -z "${_target_file_name:-}"                         ]]
+    then # only file extension in target
+      _target_selector_relative_path=""
+    elif [[ -z "${_target_file_type:-}"                         ]] ||
+         [[    "${_target_file_type}" == "${_target_basename}"  ]]
+    then # no file extension in target
+      if [[ -n "${_source_file_type}"                           ]]
+      then
+        _target_file_type="${_source_file_type}"
+      else
+        _target_file_type=
+      fi
+    fi
+
+    case "${_to_target_type:-}" in
+      '')       :                                               ;;
+      bookmark) _target_file_type="bookmark.md"                 ;;
+      note)     _target_file_type="${NB_DEFAULT_EXTENSION:-md}" ;;
+      todo)     _target_file_type="todo.md"                     ;;
+      *)        _target_file_type="${_to_target_type#.}"        ;;
+    esac
+
+    if [[ -z "${_target_file_name:-}" ]]
+    then
+      _target_file_name="${_source_file_name}"
+    fi
+
+    if [[ -n "${_target_file_type:-}" ]]
+    then
+      _target_basename="${_target_file_name}.${_target_file_type}"
+    else
+      _target_basename="${_target_file_name}"
+    fi
+  else
+    _exit_1 _help "move"
+  fi
+
+  if [[ -z  "${_target_selector_relative_path:-}" ]]
+  then
+    if [[   "${_source_relative_path}" =~ /       ]]
+    then
+      _target_selector_relative_path="${_source_relative_path%/*}/${_target_basename}"
+    else
+      _target_selector_relative_path="${_target_basename}"
+    fi
+  fi
+
+  local _target_info=
+  local _target_notebook_path=
+
+  if [[       "${_target_selector:-}" =~ :  ]]
+  then
+    _target_notebook_path="$(
+      _notebooks show "${_target_selector:-}" --path 2>/dev/null || :
+    )"
+
+    if [[ -z  "${_target_notebook_path:-}"  ]]
+    then
+      _exit_1 printf "Target notebook not found: %s\\n" "${_target_selector%%:*}"
+    fi
+  else
+    _target_notebook_path="$(_notebooks current --path)"
+  fi
+
+  if _notebooks current --selected ||
+     [[ "${_target_notebook_path}" != "$(_notebooks current --path)" ]]
+  then
+    _target_info="$(_notebooks show "${_target_notebook_path}" --name --no-color):"
+  fi
+
+  local _target_folder_relative_path=
+
+  if [[ -n "${_target_selector_relative_path:-}"  ]]
+  then
+    _target_folder_relative_path="$(
+      _selector_resolve_folders "${_target_selector_relative_path}" --build || :
+    )"
+
+    if [[ -z "${_target_folder_relative_path:-}"  ]]
+    then
+      _target_folder_relative_path="${_target_selector_relative_path%\/*}"
+    fi
+  fi
+
+  local _target_folder_path=
+  local _target_relative_path=
+
+  if [[   "${_target_selector_relative_path:-}" =~ /            ]]
+  then
+    _target_folder_path="${_target_notebook_path}/${_target_folder_relative_path}"
+    _target_relative_path="${_target_folder_relative_path}/${_target_basename}"
+  else
+    _target_folder_path="${_target_notebook_path}"
+    _target_relative_path="${_target_basename}"
+  fi
+
+  _target_info+="${_target_relative_path}"
+
+  if [[ -e  "${_target_notebook_path}/${_target_relative_path}" ]]
+  then
+    _exit_1 printf "File already exists: %s\\n"         \
+      "$(_color_primary "${_target_info}")"
+  fi
+
+  if ! ((_force))
+  then
+    printf "Moving:   %s\\n" "$(_show "${_source_path}" --info-line)"
+    printf "To:       %s\\n" "$(_color_primary "${_target_info}")"
+
+    while true
+    do
+      local __yn=
+      IFS='' read -r -e -d $'\n' -p                     \
+"$(_color_primary "Proceed?")  $(_color_brackets "y/N") " __yn
+
+      case "${__yn}" in
+        [Yy]*)
+          break
+          ;;
+        *)
+          printf "Exiting%s\\n" "$(_color_muted "...")"
+
+          exit 0
+          ;;
+      esac
+    done
+  fi
+
+  if [[ ! -e "${_target_folder_path}" ]]
+  then
+    mkdir -p "${_target_folder_path}" ||
+      _exit_1 printf "Unable to create folder: %s\\n"   \
+        "$(_color_primary "${_target_folder_path}")"
+  fi
+
+  mv "${_source_path}" "${_target_notebook_path}/${_target_relative_path}" ||
+    _exit_1 printf "Move failed.\\n"
+
+  if [[ -e "${_source_folder_path:-}/.pindex"           ]]  &&
+     grep -q  "^${_source_basename}$"     "${_source_folder_path:-}/.pindex"
+  then
+    if [[ "${_source_folder_path}" == "${_target_folder_path}"    ]]
+    then
+      _sed_i -e                                         \
+        "s/^${_source_basename}$/${_target_basename}/"  \
+        "${_source_folder_path:-}/.pindex"
+    else
+      _sed_i -e                                         \
+        "/^${_source_basename}$/d"                      \
+        "${_source_folder_path:-}/.pindex"
+
+      if [[ ! -e "${_target_folder_path:-}/.pindex"     ]]
+      then
+        touch "${_target_folder_path:-}/.pindex"
+      fi
+
+      printf "%s\\n" "${_target_basename}" >> "${_target_folder_path:-}/.pindex"
+    fi
+  fi
+
+  if [[ "${_source_notebook_path}" == "${_target_notebook_path}"  ]]
+  then
+    if [[ "${_source_folder_path}" == "${_target_folder_path}"    ]]
+    then
+      _index update               \
+        "${_source_basename}"     \
+        "${_target_basename}"     \
+        "${_source_folder_path}"
+    else
+      _index delete "${_source_basename}" "${_source_folder_path}"  &&
+        _index add  "${_target_basename}" "${_target_folder_path}"
+    fi || _exit_1 printf "Move index update failed.\\n"
+
+    _git checkpoint "${_target_notebook_path}"  \
+      "[${_ME}] Move: ${_source_relative_path} to ${_target_relative_path}"
+  else
+    _index delete "${_source_basename}" "${_source_folder_path}"
+
+    _git checkpoint "${_source_notebook_path}"  \
+      "[${_ME}] Delete: ${_source_relative_path}"
+
+    _index add "${_target_basename}" "${_target_folder_path}"
+
+    _git checkpoint "${_target_notebook_path}"  \
+      "[${_ME}] Add: ${_target_relative_path}"
+  fi
+
+  printf "Moved to: %s\\n" "$(
+    _show "${_target_notebook_path}/${_target_relative_path}" --info-line
+  )"
+}
+_alias_subcommand "move" "mv"
+_alias_subcommand "move" "rename"
+
+# open ################################################################### open
+
+_describe_open() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} open ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+
+$(_color_primary "Description"):
+  Open an item or notebook. When the item is a bookmark, open the bookmarked
+  page in your system's primary web browser. When the item is in a text format
+  or any other file type, \`open\` is the equivalent of \`edit\`. \`open\`
+  with a notebook opens the notebook folder in the system's file browser.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#viewing-bookmarks
+
+$(_color_primary "See also"):
+  ${_ME} help bookmark
+  ${_ME} help browse
+  ${_ME} help peek
+  ${_ME} help show
+
+$(_color_primary "Examples"):
+  ${_ME} open 3
+  ${_ME} open example.bookmark.md
+  ${_ME} 3 open
+  ${_ME} example:open 12
+  ${_ME} open example:12
+  ${_ME} example:12 open
+  ${_ME} o 3
+  ${_ME} 3 o
+  ${_ME} o example:12
+  ${_ME} example:12 o
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} o
+HEREDOC
+}
+_open() {
+  if [[ -z "${1:-}" ]]
+  then
+    _exit_1 _help "open"
+  fi
+
+  _bookmark open "${@:-}"
+}
+_alias_subcommand "open" "o"
+
+# peek ################################################################### peek
+
+_describe_peek() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} peek ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+
+$(_color_primary "Description"):
+  View an item or notebook in the terminal. When the item is a bookmark, view
+  the bookmarked page in your terminal web browser. When the note is in a text
+  format or any other file type, \`peek\` is the equivalent of \`show\`. When
+  used with a notebook, \`peek\` opens the notebook folder first tool found in
+  the following list: \`ranger\` [1], \`mc\` [2], \`vifm\` [3], \`joshuto\` [4],
+  \`exa\` [5], or \`ls\`.
+
+    1. https://ranger.github.io/
+    2. https://en.wikipedia.org/wiki/Midnight_Commander
+    3. https://vifm.info/
+    4. https://github.com/kamiyaa/joshuto
+    5. https://github.com/ogham/exa
+
+$(_color_primary "Read More"):
+  ${_README_URL}#viewing-bookmarks
+
+$(_color_primary "See also"):
+  ${_ME} help bookmark
+  ${_ME} help browse
+  ${_ME} help open
+  ${_ME} help show
+
+$(_color_primary "Examples"):
+  ${_ME} peek 3
+  ${_ME} peek example.bookmark.md
+  ${_ME} 3 peek
+  ${_ME} example:peek 12
+  ${_ME} peek example:12
+  ${_ME} example:12 peek
+  ${_ME} p 3
+  ${_ME} 3 p
+  ${_ME} p example:12
+  ${_ME} example:12 p
+
+$(_color_primary "Alias"):
+  ${_ME} preview
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} p
+HEREDOC
+}
+_peek() {
+  if [[ -z "${1:-}" ]]
+  then
+    _exit_1 _help "peek"
+  fi
+
+  _bookmark peek "${@}"
+}
+_alias_subcommand "peek" "p"
+_alias_subcommand "peek" "preview"
+
+# pin ##################################################################### pin
+
+_describe_pin() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} pin ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+
+$(_color_primary "Description"):
+  Pin an item so it appears first in lists.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-pinning
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help list
+  ${_ME} help ls
+  ${_ME} help unpin
+
+$(_color_primary "Examples"):
+  ${_ME} pin 123
+  ${_ME} pin example:sample/321
+HEREDOC
+}
+_pin() {
+  local _selector=
+  local _subcommand="pin"
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg:-}" in
+      unpin)  _subcommand="unpin"     ;;
+      *)      _selector="${__arg:-}"  ;;
+    esac
+  done
+
+  if [[ -z "${_selector:-}" ]]
+  then
+    _warn _help "${_subcommand}"
+
+    return 1
+  fi
+
+  local _item_path=
+  _item_path="$(_show "${_selector}" --path)" || return 1
+
+  local _basename="${_item_path##*\/}"
+  local _folder_path="${_item_path%\/*}"
+  local _pindex_path="${_folder_path}/.pindex"
+
+  local _notebook_path=
+  _notebook_path="$(
+    _notebooks show "${_selector}" --path 2>/dev/null ||
+      _notebooks current --path
+  )"
+
+  local _relative_path=
+  _relative_path="$(_show "${_selector}" --relative-path)"
+
+  if [[ ! -e "${_item_path:-}"        ]] ||
+     [[ ! -d "${_folder_path:-}"      ]] ||
+     [[   -z "${_basename:-}"         ]] ||
+     [[   -z "${_notebook_path:-}"    ]] ||
+     [[   -z "${_relative_path:-}"    ]]
+  then
+    _warn printf "Not found: %s\\n" "${_selector}"
+
+    return 1
+  fi
+
+  case "${_subcommand:-}" in
+    unpin)
+      if [[ ! -e "${_pindex_path}"    ]] ||
+         ! grep -q "^${_basename}$" "${_pindex_path}"
+      then
+        _warn printf                  \
+          "Not pinned: %s\\n"         \
+          "$(_color_primary "${_selector}")"
+
+        return 1
+      fi
+
+      _sed_i -e "s/^${_basename}$//g"   "${_pindex_path}"
+      _sed_i -e '/^[[:space:]]*$/d'     "${_pindex_path}" # remove blank line
+
+      if [[ ! -s "${_pindex_path:?}"  ]]
+      then
+        rm -f "${_pindex_path:?}"
+      fi
+
+      _git checkpoint "${_notebook_path}" "[${_ME}] Unpinned: ${_relative_path}"
+
+      printf "Unpinned: %s\\n" "$(_show "${_selector}" --info-line)"
+      ;;
+    *)
+      if [[ ! -e "${_pindex_path}"    ]]
+      then
+        touch "${_pindex_path}"
+      fi
+
+      if grep -q "^${_basename}$" "${_pindex_path}"
+      then
+        _warn printf                  \
+          "Already pinned: %s\\n"     \
+          "$(_color_primary "${_selector}")"
+
+        return 1
+      else
+        printf "%s\\n" "${_basename}" >> "${_pindex_path}"
+        _sed_i -e '/^[[:space:]]*$/d'    "${_pindex_path}" # remove blank lines
+
+        _git checkpoint "${_notebook_path}" "[${_ME}] Pinned: ${_relative_path}"
+
+        printf "Pinned: %s\\n" "$(_show "${_selector}" --info-line)"
+      fi
+      ;;
+  esac
+}
+
+# run ##################################################################### run
+
+_describe_run() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} run <command> [<arguments>...]
+
+$(_color_primary "Description"):
+  Run shell commands within the current notebook directory.
+
+$(_color_primary "See Also"):
+  ${_ME} help git
+  ${_ME} help shell
+
+$(_color_primary "Examples"):
+  ${_ME} run ls -la
+  ${_ME} run find . -name 'example*'
+  ${_ME} run rg example
+HEREDOC
+}
+_run() {
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  cd "${_notebook_path}"  || _exit_1 printf "_run() \`cd\` failed.\\n"
+  [[ -n "${*}" ]]         || _exit_1 printf "Command required.\\n"
+
+  if ! _command_exists "${1:-}"
+  then
+    _exit_1 printf "Command not found: %s\\n" "$(_color_primary "${1:-}")"
+  fi
+
+  ("${@}")
+}
+_alias_subcommand "run" "r"
+
+# search ############################################################### search
+
+_describe_search() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} search ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+            <query>... [-a | --all] [--and <query>] [--or <query>]
+            [-l | --list] [--path] [-t <tag1>,<tag2>... | --tag <tag1>,<tag2>...]
+            [-t | --tags] [--type <type> | --<type>] [--utility <name>]
+
+$(_color_primary "Options"):
+  -a, --all                     Search all unarchived notebooks.
+  --and <query>                 Add a AND query.
+  -l, --list                    Print the id, filename, and title listing for
+                                each matching file, without the excerpt.
+  --or <query>                  Add an OR query.
+  --path                        Print the full path for each matching file.
+  -t, --tag <tag1>,<tag2>...    A comma-separated list of tags.
+  -t, --tags                    List all tags found in the notebook.
+  --type <type>, --<type>       Search items of <type>. <type> can be a file
+                                extension or one of the following types:
+                                note, bookmark, document, archive, image,
+                                video, audio, folder, text
+  --utility <name>              The name of the search utility to search with.
+
+$(_color_primary "Description"):
+  Perform a full text search.
+
+  Multiple query arguments are treated as AND queries, returning items that
+  match all queries. AND queries can also be specified with the --and <query>
+  option. The --or <query> option can be used to specify an OR query,
+  returning items that match at least one of the queries.
+
+  \`${_ME} search\` is powered by Git's built-in \`git grep\` tool. \`${_ME}\` also
+  supports performing searches with alternative search tools using the
+  --utility <name> option.
+
+  Supported alternative search tools:
+    1. \`rga\`   https://github.com/phiresky/ripgrep-all
+    2. \`rg\`    https://github.com/BurntSushi/ripgrep
+    3. \`ag\`    https://github.com/ggreer/the_silver_searcher
+    4. \`ack\`   https://beyondgrep.com/
+    5. \`grep\`  https://en.wikipedia.org/wiki/Grep
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-search
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help list
+  ${_ME} help ls
+
+$(_color_primary "Examples"):
+  # search current notebook for "example query"
+  ${_ME} search "example query"
+
+  # search the notebook "example" for "example query"
+  ${_ME} search example: "example query"
+
+  # search all notebooks for "example query" and list matching items
+  ${_ME} search "example query" --all --list
+
+  # search for items matching "Example" AND "Demo"
+  ${_ME} search "Example" "Demo"
+  ${_ME} search "Example" --and "Demo"
+
+  # search for items matching "Example" OR "Sample"
+  ${_ME} search "Example|Sample"
+  ${_ME} search "Example" --or "Sample"
+
+  # search with a regular expression
+  ${_ME} search "\d\d\d-\d\d\d\d"
+
+  # search for tags
+  ${_ME} search --tag tag1 -t tag2
+
+  # search the current notebook for "example query"
+  ${_ME} q "example query"
+
+  # search all notebooks for "example query" and list matching items
+  ${_ME} q -la "example query"
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} q
+HEREDOC
+}
+_search() {
+  # Usage: _search_with <command-name> <search-utility>
+  _search_with() {
+    _command_exists "${1:?}" && [[ "${2:-}" == "${1:?}" ]]
+  }
+
+  local _all=0
+  local _and_queries=()
+  local _arguments=()
+  local _last_path=
+  local _limit=0
+  local _max_columns="2000"
+  local _max_depth=0
+  local _only_list=0
+  local _option_tags=()
+  local _or_queries=()
+  local _page=1
+  local _print_notebook_selectors=0
+  local _print_paths=0
+  local _query=
+  local _replacement=
+  local _search_args=()
+  local _search_for_tags=0
+  local _search_utility=
+  local _selectors=()
+  local _sort=0
+  local _type=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -a|--all)
+        _all=1
+        ;;
+      --and|--or)
+        local _option_and=1
+
+        if [[ "${1:-}" == "--or"  ]]
+        then
+          _option_and=0
+        fi
+
+        if [[ "${2:-}" == "-e"    ]]
+        then
+          shift
+        fi
+
+        if [[ "${2:-}" =~ (^-t$|^--tag*|^--hashtag*) ]] &&
+           _option_value_is_present "${3:-}"
+        then
+          shift
+
+          IFS=' ' read -ra _option_tags <<< "$(
+            _option_get_tags "${1:-}" "${2:-}"
+          )"
+
+          if ((_option_and))
+          then
+            _and_queries+=(${_option_tags[@]:-})
+          else
+            _or_queries+=(${_option_tags[@]:-})
+          fi
+
+          shift
+        else
+          if ((_option_and))
+          then
+            _and_queries+=("$(_option_get_value "--and" "${2:-}")")
+          else
+            _or_queries+=("$(_option_get_value "--or" "${2:-}")")
+          fi
+
+          shift
+        fi
+        ;;
+      --limit|-n|--num|--number|--per*)
+        _limit="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      -l|--list)
+        _only_list=1
+        ;;
+      --no*color)
+        _COLOR_ENABLED=0
+        ;;
+      --no*recur*)
+        _max_depth=1
+        ;;
+      --notebook-selectors)
+        _print_notebook_selectors=1
+        ;;
+      --page)
+        _page="$(_option_get_value "${1}" "${2:-}")"
+        ((_page)) || _page=1
+
+        shift
+        ;;
+      --path*)
+        _print_paths=1
+        _COLOR_ENABLED=0
+        ;;
+      -q|--query|-e)
+        _and_queries+=("$(_option_get_value "${1}" "${2:-}")")
+
+        shift
+        ;;
+      --replace*)
+        # TODO
+        _replacement="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      -s|--sort)
+        _sort=1
+        ;;
+      -t|--tag*|--hashtag*)
+        if _option_value_is_present "${2:-}"
+        then
+          IFS=' ' read -ra _option_tags <<< "$(
+            _option_get_tags "${1:-}" "${2:-}"
+          )"
+
+          _and_queries+=(${_option_tags[@]:-})
+
+          shift
+        else
+          _search_for_tags=1
+        fi
+        ;;
+      --*tool|--*utility)
+        _search_utility="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --type)
+        _type="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --use*grep)
+        # TODO: Remove. Replaced with the --tool / --utility option.
+        _search_utility="grep"
+        ;;
+      *)
+        if [[ "${1:-}" =~ ^-- ]]
+        then
+          _type="${1:2}"
+        else
+          _arguments+=("${1}")
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  local _current_notebook_path=
+  _current_notebook_path="$(_notebooks current --path)"
+
+  local _local_notebook_path=
+  _local_notebook_path="$(_notebooks --local --path || :)"
+
+  local _target_paths=()
+
+  if ((_all))
+  then
+    _target_paths=($(_notebooks --paths --unarchived))
+  fi
+
+  local i=
+  for ((i=0; i < ${#_arguments[@]}; i++))
+  do
+    local _maybe_path=
+
+    if [[ -z "${_arguments[i]:-}"     ]]
+    then
+      continue
+    elif [[ "${_arguments[i]}" =~ :$  ]]
+    then
+      _maybe_path="$(
+        _notebooks show "${_arguments[i]}" --path 2>/dev/null || :
+      )"
+
+      if [[ -n "${_maybe_path:-}"     ]]
+      then
+        _notebooks select "${_arguments[i]}"
+      fi
+    else
+      if [[ "${_arguments[i]}" =~ ^/  ]]
+      then
+        _maybe_path="${_arguments[i]%/}"
+      else
+        _maybe_path="$(
+          _selector_resolve_path "${_arguments[i]:-}" \
+            --full                                    \
+            --skip-titles                             \
+            2>/dev/null || :
+        )"
+      fi
+    fi
+
+    if [[ -z "${_maybe_path:-}"                     ]] ||
+       {
+         [[ "${i}" -eq "$((${#_arguments[@]} - 1))" ]] &&
+         [[ -z "${_and_queries[*]:-}"               ]]
+       }
+    then
+      local _query_argument="${_arguments[i]:-}"
+
+      if [[ "${_query_argument:-}"    =~ ^[^/]*/$   ]]
+      then
+        if [[ -d "${_maybe_path:-}"   ]]
+        then
+          _query_argument=
+        else
+          _query_argument="${_query_argument%\/}"
+        fi
+      fi
+
+      if _notebooks current --selected
+      then
+        _and_queries+=("${_query_argument#*:}")
+      else
+        _and_queries+=("${_query_argument}")
+      fi
+    fi
+
+    if [[ -n "${_maybe_path:-}"       ]] &&
+       [[ -z "${_target_paths[*]:-}"  ]] &&
+       {
+         _notebooks current --selected   ||
+         [[ "${#_arguments[@]}" -gt 1 ]] ||
+         ((_search_for_tags))
+       }
+    then
+      _target_paths+=("${_maybe_path}")
+      _selectors+=("${_arguments[i]}")
+    fi
+  done
+
+  if [[ -z "${_target_paths[*]:-}"    ]]
+  then
+    _target_paths=("${_current_notebook_path}")
+  fi
+
+  local _xargs=("-0")
+
+  if xargs --help &> /dev/null
+  then # GNU (BSD does this by default)
+    _xargs+=("--no-run-if-empty")
+  fi
+
+  if ((_search_for_tags))
+  then
+    local _git_major_version=
+    _git_major_version="$(git --version | cut -d " "  -f 3 | cut -d "." -f 1)"
+
+    local _git_minor_version=
+    _git_minor_version="$(git --version | cut -d " "  -f 3 | cut -d "." -f 2)"
+
+    local _use_git_grep=0
+
+    if ((_GIT_ENABLED))                           &&
+       [[ "${_git_major_version:-}"   -gt 2   ]]  ||  {
+         [[ "${_git_major_version:-}" ==  2   ]]  &&
+         [[ "${_git_minor_version:-}" -ge 19  ]]
+    }
+    then # git 2.19+ has --only-matching option
+      _use_git_grep=1
+    fi
+
+    local _grep_arguments=(
+      "--color=never"
+      "--extended-regexp"
+      "-I"
+      "--ignore-case"
+      "--only-matching"
+      -e '\s#[A-Za-z0-9_-]+'
+      -e '^#[A-Za-z0-9_-]+'
+    )
+
+    {
+      local __target_path=
+      for   __target_path in "${_target_paths[@]:-}"
+      do
+        [[ -n "${__target_path:-}"    ]] || continue
+
+        if [[ -d "${__target_path:-}" ]]
+        then
+          local _target_folder_path="${__target_path:-}"
+        else
+          local _target_folder_path="${__target_path%/*}"
+        fi
+
+        {
+          if ((_use_git_grep))
+          then
+            GIT_PAGER=''                      \
+              git -C "${_target_folder_path}" \
+              grep                            \
+              "${_grep_arguments[@]:-}"       \
+              --files-with-matches            \
+              --null                          \
+              "${__target_path}"              \
+              2>/dev/null || true
+          else
+            {
+              find "${__target_path}"         \
+                ! -path '*/.git*'             \
+                -path '*/[^.]*'               \
+                -type f                       \
+                -print0
+            } | {
+              xargs "${_xargs[@]}"            \
+                grep                          \
+                "${_grep_arguments[@]:-}"     \
+                --files-with-matches          \
+                --null
+            }
+          fi
+        } | {
+          if ((_use_git_grep))
+          then
+            GIT_PAGER=''                      \
+              xargs "${_xargs[@]}"            \
+              git -C "${_target_folder_path}" \
+              grep                            \
+              "${_grep_arguments[@]:-}"       \
+              -e "## Comment"                 \
+              -e "## Tags"                    \
+              -e "## Content"                 \
+              -e "## Page Content"            \
+              -e "## Source"                  \
+              2>/dev/null || true
+          else
+            xargs "${_xargs[@]}"              \
+              grep                            \
+              "${_grep_arguments[@]:-}"       \
+              -e "## Comment"                 \
+              -e "## Tags"                    \
+              -e "## Content"                 \
+              -e "## Page Content"            \
+              -e "## Source"                  \
+              2>/dev/null || true
+          fi
+        }
+      done
+    } | {
+      local _last_match_path=
+      local _match_path=
+      local _seen_matches=()
+      local _skip=1
+
+      local         __match=
+      while read -r __match
+      do
+        if [[ "${__match:-}" =~ : ]]
+        then
+          _match_path="${__match%:*}"
+        fi
+
+        local _normalized_match="${__match##*:}"
+        _normalized_match="${_normalized_match#"${_normalized_match%%[![:space:]]*}"}"
+        _normalized_match="${_normalized_match%"${_normalized_match##*[![:space:]]}"}"
+
+        if [[ "${_match_path:-}"              =~ \.bookmark\.md$    ]]
+        then
+          if [[ "${_last_match_path:-}"       != "${_match_path:-}" ]]
+          then
+            _skip=1
+            _last_match_path="${_match_path}"
+          fi
+
+          if [[ "${_normalized_match:-}"      =~ ^##                ]]
+          then
+            if [[ "${_normalized_match:-}"    =~ (Comment|Tags)     ]]
+            then
+              _skip=0
+            elif [[ "${_normalized_match:-}"  =~ (Content|Source)   ]]
+            then
+              _skip=1
+            fi
+
+            continue
+          fi
+
+          if ((_skip))
+          then
+            continue
+          fi
+        elif [[ "${_normalized_match:-}"      =~ ^##                ]]
+        then
+          continue
+        fi
+
+        if ! _contains "${_normalized_match}" "${_seen_matches[@]:-}"
+        then
+          printf "%s\\n" "${_normalized_match:-}"
+          _seen_matches+=("${_normalized_match:-}")
+        fi
+      done
+
+      if ! ((${#_seen_matches[@]}))
+      then
+        printf "No #hashtags found.\\n"
+      fi
+    }
+
+    return 0
+  fi
+
+  if [[ -z "${_and_queries[*]:-}" ]]
+  then
+    _exit_1 _help "search"
+  fi
+
+  local _queries=()
+
+  local __and_query=
+  for   __and_query in "${_and_queries[@]:-}"
+  do
+    [[ -n "${__and_query:-}"      ]] || continue
+
+    if ((${#_or_queries[@]}))
+    then
+      local _or_query_string=
+
+      local __or_query=
+      for   __or_query in "${_or_queries[@]:-}"
+      do
+        [[ -n "${__or_query:-}"   ]] || continue
+
+        _or_query_string="${_or_query_string}|${__or_query}"
+      done
+
+      _queries+=("${__and_query}${_or_query_string}")
+    else
+      _queries+=("${__and_query}")
+    fi
+  done
+
+  local _query=
+  _query="$(_join "|" "${_queries[@]:-}")"
+
+  {
+    local __target_path=
+    for   __target_path in "${_target_paths[@]:-}"
+    do
+      if [[ -d "${__target_path}" ]]
+      then
+        local _target_folder_path="${__target_path}"
+      else
+        local _target_folder_path="${__target_path%\/*}"
+      fi
+
+      local _max_id=
+      _max_id="$(_index get_max_id "${_target_folder_path}")"
+
+      {
+        if _search_with "rg" "${_search_utility:-}"
+        then
+          local _rg_command="rg"
+
+          if _command_exists "rga"
+          then
+            _rg_command="rga"
+          fi
+
+          if ((_max_depth))
+          then
+            _search_args+=("--max-depth" "${_max_depth}")
+          fi
+
+          if ((_COLOR_ENABLED))
+          then
+            _search_args+=("--color" "always")
+          else
+            _search_args+=("--color" "never")
+          fi
+
+          if ((_sort))
+          then
+            _search_args+=("--sort-files")
+          fi
+
+          local _search_paths=("${__target_path}")
+
+          if [[ -f "${__target_path}"     ]] &&
+             [[ "${#_arguments[@]}" -le 1 ]]
+          then
+            _search_paths+=("${__target_path%\/*}/.index")
+          fi
+
+          "${_rg_command}"                  \
+            --hidden                        \
+            --iglob '!.git'                 \
+            --ignore-case                   \
+            --line-number                   \
+            --max-columns "${_max_columns}" \
+            --max-columns-preview           \
+            --no-heading                    \
+            --with-filename                 \
+            "${_search_args[@]}"            \
+            "${_query}"                     \
+            "${_search_paths[@]:-}"         \
+              || return 0 # Don't fail out within a single scope.
+        elif _search_with "ag" "${_search_utility:-}"
+        then
+          if ((_max_depth))
+          then
+            _search_args+=("--norecurse")
+          fi
+
+          if ((_COLOR_ENABLED))
+          then
+            _search_args+=("--color")
+            _search_args+=("--color-line-number"  "32")
+            _search_args+=("--color-match"        "1;35")
+          else
+            _search_args+=("--nocolor")
+          fi
+
+          # TODO: ag doesn't support sorting directly.
+          # if ((_sort))
+          # then
+          #   _search_args+=("--workers" "1")
+          # fi
+
+          local _search_paths=("${__target_path}")
+
+          if [[ -f "${__target_path}"     ]] &&
+             [[ "${#_arguments[@]}" -le 1 ]]
+          then
+            _search_paths+=("${__target_path%\/*}/.index")
+          fi
+
+          ag                      \
+            --filename            \
+            --hidden              \
+            --ignore ".git"       \
+            --ignore-case         \
+            --noheading           \
+            "${_search_args[@]}"  \
+            "${_query}"           \
+            "${_search_paths[@]}" \
+              || return 0 # Don't fail out within a single scope.
+        elif _search_with "ack" "${_search_utility:-}"
+        then # ack is available.
+          if ((_max_depth))
+          then
+            _search_args+=("--no-recurse")
+          fi
+
+          if ((_COLOR_ENABLED))
+          then
+            _search_args+=("--color")
+            _search_args+=("--color-lineno=bold green")
+            _search_args+=("--color-match=blue on_black")
+          else
+            _search_args+=("--nocolor")
+          fi
+
+          if ((_sort))
+          then
+            _search_args+=("--sort-files")
+          fi
+
+          local _search_paths=("${__target_path}")
+
+          if [[ -f "${__target_path}"     ]] &&
+             [[ "${#_arguments[@]}" -le 1 ]]
+          then
+            _search_paths+=("${__target_path%\/*}/.index")
+          fi
+
+          ack                     \
+            --ignore-case         \
+            --noheading           \
+            --with-filename       \
+            "${_search_args[@]}"  \
+            "${_query}"           \
+            "${_search_paths[@]}" \
+              || return 0 # Don't fail out within a single scope.
+        elif _search_with "grep" "${_search_utility:-}"
+        then
+          if ((_COLOR_ENABLED))
+          then
+            _search_args+=("--color=always")
+          else
+            _search_args+=("--color=never")
+          fi
+
+          set +f
+          {
+            if [[ -f "${__target_path:-}"     ]]
+            then
+              if [[ "${#_arguments[@]}" -le 1 ]]
+              then
+                # Print .index with null byte delimeter so it's included in
+                # the list of files to search.
+                printf "%s/.index\0%s" "${__target_path%\/*}" "${__target_path}"
+              else
+                printf "%s" "${__target_path}"
+              fi
+            elif [[ "${_max_depth}" == 1      ]]
+            then
+              # Print .index with null byte delimeter so it's included in
+              # the list of files to search.
+              printf "%s/.index\0" "${__target_path}"
+              find "${__target_path}"/*   \
+                \( -name . -o -prune \)   \
+                -type f                   \
+                -print0
+            else
+              find "${__target_path}"                     \
+                ! -path '*/.git*'                         \
+                \( -path '*/.index' -o -path '*/[^.]*' \) \
+                -type f                                   \
+                -print0
+            fi
+          } | {
+            # Add /dev/null so file path is printed even if there is only one
+            # matching file. Reference: https://stackoverflow.com/a/15432718
+            xargs -0 grep           \
+              -E                    \
+              --ignore-case         \
+              "${_search_args[@]}"  \
+              --text                \
+              -n                    \
+              "${_query}"           \
+              /dev/null             \
+                || return 0 # Don't fail out within a single scope.
+          }
+          set -f
+        else
+          local _notebook_path=
+          _notebook_path="$(_notebooks show "${__target_path:-}" --path)"
+
+          local _escaped_notebook_path=
+          _escaped_notebook_path="$(
+            printf "%s\\n" "${_notebook_path:-}" | sed 's/\//\\\//g'
+          )"
+
+          if ((_max_depth))
+          then
+            _search_args+=("--no-recursive")
+          fi
+
+          local _search_args_no_color=("--color=never")
+
+          if [[ -n "${_search_args[*]:-}" ]]
+          then
+            _search_args_no_color+=("${_search_args[@]:-}")
+          fi
+
+          if ((_COLOR_ENABLED))
+          then
+            _search_args+=("--color=always")
+          else
+            _search_args+=("--color=never")
+          fi
+
+          local _search_paths=("${__target_path}")
+
+          if [[ -f "${__target_path}"     ]] &&
+             [[ "${#_arguments[@]}" -le 1 ]]
+          then
+            _search_paths+=("${__target_path%\/*}/.index")
+          fi
+
+          if [[ "${#_queries[@]}"   -le 1 ]]
+          then
+            GIT_PAGER='' git -C "${_notebook_path}"     \
+              grep                                      \
+              --extended-regexp                         \
+              --ignore-case                             \
+              --line-number                             \
+              --text                                    \
+              "${_search_args[@]:-}"                    \
+              -e "${_query:-}"                          \
+              "${_search_paths[@]:-}"                   \
+            | sed -e "s/^/${_escaped_notebook_path}\//" \
+              || return 0  # Don't fail out within a single scope.
+          else
+            local __search_group=
+            for   __search_group in "index" "files"
+            do
+              {
+                if [[ "${__search_group}" == "index" ]]
+                then
+                  # list all .index files
+                  GIT_PAGER='' git -C "${_notebook_path}" \
+                    ls-files -z '*.index'
+                else
+                  # list all non-.index files
+                  GIT_PAGER='' git -C "${_notebook_path}" \
+                    ls-files -z -- . ':!:*.index'
+                fi
+              } | {
+                local _last_pipe=
+                local _this_pipe=
+
+                local __and_query=
+                for   __and_query in "${_queries[@]:-}"
+                do
+                  [[ -n "${__and_query:-}"    ]] || continue
+
+                  _this_pipe=$(_temp file --touch) && {
+                    rm -f   "${_this_pipe}"
+                    mkfifo  "${_this_pipe}"
+                  }
+
+                  if [[ -p "${_last_pipe:-}"  ]]
+                  then
+                    <"${_last_pipe:-}" cat
+                  else
+                    cat
+                  fi | {
+                    GIT_PAGER='' xargs "${_xargs[@]}" \
+                      git -C "${_notebook_path}"      \
+                      grep                            \
+                      --extended-regexp               \
+                      --files-with-matches            \
+                      --ignore-case                   \
+                      --null                          \
+                      --text                          \
+                      "${_search_args_no_color[@]:-}" \
+                      -e "${__and_query:-}"           \
+                        || return 0  # Don't fail out within a single scope.
+                  } > "${_this_pipe:-}" &
+
+                  _last_pipe="${_this_pipe:-}"
+                done
+
+                if [[ -p "${_last_pipe:-}"    ]]
+                then
+                  <"${_last_pipe:-}" cat
+                else
+                  cat
+                fi
+              } | {
+                if [[ "${__search_group}" == "index" ]]
+                then
+                  local i=
+                  for ((i=0; i < ${#_queries[@]}; i++))
+                  do
+                    [[ -n "${_queries[i]:-}"  ]] || continue
+
+                    if ! ((i))
+                    then
+                      _search_args+=("-e" "${_queries[i]:-}")
+                    else
+                      _search_args+=("--and" "-e" "${_queries[i]:-}")
+                    fi
+                  done
+
+                  GIT_PAGER='' xargs "${_xargs[@]}"           \
+                    git -C "${_notebook_path}"                \
+                    grep                                      \
+                    --extended-regexp                         \
+                    --ignore-case                             \
+                    --line-number                             \
+                    --text                                    \
+                    "${_search_args[@]:-}"                    \
+                  | sed -e "s/^/${_escaped_notebook_path}\//" \
+                    || return 0  # Don't fail out within a single scope.
+                else
+                  GIT_PAGER='' xargs "${_xargs[@]}"           \
+                    git -C "${_notebook_path}"                \
+                    grep                                      \
+                    --extended-regexp                         \
+                    --ignore-case                             \
+                    --line-number                             \
+                    --text                                    \
+                    "${_search_args[@]:-}"                    \
+                    -e "${_query:-}"                          \
+                  | sed -e "s/^/${_escaped_notebook_path}\//" \
+                    || return 0  # Don't fail out within a single scope.
+                fi
+              }
+            done
+          fi
+        fi
+      } | {
+        local _binary_match_message_printed=0
+        local _paginated_count=0
+        local _pagination_max="$((_page * _limit))"
+        local _pagination_min="$(((_page * _limit) - _limit))"
+
+        local         __line=
+        while read -r __line
+        do
+          local _content=
+          local _content_line_with_hit=
+          local _file_info=
+          local _file_info_color=
+          local _filename=
+          local _filename_color=
+          local _filename_hit=0
+          local _id=
+          local _line_path_segment="${__line%%:*}"
+          local _path=
+          local _skip=0
+
+          if ((_print_paths))
+          then
+            _path="${_line_path_segment:-}"
+          else
+            # Use `sed` to remove color and 'matches' suffix from output.
+            # https://unix.stackexchange.com/a/140255
+            _path="$(
+              printf "%s\\n" "${_line_path_segment}"              \
+                | sed                                             \
+                    -e "s,$(printf '\033')\\[[0-9;]*[a-zA-Z],,g"  \
+                    -e 's/ matches//g'
+            )"
+          fi
+
+          if ((_only_list))                       &&
+             [[ "${_last_path}" == "${_path}" ]]  &&
+             [[ ! "${_path}"    =~ .index$    ]]
+          then
+            [[ -n "${_path}" ]] && _last_path="${_path}"
+
+            continue
+          fi
+
+          if [[ "${_path}"      =~ \.pindex$  ]]
+          then
+            [[ -n "${_path}" ]] && _last_path="${_path}"
+
+            continue
+          fi
+
+          if [[ "${_last_path}" != "${_path}" ]]
+          then
+            if   [[ ! "${_path}" =~ .index    ]] &&
+                 [[ -z "$(sed -E "${_IGNORE_PATTERNS[@]:-}" <<< "${_path##*/}")" ]]
+            then
+              _skip=1
+            elif [[ -n "${_type:-}"           ]]
+            then
+              if [[  "${_path}" =~ ${_type}$  ]]
+              then
+                _skip=0
+              elif {
+                [[ "${_type}" =~ (^bookmark$|^bookmarks$)                   ]] &&
+                  _file_is_bookmark "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^note$|^notes$|^text$)                  ]] &&
+                  _file_is_text "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^folder$|^folders$)                     ]] &&
+                  [[ "$(dirname "${_path}")" != "${__target_path}"          ]]
+                } || {
+                  [[ "${_type}" =~ ^archive$                                ]] &&
+                  _file_is_archive "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^audio$|^music$)                        ]] &&
+                  _file_is_audio "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^document$|^documents$|^doc$|^docs$)    ]] &&
+                  _file_is_document "${_path}"
+                } || {
+                  [[ "${_type}" =~ ^encrypted$                              ]] &&
+                  _file_is_encrypted "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^image$|^images$|^picture$|^pictures$)  ]] &&
+                  _file_is_image "${_path}"
+                } || {
+                  [[ "${_type}" =~ (^video$|^videos$)                       ]] &&
+                  _file_is_video "${_path}"
+                }
+              then
+                _skip=0
+              else
+                _skip=1
+              fi
+            fi
+          fi
+
+          if [[ -z "${__line}" ]]
+          then
+            # Print nothing, skipping the blank line in `ag` output with
+            # multiple matches.
+            :
+          elif ((_print_paths))
+          then
+            if [[ "${_last_path}" != "${_path}"   ]]
+            then # match is in a different file than the last match
+              printf "%s\\n" "${_path}"
+            fi
+          else
+            if ((_skip))
+            then
+              continue
+            fi
+
+            local _folder_path="${_path%\/*}"
+
+            if [[ ! -e "${_folder_path}/.index"   ]]
+            then # skip unindexed folders
+              continue
+            fi
+
+            if ((_limit)) &&
+               {
+                 [[ "${_last_path}" != "${_path}" ]] ||
+                 [[ "${_path}"      =~ \.index$   ]]
+               }
+            then
+              _paginated_count=$((_paginated_count+1))
+
+              if [[ "${_paginated_count}"   -le "${_pagination_min}"  ]]
+              then
+                [[ -n "${_path}" ]] && _last_path="${_path}"
+
+                continue
+              elif [[ "${_paginated_count}" -gt "${_pagination_max}"  ]]
+              then
+                break
+              fi
+            fi
+
+            if [[ -n "${_local_notebook_path:-}"                ]] &&
+               [[ "${_folder_path}" =~ ${_local_notebook_path}  ]]
+            then
+              local _notebook_path="${_local_notebook_path}"
+            else
+              local _notebook_and_folder_path="${_folder_path#"${NB_DIR}"/}"
+              local _notebook_path="${NB_DIR}/${_notebook_and_folder_path%%/*}"
+            fi
+
+            local _relative_folder_path="${_folder_path#"${_notebook_path}"/}"
+            _relative_folder_path="${_relative_folder_path#"${_notebook_path}"}"
+
+            _filename="$(basename "${_path}")"
+            _filename_color="${_filename}"
+
+            # Use ".index" to match filenames.
+            if [[ -n "${_filename:-}" ]] && [[ "${_filename:-}" == ".index" ]]
+            then
+              _filename_hit=1
+              _filename_color="$(printf "%s\\n" "${__line}" | cut -d: -f 3-)"
+              _filename="$(
+                printf "%s\\n" "${_filename_color}" \
+                  | sed "s,$(printf '\033')\\[[0-9;]*[a-zA-Z],,g"
+              )"
+            fi
+
+            local _maybe_id_path=
+            local _relative_path="${_filename}"
+
+            if [[ -n "${_relative_folder_path:-}" ]]
+            then
+              _max_id="$(_index get_max_id "${_folder_path}")"
+              _maybe_id_path="${_relative_folder_path}/"
+              _relative_path="${_relative_folder_path}/${_filename}"
+            fi
+
+            _id="$(_index get_id "${_filename}" "${_folder_path}")"
+
+            if ((_filename_hit))
+            then
+              _content="$(_get_content "${_folder_path}/${_filename}")"
+
+              if [[ -n "${_content}"                  ]] &&
+                 [[ ! "${_content}" =~ ^__first_line: ]]
+              then
+                _file_info="${_filename} ${_MD} ${_content}"
+                _file_info_color="${_filename_color} ${_MD} ${_content}"
+              else
+                _file_info="${_filename}"
+                _file_info_color="${_filename_color}"
+              fi
+            else
+              _content="$(_get_content "${_path}")"
+
+              if [[ "${_content:-}" =~ ^__first_line: ]]
+              then
+                _file_info="${_filename} ${_MD} \"${_content#__first_line:}\""
+                _file_info_color="${_filename_color} ${_MD} \"${_content#__first_line:}\""
+              elif [[ -n "${_content:-}" ]]
+              then
+                _file_info="${_content}"
+                _file_info_color="${_content}"
+              else
+                _file_info="${_filename}"
+                _file_info_color="${_filename_color}"
+              fi
+            fi
+
+            local _indicators=
+            _indicators="$(
+              NB_NOTEBOOK_PATH="${_notebook_path}" \
+                _show "${_relative_path}" --indicators
+            )"
+
+            local _info_line=
+            local _info_line_color=
+            local _max_identifier=
+
+            if ((_all))                       ||
+               ((_print_notebook_selectors))  ||
+               _notebooks current --selected
+            then
+              local _notebook_name=
+              _notebook_name="$(
+                _notebooks show "${_notebook_path}" --name --no-color
+              )"
+
+              _info_line="[${_notebook_name}:${_maybe_id_path}${_id}] "
+              _info_line_color+="$(_color_brackets "${_notebook_name}:${_maybe_id_path}${_id}") "
+              _max_identifier="[${_notebook_name}:${_maybe_id_path}${_max_id}] "
+            else
+              _info_line="[${_maybe_id_path}${_id}] "
+              _info_line_color+="$(_color_brackets "${_maybe_id_path}${_id}") "
+              _max_identifier="[${_maybe_id_path}${_max_id}] "
+            fi
+
+            # Use calculated number of spaces for nicer formatting.
+            local _spaces=''
+            local _spaces_length=0
+
+            if ((_only_list))
+            then
+              _spaces_length=$(( ${#_max_identifier} - ${#_info_line} ))
+            fi
+
+            if ((_spaces_length))
+            then
+              printf -v _spaces '%*s' "${_spaces_length}" ""
+
+              _info_line+="${_spaces}"
+              _info_line_color+="${_spaces}"
+            fi
+
+            if [[ -n "${_indicators:-}" ]]
+            then
+              _info_line+="${_indicators}"
+              _info_line_color+="${_indicators}"
+            fi
+
+            _info_line+="${_file_info}"
+            _info_line_color+="${_file_info_color}"
+
+            if [[ "${_last_path}" != "${_path}" ]] || ((_filename_hit))
+            then # match is in a different file than the last match
+              ((_COLOR_ENABLED)) && _wrap off
+
+              printf "%s" "${_info_line_color}"
+
+              ((_COLOR_ENABLED)) && _wrap on
+
+              printf "\\n"
+
+              _binary_match_message_printed=0
+            fi
+
+            if ((_only_list)) || ((_binary_match_message_printed))
+            then
+              [[ -n "${_path}" ]] && _last_path="${_path}"
+
+              continue
+            fi
+
+            if [[ "${_last_path}" != "${_path}" ]] || ((_filename_hit))
+            then # match is in a different file than the last match
+              ((_COLOR_ENABLED)) && _wrap off
+
+              local _visible_line_length=
+              _visible_line_length="$(
+                _get_visible_length "${_info_line:-}"
+              )"
+
+              _print_line "$(printf "%-${_visible_line_length}s" '.')"
+
+              ((_COLOR_ENABLED)) && _wrap on
+            fi
+
+            if ((_filename_hit))
+            then
+              local _filename_type_label="Filename"
+
+              if [[ -d "${_folder_path}/${_filename}" ]]
+              then
+                _filename_type_label="Folder Name"
+              fi
+
+              _content_line_with_hit="${_filename_type_label} Match: $(
+                printf "%s\\n" "${__line}" | cut -d: -f 3-
+              )"
+            elif ! _file_is_text "${_folder_path}/${_filename}"
+            then
+              _content_line_with_hit="Binary file matches."
+              _binary_match_message_printed=1
+            else
+              _content_line_with_hit="$(
+                printf "%s\\n" "${__line}" | cut -d: -f 2-
+              )"
+            fi
+
+            # Truncate long lines.
+            local _line_length=
+            _line_length="$(
+              printf "%s\\n" "${_content_line_with_hit}" | awk '{print length}'
+            )"
+
+            local _line_length_diff=
+            _line_length_diff=$((_line_length-_max_columns-100))
+
+            if [[ "${_line_length_diff}" -gt 0      ]]
+            then
+              _content_line_with_hit="$(
+                printf "%s\\n" "${_content_line_with_hit}" \
+                  | awk '{ print substr($0, 1, 2000) }'
+              )"
+
+              _content_line_with_hit+="$(
+                _color_primary "... [${_line_length_diff} characters omitted]"
+              )"
+            fi
+
+            printf "%s\\n\\n" "${_content_line_with_hit}"
+          fi
+
+          [[ -n "${_path}" ]] && _last_path="${_path}"
+        done
+      }
+    done
+  } | {
+    local       __search_output_line=
+    if read -r  __search_output_line
+    then # output is present
+      # Print the test line then `cat` the rest.
+      printf "%s\\n" "${__search_output_line:-}"
+
+      cat
+
+      return 0
+    else
+      if ((_all))
+      then
+        printf "Not found in any notebook: %s\\n"   \
+          "$(_color_primary "${_query:-}")"
+      else
+        local _search_selector=
+
+        if [[ -n "${_selectors[0]:-}"               ]]
+        then
+          _search_selector="${_selectors[0]}"
+
+          if [[ -f "${_target_paths[0]:-}"          ]] &&
+             [[ "${_search_selector:-}" =~ /$       ]]
+          then # strip trailing slash from files
+            _search_selector="${_search_selector%/}"
+          elif [[ "${_search_selector:-}" =~ :$     ]]
+          then
+            _search_selector="${_search_selector%:}"
+          elif [[ -d "${_target_paths[0]:-}"        ]] &&
+               [[ !  "${_search_selector:-}" =~ /$  ]]
+          then # add trailing slash to folders
+            _search_selector="${_search_selector}/"
+          fi
+        else
+          _search_selector="$(_notebooks current --name)"
+        fi
+
+        local _query_message=
+
+        if [[ "${#_queries[@]}" -le 1 ]]
+        then
+          _query_message="${_query}"
+        else
+          local i=
+          for ((i=0; i < ${#_queries[@]}; i++))
+          do
+            if ((i))
+            then
+              _query_message+=" + ${_queries[i]:-}"
+            else
+              _query_message="${_queries[i]:-}"
+            fi
+          done
+        fi
+
+        if [[ "${_page:-0}" -gt 1     ]]
+        then
+          return 0
+        else
+          printf "Not found in %s: %s\\n"               \
+            "$(_color_primary "${_search_selector:-}")" \
+            "$(_color_primary "${_query_message:-}")"
+        fi
+      fi
+
+      return 1
+    fi
+  }
+}
+_alias_subcommand "search" "q"
+_alias_subcommand "search" "grep"
+
+# show ################################################################### show
+
+_describe_show() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} show ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [[-a | --added] | [--authors] | [-b | --browse] | --filename | --id |
+          --info-line | --path | [-p | --print] | --relative-path | [-r |
+          --render] | --title | --type [<type>] | [-u | --updated]] [--no-color]
+  ${_ME} show <notebook>
+
+$(_color_primary "Options"):
+  -a, --added      Print the date and time when the item was added.
+  --authors        List the git commit authors of an item.
+  -b, --browse     Open the item with \`${_ME} browse\`.
+  --filename       Print the filename of the item.
+  --id             Print the id number of the item.
+  --info-line      Print the id, filename, and title of the item.
+  --no-color       Show without syntax highlighting.
+  --path           Print the full path of the item.
+  -p, --print      Print to standard output / terminal.
+  --relative-path  Print the item's path relative within the notebook.
+  -r, --render     Use \`pandoc\` [1] to render the file to HTML and display
+                   in the terminal web browser. If either \`pandoc\` or a
+                   browser are unavailable, \`-r\` / \`--render\` is ignored.
+  --title          Print the title of the note.
+  --type [<type>]  Print the file extension or, when <type> is specified,
+                   return true if the item matches <type>. <type> can be a
+                   file extension or one of the following types:
+                   archive, audio, bookmark, document, folder, image,
+                   text, video
+  -u, --updated    Print the date and time of the last recorded change.
+
+$(_color_primary "Description"):
+  Show an item or notebook. Notes in text file formats can be rendered or
+  printed to standard output. Non-text files are opened in your system's
+  preferred app or program for that file type.
+
+  By default, the item is opened using \`less\` or the program configured
+  in the \`\$PAGER\` environment variable. Use the following keys to navigate
+  in \`less\` (see \`man less\` for more information):
+
+    Key               Function
+    ---               --------
+    mouse scroll      Scroll up or down
+    arrow up or down  Scroll one line up or down
+    f                 Jump forward one window
+    b                 Jump back one window
+    d                 Jump down one half window
+    u                 Jump up one half window
+    /<query>          Search for <query>
+    n                 Jump to next <query> match
+    q                 Quit
+
+  To skip the pager and print to standard output, use the \`-p\` / \`--print\`
+  option.
+
+  \`-r\` / \`--render\` automatically uses either \`w3m\` [2] or \`links\` [3].
+  To specify a preferred browser, set the \`\$BROWSER\` environment variable
+  in your .bashrc, .zshrc, or equivalent, e.g.: export BROWSER="links"
+
+  If \`bat\` [5], \`highlight\` [6], or Pygments [7] is installed, notes are
+  printed with syntax highlighting.
+
+    1. https://pandoc.org/
+    2. https://en.wikipedia.org/wiki/W3m
+    3. https://en.wikipedia.org/wiki/Links_(web_browser)
+    5. https://github.com/sharkdp/bat
+    6. http://www.andre-simon.de/doku/highlight/en/highlight.php
+    7. https://pygments.org/
+
+$(_color_primary "Read More"):
+  ${_README_URL}#viewing
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help open
+  ${_ME} help peek
+
+$(_color_primary "Examples"):
+  ${_ME} show 1
+  ${_ME} show example.md --render
+  ${_ME} show "A Document Title" --print --no-color
+  ${_ME} 1 show
+  ${_ME} example:show 12
+  ${_ME} show example:12
+  ${_ME} example:12 show
+  ${_ME} s 1
+  ${_ME} 1 s
+  ${_ME} s example:12
+  ${_ME} example:12 s
+
+$(_color_primary "Alias"):
+  ${_ME} view
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} s
+HEREDOC
+}
+_show() {
+  # _show_indicators()
+  #
+  # Usage:
+  #   _show_indicators <path> [--done]
+  #
+  # Description:
+  #   Print a list of indicators based on the file type.
+  #
+  # NOTE: Indicator logic is also specified in `list` for performance.
+  _show_indicators() {
+    local _done=0
+    local _indicators=
+    local _path="${1:-}"
+
+    case "${2:-}" in
+      --done) _done=1 ;;
+    esac
+
+    local _pindex_path="${_path%/*}/.pindex"
+
+    if [[ -e "${_pindex_path}"  ]]
+    then
+      # shellcheck disable=SC2046
+      if _contains "${_path##*/}" $(cat "${_pindex_path}")
+      then
+        _indicators+="${_NB_INDICATOR_PINNED:-}"
+      fi
+    fi
+
+    if [[ -d "${_path}"         ]]
+    then
+      _indicators+="${_NB_INDICATOR_FOLDER:-}"
+    elif _file_is_bookmark "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_BOOKMARK:-}"
+    elif _file_is_image "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_IMAGE:-}"
+    elif _file_is_document "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_DOCUMENT:-}"
+    elif _file_is_video "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_VIDEO:-}"
+    elif _file_is_audio "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_AUDIO:-}"
+    elif [[ "${_path}" =~ \.epub$ ]]
+    then
+      _indicators+="${_NB_INDICATOR_EBOOK:-}"
+    fi
+
+    if _file_is_encrypted "${_path}"
+    then
+      _indicators+="${_NB_INDICATOR_ENCRYPTED:-}"
+    fi
+
+    if _file_is_todo "${_path}"
+    then
+      if ((_done))
+      then
+        _indicators+="${_NB_INDICATOR_TODO_DONE% } "
+      else
+        _indicators+="${_NB_INDICATOR_TODO% } "
+      fi
+    fi
+
+    printf "%s\\n" "${_indicators:-}"
+  }
+
+  local _browse=0
+  local _check_type=0
+  local _limit="${NB_BROWSE_LIMIT:-20}"
+  local _list_page=1
+  local _password=
+  local _print_added=0
+  local _print_authors=0
+  local _print_bookmark_url=0
+  local _print_filename=0
+  local _print_folder_path=0
+  local _print_id=0
+  local _print_indicators=0
+  local _print_info=0
+  local _print_output=0
+  local _print_path=0
+  local _print_relative_path=0
+  local _print_selector_id=0
+  local _print_title=0
+  local _print_updated=0
+  local _render=0
+  local _selector=
+  local _skip_notebook_fallback=0
+  local _tool=
+  local _type=
+  local _unresolved_arguments=()
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      -a|--added*)
+        _print_added=1
+        _skip_notebook_fallback=1
+        ;;
+      --auth*)
+        _print_authors=1
+        ;;
+      -b|--br|--browse)
+        _browse=1
+        ;;
+      --filename|--basename)
+        _print_filename=1
+        _skip_notebook_fallback=1
+        ;;
+      --folder-path)
+        _print_folder_path=1
+        ;;
+      --id|--index)
+        _print_id=1
+        _skip_notebook_fallback=1
+        ;;
+      --indicators)
+        _print_indicators=1
+        _skip_notebook_fallback=1
+        ;;
+      --info*line)
+        _print_info=1
+        _skip_notebook_fallback=1
+        ;;
+      --limit|-n|--num|--number|--per*)
+        _limit="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --no*color|--raw)
+        _COLOR_ENABLED=0
+        ;;
+      --notebook*|--include*notebook*|--with*notebook*)
+        _skip_notebook_fallback=0
+        ;;
+      --page)
+        _list_page="$(_option_get_value "${1}" "${2:-}")"
+        ((_list_page)) || _list_page=1
+
+        shift
+        ;;
+      --password)
+        _password="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --path)
+        _print_path=1
+        _skip_notebook_fallback=1
+        ;;
+      -p|--print|--dump|--skip*pager|--no*pager)
+        _print_output=1
+        ;;
+      --relative-path)
+        _print_relative_path=1
+        _skip_notebook_fallback=1
+        ;;
+      -r|--render)
+        _render=1
+        ;;
+      --selector*id)
+        _print_selector_id=1
+        _skip_notebook_fallback=1
+        ;;
+      --title)
+        _print_title=1
+        _skip_notebook_fallback=1
+        ;;
+      --tool|--utility)
+        _tool="$(_option_get_value "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --type)
+        _check_type=1
+        _skip_notebook_fallback=1
+
+        if _option_value_is_present "${2:-}"
+        then
+          _type="${2}"
+
+          shift
+        fi
+        ;;
+      -u|--updated*)
+        _print_updated=1
+        _skip_notebook_fallback=1
+        ;;
+      --url)
+        _print_bookmark_url=1
+        ;;
+      *)
+        if [[ -z "${_selector:-}" ]]
+        then
+          _selector="${1}"
+        else
+          _unresolved_arguments+=("${1}")
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  if [[ -z "${_selector:-}" ]]
+  then
+    _exit_1 _help "show"
+  fi
+
+  if ((_print_selector_id))
+  then
+    _selector_get_identifier "${_selector:-}"
+
+    return 0
+  fi
+
+  local _notebook_path=
+
+  if [[ "${_selector:-}" =~ : ]] && [[ ! "${_selector:-}" =~ /.*: ]]
+  then
+    _notebook_path="$(_notebooks show "${_selector%%:*}" --path)" || return 1
+
+    if ((_print_path)) && [[ "${_selector:-}" =~ :$ ]]
+    then
+      printf "%s\\n" "${_notebook_path}"
+
+      return 0
+    fi
+  elif [[ "${_selector:-}" =~ ^${NB_DIR}  ]]
+  then
+    local _selector_relative_path="${_selector#"${NB_DIR}"/}"
+
+    _notebook_path="$(_notebooks show "${_selector_relative_path%%/*}" --path)"
+  elif [[ "${_selector:-}" =~ ^/          ]]
+  then
+    _notebook_path="$(_notebooks show "${_selector}" --path)"
+  fi
+
+  if [[ -z "${_notebook_path:-}"          ]]
+  then
+    _notebook_path="$(_notebooks current --path)"
+  fi
+
+  local _relative_path=
+  _relative_path="$(
+    _selector_resolve_path "${_selector}" "${_notebook_path}" --relative
+  )"
+
+  local _folder_path="${_notebook_path:?}"
+  local _relative_folder_path=
+
+  if [[ "${_relative_path:-}" =~ /        ]]
+  then
+    _folder_path="${_notebook_path}/${_relative_path%\/*}"
+    _relative_folder_path="${_relative_path%\/*}"
+  fi
+
+  local _basename=
+  _basename="$(basename "${_relative_path}")"
+
+  local _target_path="${_notebook_path}/${_relative_path}"
+
+  if [[ -z "${_relative_path:-}"    ]] && ! ((_skip_notebook_fallback))
+  then
+    local _maybe_notebook="${_selector:-}"
+
+    if [[ "${_maybe_notebook:-}" =~ ^${NB_DIR}    ]]
+    then
+      _maybe_notebook="${_maybe_notebook##*\/}"
+    fi
+
+    _maybe_notebook="${_maybe_notebook%:}"
+
+    if [[ -d "${NB_DIR}/${_maybe_notebook}/.git"  ]]
+    then
+      if ((_print_path))
+      then
+        printf "%s\\n" "${NB_DIR}/${_maybe_notebook}"
+      elif ((_print_relative_path)) || ((_print_folder_path))
+      then
+        printf ""
+      else
+        NB_NOTEBOOK_PATH="${NB_DIR}/${_maybe_notebook}" \
+          _ls "${_unresolved_arguments[@]:-}"
+      fi
+
+      return 0
+    else
+      _warn printf "Not found: %s\\n" "$(_color_primary "${_selector}")"
+
+      return 1
+    fi
+  fi
+
+  if [[ ! "${_selector}" =~ :$      ]] && {
+       [[ -z "${_relative_path:-}"  ]] ||
+       [[ ! -e "${_target_path}"    ]]
+     }
+  then
+    _warn printf "Not found: %s\\n" "$(_color_primary "${_selector:-}")"
+
+    return 1
+  fi
+
+  if ((_print_folder_path))
+  then
+    if [[ "${_selector:-}" =~ /$                      ]] &&
+       [[ -d "${_notebook_path}/${_relative_path:-}"  ]]
+    then
+      printf "%s\\n" "${_relative_path}"
+    elif [[ "${_relative_path:-}" =~ / ]]
+    then
+      printf "%s\\n" "${_relative_path%\/*}"
+    else
+      printf ""
+    fi
+
+    return 0
+  fi
+
+  if ((_print_relative_path))
+  then
+    printf "%s\\n" "${_relative_path}"
+
+    return 0
+  fi
+
+  if ((_print_path))
+  then # `show --path`
+    printf "%s/%s\\n" "${_notebook_path}" "${_relative_path}"
+
+    return 0
+  fi
+
+  if ((_print_filename))
+  then
+    printf "%s\\n" "${_basename}"
+
+    return 0
+  fi
+
+  if ((_print_id))
+  then
+    printf "%s\\n" "$(
+      _index get_id "${_relative_path##*/}" "${_folder_path}"
+    )"
+
+    return 0
+  fi
+
+  if ((_print_title))
+  then
+    _get_content "${_notebook_path}/${_relative_path}" --title
+
+    return 0
+  fi
+
+  if ((_print_authors))
+  then
+    GIT_PAGER='' git -C "${_notebook_path}" shortlog              \
+      --summary --email -- "${_notebook_path}/${_relative_path}"  \
+      | sed "s/^[[:space:]]\{1,\}[[:digit:]]\{1,\}[[:space:]]\{1,\}//g"
+
+    return 0
+  fi
+
+  if ((_print_indicators))
+  then
+    local _indicator_arguments=("${_notebook_path}/${_relative_path}")
+
+    if [[ "${_relative_path:-}" =~ todo\.md ]]
+    then
+      local _todo_title=
+      _todo_title="$(
+        _get_content "${_notebook_path}/${_relative_path}" --title
+      )"
+
+      if [[ "${_todo_title}" =~ ^\[x\]      ]]
+      then
+        _indicator_arguments+=(--done)
+      fi
+    fi
+
+    _show_indicators "${_indicator_arguments[@]:-}"
+
+    return 0
+  fi
+
+  if ((_check_type))
+  then
+    if [[ -z "${_type}"       ]]
+    then
+      if [[ -d "${_notebook_path}/${_relative_path}"  ]]
+      then
+        printf "%s\\n" "folder"
+      else
+        printf "%s\\n" "${_relative_path#*.}"
+      fi
+
+      return 0
+    else
+      if _contains "${_type}" "${_FILE_TYPES[@]:-}"
+      then
+        "_file_is_${_type}" "${_notebook_path}/${_relative_path}"
+
+        return $?
+      else
+        [[ "${_type}" == "${_relative_path#*.}"       ]]
+
+        return $?
+      fi
+    fi
+  fi
+
+  if ((_print_info))
+  then
+    local _id=
+
+    if [[ -n "${_basename:-}" ]]
+    then
+      _id="$(_index get_id "${_basename}" "${_folder_path}")"
+    fi
+
+    local _maybe_scoped_relative_path="${_relative_path}"
+
+    local _maybe_scoped_id=
+    _maybe_scoped_id="${_relative_folder_path:+"${_relative_folder_path}/"}${_id}"
+
+    if _notebooks current --selected ||
+       [[ "${_notebook_path}" != "$(_notebooks current --path)" ]]
+    then
+      local _notebook_name=
+      _notebook_name="$(
+        _notebooks show "${_notebook_path}" --name --no-color
+      )"
+
+      _maybe_scoped_id="${_notebook_name}:${_maybe_scoped_id}"
+      _maybe_scoped_relative_path="${_notebook_name}:${_maybe_scoped_relative_path}"
+    fi
+
+    local _info_line=
+    _info_line+="$(_color_brackets "${_maybe_scoped_id}") "
+
+    local _indicators=
+    _indicators="$(_show "${_notebook_path}/${_relative_path}" --indicators)"
+
+    if [[ -n "${_indicators:-}" ]]
+    then
+      _info_line+="${_indicators}"
+    fi
+
+    _info_line+="$(_color_primary "${_maybe_scoped_relative_path}") "
+
+    local _title=
+    _title="$(_get_content "${_notebook_path}/${_relative_path}" --title)"
+
+    if [[ -n "${_title:-}"      ]]
+    then
+      if [[ "${_relative_path}"  =~ todo\.md$ ]] && ((_COLOR_ENABLED))
+      then
+        _title="\
+${_title/\[x\]/${_TPUT_SETAF_8}[${_TPUT_COLOR_PRIMARY}x${_TPUT_SETAF_8}]${_TPUT_SGR0}}"
+        _title="\
+${_title/\[$' '\]/${_TPUT_SETAF_8}[ ]${_TPUT_SGR0}}"
+      fi
+
+      _info_line+="\"${_title}\""
+    fi
+
+    # trim leading and trailing whitepace
+    IFS=' ' read -r _info_line <<<"${_info_line:-}"
+
+    printf "%s\\n" "${_info_line:-}"
+
+    return 0
+  fi
+
+  if ((_print_added))
+  then
+    git -C "${_notebook_path}" --no-pager \
+      log                                 \
+      --follow                            \
+      --diff-filter=A                     \
+      --date=iso-local                    \
+      --pretty='%ad'                      \
+      "${_relative_path}"
+
+    return 0
+  fi
+
+  if ((_print_updated))
+  then
+    git -C "${_notebook_path}" --no-pager \
+      log                                 \
+      -1                                  \
+      --follow                            \
+      --date=iso-local                    \
+      --pretty='%ad'                      \
+      "${_relative_path}"
+
+    return 0
+  fi
+
+  if _file_is_encrypted "${_target_path}"
+  then
+    local _encrypted_path=
+    _encrypted_path="${_target_path}"
+
+    local _decryption_tool=
+    _decryption_tool="$(_get_decryption_tool "${_encrypted_path:-}")"
+
+    if [[    "${_decryption_tool:-}" != "age" ]] &&
+       [[ -z "${_password}"                   ]]
+    then
+      # request password without displaying it
+      printf "%s: " "$(_color_primary "Password")"
+
+      local _password=
+      IFS='' read -r -e -d $'\n' -s _password </dev/tty
+      printf "\\n" # print newline to stop `read`
+
+      if [[ -z "${_password}"                 ]]
+      then
+        _exit_1 printf "Password required.\\n"
+      fi
+    fi
+
+    local _decrypted_path=
+    _decrypted_path="$(_decrypt_file "${_target_path}" "${_password}")"
+
+    _target_path="${_decrypted_path}"
+  fi
+
+  if ((_print_bookmark_url))
+  then
+    if ! _file_is_bookmark "${_target_path:-}"
+    then
+      _warn printf "%s\\n" "Not a bookmark.\\n"
+    fi
+
+    local _url_match_patterns=()
+
+    local __url_match_pattern=
+    for   __url_match_pattern in "${_URL_PATTERNS[@]}"
+    do
+      _url_match_patterns+=(-e "<${__url_match_pattern}>")
+    done
+
+    local _target_url=
+    _target_url="$(
+      grep -E --color=never           \
+        "${_url_match_patterns[@]:-}" \
+        "${_target_path}"             \
+        | head -n 1                   \
+        | sed "s/^[[:space:]]*<//g"   \
+        | sed "s/>[[:space:]]*$//g"   || :
+    )"
+
+    if [[ -z "${_target_url:-}"       ]]
+    then
+      _warn printf "No URL found.\\n"
+
+      return 1
+    fi
+
+    printf "%s\\n" "${_target_url:-}"
+
+    return 0
+  fi
+
+  if _file_is_archive "${_target_path}"     &&
+     [[ ! "${_target_path}" =~ docx$  ]]
+  then
+    _exit_1 printf "\
+Can't show archives. Export archive and expand to edit.\\n"
+  fi
+
+  # change directory to folder path to enable relative paths
+  cd "${_folder_path}"
+
+  # turn on case-insensitive matching
+  shopt -s nocasematch
+
+  if [[ -z "${_tool:-}" ]]                  &&
+     _file_is_image "${_target_path:-}"     &&
+     _contains      "${NB_IMAGE_TOOL:-}"    \
+        "catimg"                            \
+        "chafa"                             \
+        "icat"                              \
+        "imgcat"                            \
+        "magick"                            \
+        "timg"                              \
+        "term-image"                        \
+        "viu"
+  then
+    _tool="${NB_IMAGE_TOOL:-}"
+  fi
+
+  if _contains "${_target_path##*.}"        \
+       "csv" "json" "mysql" "postgres"      \
+       "sqlite" "tab" "tar" "tsv" "usv" "vds" "xml" "xlsx" "zip"      &&
+     _command_exists "vd"                                             &&
+     _contains "${_tool:-${NB_DATA_TOOL:-vd}}" "vd" "visidata"
+  then
+    vd "${_target_path}"
+  elif _contains "${_target_path##*.}" "csv" "sc" "tab" "tsv" "xlsx"  &&
+       _command_exists "sc-im"                                        &&
+       [[ "${_tool:-${NB_DATA_TOOL:-sc-im}}" == "sc-im"      ]]
+  then
+    sc-im "${_target_path}"
+  elif _contains "${_target_path##*.}" "csv" "psv" "tsv"              &&
+       _command_exists "tv"                                           &&
+       _contains "${_tool:-${NB_DATA_TOOL:-tv}}" "tv" "tidy-viewer" "tidyviewer"
+  then
+    tv "${_target_path}"
+  elif ! _file_is_text "${_target_path}"    &&
+     ! {
+       ((_render))                          &&
+       [[       "${_target_path:-}" =~ (\.docx$|\.epub$|\.odt$) ]]
+     } || [[ -d "${_target_path:-}"                             ]]
+  then
+    if [[ -d "${_target_path}"  ]]
+    then
+      if [[ -z "${_tool:-}"     ]]          &&
+        _contains "${NB_DIRECTORY_TOOL:-}" "ranger" "mc" "vifm" "joshuto" "exa"  &&
+        _command_exists "${NB_DIRECTORY_TOOL:-}"
+      then
+        _tool="${NB_DIRECTORY_TOOL}"
+      fi
+
+      if _command_exists "ncat"             &&
+         _command_exists "pandoc"           &&
+         _web_browser --check               &&
+         [[ -z "${_tool:-}"     ]]
+      then
+        cd "${_CURRENT_WORKING_DIR}"
+
+        _defer "_browse" "${_target_path}/"
+
+        return 0
+      elif _command_exists "ranger"   && [[ "${_tool:-ranger}"  == "ranger"   ]]
+      then
+        ranger "${_target_path}"
+      elif _command_exists "mc"       && [[ "${_tool:-mc}"      == "mc"       ]]
+      then
+        mc "${_target_path}"
+      elif _command_exists "vifm"     && [[ "${_tool:-vifm}"    == "vifm"     ]]
+      then
+        vifm "${_target_path}"
+      elif _command_exists "joshuto"  && [[ "${_tool:-joshuto}"  == "joshuto" ]]
+      then
+        joshuto --path "${_target_path}"
+      elif _command_exists "exa"      && [[ "${_tool:-exa}"     == "exa"      ]]
+      then
+        exa -lah --git "${_target_path}"
+      else
+        # gnu || bsd
+        ls -lah --color=always "${_target_path}" 2>/dev/null  ||
+          ls -lah -G "${_target_path}"
+      fi
+    elif _command_exists "term-image"     &&
+         _file_is_image "${_target_path}" &&
+         [[   "${_tool:-term-image}"  == "term-image" ]]
+    then
+      local _render_style="auto"
+
+      if    [[ -n "${VIMRUNTIME:-}"                   ]]
+      then
+        _render_style="block"
+      elif  [[    "${TERM_PROGRAM:-}" == "iTerm.app"  ]]
+      then
+        _render_style="iterm2"
+      elif  [[ -n "${KITTY_WINDOW_ID:-}"              ]]
+      then
+        _render_style="kitty"
+      fi
+
+      term-image "${_target_path}"  \
+        --cli                       \
+        --force-style               \
+        --quiet                     \
+        --style "${_render_style}"  |   {
+        if _command_exists "less"   &&  ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif _command_exists "imgcat"                     &&
+         _file_is_image "${_target_path}"             &&
+         [[ ! "${_target_path}"   =~ \.afphoto$   ]]  &&
+         [[ ! "${_target_path}"   =~ \.svg$       ]]  &&
+         [[   "${TERM_PROGRAM:-}" == "iTerm.app"  ]]  &&
+         [[   "${_tool:-imgcat}"  == "imgcat"     ]]
+    then
+      imgcat "${_target_path}"    |   {
+        if _command_exists "less" &&  ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif _command_exists "chafa"                      &&
+         _file_is_image "${_target_path}"             &&
+         [[ ! "${_target_path}"   =~ \.afphoto$   ]]  &&
+         [[ ! "${_target_path}"   =~ \.svg$       ]]  &&
+         [[   "${_tool:-chafa}"   == "chafa"      ]]
+    then
+      chafa "${_target_path}"     |   {
+        if _command_exists "less" &&  ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif _command_exists "timg"                       &&
+         _file_is_image "${_target_path}"             &&
+         [[ ! "${_target_path}"   =~ \.afphoto$   ]]  &&
+         [[ ! "${_target_path}"   =~ \.svg$       ]]  &&
+         [[   "${_tool:-timg}"    == "timg"       ]]
+    then
+      timg "${_target_path}"      |   {
+        if _command_exists "less" &&  ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif _command_exists "viu"                        &&
+         _file_is_image "${_target_path}"             &&
+         [[   "${_tool:-viu}"  == "viu"           ]]
+    then
+      viu "${_target_path}"
+    elif _command_exists "catimg"                     &&
+         _file_is_image "${_target_path}"             &&
+         [[   "${_tool:-catimg}"  == "catimg"     ]]
+    then
+      catimg "${_target_path}"
+    elif _command_exists "magick"                     &&
+         _file_is_image "${_target_path}"             &&
+         [[ ! "${_target_path}"   =~ afphoto$     ]]  &&
+         {
+           # Detect sixel support. Via: https://git.io/JfCel
+           local __reply=
+           IFS=";" read -ra __reply -s -t 1 -d "c" -p $'\e[c' >&2
+
+           [[ "${__reply[*]}"     =~ 4            ]]  ||
+           [[ "$TERM"             == yaft*        ]]
+         } && {
+           [[ "${_tool:-magick}"  == "magick"     ]]
+         }
+    then
+      magick "${_target_path}" sixel:-  | {
+        if _command_exists "less" &&    ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif [[ -n  "${KITTY_WINDOW_ID:-}"            ]]  &&
+         _file_is_image "${_target_path}"             &&
+         [[     "${_tool:-icat}"  == "icat"       ]]
+    then
+      kitty +kitten icat "${_target_path}"  | {
+        if _command_exists "less" &&  ! ((_print_output))
+        then
+          less -r --prompt="$(_less_prompt)"
+        else
+          cat
+        fi
+      }
+    elif ((${NB_VIDEO_TO_ASCII_ENABLED:-0}))          &&
+         _command_exists "video-to-ascii"             &&
+         _file_is_video "${_target_path:-}"           &&
+         [[ "${_tool:-"video-to-ascii"}" == "video-to-ascii"        ]]
+    then # https://github.com/joelibaceta/video-to-ascii
+      video-to-ascii -f "${_target_path:-}"
+    elif _command_exists "mplayer"                    &&
+         _file_is_audio "${_target_path}"             &&
+         [[ "${_tool:-${NB_AUDIO_TOOL:-mplayer}}"   == "mplayer"    ]]
+    then
+      printf "Playing audio. Press %s to quit.\\n" "$(_color_primary "Ctrl-C")"
+      mplayer "${_target_path}"
+    elif _command_exists "afplay"                     &&
+         _file_is_audio "${_target_path}"             &&
+         [[ "${_tool:-${NB_AUDIO_TOOL:-afplay}}"      == "afplay"   ]]
+    then
+      printf "Playing audio. Press %s to quit.\\n" "$(_color_primary "Ctrl-C")"
+      afplay "${_target_path}"
+    elif _command_exists "mpg123"                     &&
+         _file_is_audio "${_target_path}"             &&
+         [[ "${_tool:-afplay}"    == "afplay"     ]]  &&
+         [[ "${_target_path}"     =~ mp[(1|2|3)]$ ]]  &&
+         [[ "${_tool:-${NB_AUDIO_TOOL:-mpg123}}"      == "mpg123"   ]]
+    then
+      printf "Playing audio. Press %s to quit.\\n" "$(_color_primary "Ctrl-C")"
+      mpg123 "${_target_path}"
+    elif _command_exists "ffplay"                     &&
+         _file_is_audio "${_target_path}"             &&
+         [[ "${_tool:-${NB_AUDIO_TOOL:-ffplay}}"      == "ffplay"   ]]
+    then
+      printf "Playing audio. Press %s to quit.\\n" "$(_color_primary "Ctrl-C")"
+      ffplay -loglevel quiet "${_target_path}"
+    elif _command_exists "termpdf.py"                 &&
+         [[     "${_target_path}" =~ pdf$         ]]  &&
+         [[ -n  "${KITTY_WINDOW_ID:-}"            ]]  &&
+         _contains "${_tool:-termpdf.py}" "termpdf.py" "termpdf"
+    then
+      termpdf.py "${_target_path}"
+    elif _command_exists "pdftotext"                  &&
+         [[     "${_target_path}" =~ pdf$         ]]  &&
+         [[ "${_tool:-pdftotext}" == "pdftotext"  ]]
+    then
+      pdftotext "${_target_path}" - | tr -d '\014'  | {
+        if ! ((_print_output))
+        then
+          _pager
+        else
+          cat
+        fi
+      }
+    elif [[ "${_target_path}" =~ docx$  ]]  &&
+         _command_exists "pandoc"
+    then
+      pandoc                                \
+        --from  docx                        \
+        --to    markdown                    \
+        "${_target_path}"                   \
+        | sed -E                            \
+          -e 's/\\\[\\\[/\[\[/g'            \
+          -e 's/\\\]\\\]/\]\]/g'            \
+          | _highlight_syntax_if_available  \
+          | if ! ((_print_output))
+            then
+              _pager
+            else
+              cat
+            fi
+    elif [[ "${_target_path}" =~ epub$  ]]  &&
+         _command_exists "pandoc"           &&
+         _web_browser --check
+    then
+      pandoc          \
+        --from  epub  \
+        --to    html  \
+        "${_target_path}" | _web_browser
+    elif _open_in_gui_app "${_target_path:-}"
+    then
+      return 0
+    else
+      _exit_1 printf                                \
+        "%s doesn't know how to show this item.\\n" \
+        "$(_color_primary "${_ME}")"
+    fi
+  else # file is text
+    if ((_browse))                  &&
+         _command_exists "ncat"     &&
+         _command_exists "pandoc"   &&
+         _web_browser --check
+    then
+      cd "${_CURRENT_WORKING_DIR}"
+
+      local _browse_arguments=("${_target_path}")
+      ((_print_output)) && _browse_arguments+=("--print")
+
+      _defer "_browse" "${_browse_arguments[@]:-}"
+
+      return 0
+    elif ((_render))                &&
+         _command_exists "pandoc"   &&
+         _web_browser --check
+    then
+      local _rendered_temp_file_path=
+      _rendered_temp_file_path="$(_temp file ".html" --touch)"
+
+      if [[ "${_target_path}" =~ \.org  ]]
+      then # resolve Org [[wiki-style links]] before rendering to HTML
+        {
+          cat "${_target_path}"
+        } | {
+          _resolve_links "${_notebook_path}" --type org
+        } | {
+          # avoid pandoc bug with brackets in Org link descriptions
+          LC_ALL=C sed -E                                   \
+            -e "s/\]\[\[\[/\]\[${_ME}-placeholder-${_ME}/g" \
+            -e "s/\]\]\]\]/${_ME}-placeholder-${_ME}\]\]/g"
+        } | {
+          _pandoc --standard-input --from org --to html
+        } | {
+          LC_ALL=C sed -E                                   \
+            -e "s/>${_ME}-placeholder-${_ME}/>\[\[/g"       \
+            -e "s/${_ME}-placeholder-${_ME}</\]\]</g"
+        } | {
+          _render
+        } | {
+          cat >> "${_rendered_temp_file_path}"
+        }
+      else # render non-Org to HTML before resolving [[wiki-style links]]
+        {
+          _render "${_target_path}" --pandoc --body
+        } | {
+          _resolve_links "${_notebook_path}"
+        } | {
+          _render
+        } | {
+          cat >> "${_rendered_temp_file_path}"
+        }
+      fi
+
+      if ((_print_output))
+      then
+        if ((_COLOR_ENABLED))
+        then
+          cat "${_rendered_temp_file_path}" | _web_browser --dump
+        else
+          cat "${_rendered_temp_file_path}"
+        fi
+      elif _web_browser --gui
+      then
+        (_web_browser "file://${_rendered_temp_file_path:-}") &
+
+        printf "Serving: %s\\n" "$(_color_primary "${_rendered_temp_file_path}")"
+
+        while true
+        do
+          read -n 1 -s -r -p "Press any key to quit$(_color_muted "...")"
+
+          printf "\\n"
+
+          exit 0
+        done
+      else
+        _web_browser "file://${_rendered_temp_file_path:-}"
+      fi
+
+      rm -f "${_rendered_temp_file_path:?}"
+    else # default
+      if ((_print_output))
+      then # `show --print [--no-color]`
+        if ((_COLOR_ENABLED))
+        then # `show --print`
+          _highlight_syntax_if_available "${_target_path}"
+        else # `show --print --no-color`
+          cat "${_target_path}"
+        fi
+      else # `show`
+        local _target_extension=
+        local _target_filename="${_target_path##*/}"
+
+        if [[ "${_target_filename:-}" =~ \. ]]
+        then
+          _target_extension="${_target_filename##*.}"
+        fi
+
+        cat "${_target_path}"                                       \
+          | LC_ALL=C sed -E                                         \
+              -e "s/^([[:space:]]*-) /\1${_ME}-ph-${_ME}/g"         \
+              -e "s/^([[:space:]]*\*) /\1${_ME}-ph-${_ME}/g"        \
+          | LC_ALL=C fold -s -w "${_COLUMNS}"                       \
+          | LC_ALL=C sed -E                                         \
+              -e "s/^([[:space:]]*-)${_ME}-ph-${_ME}/\1 /g"         \
+              -e "s/^([[:space:]]*\*)${_ME}-ph-${_ME}/\1 /g"        \
+          | _highlight_syntax_if_available "${_target_extension:-}" \
+          | _pager
+      fi
+    fi
+  fi
+
+  # turn off case-insensitive matching
+  shopt -u nocasematch
+
+  if [[ -n "${_decrypted_path:-}" ]] && [[ -e "${_decrypted_path}" ]]
+  then
+    rm "${_decrypted_path:?}"
+  fi
+}
+_alias_subcommand "show" "s"
+_alias_subcommand "show" "view"
+
+# unpin ################################################################# unpin
+
+_describe_unpin() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} unpin ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+
+$(_color_primary "Description"):
+  Unpin a pinned item.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-pinning
+
+$(_color_primary "See Also"):
+  ${_ME} help browse
+  ${_ME} help list
+  ${_ME} help ls
+  ${_ME} help pin
+
+$(_color_primary "Examples"):
+  ${_ME} unpin 123
+  ${_ME} unpin example:sample/321
+HEREDOC
+}
+_unpin() {
+  _pin unpin "${@:-}"
+}
+
+# use ##################################################################### use
+
+_describe_use() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} use <notebook>
+
+$(_color_primary "Description"):
+  Switch to the specified notebook. Shortcut for \`${_ME} notebooks use\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-notebooks
+
+$(_color_primary "See Also"):
+  ${_ME} help notebooks
+
+$(_color_primary "Example"):
+  ${_ME} use example
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} u
+HEREDOC
+}
+_use() {
+  local _name="${1:-}"
+  if [[ -z "${_name}" ]]
+  then
+    _exit_1 _help use
+  fi
+  _notebooks use "${_name}"
+}
+_alias_subcommand "use" "u"
+
+# version ############################################################# version
+
+_describe_version() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} version
+
+$(_color_primary "Description"):
+  Display version information.
+
+$(_color_primary "See Also"):
+  ${_ME} help env
+  ${_ME} help update
+HEREDOC
+}
+_version() {
+  printf "%s\\n" "${_VERSION}"
+}
+
+###############################################################################
+# Call Deferred Command: Group 2                 Call Deferred Command: Group 2
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+_call_deferred_command --group 2
+
+###############################################################################
+# Subcommands: Group 3                                     Subcommands: Group 3
+# --------------------                                     --------------------
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+# archive ############################################################# archive
+
+_describe_archive() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} archive [<name>]
+
+$(_color_primary "Description"):
+  Set the current notebook or notebook <name> to "archived" status.
+
+  This is an alias for \`${_ME} notebooks archive\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#archiving-notebooks
+
+$(_color_primary "See Also"):
+  ${_ME} help notebooks
+  ${_ME} help status
+  ${_ME} help unarchive
+
+$(_color_primary "Examples"):
+  ${_ME} archive
+  ${_ME} archive example
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} ar
+HEREDOC
+}
+_archive() {
+  _notebooks archive "${@:-}"
+}
+_alias_subcommand "archive" "ar"
+
+# browse ############################################################### browse
+
+_describe_browse() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} browse [<notebook>:][<folder-path>/][<id> | <filename> | <title>]
+            [-g | --gui] [-n | --notebooks] [-p | --print] [-q | --query <query>]
+            [-s | --serve] [-t <tag> | --tag <tag> | --tags <tag1>,<tag2>...]
+  ${_ME} browse add [<notebook>:][<folder-path>/][<filename>]
+            [-c <content> | --content <content>] [--tags <tag1>,<tag2>...]
+            [-t <title> | --title <title>]
+  ${_ME} browse delete ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+  ${_ME} browse edit ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+
+$(_color_primary "Subcommands"):
+  (default)  Open a notebook, folder, or item in the terminal or GUI web browser.
+  add        Open the add view in the browser.
+             Shortcut Aliases: \`a\`, \`+\`
+  delete     Open the delete view in the browser.
+             Shortcut Aliases: \`d\`, \`-\`
+  edit       Open the edit view in the browser.
+             Shortcut Alias:   \`e\`
+
+$(_color_primary "Options"):
+  -c, --content <content>      Add content to the new note.
+  -g, --gui                    Open in the system's primary GUI web browser.
+  -n, --notebooks              Browse notebooks.
+  -p, --print                  Print to standard output.
+  -q, --query <query>          Open to the search results for <query>.
+  -s, --serve                  Start the web application server.
+  -t, --tag <tag>              Search for a tag.
+  --tags <tag1>,<tag2>...      A comma-separated list of tags.
+  -t, --title <title>          Add a title to the new note.
+
+$(_color_primary "Description"):
+  Browse, view, and edit linked notes, bookmarks, notebooks, folders, and
+  other items using terminal and GUI web browsers.
+
+  \`browse\` includes an embedded web application designed for terminal
+  and GUI web browsers that renders [[wiki-style links]] and #tags as
+  internal links, providing the ability to browse notes and notebooks,
+  as well as seamlessly browse to and from the offsite links in
+  bookmarks and notes.
+
+  To link to a note or bookmark from another, include the selector for the
+  target item within double square brackets anywhere in the linking document:
+
+    # link to item 123 in the "sample" folder in the "example" notebook
+    [[example:sample/123]]
+
+    # link to the item titled "Example Title" in the "demo" notebook
+    [[demo:Example Title]]
+
+  \`browse\` supports \`w3m\` [1] and \`links\` [2], and depends on
+  \`ncat\` [3] and \`pandoc\` [4]:
+
+    1. https://en.wikipedia.org/wiki/W3m
+    2. https://en.wikipedia.org/wiki/Links_(web_browser)
+    3. https://nmap.org/ncat/
+    4. https://pandoc.org/
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-browsing
+
+$(_color_primary "See Also"):
+  ${_ME} help add
+  ${_ME} help delete
+  ${_ME} help edit
+  ${_ME} help list
+  ${_ME} help ls
+  ${_ME} help open
+  ${_ME} help peek
+  ${_ME} help pin
+  ${_ME} help search
+  ${_ME} help show
+  ${_ME} help unpin
+
+$(_color_primary "Examples"):
+  ${_ME} browse
+  ${_ME} browse example:
+  ${_ME} browse Example\ Folder/
+  ${_ME} browse 123
+  ${_ME} browse demo:456
+  ${_ME} br
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} b
+HEREDOC
+}
+_browse() {
+  # Inspired by bashttpd: https://github.com/avleen/bashttpd
+
+  # _browse_http_response_message()
+  #
+  # Usage:
+  #   _browse_http_response_message <status-code>
+  #
+  # Description:
+  #   Print the response message for a given status code.
+  _browse_http_response_message() {
+    local _status_code="${1:-}"
+
+    case "${_status_code}" in
+      200) printf "OK\\n"                     ;;
+      302) printf "Found\\n"                  ;;
+      400) printf "Bad Request\\n"            ;;
+      403) printf "Forbidden\\n"              ;;
+      404) printf "Not Found\\n"              ;;
+      405) printf "Method Not Allowed\\n"     ;;
+      415) printf "Unsupported Media Type\\n" ;;
+      500) printf "Internal Server Error\\n"  ;;
+    esac
+  }
+
+  # _browse_item_create()
+  #
+  # Usage:
+  #   _browse_item_create <container-path> --message-body <message-body>
+  #
+  # Description:
+  #   Add a new item in the folder or notebook at <container-path>.
+  _browse_item_create() {
+    local _message_body=
+    local _selector=
+    local _subcommand_options=()
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*|--limit|--local|--page|-n|--num|--number|--per*)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --message*body)
+          _message_body="$(_option_get_value "${1:-}" "${2:-}")"
+
+          shift
+          ;;
+        --terminal)
+          :
+          ;;
+        *)
+          if [[ -z "${_selector:-}" ]]
+          then
+            _selector="${1:-}"
+          else
+            _subcommand_options+=("${1:-}")
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -z "${_selector:-}"       ]]
+    then
+      _browse_respond_with 404
+    fi
+
+    local _notebook_path=
+    _notebook_path="$(
+      _notebooks show "${_selector:-}" --path 2>/dev/null ||
+        _notebooks current --path
+    )"
+
+    local _fields=()
+    IFS='&' read -r -a _fields <<< "${_message_body}"
+
+    local _add_options=()
+    local _prepared_encoded_content=
+
+    local __field=
+    for   __field in "${_fields[@]:-}"
+    do
+      case "${__field:-}" in
+        content=*)
+          _prepared_encoded_content="${__field#content=}"
+          _prepared_encoded_content="${_prepared_encoded_content//+/ }"
+          _prepared_encoded_content="${_prepared_encoded_content//%/\\x}"
+          ;;
+        *)
+          if [[ "${__field:-}" =~ \= ]]
+          then
+            _add_options+=("${__field%%=*}")
+
+            local _value=
+            _value="$(_get_uri --decode "${__field#*=}")"
+            _value="${_value//$'\r'}"
+
+            _add_options+=("${_value:-}")
+          else
+            _add_options+=("${__field:-}")
+          fi
+          ;;
+      esac
+    done
+
+    if [[   -n "${_prepared_encoded_content:-}" ]]
+    then
+      if [[ -n "${_selector:-}"                 ]]
+      then
+        _add_options=("${_selector:-}" "${_add_options[@]:-}")
+      fi
+
+      _add_options=("--no-color" "${_add_options[@]:-}")
+
+      local _new_info_line=
+      _new_info_line="$(
+        printf "%b\\n" "${_prepared_encoded_content:-}" \
+          | tr -d $'\r'                                 \
+          | _add "${_add_options[@]:-}"
+      )"
+
+      local _new_selector="${_new_info_line#*[}"
+      _new_selector="${_new_selector%%]*}"
+      _new_selector="${_new_selector//'\ '/ }"
+
+      printf "%s\\n" "${_new_selector}"
+    fi
+  }
+
+  # _browse_item_delete()
+  #
+  # Usage:
+  #   _browse_item_delete <path>
+  #
+  # Description:
+  #   Delete the item at <path>.
+  _browse_item_delete() {
+    local _source_path=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*|--limit|--local|-n|--num|--number|--page|--per*|--raw-url)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --terminal)
+          :
+          ;;
+        *)
+          _source_path="${1:-}"
+          ;;
+      esac
+
+      shift
+    done
+
+    [[ -z "${_source_path:-}" ]] && _browse_respond_with 404
+
+    _delete "${_source_path:-}" --force
+  }
+
+  # _browse_item_update()
+  #
+  # Usage:
+  #   _browse_item_update <path> --message-body <message-body>
+  #
+  # Description:
+  #   Update the content of item at <path>.
+  _browse_item_update() {
+    local _message_body=
+    local _source_path=
+    local _subcommand_options=()
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*|--limit|--local|-n|--num|--number|--page|--per*|--raw-url)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --message*body)
+          _message_body="$(_option_get_value "${1:-}" "${2:-}")"
+
+          shift
+          ;;
+        --terminal)
+          :
+          ;;
+        *)
+          if [[ -z "${_source_path:-}" ]] && [[ "${1:-}" =~ ^/ ]]
+          then
+            _source_path="${1:-}"
+          else
+            _subcommand_options+=("${1:-}")
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -z "${_source_path:-}" ]]
+    then
+      _browse_respond_with 404
+    fi
+
+    local _notebook_path=
+    _notebook_path="$(
+      _notebooks show "${_source_path:-}" --path 2>/dev/null ||
+        _notebooks current --path
+    )"
+
+    if [[ "${_message_body:-}" =~ ^content= ]]
+    then
+      local _prepared_encoded_content="${_message_body#content=}"
+      _prepared_encoded_content="${_prepared_encoded_content//+/ }"
+      _prepared_encoded_content="${_prepared_encoded_content//%/\\x}"
+
+      printf "%b\\n" "${_prepared_encoded_content:-}" \
+        | tr -d $'\r'                                 \
+        > "${_source_path}"
+
+      _git checkpoint "${_notebook_path}"             \
+        "[${_ME}] Edit: ${_source_path#"${_notebook_path}"/}"
+    fi
+  }
+
+  # _browse_render_add()
+  #
+  # Usage:
+  #   _browse_render_add [--columns <columns>] [--content <content>]
+  #                      [--limit <limit>] [--local <url-encoded-path>]
+  #                      [--tags <tag-list>] [--terminal] [--title <title>]
+  #                      [--type <type>] [<add-option>...]
+  #
+  # Description:
+  #   Print an HTML page for creating a text file.
+  _browse_render_add() {
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _content=
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _pagination_options=()
+    local _selector=
+    local _subcommand_options=()
+    local _tag_list=
+    local _target_type=
+    local _title=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        -c|--content)
+          _content="$(_option_get_value "${1:-}" "${2:-}")"
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _encoded_local_notebook_path="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --page)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --tags)
+          _tag_list="$(_option_get_tags "${1:-}" "${2:-}")"
+
+          shift
+          ;;
+        --terminal)
+          _pagination_options+=("--terminal")
+          ;;
+        -t|--title)
+          _title="$(_option_get_value "${1:-}" "${2:-}")"
+
+          shift
+          ;;
+        --type)
+          _target_type="$(_option_get_value "${1:-}" "${2:-}")"
+          _subcommand_options+=("${1:-}" "${2:-}")
+
+          shift
+          ;;
+        --*)
+          _subcommand_options+=("${1:-}")
+
+          if _option_value_is_present "${2:-}"
+          then
+            _subcommand_options+=("${2:-}")
+
+            shift
+          fi
+          ;;
+        -*)
+          _subcommand_options+=("${1:-}")
+          ;;
+        *)
+          if [[ -z "${_selector:-}" ]]
+          then
+            _selector="${1:-}"
+          else
+            _subcommand_options+=("${1:-}")
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ "${_selector:-}" =~ ^/    ]] &&
+       [[ -d "${_selector}"         ]]
+    then # file already exists
+      _browse_respond_with 302 \
+"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/$(_get_id_selector "${_selector:-}"  --notebook)"
+    elif [[ -n "${_selector:-}"     ]]
+    then
+      local _notebook_name=
+      _notebook_name="$(
+        _notebooks show "${_selector:-}" --name 2>/dev/null ||
+          _notebooks current --name
+      )"
+
+      if [[ ! "${_selector:-}" =~ : ]]
+      then
+        _selector="${_notebook_name}:${_selector:-}"
+      fi
+    fi
+
+    local _html_title="${_ME} browse add ${_selector// /\\\ }"
+    local _rows=30
+    local _text_area_columns="${_columns:-}"
+    local _url_params=
+
+    if _contains "--terminal" "${_pagination_options[@]:-}"
+    then
+      _url_params+="&--columns=${_columns}"
+      _text_area_columns="$((_text_area_columns - 3))"
+
+      _url_params+="&--limit=${_limit}"
+      _rows="$((_limit + 2))"
+    fi
+
+    if [[ "${_target_type:-not-folder}" != "folder" ]]
+    then
+      _target_type="${NB_DEFAULT_EXTENSION:-}"
+    fi
+
+    if [[ -n "${_encoded_local_notebook_path:-}"    ]]
+    then
+      _url_params+="&--local=${_encoded_local_notebook_path}"
+    fi
+
+    local _form_content=
+
+    if [[ -n  "${_title:-}"                 ]]
+    then
+      if [[   "${_target_type:-}" == "org"  ]]
+      then
+        _form_content+="#+TITLE: ${_title}${_NEWLINE}"
+      else
+        _form_content+="# ${_title}${_NEWLINE}"
+      fi
+    fi
+
+    if [[ -n "${_tag_list:-}"     ]]
+    then
+      [[ -n "${_form_content:-}"  ]] && _form_content+="${_NEWLINE}"
+
+      _form_content+="${_tag_list:-}${_NEWLINE}"
+    fi
+
+    if [[ -n "${_content:-}"      ]]
+    then
+      [[ -n "${_form_content:-}"  ]] && _form_content+="${_NEWLINE}"
+
+      _form_content+="${_content:-}${_NEWLINE}"
+    fi
+
+    {
+      # TODO: https://stackoverflow.com/a/15844977
+      cat <<HEREDOC
+<form
+  accept-charset="UTF-8"
+  action="/${_selector//' '/%20}?--add${_url_params:-}"
+  method="post">
+<textarea
+  class="content"
+  cols="${_text_area_columns}"
+  id="content"
+  name="content"
+  rows="${_rows}">${_form_content:-}</textarea>
+<br><br>
+<input
+  type="submit"
+  value="add">
+$(_browse_render_option_fields "${_subcommand_options[@]:-}")
+</form>
+HEREDOC
+    } | {
+      printf "%s\\n" "$(
+        _browse_render_header           \
+          "${_selector}"                \
+          "${_pagination_options[@]:-}" \
+          --add
+      )"
+
+      printf "<div class=\"main\">\\n"
+
+      cat
+
+      printf "</div>\\n"
+    } | {
+      _render                                             \
+        --source-extension "${NB_DEFAULT_EXTENSION:-md}"  \
+        --title "${_html_title}"
+    }
+  }
+
+  # _browse_render_container()
+  #
+  # Usage:
+  #   _browse_render_container <target-path> [--columns <columns>]
+  #                            [--local <url-encoded-path>]
+  #                            [--page <page-number>] [--limit <limit>]
+  #                            [--query <query>] [--terminal]
+  #
+  # Description:
+  #   Render a notebook or folder as an HTML page.
+  _browse_render_container() {
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _current_page=1
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _pagination_options=()
+    local _query=
+    local _target_path=
+    local _terminal_browser=0
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _encoded_local_notebook_path="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:-}" "${2:?}")
+          ;;
+        --page)
+          _current_page="${2:?}"
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --query)
+          if [[ -n "${2:-}" ]]
+          then
+            _query="${2:-}"
+          else
+            _exit_1 printf                        \
+              "%s requires a valid argument.\\n"  \
+              "$(_color_primary "${1:-}")"
+          fi
+
+          shift
+          ;;
+        --terminal)
+          _terminal_browser=1
+          _pagination_options+=("${1:-}")
+          ;;
+        *)
+          _target_path="${1:-}"
+          _pagination_options+=("${1:-}")
+          ;;
+      esac
+
+      shift
+    done
+
+    if [[ -z "${_target_path:-}"  ]]
+    then
+      _target_path="$(_notebooks current --path)"
+    fi
+
+    local _encoded_query=
+
+    if [[ -n "${_query:-}"        ]]
+    then
+      _query_arguments=($(
+        printf "%s\\n" "${_query}" | xargs -n 1 printf "%s\\n" 2>/dev/null
+      )) || IFS=' ' read -ra _query_arguments <<< "${_query}"
+
+      _encoded_query="$(
+        LC_ALL=C sed          \
+          -e "s/&/\&amp;/g"   \
+          -e "s/</\&lt;/g"    \
+          -e "s/>/\&gt;/g"    \
+          -e "s/\"/\&quot;/g" \
+          -e "s/#/\&#35;/g"   \
+          -e "s/'/\&#39;/g"   <<< "${_query}"
+      )"
+    fi
+
+    [[ ! "${_target_path}" =~ /$ ]] && _target_path="${_target_path}/"
+
+    local _url_params=
+
+    if ((_terminal_browser))
+    then
+      _url_params+="?--columns=${_columns}&--limit=${_limit}"
+    fi
+
+    if [[   -n "${_encoded_local_notebook_path:-}"  ]]
+    then
+      if [[ -z "${_url_params:-}"                   ]]
+      then
+        _url_params+="?"
+      else
+        _url_params+="&"
+      fi
+
+      _url_params+="--local=${_encoded_local_notebook_path:-}"
+    fi
+
+    local _current_selector=
+    local _maybe_local_input=
+
+    local _local_notebook_path=
+    _local_notebook_path="$(_get_uri --decode "${_encoded_local_notebook_path:-}")"
+
+    if [[ "${_target_path%/}" == "${_local_notebook_path%/}" ]]
+    then
+      _current_selector="local:"
+      _maybe_local_input="\
+<input type=\"hidden\" name=\"--local\"     value=\"${_local_notebook_path}\">${_NEWLINE}"
+    else
+      _current_selector="$(_get_id_selector "${_target_path%/}" || :)"
+    fi
+
+    local _url_encoded_selector="${_current_selector//' '/%20}"
+
+    {
+      if [[ -n "${_query:-}" ]]
+      then
+        _search "${_target_path}"         \
+          "${_query_arguments[@]:-}"      \
+          --limit "${_limit}"             \
+          --list                          \
+          --no-color                      \
+          --notebook-selectors            \
+          --page  "${_current_page}"      || :
+      else
+        _list "${_target_path}"           \
+          --limit "${_limit}"             \
+          --no-color                      \
+          --notebook-selectors            \
+          --page  "${_current_page}"      \
+          --with-pinned
+      fi
+    } | {
+      local _truncate_length=9999
+
+      if ((_terminal_browser))
+      then
+        case "${BROWSER:-}" in
+          # TODO: improve
+          *elinks*) _truncate_length="$((_columns - 23))" ;;
+          *links*)  _truncate_length="$((_columns - 5))"  ;;
+          *)        _truncate_length="$((_columns - 2))"  ;;
+        esac
+      else
+        _truncate_length="$((_columns + 6))"
+      fi
+
+      local         __list_item=
+      while read -r __list_item
+      do
+        if [[ -n "${_truncate_length:-}"          ]] &&
+           [[ ! "${__list_item:-}" =~ Not\ found  ]]
+        then
+          local _list_item_length="${#__list_item}"
+          local _list_item_visible_length=
+          _list_item_visible_length="$(_get_visible_length "${__list_item}")"
+
+          local _difference=
+          _difference="$((_list_item_visible_length - _list_item_length))"
+
+          local _adjusted_truncate_length=
+          _adjusted_truncate_length="$((_truncate_length - _difference))"
+
+          if [[ "${_list_item_visible_length}" -ge "${_adjusted_truncate_length}" ]]
+          then
+            __list_item="${__list_item:0:$((_adjusted_truncate_length))}…"
+          fi
+        fi
+
+        local _display_item="${__list_item:-}"
+
+        local _maybe_escaped_ampersand='\&'
+
+        if [[ "${BASH_VERSINFO[0]:-999999999}"  -lt 5   ]]  ||  {
+             [[ "${BASH_VERSINFO[0]:-999999999}"  ==  5 ]]  &&
+             [[ "${BASH_VERSINFO[1]:-999999999}"  -lt 2 ]]
+           }
+        then
+          _maybe_escaped_ampersand="&"
+        fi
+
+        local _35="${_maybe_escaped_ampersand}#35;"
+        local _36="${_maybe_escaped_ampersand}#36;"
+        local _40="${_maybe_escaped_ampersand}#40;"
+        local _41="${_maybe_escaped_ampersand}#41;"
+        local _60="${_maybe_escaped_ampersand}#60;"
+        local _62="${_maybe_escaped_ampersand}#62;"
+        local _64="${_maybe_escaped_ampersand}#64;"
+
+        _display_item="${_display_item//'&'/&amp;}"
+        _display_item="${_display_item//'#'/${_35}}"
+        _display_item="${_display_item//'$'/${_36}}"
+        _display_item="${_display_item//'('/${_40}}"
+        _display_item="${_display_item//')'/${_41}}"
+        _display_item="${_display_item//'<'/${_60}}"
+        _display_item="${_display_item//'>'/${_62}}"
+        _display_item="${_display_item//'@'/${_64}}"
+        _display_item="${_display_item//\\\ /${_NBSP}}"
+        _display_item="${_display_item//' '/${_NBSP}}"
+
+        # shellcheck disable=SC2140
+        _display_item="${_display_item//\[/<span class=\"muted\">[</span><span class=\"identifier\">}"
+        _display_item="${_display_item//\]/</span><span class=\"muted\">]</span>}"
+
+        if [[   "${_display_item:-}" =~ ^0${_NBSP}items.  ]]
+        then
+          printf "%s\\n<br>\\n" "${_display_item}"
+
+          break
+        elif [[ "${_display_item:-}" =~ ^Not${_NBSP}found ]]
+        then
+          printf "%s\\n<br>\\n" "${_display_item//${_NBSP}in*:/:}"
+
+          break
+        fi
+
+        local _item_selector="${__list_item%%]*}"
+        _item_selector="${_item_selector#[}"
+        _item_selector="${_item_selector//\\/}"
+
+        local _link_selector=
+        _link_selector="$(_get_id_selector "${_item_selector}" --notebook)"
+        _link_selector="${_link_selector//' '/%20}"
+
+        printf "<a href=\"//%s:%s/%s%s\" class=\"list-item\">%s</a><br>\\n"  \
+          "${NB_SERVER_HOST}"                                                \
+          "${NB_SERVER_PORT}"                                                \
+          "${_link_selector:-}"                                              \
+          "${_url_params:-}"                                                 \
+          "${_display_item:-}"
+      done
+    } | {
+      local _list_count=
+      _list_count="$(_count "${_target_path}")"
+
+      local _print_prev=0
+
+      if ((_list_count)) && [[ "${_current_page}" -gt 1 ]]
+      then
+        _print_prev=1
+      fi
+
+      local _print_next=0
+
+      if ((_list_count)) &&
+         [[ "$((_current_page * _limit))" -lt "${_list_count}" ]]
+      then
+        _print_next=1
+      fi
+
+      cat <<HEREDOC
+<form
+  accept-charset="UTF-8"
+  action="/${_url_encoded_selector}${_url_params:-}"
+  id="search"
+  method="get">
+<label for="search-input">search:</label>
+<input
+  autocapitalize="off"
+  autocomplete="off"
+  id="search-input"
+  name="--query"
+  placeholder="search"
+  type="text"
+  value="${_encoded_query}">
+<i></i>
+<input type="hidden" name="--limit" value="${_limit}">
+<input type="hidden" name="--page"  value="${_current_page}">
+${_maybe_local_input:-}</form>
+<br>
+HEREDOC
+
+      printf "<p class=\"item-list\">\\n"
+
+      local _pagination_count=0
+
+      local         __line=
+      while read -r __line
+      do
+        printf "%s\\n" "${__line}"
+
+        _pagination_count="$((_pagination_count+1))"
+      done
+
+      printf "</p>\\n"
+
+      if [[ -n "${_query:-}"                              ]] &&
+         [[ "${_pagination_count}" -lt "${_limit:-0}"  ]]
+      then
+        _print_next=0
+      fi
+
+      if ((_print_prev)) || ((_print_next))
+      then
+        printf "<p class=\"pagination\">\\n"
+      fi
+
+      if [[ -n "${_query:-}" ]]
+      then
+        local _url_encoded_query=
+        _url_encoded_query="$(_get_uri --encode "${_query:-}")"
+
+        _url_params+="&--query=${_url_encoded_query}"
+      fi
+
+      if ! ((_terminal_browser)) &&
+         _contains "--limit" "${_pagination_options[@]:-}"
+      then
+        _url_params+="&--limit=${_limit}"
+      fi
+
+      if ((_print_prev))
+      then
+        local _prev_page_number=
+        _prev_page_number="$((_current_page - 1))"
+
+        local _prev_url_params="${_url_params#$'?'}"
+
+        if [[ "${_prev_page_number:-0}" -gt 1     ]]
+        then
+          _prev_url_params+="&--page=${_prev_page_number:-}"
+        fi
+
+        _prev_url_params="${_prev_url_params#$'&'}"
+
+        if [[ -n "${_prev_url_params:-}"          ]]
+        then
+          _prev_url_params="?${_prev_url_params:-}"
+        fi
+
+        printf                                    \
+          "<a href=\"//%s:%s/%s%s\">%s prev</a>"  \
+          "${NB_SERVER_HOST}"                     \
+          "${NB_SERVER_PORT}"                     \
+          "${_url_encoded_selector}"              \
+          "${_prev_url_params:-}"                 \
+          "${_CHEVRON_LEFT}"
+      fi
+
+      if ((_print_prev)) && ((_print_next))
+      then
+        printf " <span class=\"muted\">%s</span> " "${_MD}"
+      fi
+
+      if ((_print_next))
+      then
+        local _next_url_params=
+        _next_url_params="${_url_params#$'?'}&--page=$((_current_page + 1))"
+
+        printf                                    \
+          "<a href=\"//%s:%s/%s?%s\">next %s</a>" \
+          "${NB_SERVER_HOST}"                     \
+          "${NB_SERVER_PORT}"                     \
+          "${_url_encoded_selector}"              \
+          "${_next_url_params#$'&'}"              \
+          "${_CHEVRON_RIGHT}"
+      fi
+
+      if ((_print_prev)) || ((_print_next))
+      then
+        printf "</p>\\n"
+      fi
+    } | {
+      printf "%s\\n" "$(_browse_render_header "${_pagination_options[@]:-}")"
+
+      printf "<div class=\"main\">\\n"
+
+      cat
+
+      printf "</div>\\n"
+    } | {
+      local _html_title="${_ME} browse"
+
+      if [[ -n "${_current_selector:-}" ]]
+      then
+        _html_title+=" ${_current_selector// /\\ }"
+      fi
+
+      if [[ -n "${_encoded_query:-}"    ]]
+      then
+        _html_title+=" --query \"${_encoded_query:-}\""
+      fi
+
+      if [[ "${_current_page:-0}" -gt 1 ]]
+      then
+        _html_title+=" --page ${_current_page}"
+      fi
+
+      _render --title "${_html_title}"
+    }
+  }
+
+  # _browse_render_delete()
+  #
+  # Usage:
+  #   _browse_render_delete <path> [--columns <columns>]
+  #                         [--limit <limit>] [--local <url-encoded-path>]
+  #                         [--terminal]
+  #
+  # Description:
+  #   Print an form for deleting an item.
+  _browse_render_delete() {
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _pagination_options=()
+    local _raw_url=
+    local _source_path=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _encoded_local_notebook_path="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --page)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --raw-url)
+          _raw_url="${2:?}"
+
+          shift
+          ;;
+        --terminal)
+          _pagination_options+=("--terminal")
+          ;;
+        *)
+          _source_path="${1:-}"
+          ;;
+      esac
+
+      shift
+    done
+
+    local _info_line=
+    _info_line="$(_show "${_source_path}" --info-line --no-color)"
+
+    local _id_selector=
+    _id_selector="$(_get_id_selector "${_source_path}")"
+
+    local _url_params=
+
+    if [[ -n "${_encoded_local_notebook_path:-}" ]]
+    then
+      _url_params+="&--local=${_encoded_local_notebook_path}"
+    fi
+
+    if _contains "--terminal" "${_pagination_options[@]:-}"
+    then
+      _url_params+="&--columns=${_columns}"
+      _url_params+="&--limit=${_limit}"
+    fi
+
+    {
+      cat <<HEREDOC
+<h2 align="center">deleting</h2>
+
+<p align="center">
+<a href="//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_id_selector}${_url_params/&/?}">
+${_info_line//'\ '/ }
+</a>
+</p>
+<p align="center" class="muted">
+  This item will still be available in git history.
+</p>
+<div align="center">
+<form
+  accept-charset="UTF-8"
+  action="/${_id_selector:-}?--delete${_url_params:-}"
+  align="center"
+  method="post">
+<input
+  align="center"
+  type="submit"
+  value="delete">
+</form>
+</div>
+HEREDOC
+    } | {
+      printf "%s\\n" "$(
+        _browse_render_header           \
+          "${_source_path}"             \
+          "${_pagination_options[@]:-}" \
+          --raw-url "${_raw_url}"       \
+          --delete
+      )"
+
+      printf "<div class=\"main\">\\n"
+
+      cat
+
+      printf "</div>\\n"
+    } | {
+      _render --title "${_ME} browse delete ${_id_selector// /\\ }"
+    }
+  }
+
+  # _browse_render_edit()
+  #
+  # Usage:
+  #   _browse_render_edit <path> [--columns <columns>]
+  #                       [--limit <limit>] [--local <url-encoded-path>]
+  #                       [--terminal] [<edit-option>...]
+  #
+  # Description:
+  #   Print an HTML page for editing a text file.
+  _browse_render_edit() {
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _pagination_options=()
+    local _raw_url=
+    local _source_path=
+    local _subcommand_options=()
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _encoded_local_notebook_path="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --page)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --raw-url)
+          _raw_url="${2:?}"
+
+          shift
+          ;;
+        --terminal)
+          _pagination_options+=("--terminal")
+          ;;
+        *)
+          if [[ -z "${_source_path:-}"  ]] && [[    "${1:-}" =~ ^/    ]]
+          then
+            _source_path="${1:-}"
+          elif [[ "${1:-}" =~ :         ]] && [[ !  "${1:-}" =~ \-\-  ]]
+          then
+            : # skip selector
+          else
+            _subcommand_options+=("${1:-}")
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    local _content=
+    _content="$(_show "${_source_path}" --print --no-color)"
+
+    local _id_selector=
+    _id_selector="$(_get_id_selector "${_source_path}" --notebook)"
+
+    local _form_action_selector=
+    _form_action_selector="${_id_selector// /%20}"
+
+    local _last_saved_at=
+    _last_saved_at="$(_show "${_source_path}" --updated)"
+    _last_saved_at="${_last_saved_at% -[0-9][0-9][0-9][0-9]}"
+
+    local _rows=30
+    local _text_area_columns="${_columns:-}"
+    local _url_params=
+
+    if _contains "--terminal" "${_pagination_options[@]:-}"
+    then
+      _url_params+="&--columns=${_columns}"
+      _text_area_columns="$((_text_area_columns - 3))"
+
+      _url_params+="&--limit=${_limit}"
+      _rows="$((_limit + 2))"
+    fi
+
+    if [[ -n "${_encoded_local_notebook_path:-}" ]]
+    then
+      _url_params+="&--local=${_encoded_local_notebook_path}"
+    fi
+
+    {
+      # TODO: https://stackoverflow.com/a/15844977
+      cat <<HEREDOC
+<form
+  accept-charset="UTF-8"
+  action="/${_form_action_selector:-}?--edit${_url_params:-}"
+  method="post">
+<textarea
+  class="content"
+  cols="${_text_area_columns}"
+  id="content"
+  name="content"
+  rows="${_rows}">${_content}</textarea>
+<br><br>
+<input
+  type="submit"
+  value="save"> <span class="muted">${_MD}</span> <span class="muted last-saved">last: ${_last_saved_at}</span>
+$(_browse_render_option_fields "${_subcommand_options[@]:-}")
+</form>
+HEREDOC
+    } | {
+      printf "%s\\n" "$(
+        _browse_render_header           \
+          "${_source_path}"             \
+          "${_pagination_options[@]:-}" \
+          --raw-url "${_raw_url}"       \
+          --edit
+      )"
+
+      printf "<div class=\"main\">\\n"
+
+      cat
+
+      printf "</div>\\n"
+    } | {
+      _render                                     \
+        --source-extension "${_source_path##*.}"  \
+        --title "${_ME} browse edit ${_id_selector// /\\ }"
+    }
+  }
+
+  # _browse_render_header()
+  #
+  # Usage:
+  #   _browse_render_header <selector> [--columns <columns>]
+  #                         [--local <url-encoded-path>] [--limit <limit>]
+  #                         [--raw-url <url>] [--terminal]
+  #
+  # Description:
+  #   Print a context-aware, linked nav header.
+  _browse_render_header() {
+    local _action=
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _raw_url=
+    local _selector=
+    local _terminal_browser=0
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        '') : ;;
+        --add|--delete|--edit)
+          _action="${1#--}"
+          ;;
+        --col*)
+          _columns="${2:?}"
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+
+          shift
+          ;;
+        --local)    _encoded_local_notebook_path="${2:?}" && shift  ;;
+        --page)     _option_value_is_present     "${2:-}" && shift  ;;
+        --raw-url)  _raw_url="${2:?}"                     && shift  ;;
+        --terminal) _terminal_browser=1                             ;;
+        --*)        _option_value_is_present "${2:-}"     && shift  ;;
+        -*)         :                                               ;;
+        *)          _selector="${1:-}"                              ;;
+      esac
+
+      shift
+    done
+
+    local _url_params=()
+
+    if [[ -n "${_encoded_local_notebook_path:-}" ]]
+    then
+      _url_params+=("--local=${_encoded_local_notebook_path}")
+    fi
+
+    if ((_terminal_browser))
+    then
+      _url_params+=(
+        "--columns=${_columns}"
+        "--limit=${_limit}"
+      )
+    fi
+
+    local _url_param_string=
+    _url_param_string="$(_join "&" "${_url_params[@]:-}")"
+
+    if [[ -n "${_url_param_string:-}" ]]
+    then
+      _url_param_string="?${_url_param_string}"
+      local _url_params_ext="${_url_param_string}&"
+    else
+      local _url_params_ext="?"
+    fi
+
+    local _header_content="\
+<a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_url_param_string:-}\">"
+    _header_content+="<span class=\"muted\">${_CHEVRON_RIGHT}</span>${_ME}</a>"
+    _header_content+=" <span class=\"muted\">${_MD}</span>"
+
+    if [[ -z "${_selector:-}"         ]]
+    then
+      _header_content+=" <span class=\"muted\">notebooks</span>"
+    else
+      local _notebook_name=
+
+      if [[ "${_selector}" =~ (:|^/)  ]]
+      then
+        _notebook_name="$(_notebooks show "${_selector}" --name)"
+      fi
+
+      if [[ -z "${_notebook_name}"    ]]
+      then
+        _notebook_name="$(_notebooks current --name)"
+      fi
+
+      local _notebook_path=
+      _notebook_path="$(_notebooks show "${_notebook_name}" --path)"
+
+      _notebooks select "${_notebook_path}"
+
+      _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_notebook_name//' '/%20}:${_url_param_string:-}\">${_notebook_name}</a>"
+      _header_content+=" <span class=\"muted\">:</span>"
+
+      local _relative_folder_path=
+      local _selector_relative_folder_path=
+
+      if [[ "${_selector}" =~ ^/      ]]
+      then
+        local _relative_path="${_selector#"${_notebook_path}"/}"
+
+        if [[ "${_relative_path:-}" == "${_notebook_path:-}" ]]
+        then
+          _relative_path=
+        fi
+
+        if [[ -d "${_selector}"       ]]
+        then
+          _relative_folder_path="${_relative_path:-}"
+        else
+          if [[ "${_relative_path:-}" =~ / ]]
+          then
+            _relative_folder_path="${_relative_path%/*}"
+          else
+            _relative_folder_path=
+          fi
+        fi
+
+        _selector_relative_folder_path="${_relative_folder_path:-}"
+      else
+        _selector_relative_folder_path="${_selector#*:}"
+        _relative_folder_path="$(
+          _selector_resolve_folders "${_selector_relative_folder_path}" || :
+        )"
+      fi
+
+      if [[ -n "${_relative_folder_path:-}"                  ]] &&
+         [[ -d "${_notebook_path}/${_relative_folder_path}"  ]]
+      then
+        local _selector_folders=()
+        IFS='/' read -ra _selector_folders <<< "${_relative_folder_path}"
+
+        local _folder_id_path=
+        _folder_id_path="$(
+          _get_id_selector "$(
+            _join "/" "${_selector_folders[@]:-}"
+          )/" "${_notebook_path}"
+        )"
+
+        local _selector_folder_ids=()
+        IFS='/' read -ra _selector_folder_ids <<< "${_folder_id_path}"
+
+        local _url_path="${_notebook_name}:"
+
+        local i=
+        for ((i=0; i < ${#_selector_folders[@]}; i++))
+        do
+          _url_path+="${_selector_folder_ids[i]:-}/"
+
+          _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_url_path}${_url_param_string:-}\">${_selector_folders[i]}</a>"
+          _header_content+=" <span class=\"muted\">/</span>"
+        done
+      fi
+    fi
+
+    local _item_path=
+    _item_path="$(_show "${_selector:-}" --path 2>/dev/null || :)"
+
+    if [[ -f "${_item_path:-}"  ]]
+    then
+      local _id_selector=
+      _id_selector="$(_get_id_selector "${_selector:-}" --notebook)"
+
+      local _selector_id="${_id_selector#*:}"
+      _selector_id="${_selector_id##*/}"
+
+      if _contains "${_action:-}" "edit" "delete"
+      then
+        _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_id_selector:-}${_url_param_string:-}\">${_selector_id:-}</a>"
+      elif [[ "${_action:-}" != "add"   ]]
+      then
+        _header_content+=" <span class=\"muted\">${_selector_id:-}</span>"
+      fi
+
+      # NOTE: backup _raw_url calculation. TODO: remove
+      if [[ -z "${_raw_url:-}"  ]]
+      then
+        local _raw_url="//${NB_SERVER_HOST}:${NB_SERVER_PORT}/--original/"
+
+        if [[ !   "${_item_path:-}" =~ ^${NB_DIR}     ]] &&
+           [[ -n  "${_encoded_local_notebook_path:-}" ]]
+        then
+          local _local_notebook_path=
+          _local_notebook_path="$(_get_uri --decode "${_encoded_local_notebook_path}")"
+
+          _raw_url+="local/${_item_path#"${_local_notebook_path}"/}?--local=${_encoded_local_notebook_path}"
+        else
+          _raw_url+="${_item_path#"${NB_DIR}"/}"
+        fi
+      fi
+
+      if [[ -n "${_raw_url:-}"  ]]
+      then
+        _header_content+=" <span class=\"muted\">${_MD}</span>"
+        _header_content+=" <a href=\"${_raw_url}\">↓</a>"
+      fi
+
+      if [[ "${_action:-}"  == "edit"   ]]
+      then
+        _header_content+=" <span class=\"muted\">${_MD}</span>"
+        _header_content+=" <span class=\"muted\">editing</span>"
+      elif _file_is_text "${_selector:-}"
+      then
+        _header_content+=" <span class=\"muted\">${_MD}</span>"
+        _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_id_selector:-}${_url_params_ext:-}--edit\">edit</a>"
+      fi
+
+      case "${_action:-}" in
+        delete)
+          _header_content+=" <span class=\"muted\">${_MD}</span>"
+          _header_content+=" <span class=\"muted\">-</span>"
+          _header_content+=" <span class=\"muted\">|</span>"
+          ;;
+        edit)
+          _header_content+=" <span class=\"muted\">${_MD}</span>"
+          _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_id_selector:-}${_url_params_ext:-}--delete\">-</a>"
+          _header_content+=" <span class=\"muted\">|</span>"
+          ;;
+        *)
+          _header_content+=" <span class=\"muted\">|</span>"
+          ;;
+      esac
+    fi
+
+    if [[ -n "${_selector:-}"           ]]
+    then
+      if [[ "${_action:-}"  == "add"    ]]
+      then
+        _header_content+=" <span class=\"muted\">+</span>"
+      else
+        _header_content+="\
+ <a href=\"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_notebook_name}:${_folder_id_path:-}${_url_params_ext:-}--add\">+</a>"
+      fi
+    fi
+
+    cat <<HEREDOC
+<nav class="header-crumbs"><strong>${_header_content:-}</strong></nav>
+<p class="header-crumbs-spacer"></p>
+HEREDOC
+  }
+
+  # _browse_render_item()
+  #
+  # Usage:
+  #   _browse_render_item <path> [--columns <columns>]
+  #                       [--limit <limit>] [--local <url-encoded-path>]
+  #                       [--raw-url <url>] [--terminal]
+  #
+  # Description:
+  #   Render an item to HTML with links resolved to internal web server.
+  _browse_render_item() {
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _pagination_options=()
+    local _raw_url=
+    local _respond_with_arguments=("--standard-input")
+    local _source_path=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --headers)
+          _respond_with_arguments+=("${1:-}")
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --page)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --raw-url)
+          _raw_url="${2:?}"
+
+          shift
+          ;;
+        --terminal)
+          _pagination_options+=("--terminal")
+          ;;
+        *)
+          if [[ -z "${_source_path:-}"  ]]
+          then
+            _source_path="${1:-}"
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    local _header_options=("${_pagination_options[@]:-}")
+
+    if [[ -n "${_raw_url:-}" ]]
+    then
+      _header_options+=("--raw-url" "${_raw_url}")
+    fi
+
+    local _id_selector=
+    _id_selector="$(_get_id_selector "${_source_path:-}" --notebook)"
+
+    local _html_title="${_ME} browse ${_id_selector// /\\\ }"
+
+    local _render_type=
+
+    if _file_is_text "${_source_path:-}"  ||
+       [[   "${_source_path:-}" =~ (\.docx$|\.epub$|\.odt$) ]]
+    then
+      _render_type="pandoc"
+    elif _contains "${_source_path##*.}"  \
+           apng avif gif jfif jpeg jpg pjpeg pjp png svg webp
+    then
+      _render_type="image"
+    elif _file_is_audio "${_source_path:-}"
+    then
+      _render_type="audio"
+    elif _file_is_video "${_source_path:-}"
+    then
+      _render_type="video"
+    elif [[ "${_source_path}" =~ \.pdf    ]]
+    then
+      _render_type="pdf"
+    else
+      {
+        printf "%s\\n" "$(
+          _browse_render_header           \
+            "${_source_path}"             \
+            "${_header_options[@]:-}"
+        )"
+
+        printf "<div class=\"main\">\\n<p>\\n"
+
+        if _file_is_encrypted "${_source_path:-}"
+        then
+          printf "415 %s: File is encrypted\\n" \
+            "$(_browse_http_response_message 415)"
+        else
+          printf "415 %s\\n"                    \
+            "$(_browse_http_response_message 415)"
+        fi
+
+        printf "</p>\\n</div>\\n"
+      } | {
+        _render --title "${_html_title}"
+      } | {
+        _browse_respond_with 415 "${_respond_with_arguments[@]:-}"
+      }
+
+      return 1
+    fi
+
+    local _notebook_path=
+    _notebook_path="$(
+      _notebooks show "${_source_path:-}" --path 2>/dev/null  ||
+        _notebooks current --path
+    )"
+
+    if [[ "${_source_path:-}" =~ \.org$   ]] &&
+       _file_is_text "${_source_path:-}"
+    then # resolve Org [[wiki-style links]] before rendering to HTML
+      {
+        cat "${_source_path}"
+      } | {
+        _resolve_links                    \
+          "${_notebook_path}"             \
+          "${_pagination_options[@]:-}"   \
+          --browse                        \
+          --type org
+      } | {
+        # avoid pandoc bug with brackets in Org link descriptions
+        LC_ALL=C sed -E                                   \
+          -e "s/\]\[\[\[/\]\[${_ME}-placeholder-${_ME}/g" \
+          -e "s/\]\]\]\]/${_ME}-placeholder-${_ME}\]\]/g"
+      } | {
+        if _command_exists "pandoc"
+        then
+          _pandoc             \
+            --standard-input  \
+            --from  org       \
+            --to    html
+        else
+          cat
+        fi
+      } | {
+        LC_ALL=C sed -E                                   \
+          -e "s/>${_ME}-placeholder-${_ME}/>\[\[/g"       \
+          -e "s/${_ME}-placeholder-${_ME}</\]\]</g"
+      } | {
+        # undo pandoc adding "file://" or "file:///" to protocol-relative URLs
+        LC_ALL=C sed -E -e "s/file:\/\/\/\/\/?/\/\//g"
+      } | {
+        printf "%s\\n" "$(
+          _browse_render_header           \
+            "${_source_path}"             \
+            "${_header_options[@]:-}"
+        )"
+
+        printf "<div class=\"main\">\\n"
+
+        cat
+
+        printf "</div>\\n"
+      } | {
+        _render --title "${_html_title}"
+      }
+    else # render non-Org to HTML before resolving [[wiki-style links]]
+      {
+        case "${_render_type:-}" in
+          pandoc)
+            local _render_options=("--pandoc" "--body" "--title" "${_html_title}")
+
+            if [[ "${_source_path:-}" =~ \.bookmark\.md ]]
+            then
+              _render_options+=("--bookmark")
+            fi
+
+            {
+              printf "" | _render "${_source_path}" "${_render_options[@]:-}"
+            } | {
+              if _command_exists "pandoc"
+              then
+                cat
+              else
+                if ! _contains "--terminal" "${_pagination_options[@]:-}"
+                then
+                  printf "<br>"
+                fi
+
+                LC_ALL=C sed -E                               \
+                  -e "/<span class=\"muted\"/!s/</\&lt;/g"    \
+                  -e "/<span class=\"muted\"/!s/\//\&#47;/g"  \
+                  -e "s/.*/&<br>/g" # " TODO: vim highlighting bug
+              fi
+            }
+            ;;
+          *)
+            { # begin media markup pipeline
+              case "${_render_type:-}" in
+                audio)
+                  local _mime_type=
+                  _mime_type="$(file -b --mime-type "${_source_path}" 2>/dev/null || :)"
+
+                  # handle `file` 5.40 bug: https://bugs.astron.com/view.php?id=259
+                  _mime_type="${_mime_type//audio\/mpegapplication\/octet-stream/audio/mpeg}"
+                  _mime_type="${_mime_type//audio\/mpegaudio\/mpeg/audio/mpeg}"
+
+                  cat <<HEREDOC
+<audio controls>
+  <source src="${_raw_url}" type="${_mime_type:-}">
+</audio>
+HEREDOC
+                  ;;
+                image)
+                  cat <<HEREDOC
+<a href="${_raw_url}">
+  <img src="${_raw_url}" alt="${_NB_INDICATOR_IMAGE:-}${_source_path##*/}" />
+</a>
+HEREDOC
+                  ;;
+                pdf)
+                  if ((${NB_BROWSE_PDF_TO_TEXT_ENABLED:-0}))  &&
+                     _command_exists "pdftotext"
+                  then
+                    # TODO: spacing
+                    # NOTE: add uniform newlines: `sed  '/^$/d' | sed G`
+                    pdftotext "${_source_path}" - \
+                      | tr -d '\014'              \
+                      | _render --from="md" --pandoc --body
+                  else
+                    cat <<HEREDOC
+<iframe src="${_raw_url}" width="100%" height="700px"></iframe>
+HEREDOC
+                  fi
+                  ;;
+                video)
+                  local _mime_type=
+                  _mime_type="$(file -b --mime-type "${_source_path}" 2>/dev/null || :)"
+
+                  cat <<HEREDOC
+<video width="320" height="240" controls>
+  <source src="${_raw_url}" type="${_mime_type}">
+</video>
+HEREDOC
+                  ;;
+              esac
+            } | { # media markup pipeline
+              cat <<HEREDOC
+<div align="center" class="media-item">
+  $(cat)
+</div>
+
+<p align="center" class="media-caption">
+  <a href="${_raw_url}">
+    ${_source_path##*/}
+  </a>
+</p>
+HEREDOC
+            } # end media markup pipeline
+            ;;
+        esac
+      } | {
+        printf "%s\\n" "$(
+          _browse_render_header           \
+            "${_source_path}"             \
+            "${_header_options[@]:-}"
+        )"
+
+        printf "<div class=\"main\">\\n"
+
+        cat
+
+        printf "</div>\\n"
+      } | {
+        _resolve_links                    \
+          "${_notebook_path}"             \
+          "${_pagination_options[@]:-}"   \
+          --browse
+      } | {
+        _render --title "${_html_title}"
+      }
+    fi | {
+      # rewrite relative image paths to use --original URLs
+
+      local _encoded_notebook_name="${_raw_url#//"${NB_SERVER_HOST}":"${NB_SERVER_PORT}"/--original/}"
+      _encoded_notebook_name="${_encoded_notebook_name%%/*}"
+
+      local _raw_url_base_pattern="\/\/${NB_SERVER_HOST}:${NB_SERVER_PORT}\/--original\/${_encoded_notebook_name}\/"
+      local _raw_url_pattern="${_raw_url_base_pattern}\1"
+
+      local _sed_arguments=()
+
+      _sed_arguments+=(
+-e "s/<img src=\"([^\"]+)\"/<img src=\"${_raw_url_pattern}\"/g"
+-e "s/<img src=\"${_raw_url_base_pattern}(https?:[^\"]+)\"/<img src=\"\1\"/g"
+-e "s/<img src=\"${_raw_url_base_pattern}(\/\/[^\"]+)\"/<img src=\"\1\"/g"
+      )
+
+      if [[ -n "${_encoded_local_notebook_path:-}" ]]
+      then
+        local _local_param_pattern="\1\?--local=${_encoded_local_notebook_path}"
+
+        _sed_arguments+=(
+-e "s/<img src=\"(${_raw_url_base_pattern}[^\"]+)\"/<img src=\"${_local_param_pattern}\"/g"
+-e "s/<img src=\"([^\"]+\?--local=[^\"]+)\?--local=[^\"]+\"/<img src=\"\1\"/g"
+        )
+      fi
+
+      LC_ALL=C sed -E "${_sed_arguments[@]:-}"
+    } | {
+      _browse_respond_with 200 "${_respond_with_arguments[@]:-}"
+    }
+
+    return 0
+  }
+
+  # _browse_render_notebooks()
+  #
+  # Usage:
+  #   _browse_render_notebooks [--columns <columns>]
+  #                            [--limit <limit>] [--local <url-encoded-path>]
+  #                            [--terminal]
+  #
+  # Description:
+  #   Print an HTML page listing notebooks.
+  _browse_render_notebooks() {
+    local _add_line_breaks=0
+    local _columns="${NB_BROWSE_COLUMNS:-70}"
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _pagination_options=()
+    local _user_agent=
+
+    while ((${#}))
+    do
+      case "${1:-}" in
+        --col*)
+          _columns="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:-}" "${2:?}")
+          _add_line_breaks=1
+
+          shift
+          ;;
+        --limit|-n|--num|--number|--per*)
+          _limit="${2:?}"
+          _pagination_options+=("${1:-}" "${2:?}")
+
+          shift
+          ;;
+        --local)
+          _encoded_local_notebook_path="$(_option_get_value "${1:-}" "${2:-}")"
+          _pagination_options+=("${1:?}" "${2:?}")
+
+          shift
+          ;;
+        --page)
+          _option_value_is_present "${2:-}" && shift
+          ;;
+        --terminal)
+          _pagination_options+=("--terminal")
+          _add_line_breaks=1
+          ;;
+        --user-agent)
+          if [[ -n "${2:-}" ]]
+          then
+            _user_agent="$(_option_get_value "${1:-}" "${2:-}")"
+
+            shift
+          fi
+          ;;
+      esac
+
+      shift
+    done
+
+    local _notebook_names=()
+    _notebook_names=($(_notebooks --names --unarchived --no-color --global))
+
+    local _url_param_string=
+
+    if [[ -n "${_encoded_local_notebook_path:-}" ]]
+    then
+      _notebook_names=("local" "${_notebook_names[@]:-}")
+      _url_param_string+="&--local=${_encoded_local_notebook_path}"
+    fi
+
+    if _contains "--terminal" "${_pagination_options[@]:-}"
+    then
+      _url_param_string+="&--columns=${_columns}&--limit=${_limit}"
+    fi
+
+    # turn on case-insensitive matching
+    shopt -s nocasematch
+    case "${_user_agent:-}" in
+      *elinks*)
+        _columns="$((_columns - 30))"
+        ;;
+      *links*)
+        _columns="$((_columns - 5))"
+        ;;
+    esac
+    # turn off case-insensitive matching
+    shopt -u nocasematch
+
+    {
+      printf "<p>"
+
+      local _first=1
+      local _test_line=
+
+      local __name=
+      for   __name in "${_notebook_names[@]:-}"
+      do
+        if ((_first))
+        then
+          _first=0
+          _test_line+="${__name}${_NBSP}${_MD}"
+        else
+          _test_line+=" ${__name}${_NBSP}${_MD}"
+
+          if ((_add_line_breaks)) && [[ "${#_test_line}" -gt "${_columns}" ]]
+          then
+            printf "<br>\\n"
+            _test_line="${__name}${_NBSP}${_MD}"
+          else
+            printf "%s<span class=\"muted\">%s</span> " "${_NBSP}" "${_MD}"
+          fi
+        fi
+
+        printf                                \
+          "<a href=\"//%s:%s/%s:%s\">%s</a>"  \
+          "${NB_SERVER_HOST}"                 \
+          "${NB_SERVER_PORT}"                 \
+          "${__name//' '/%20}"                \
+          "${_url_param_string/&/?}"          \
+          "${__name//\ /${_NBSP}}"
+      done
+
+      printf "</p>\\n"
+    } | {
+      printf "%s\\n" "$(_browse_render_header "${_pagination_options[@]:-}")"
+
+      printf "<div class=\"main\">\\n"
+
+      cat
+
+      printf "</div>\\n"
+    } | {
+      _render --title "${_ME} browse --notebooks"
+    }
+  }
+
+  # _browse_render_option_fields
+  #
+  # Usage:
+  #   _browse_render_option_fields <option>...
+  #
+  # Description:
+  #   Render a series of hidden form fields for the given options.
+  _browse_render_option_fields() {
+    local _subcommand_options=("${@:-}")
+
+    local i=
+    for ((i=0; i < ${#_subcommand_options[@]}; i++))
+    do
+      if [[   "${_subcommand_options[i]}"           =~ \--  ]] &&
+         [[ ! "${_subcommand_options[$((i+1))]:--}" =~ ^-   ]]
+      then
+        printf "<input type=\"hidden\" name=\"%s\" value=\"%s\">\\n"  \
+          "$(_get_uri --encode "${_subcommand_options[i]}")"          \
+          "$(_get_uri --encode "${_subcommand_options[$((i+1))]}")"
+
+        i="$((i+1))"
+      elif [[ -n "${_subcommand_options[i]:-}" ]]
+      then
+        printf "<input type=\"hidden\" name=\"%s\">\\n"               \
+          "$(_get_uri --encode "${_subcommand_options[i]}")"
+      fi
+    done
+  }
+
+  # _browse_respond()
+  #
+  # Usage:
+  #   _browse_respond
+  #
+  # Description:
+  #   Build a response using standard input and print to standard output.
+  _browse_respond() {
+    # ---------------
+    # Request parsing
+
+    # Request-Line HTTP RFC 2616 §5
+    # https://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html
+    local   _request_line=
+    read -r _request_line || _browse_respond_with 400
+
+    # strip trailing CR if it exists
+    _request_line="${_request_line%%$'\r'}"
+
+    local _request_http_version=
+    local _request_method=
+    local _request_uri=
+
+    IFS=' ' read -r   \
+      _request_method \
+      _request_uri    \
+      _request_http_version <<< "${_request_line}"
+
+    if [[ -z "${_request_method:-}"       ]] ||
+       [[ -z "${_request_uri:-}"          ]] ||
+       [[ -z "${_request_http_version:-}" ]]
+    then
+      _browse_respond_with 400
+    fi
+
+    # parse headers and message body
+
+    local _content_length=
+
+    case "${_request_method:-}" in
+      POST) local _looking_for_content_length=1 ;;
+      *)    local _looking_for_content_length=0 ;;
+    esac
+
+    local _looking_for_end_of_headers=1
+    local _looking_for_user_agent=1
+    local _request_user_agent=
+    local _terminal_browser=1
+
+    while ((_looking_for_user_agent))     ||
+          ((_looking_for_content_length)) ||
+          ((_looking_for_end_of_headers))
+    do
+      local   __request_line=
+      read -r __request_line
+
+      if ((_looking_for_user_agent))  &&
+         [[ "${__request_line:-}"     =~ User-Agent             ]]
+      then # detect browser type
+        # turn on case-insensitive matching
+        shopt -s nocasematch
+        if [[ ! "${__request_line}"   =~ (curl|Links|Lynx|w3m)  ]]
+        then
+          _terminal_browser=0
+        fi
+        # turn off case-insensitive matching
+        shopt -u nocasematch
+
+        _looking_for_user_agent=0
+        _request_user_agent="${__request_line:-}"
+      elif ((_looking_for_content_length)) &&
+           [[ "${__request_line:-}"   =~ Content-Length ]]
+      then # assign content length
+        _content_length="${__request_line##*: }"
+        _content_length="${_content_length%%$'\r'}"
+
+        _looking_for_content_length=0
+      elif [[ -z "${__request_line%%$'\r'}"             ]]
+      then
+        _looking_for_end_of_headers=0
+
+        break
+      fi
+    done
+
+    # get message body
+
+    local _message_body=
+
+    if [[ "${_request_method}"  == "POST"     ]]  &&
+       ((${_content_length:-0}))
+    then
+      read -r -n "${_content_length}" _message_body
+    fi
+
+    # serve ace editor files
+
+    if [[ "${_request_uri}"     =~ /--ace/.*  ]]
+    then
+      local _target_relative_path="${_request_uri#/--ace/}"
+
+      _browse_respond_with 200 \
+        "${NB_DIR}/.assets/ace-builds/src-min-noconflict/${_target_relative_path}"
+
+      return 0
+    fi
+
+    # query string
+
+    local _query_string=
+
+    if [[ "${_request_uri:-}" =~ \? ]]
+    then
+      _query_string="${_request_uri#*\?}"
+    fi
+
+    local _action=
+    local _columns=1
+    local _encoded_local_notebook_path=
+    local _limit="${NB_BROWSE_LIMIT:-30}"
+    local _local_notebook_path=
+    local _page_number=1
+    local _query=
+    local _render_function_options=()
+    local _request_parameters=()
+
+    if [[ -n "${_query_string:-}"   ]]
+    then
+      IFS='&' read -r -a _request_parameters <<< "${_query_string}"
+
+      local __parameter=
+      for   __parameter in "${_request_parameters[@]:-}"
+      do
+        case "${__parameter:-}" in
+          url=*)
+            _browse_respond_with 302 "$(_get_uri --decode "${__parameter#*=}")"
+            ;;
+          --add|--delete|--edit)
+            _action="${__parameter#--}"
+            ;;
+          --columns=*)
+            _columns="${__parameter#*=}"
+            _render_function_options+=("--columns" "${_columns}")
+            ;;
+          --gui)
+            _terminal_browser=0
+            ;;
+          --limit=*|-n=*|-num=*|--number=*|--per*page=*)
+            _limit="${__parameter#*=}"
+            _render_function_options+=("--limit" "${_limit}")
+            ;;
+          --local=*)
+            _encoded_local_notebook_path="${__parameter#*=}"
+            _local_notebook_path="$(
+              _get_uri --decode "${_encoded_local_notebook_path}"
+            )"
+            ;;
+          --page=*)
+            _page_number="${__parameter#*=}"
+            ;;
+          --query=*)
+            _query="$(_get_uri --decode "${__parameter#*=}")"
+            ;;
+          --terminal)
+            _terminal_browser=1
+            ;;
+          -*)
+            _render_function_options+=("${__parameter%=*}")
+
+            if [[ "${__parameter:-}" =~ \=    ]]
+            then
+              _render_function_options+=("$(
+                _get_uri --decode "${__parameter#*=}"
+              )")
+            fi
+            ;;
+        esac
+      done
+    fi
+
+    # serve raw files
+
+    if [[ "${_request_uri}" =~ /--original/.* ]]
+    then
+      local _target_relative_path_with_notebook="${_request_uri#/--original/}"
+      _target_relative_path_with_notebook="${_target_relative_path_with_notebook%%\?*}"
+
+      _target_relative_path_with_notebook="$(
+        _get_uri --decode "${_target_relative_path_with_notebook:-}"
+      )"
+
+      if [[ "${_target_relative_path_with_notebook}" =~ ^local/ ]] &&
+         [[ -n "${_local_notebook_path:-}"                      ]]
+      then
+        _browse_respond_with 200  \
+          --original              \
+          "${_local_notebook_path:-}/${_target_relative_path_with_notebook#*/}"
+      else
+        _browse_respond_with 200  \
+          --original              \
+          "${NB_DIR}/${_target_relative_path_with_notebook}"
+      fi
+
+      return 0
+    fi
+
+    # prepare response
+
+    local _request_uri_base="${_request_uri%\?--*}" # strip parameters
+    local _target_selector="${_request_uri_base#\/}"
+
+    _target_selector="${_target_selector//"\%20"/ }"
+    _target_selector="${_target_selector//"%20"/ }"
+
+    local _response_url_params=
+
+    if ((_terminal_browser))
+    then
+      _render_function_options+=("--terminal")
+      _response_url_params+="&--limit=${_limit}"
+    fi
+
+    if [[ -n "${_encoded_local_notebook_path:-}"  ]]
+    then
+      _render_function_options+=("--local" "${_encoded_local_notebook_path:-}")
+      _response_url_params+="&--local=${_encoded_local_notebook_path:-}"
+    fi
+
+    _response_url_params="${_response_url_params/&/?}"
+
+    local _respond_with_200_arguments=("--standard-input")
+
+    case "${_request_method}" in
+      HEAD) _respond_with_200_arguments+=("--headers")  ;;
+    esac
+
+    # respond
+
+    if [[ -z "${_target_selector:-}"  ]]
+    then
+      _browse_render_notebooks                    \
+        "${_render_function_options[@]:-}"        \
+        --user-agent "${_request_user_agent:-}"   \
+        | _browse_respond_with 200                \
+          "${_respond_with_200_arguments[@]:-}"
+
+      return 0
+    fi
+
+    if [[ "${_action:-}" == "add"     ]]
+    then
+      _render_function_options+=("${_target_selector:-}")
+
+      case "${_request_method:-}" in
+        GET)
+            _browse_render_add                    \
+              "${_render_function_options[@]:-}"  \
+              | _browse_respond_with 200          \
+                "${_respond_with_200_arguments[@]:-}"
+          ;;
+        POST)
+          local _new_selector=
+          _new_selector="$(
+            _browse_item_create                   \
+              "${_render_function_options[@]:-}"  \
+              --message-body "${_message_body:-}"
+          )"
+
+          _browse_respond_with 302                \
+"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_new_selector}${_response_url_params:-}"
+          ;;
+      esac
+
+      return 0
+    fi
+
+    local _selector_path=
+
+    if [[ "${_target_selector}" =~ ^local:  ]]
+    then
+      if [[ -z "${_local_notebook_path:-}"  ]]
+      then
+        _browse_respond_with 400
+
+        return 1
+      fi
+
+      _selector_path="$(
+        cd "${_local_notebook_path:-}"      &&
+          __set_notebook_paths              &&
+          _show "${_target_selector%%\?*}" --path --no-color 2>&1 || :
+      )"
+    else
+      _selector_path="$(
+        _show "${_target_selector%%\?*}" --path 2>/dev/null || :
+      )"
+    fi
+
+    if [[ -n "${_selector_path:-}"    ]]
+    then
+      _render_function_options+=("${_selector_path}")
+    else
+      _browse_respond_with 404
+
+      return 1
+    fi
+
+    if [[ -d "${_selector_path:-}"    ]]
+    then
+      if [[ -n "${_page_number:-}"    ]]
+      then
+        _render_function_options+=("--page" "${_page_number}")
+      fi
+
+      if [[ -n "${_query:-}"          ]]
+      then
+        _render_function_options+=("--query" "${_query}")
+      fi
+
+      _browse_render_container "${_render_function_options[@]:-}"   \
+        | _browse_respond_with 200 "${_respond_with_200_arguments[@]:-}"
+
+      return 0
+    fi
+
+    local _raw_url="//${NB_SERVER_HOST}:${NB_SERVER_PORT}/--original/"
+
+    if [[ !   "${_selector_path:-}" =~ ^${NB_DIR} ]] &&
+       [[ -n  "${_encoded_local_notebook_path:-}" ]] &&
+       [[ -n  "${_local_notebook_path:-}"         ]]
+    then
+      _raw_url+="local/${_selector_path#"${_local_notebook_path}"/}?--local=${_encoded_local_notebook_path}"
+    else
+      _raw_url+="${_selector_path#"${NB_DIR}"/}"
+    fi
+
+    _render_function_options+=("--raw-url" "${_raw_url}")
+
+    if [[ "${_action:-}" == "delete"  ]]
+    then
+      case "${_request_method:-}" in
+        GET)
+          _browse_render_delete                 \
+            "${_render_function_options[@]:-}"  \
+            | _browse_respond_with 200          \
+              "${_respond_with_200_arguments[@]:-}"
+          ;;
+        POST)
+          local _container_id_selector=
+          _container_id_selector="$(
+            _get_id_selector "${_selector_path%/*}" --notebook
+          )"
+
+          _browse_item_delete         \
+            "${_render_function_options[@]:-}" &>/dev/null
+
+          _browse_respond_with 302    \
+"//${NB_SERVER_HOST}:${NB_SERVER_PORT}/${_container_id_selector}${_response_url_params:-}"
+          ;;
+      esac
+
+      return 0
+    elif [[ "${_action:-}" == "edit"  ]]        &&
+         _file_is_text "${_selector_path:-}"
+    then
+      if [[ "${_request_method}"  == "POST"     ]]
+      then
+        _browse_item_update                     \
+          "${_render_function_options[@]:-}"    \
+          --message-body "${_message_body:-}"
+      fi
+
+      _browse_render_edit                       \
+        "${_render_function_options[@]:-}"      \
+        | _browse_respond_with 200              \
+          "${_respond_with_200_arguments[@]:-}"
+
+      return 0
+    else
+      _browse_render_item                       \
+        "${_render_function_options[@]:-}"      \
+        "${_respond_with_200_arguments[@]:-}"
+
+      return 0
+    fi
+
+    # fall back to 500 response
+
+    _browse_respond_with 500
+
+    return 1
+  }
+
+  # _browse_respond_with()
+  #
+  # Usage:
+  #   _browse_respond_with <status-code> [<path> | <string>] [--headers]
+  #                        [--standard-input]
+  #
+  # Options:
+  #   --headers  Only print headers.
+  #
+  # Description:
+  #   Send a response with <status-code> as status and an optional <file>
+  #   or <string>.
+  #
+  # Exit / Error / Return Status:
+  #   0 (success, true)  HTTP status 200 or 302.
+  #   1 (error,  false)  All others.
+  _browse_respond_with() {
+    local _only_headers=0
+    local _path=
+    local _read_from_standard_input=0
+    local _serve_original_file=0
+    local _status_code="${1:-}"
+    local _string=
+
+    local _date=
+    _date=$(date +"%a, %d %b %Y %H:%M:%S %Z")
+
+    local _response_headers=(
+         "Date: ${_date}"
+      "Expires: ${_date}"
+       "Server: ${_ME}"
+    )
+
+    local __arg=
+    for   __arg in "${@:-}"
+    do
+      case "${__arg:-}" in
+        '')
+          :
+          ;;
+        --*header*)
+          _only_headers=1
+          ;;
+        --original)
+          _serve_original_file=1
+          ;;
+        --standard*input)
+          _read_from_standard_input=1
+          ;;
+        *)
+          if [[     "${__arg:-}" =~ ^/  ]] &&
+             [[ -f  "${__arg:-}"        ]]
+          then
+            _path="${__arg:-}"
+          fi
+          ;;
+      esac
+    done
+
+    if [[ -n "${_path:-}"             ]]
+    then
+      if _file_is_text "${_path}" && ((_serve_original_file))
+      then
+        _response_headers+=("Content-Type: text/plain; charset=UTF-8")
+      elif [[ "${_path}" =~ \.svg$    ]]
+      then
+        _response_headers+=("Content-Type: image/svg+xml")
+      else
+        if _command_exists "file"
+        then
+          _response_headers+=("Content-Type: $(file -b --mime-type "${_path}")")
+        fi
+      fi
+
+      local _content_length=
+      _content_length="$(wc -c < "${_path}" | xargs)"
+
+      if [[ -n "${_content_length:-}" ]]
+      then
+        _response_headers+=("Content-Length: ${_content_length}")
+      fi
+    elif _contains "${_status_code:-}" "302"
+    then
+      _only_headers=1
+      _response_headers+=("Location: ${2:-}")
+    else
+      _string="${2:-}"
+
+      _response_headers+=("Content-Type: text/html; charset=UTF-8")
+    fi
+
+    printf "%s\\r\\n" \
+      "HTTP/1.0 ${_status_code} $(_browse_http_response_message "${_status_code}")"
+
+    local __response_header=
+    for   __response_header in "${_response_headers[@]:-}"
+    do
+      [[ -n "${__response_header:-}"  ]] || continue
+
+      printf "%s\\r\\n" "${__response_header:-}"
+    done
+
+    if ! ((_only_headers))
+    then
+      printf "\\r\\n"
+
+      if ((_read_from_standard_input))
+      then
+        cat
+      elif [[ -n "${_string:-}"     ]]
+      then
+        printf "%s\\n" "${_string}" | _render
+      elif [[ "${_path:-}" =~ ^/    ]]
+      then
+        cat "${_path}"
+      else
+        printf                                                            \
+          "<div class=\"main\"><h1 class=\"center\">%s %s</h1></div>\\n"  \
+          "${_status_code}"                                               \
+          "$(_browse_http_response_message "${_status_code}")"            \
+          | _render
+      fi
+    fi
+
+    if _contains "${1:-}" "200" "302"
+    then
+      return 0
+    else
+      return 1
+    fi
+  }
+
+  # _browse_serve()
+  #
+  # Usage:
+  #   _browse_serve
+  #
+  # Description:
+  #   Start the HTTP server in the background.
+  _browse_serve() {
+    (ncat                                     \
+      --exec "${_MY_PATH} browse --respond"   \
+      --keep-open                             \
+      --listen                                \
+      "${NB_SERVER_HOST}" "${NB_SERVER_PORT}" \
+      2>/dev/null) &
+
+    local _pid="${!}"
+
+    _temp pid "${_pid}"
+
+    sleep 0.05
+  }
+
+  local _action=
+  local _browse_columns="${_COLUMNS}"
+  local _browse_notebooks=0
+  local _browse_limit=
+  local _daemon=0
+  local _force_terminal_request=0
+  local _only_serve=0
+  local _open_gui=0
+  local _print_browse_render_function=
+  local _print_headers=0
+  local _print_output=0
+  local _search_query=
+  local _selector=
+  local _subcommand_options=()
+  local _target_page=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      a|add|-a|--add|--create|--new|+)
+        _action="add"
+        ;;
+      --and)
+        [[ -n "${_search_query:-}" ]] && _search_query="${_search_query:-} "
+
+        case "${2:-}" in
+          -t|--tag*)
+            _search_query+="--and $(_option_get_tags "${2:-}" "${3:-}")"
+
+            shift
+            ;;
+          *)
+            _search_query+="--and ${2:-}"
+            ;;
+        esac
+
+        shift
+        ;;
+      --col*)
+        _browse_columns="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      --*container)
+        _print_browse_render_function="container"
+        ;;
+      --daemon)
+        _daemon=1
+        _only_serve=1
+        ;;
+      d|delete|-d|--delete|-)
+        _action="delete"
+        ;;
+      e|edit|-e|--edit)
+        _action="edit"
+        ;;
+      -g|--gui)
+        _open_gui=1
+        ;;
+      --*header)
+        _print_browse_render_function="header"
+        ;;
+      --headers)
+        _print_headers=1
+        ;;
+      --*item)
+        _print_browse_render_function="item"
+        ;;
+      --limit|--num|--number|--per*)
+        _browse_limit="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      ls|list|--ls|--list)
+        : # skip, since this is the default
+        ;;
+      -n)
+        if _option_value_is_present "${2:-}"
+        then
+          _browse_limit="${2:-}"
+
+          shift
+        else
+          _browse_notebooks=1
+        fi
+        ;;
+      --notebook*|--nb*)
+        _browse_notebooks=1
+        ;;
+      --or)
+        [[ -n "${_search_query:-}" ]] && _search_query="${_search_query:-} "
+
+        case "${2:-}" in
+          -t|--tag*)
+            _search_query+="--or $(_option_get_tags "${2:-}" "${3:-}")"
+
+            shift
+            ;;
+          *)
+            _search_query+="--or ${2:-}"
+            ;;
+        esac
+
+        shift
+        ;;
+      --page)
+        _target_page="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      -p|--print)
+        _print_output=1
+        ;;
+      --render*add)
+        _print_browse_render_function="add"
+        _action="add"
+        ;;
+      --render*delete)
+        _print_browse_render_function="delete"
+        _action="delete"
+        ;;
+      --render*edit)
+        _print_browse_render_function="edit"
+        _action="edit"
+        ;;
+      --render*notebooks)
+        _print_browse_render_function="notebooks"
+        ;;
+      --respond)
+        _browse_respond
+
+        exit 0
+        ;;
+      --search|search|q|-q|--query)
+        if [[ -n "${2:-}" ]]
+        then
+          _search_query="${2:-}"
+        else
+          _exit_1 printf                        \
+            "%s requires a valid argument.\\n"  \
+            "$(_color_primary "${1:-}")"
+        fi
+
+        shift
+        ;;
+      s|serve|-s|--serve*)
+        _only_serve=1
+        ;;
+      -t|--tag*)
+        [[ -n "${_search_query:-}" ]] && _search_query="${_search_query:-} "
+
+        _search_query+="$(_option_get_tags "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      --terminal)
+        _force_terminal_request=1
+        ;;
+      -*)
+        if [[ "${1:-}" =~ ^-+[0-9]+$  ]]
+        then
+          _browse_limit="${1##*-}"
+
+          _subcommand_options+=(--limit "${_browse_limit:-}")
+        else
+          _subcommand_options+=("${1:-}")
+
+          if [[ "${1:-}" =~ ^-- ]] && _option_value_is_present "${2:-}"
+          then
+            _subcommand_options+=("${2:-}")
+
+            shift
+          fi
+        fi
+        ;;
+      *)
+        if [[ -z "${_selector:-}"     ]]
+        then
+          _selector="${1:-}"
+        fi
+        ;;
+    esac
+
+    shift
+  done
+
+  if ! ((_browse_notebooks))                                        &&
+       [[   "${_print_browse_render_function}"  != "notebooks"  ]]  &&
+       [[ ! "${_selector:-}"                    =~ :            ]]
+  then
+    _selector="$(_notebooks current --name --no-color):${_selector:-}"
+  fi
+
+  local _arguments=()
+
+  if ! ((_browse_notebooks))                                        &&
+     ! [[ "${_action:-}"                        == "add"        ]]  &&
+     ! [[ "${_print_browse_render_function:-}"  == "add"        ]]  &&
+     ! [[ "${_print_browse_render_function:-}"  == "notebooks"  ]]
+  then
+    _arguments+=("$(
+      _show "${_selector:-}" --path 2>/dev/null || :
+    )")
+  fi
+
+  if ! _command_exists "ncat"
+  then
+    _show "${_selector:-}" --render
+    _warn cat <<HEREDOC
+Install \`ncat\` for full browsing and linking:
+$(_color_primary "https://nmap.org/ncat/")
+HEREDOC
+
+    exit 0
+  fi
+
+  # build initial request URL parameters and arguments
+
+  local _url_params=()
+
+  if _notebooks current --local
+  then
+    local _encoded_local_path=
+    _encoded_local_path="$(_get_uri --encode "$(_notebooks current --path)")"
+
+    _arguments+=("--local" "${_encoded_local_path}")
+    _url_params+=("--local=${_encoded_local_path}")
+  fi
+
+  if [[ -n "${_search_query:-}" ]]
+  then
+    _arguments+=("--query" "${_search_query}")
+
+    local _encoded_query=
+    _encoded_query="$(_get_uri --encode "${_search_query}")"
+    _url_params+=("--query=${_encoded_query}")
+  fi
+
+  if [[ -n "${_action:-}"       ]]
+  then
+    _arguments+=("--${_action}")
+    _url_params+=("--${_action}")
+  fi
+
+  local i=
+  for ((i=0; i < ${#_subcommand_options[@]}; i++))
+  do
+    [[ -z "${#_subcommand_options[i]}" ]] && continue
+
+    _arguments+=("${_subcommand_options[i]:-}")
+
+    if [[   "${_subcommand_options[i]}"           =~ \--  ]] &&
+       [[ ! "${_subcommand_options[$((i+1))]:--}" =~ ^-   ]]
+    then
+      local _field="${_subcommand_options[i]:-}"
+      local _value="${_subcommand_options[$((i+1))]:--}"
+
+      _arguments+=("${_field}" "${_value}")
+      _url_params+=("${_field}=$(_get_uri --encode "${_value}")")
+
+      i="$((i+1))"
+    else
+      _arguments+=("${_subcommand_options[i]:-}")
+      _url_params+=("${_subcommand_options[i]:-}")
+    fi
+  done
+
+  # configure pagination
+
+  if ((_force_terminal_request))  ||
+     ! {
+        ((_open_gui))             ||
+        _web_browser --gui        ||
+        ((_only_serve))
+     }
+  then
+    if [[ -z "${_browse_limit:-}"  ]]
+    then # set per page based on terminal height
+      if [[ "${BROWSER:-}" =~ links   ]]
+      then
+        _browse_limit="$(($(_tput lines) - 9))"
+      elif [[ "${BROWSER:-}" =~ lynx  ]]
+      then
+        _browse_limit="$(($(_tput lines) - 10))"
+      else
+        _browse_limit="$(($(_tput lines) - 8))"
+      fi
+    fi
+
+    if [[ -n "${_browse_limit:-}"  ]]
+    then
+      _arguments+=("--limit" "${_browse_limit}")
+      _arguments+=("--terminal")
+
+      _url_params+=("--limit=${_browse_limit}")
+      _url_params+=("--terminal")
+    fi
+
+    if [[ -n "${_browse_columns:-}"   ]]
+    then
+      _arguments+=("--columns" "${_browse_columns}")
+      _url_params+=("--columns=${_browse_columns}")
+    fi
+
+    if [[ -n "${_target_page:-}"      ]]
+    then
+      _arguments+=("--page" "${_target_page:-}")
+      _url_params+=("--page=${_target_page}")
+    fi
+  fi
+
+  # build initial request URL
+
+  local _request_url_base="http://${NB_SERVER_HOST}:${NB_SERVER_PORT}"
+
+  if [[ "${_action:-}" == "add" ]]
+  then
+    local _selector_path=
+    _selector_path="$(_show "${_selector:-}" --path 2>/dev/null || :)"
+
+    local _notebook_path=
+    _notebook_path="$(_notebooks show "${_selector:-}" --path 2>/dev/null || :)"
+
+    if [[ ! "${_selector}"      =~ /$                     ]] &&
+       [[ -d "${_selector_path:-}"                        ]] &&
+       [[ "${_selector_path:-}" != "${_notebook_path:-}"  ]]
+    then
+      _selector="${_selector:-}/"
+    fi
+
+    _arguments=("${_selector:-}" "${_arguments[@]:-}")
+  fi
+
+  local _request_url_base="http://${NB_SERVER_HOST}:${NB_SERVER_PORT}"
+  local _request_url="${_request_url_base}/${_selector:-}"
+
+  if ((${#_url_params[@]}))
+  then
+    _request_url+="?$(_join "&" "${_url_params[@]:-}")"
+  fi
+
+  # call functions directly
+
+  if [[ -n "${_print_browse_render_function:-}" ]]
+  then
+    case "${_print_browse_render_function:-}" in
+      add)        _browse_render_add        "${_arguments[@]:-}" ;;
+      container)  _browse_render_container  "${_arguments[@]:-}" ;;
+      delete)     _browse_render_delete     "${_arguments[@]:-}" ;;
+      edit)       _browse_render_edit       "${_arguments[@]:-}" ;;
+      header)     _browse_render_header     "${_arguments[@]:-}" ;;
+      item)       _browse_render_item       "${_arguments[@]:-}" ;;
+      notebooks)  _browse_render_notebooks  "${_arguments[@]:-}" ;;
+    esac
+
+    return 0
+  fi
+
+  # start server
+
+  _browse_serve || : # TODO: return status
+
+  # request URL
+
+  if ((_print_output))
+  then
+    local _retry_counter=0
+    local _printable_response=
+
+    while [[ -z "${_printable_response:-}"  ]]
+    do
+      ((_retry_counter)) && sleep 0.5
+
+      _printable_response="$(
+        if ((_print_headers))
+        then
+          curl -s -I      "${_request_url//\ /\%20}"  || :
+        else
+          _download_from  "${_request_url//\ /\%20}"  || :
+        fi
+      )"
+
+      _retry_counter=$((_retry_counter+1))
+    done
+
+    printf "%s\\n" "${_printable_response:-}"
+  elif ((_open_gui))  || _web_browser --gui || ((_only_serve))
+  then
+    local _display_params=
+
+    if _notebooks current --local     ||
+       _notebooks current --selected  ||
+       [[ "${_selector}" != "$(_notebooks current --name):" ]]
+    then
+      _display_params="${_request_url#"${_request_url_base}"}"
+    fi
+
+    printf "Listening: %s%s\\n"                   \
+      "$(_color_primary "${_request_url_base}")"  \
+      "${_display_params//\ /%20}"
+
+    if _web_browser --gui
+    then
+      _web_browser "${_request_url:-}"
+    elif ((_open_gui))
+    then
+      local _gui_browser_command=()
+
+      if [[ -n "${NB_GUI_BROWSER:-}"          ]]
+      then
+        _gui_browser_command=("${NB_GUI_BROWSER:-}")
+      fi
+
+      if _command_exists "${_gui_browser_command[0]:-}" ||
+         [[ -f "${_gui_browser_command[0]:-}" ]]
+      then
+        "${_gui_browser_command[@]:-}" "${_request_url:-}" 2>/dev/null &
+      else
+        _open_in_gui_app "${_request_url:-}"
+      fi
+    fi
+
+    if ((_daemon))
+    then
+      printf "Press %s%s%s to exit%s" \
+        "$(_color_muted "<")"         \
+        "$(_color_primary "CTRL-C")"  \
+        "$(_color_muted ">")"         \
+        "$(_color_muted "...")"
+
+      while true
+      do
+        sleep 1
+      done
+    else
+      while true
+      do
+        read -n 1 -s -r -p "Press any key to exit$(_color_muted "...")"
+
+        printf "\\n"
+
+        break
+      done
+    fi
+  else
+    _web_browser "${_request_url}"
+  fi
+
+  # make a final request to clear any listening process
+
+  (sleep 0.5 && _download_from "${_request_url_base}" &>/dev/null) &
+
+  exit 0
+}
+_alias_subcommand "browse" "b"
+_alias_subcommand "browse" "br"
+_alias_subcommand "browse" "browser"
+
+# copy ################################################################### copy
+
+_describe_copy() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} copy ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [[<notebook>:][<folder-path>/]<filename>]
+
+$(_color_primary "Description"):
+  Copy or duplicate an item.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-moving--renaming
+
+$(_color_primary "See Also"):
+  ${_ME} help move
+
+$(_color_primary "Examples"):
+  ${_ME} copy 321
+  ${_ME} copy 456 example:
+  ${_ME} copy 987 sample/demo.md
+
+$(_color_primary "Alias"):
+  ${_ME} duplicate
+HEREDOC
+}
+_copy() {
+  local _source_selector="${1:-}"
+  local _target_selector="${2:-}"
+
+  if [[ -z "${_source_selector:-}" ]]
+  then
+    _help "copy"
+
+    exit 1
+  fi
+
+  local _source_notebook_path=
+  _source_notebook_path="$(
+    _notebooks show "${_source_selector:-}" --path 2>/dev/null  ||
+      _notebooks current --path
+  )"
+
+  local _source_relative_path=
+  _source_relative_path="$(
+    _show "${_source_selector}" --relative-path 2>/dev/null || :
+  )"
+
+  local _source_basename="${_source_relative_path##*/}"
+
+  if [[   -z "${_source_relative_path:-}"                         ]] ||
+     [[ ! -e "${_source_notebook_path}/${_source_relative_path}"  ]]
+  then
+    _warn printf "Not found: %s\\n" "$(
+      _color_primary "${_source_selector:-}"
+    )"
+
+    return 1
+  fi
+
+  local _target_folder_path=
+  local _target_notebook_path=
+  local _target_relative_path=
+
+  if [[ -n "${_target_selector:-}" ]]
+  then
+    _target_notebook_path="$(
+      _notebooks show "${_target_selector:-}" --path 2>/dev/null  ||
+        _notebooks current --path
+    )"
+
+    local _target_folder_relative_path=
+    _target_folder_relative_path="$(
+      _selector_resolve_folders "${_target_selector:-}" --build   || :
+    )"
+
+    _target_folder_path="${_target_notebook_path:-}/${_target_folder_relative_path:-}"
+
+    _target_relative_path="$(
+      _selector_get_identifier "${_target_selector:-}"
+    )"
+
+    if [[ -z "${_target_relative_path:-}" ]]
+    then
+      _target_relative_path="${_source_basename:-}"
+    fi
+
+    _target_relative_path="${_target_relative_path%/}"
+
+    if [[ "${_target_selector:-}" =~ /$   ]]
+    then
+      _target_relative_path="${_target_relative_path:-}/${_source_basename:-}"
+    fi
+
+    if [[ -e "${_target_notebook_path:-}/${_target_relative_path:-}"  ]]
+    then
+      _warn printf "Already exists: %s\\n" "$(
+        _color_primary "${_target_selector:-}"
+      )"
+
+      return 1
+    fi
+  else
+    _target_notebook_path="$(
+      _notebooks show "${_source_selector}" --path 2>/dev/null    ||
+        _notebooks current --path
+    )"
+
+    _target_relative_path="$(
+      _notebooks current --filename "${_source_relative_path}"
+    )"
+
+    if [[ "${_target_relative_path:-}" =~ / ]]
+    then
+      _target_folder_path="${_source_notebook_path}/${_target_relative_path%/*}"
+    else
+      _target_folder_path="${_source_notebook_path}"
+    fi
+  fi
+
+  if _show "${_source_notebook_path}/${_source_relative_path}" --type text
+  then # Text can use `_add`.
+    # Print the source contents and pipe to `_add`:
+    _show "${_source_notebook_path}/${_source_relative_path}"     \
+      --no-color --print                                          \
+      | _add "${_target_notebook_path}/${_target_relative_path}"
+  else
+    local _copy_arguments=(
+      "${_source_notebook_path}/${_source_relative_path}"
+      "${_target_notebook_path}/${_target_relative_path}"
+    )
+
+    if [[ -d "${_source_notebook_path}/${_source_relative_path}"  ]]
+    then
+      _copy_arguments=("-R" "${_copy_arguments[@]:-}")
+    fi
+
+    if [[ ! -e "${_target_folder_path:-}"   ]]
+    then
+      mkdir -p "${_target_folder_path:-}"
+    fi
+
+    cp "${_copy_arguments[@]:-}"
+
+    _index add "${_target_relative_path##*/}" "${_target_folder_path}"
+
+    _git checkpoint "${_target_notebook_path:-}" "[${_ME}] Add: ${_target_relative_path}"
+
+    printf "Added: %s\\n" "$(
+      _show "${_target_notebook_path}/${_target_relative_path}" --info-line
+    )"
+  fi
+}
+_alias_subcommand "copy" "duplicate"
+
+# do ####################################################################### do
+
+_describe_do() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} do ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+        [<task-number>]
+
+$(_color_primary "Description"):
+  Mark a todo or task as done.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-todos
+
+$(_color_primary "See Also"):
+  ${_ME} help tasks
+  ${_ME} help todo
+  ${_ME} help undo
+
+$(_color_primary "Examples"):
+  ${_ME} do 123
+  ${_ME} do example:sample/321
+  ${_ME} do 543 7
+HEREDOC
+}
+_do() {
+  _todo "do" "${@:-}"
+}
+_alias_subcommand "do" "done"
+_alias_subcommand "do" "close"
+
+# folders ############################################################# folders
+
+_describe_folders() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} folders add [<notebook>:][<folder-path>/]<folder-name>
+  ${_ME} folders delete [<notebook>:][<folder-path>/]<folder-name>
+  ${_ME} folders <list-options>...
+
+$(_color_primary "Subcommands"):
+  (default)  List folders.
+  add        Add a new folder.
+  delete     Delete a folder.
+
+$(_color_primary "Description"):
+  Add, delete, and list folders.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-folders
+
+$(_color_primary "See Also"):
+  ${_ME} help add
+  ${_ME} help delete
+  ${_ME} help list
+  ${_ME} help ls
+
+$(_color_primary "Examples"):
+  ${_ME} folders
+  ${_ME} folders add example
+  ${_ME} folders delete example:sample
+
+$(_color_primary "Alias"):
+  ${_ME} folder
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} f
+HEREDOC
+}
+_folders() {
+  local _arguments=()
+  local _selector=
+  local _subcommand=
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      add|a|+)
+        _subcommand="add"
+        ;;
+      delete|d|rm|-)
+        _subcommand="delete"
+        ;;
+      list|ls)
+        _subcommand="list"
+        ;;
+      *)
+        if [[ -z "${_selector:-}" ]]
+        then
+          _selector="${1:-}"
+        fi
+
+        _arguments+=("${1:-}")
+        ;;
+    esac
+
+    shift
+  done
+
+  if [[ -z "${_subcommand:-}"     ]]
+  then
+    _subcommand="list"
+  fi
+
+  if [[ -z "${_selector:-}"       ]] &&
+     _contains "${_subcommand:-}" "+" "-" "a" "add" "d" "delete" "rm" "trash"
+  then
+    _help "folders"
+
+    return 1
+  fi
+
+  case "${_subcommand:-}" in
+    add)
+      _add folder "${_arguments[@]:-}"
+      ;;
+    delete)
+      local _target_path=
+      _target_path="$(_show "${_selector:-}" --path)"
+
+      if [[ ! -e "${_target_path:-}"    ]]
+      then
+        _warn printf "Not found: %s\\n"     \
+          "$(_color_primary "${_selector:-}")"
+
+        return 1
+      elif [[ ! -d "${_target_path:-}"  ]]
+      then
+        _warn printf "Not a folder: %s\\n"  \
+          "$(_color_primary "${_selector:-}")"
+
+        return 1
+      fi
+
+      _delete "${_arguments[@]:-}"
+      ;;
+    list)
+      if [[ -n "${_selector:-}"         ]]
+      then
+        local _selector_path=
+        _selector_path="$(_show "${_selector:-}" --path)"
+
+        if [[ -n "${_selector_path:-}"  ]]
+        then
+          _notebooks select "${_selector_path:-}"
+        fi
+      fi
+
+      _list --type folder "${_arguments[@]:-}" --with-pinned
+      ;;
+  esac
+}
+_alias_subcommand "folders" "f"
+_alias_subcommand "folders" "folder"
+
+# helpers ############################################################# helpers
+
+_describe_helpers() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} helpers <name> [<options≥...]
+
+$(_color_primary "Description"):
+  Call helper functions.
+HEREDOC
+}
+_helpers() {
+  local _name="${1:-}"
+
+  shift
+
+  local _options=("${@:-}")
+
+  case "${_name:-}" in
+    *browser*)
+      _web_browser                    "${_options[@]:-}"
+      ;;
+    build*|*related*)
+      _build_related_list             "${_options[@]:-}"
+      ;;
+    *decryption*)
+      _get_decryption_tool            "${_options[@]:-}"
+      ;;
+    decrypt*)
+      _decrypt_file                   "${_options[@]:-}"
+      ;;
+    download*)
+      _download_from                  "${_options[@]:-}"
+      ;;
+    edit*)
+      _edit_file                      "${_options[@]:-}"
+      ;;
+    encrypt*)
+      _encrypt_file                   "${_options[@]:-}"
+      ;;
+    *archive*)
+      _file_is_archive                "${_options[@]:-}"
+      ;;
+    *audio*)
+      _file_is_audio                  "${_options[@]:-}"
+      ;;
+    *bookmark*)
+      _file_is_bookmark               "${_options[@]:-}"
+      ;;
+    *document*)
+      _file_is_document               "${_options[@]:-}"
+      ;;
+    *encrypted*)
+      _file_is_encrypted              "${_options[@]:-}"
+      ;;
+    *image*)
+      _file_is_image                  "${_options[@]:-}"
+      ;;
+    *text*)
+      _file_is_text                   "${_options[@]:-}"
+      ;;
+    *video*)
+      _file_is_video                  "${_options[@]:-}"
+      ;;
+    *content*)
+      _get_content                    "${_options[@]:-}"
+      ;;
+    *d*selector)
+      _get_id_selector                "${_options[@]:-}"
+      ;;
+    *hash*)
+      _get_hash                       "${_options[@]:-}"
+      ;;
+    *http*)
+      _get_http_status                "${_options[@]:-}"
+      ;;
+    *unique*basename*|*unique*relative*)
+      _get_unique_relative_path       "${_options[@]:-}"
+      ;;
+    *unique*path*)
+      _get_unique_path                "${_options[@]:-}"
+      ;;
+    *highlight*|*syntax*)
+      _highlight_syntax_if_available  "${_options[@]:-}"
+      ;;
+    join)
+      _join                           "${_options[@]:-}"
+      ;;
+    less*|*prompt)
+      _less_prompt                    "${_options[@]:-}"
+      ;;
+    line*wrap*off|unwrap)
+      _wrap off                       "${_options[@]:-}"
+      ;;
+    line*wrap*on|wrap)
+      _wrap on                        "${_options[@]:-}"
+      ;;
+    list*files)
+      _list_files                     "${_options[@]:-}"
+      ;;
+    *line)
+      _print_line                     "${_options[@]:-}"
+      ;;
+    *norm*|*options*)
+      _print_normalized_options       "${_options[@]:-}"
+      ;;
+    *padding)
+      _print_padding                  "${_options[@]:-}"
+      ;;
+    pandoc)
+      _pandoc                         "${_options[@]:-}"
+      ;;
+    *piped*|*input*)
+      _piped_input                    "${_options[@]:-}"
+      ;;
+    *print*welcome|welcome)
+      _print_welcome                  "${_options[@]:-}"
+      ;;
+    render)
+      _render                         "${_options[@]:-}"
+      ;;
+    resolve*links)
+      _resolve_links                  "${_options[@]:-}"
+      ;;
+    *selector*folder*)
+      _selector_resolve_folders       "${_options[@]:-}"
+      ;;
+    *selector*path*)
+      _selector_resolve_path          "${_options[@]:-}"
+      ;;
+    spinner)
+      _spinner                        "${_options[@]:-}"
+      ;;
+    *email)
+      _string_is_email                "${_options[@]:-}"
+      ;;
+    *uri*)
+      _get_uri                        "${_options[@]:-}"
+      ;;
+    *url)
+      _string_is_url                  "${_options[@]:-}"
+      ;;
+    *)
+      _exit_1 _help "helpers"
+      ;;
+  esac
+}
+
+# plugins ############################################################# plugins
+
+_describe_plugins() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} plugins [<name>] [--paths]
+  ${_ME} plugins install [<path> | <url>] [--force]
+  ${_ME} plugins uninstall <name> [--force]
+
+$(_color_primary "Options"):
+  --force  Skip the confirmation prompt.
+  --paths  Print the full path to each plugin.
+
+$(_color_primary "Subcommands"):
+  (default)  List plugins.
+  install    Install a plugin from a <path> or <url>.
+  uninstall  Uninstall the specified plugin.
+
+$(_color_primary "Description"):
+  Manage plugins and themes.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-plugins
+
+$(_color_primary "Plugin Extensions"):
+  .${_ME}-theme   Plugins defining color themes.
+  .${_ME}-plugin  Plugins defining new subcommands and functionality.
+
+$(_color_primary "See Also"):
+  ${_ME} help subcommands
+
+$(_color_primary "Alias"):
+  ${_ME} plugin
+HEREDOC
+}
+_plugins() {
+  local _basename=
+  local _force=0
+  local _name=
+  local _path=
+  local _print_paths=0
+  local _subcommand=
+  local _url=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      -f|--force|--skip*|-y|--yes)
+        _force=1
+        ;;
+      --path*)
+        _print_paths=1
+        ;;
+      *)
+        if [[ "${__arg}" =~ ^install$|^uninstall$ ]]
+        then
+          _subcommand="${__arg}"
+        elif [[ "${_subcommand}" == "install"   ]]
+        then
+          if [[ "${__arg:-}" =~ (^http|^file\:) ]]
+          then
+            _url="${__arg}"
+          else
+            _path="${__arg}"
+          fi
+        else
+          _name="${__arg}"
+        fi
+        ;;
+    esac
+  done
+
+  case "${_subcommand}" in
+    install)
+      [[ ! -e "${NB_DIR}/.plugins"      ]] && mkdir "${NB_DIR}/.plugins"
+
+      if [[ -n "${_path:-}"             ]]
+      then
+        if ! [[ -f "${_path:-}"         ]] ||
+           ! [[ "${_path}" =~ ${_ME}\-  ]]
+        then
+          _exit_1 printf "Not a valid \`%s\` plugin: %s\\n" "${_ME}" "${_path}"
+        fi
+
+        _basename="$(basename -- "${_path}")"
+
+        if [[ -f "${NB_DIR}/.plugins/${_basename}"  ]]
+        then
+          _warn printf "Plugin already installed: %s\\n" "${_basename}"
+
+          if ! ((_force))
+          then
+            while true
+            do
+              local __yn=
+              IFS='' read -r -e -d $'\n' -p         \
+"$(_color_primary "Reinstall?") $(_color_brackets "y/N") " __yn
+
+              case "${__yn}" in
+                [Yy]*)
+                  break
+                  ;;
+                *)
+                  printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                  exit 0
+                  ;;
+              esac
+            done
+          fi
+        fi
+
+        if cp "${_path}" "${NB_DIR}/.plugins/${_basename}"
+        then
+          printf "Plugin installed:\\n%s\\n"        \
+            "$(_color_primary "${NB_DIR}/.plugins/${_basename}")"
+        else
+          _exit_1 printf "Unable to install plugin: %s\\n" "${_path}"
+        fi
+      else
+        _basename="$(basename -- "${_url}" | tr -d '[:space:]')"
+
+        if [[ "${_url:-}" =~ https\:\/\/github.com ]]
+        then
+          _url="$(
+            printf "%s\\n" "${_url}"  \
+              | LC_ALL=C sed          \
+                -e 's/\/blob//g'      \
+                -e 's/https:\/\/github.com/https:\/\/raw.githubusercontent.com/g'
+          )"
+        fi
+
+        if _download_from "${_url}" "${NB_DIR}/.plugins/${_basename}"
+        then
+          printf "Plugin installed:\\n%s\\n"  \
+            "$(_color_primary "${NB_DIR}/.plugins/${_basename}")"
+        else
+          _exit_1 printf "Unable to download and install: %s\\n"  "${_url}"
+        fi
+      fi
+      ;;
+    uninstall)
+      local _plugin_path=
+
+      if ! _plugin_path="$(_plugins "${_name}" --paths 2>/dev/null)"  ||
+           [[ -z "${_plugin_path:-}"  ]]                              ||
+         ! [[ -f "${_plugin_path}"    ]]
+      then
+        _exit_1 printf "Plugin not found: %s\\n" "$(_color_primary "${_name}")"
+      fi
+
+      if ! ((_force))
+      then
+        cat <<HEREDOC
+Uninstalling plugin. Warning: This will permanently delete the following file:
+$(_color_primary "${_plugin_path}")
+HEREDOC
+        while true
+        do
+          local __yn=
+          IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+          case "${__yn}" in
+            [Yy]*)
+              break
+              ;;
+            *)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+          esac
+        done
+      fi
+
+      if [[ -f "${_plugin_path}" ]] && rm "${_plugin_path:?}"
+      then
+        printf "Plugin successfully uninstalled:\\n%s\\n" \
+          "$(_color_primary "${_plugin_path}")"
+      else
+        _exit_1 printf "Unable to uninstall plugin:\\n%s\\n" "${_plugin_path}"
+      fi
+      ;;
+    *)
+      local _query="*${_ME}-*"
+
+      if [[ -n "${_name}" ]]
+      then
+        _query="${_name}"
+      fi
+
+      if [[ ! -e "${NB_DIR}/.plugins" ]]
+      then
+        (return 1)
+      else
+        {
+          if ((_print_paths))
+          then
+            find "${NB_DIR}"/.plugins \
+              ! \( -type d \)         \
+              -name "${_query}"
+          else
+            find "${NB_DIR}"/.plugins \
+              ! \( -type d \)         \
+              -name "${_query}"       \
+              -exec basename {} \;
+          fi
+        } | {
+          # `grep` for non-0 `find`. More info: https://serverfault.com/a/855083
+          grep . | sort
+        }
+      fi || if [[ -n "${_name:-}" ]]
+            then
+              _exit_1 printf "No matching plugins found: %s\\n" "${_name}"
+            else
+              _exit_1 printf "No plugins found.\\n"
+            fi
+      ;;
+  esac
+}
+_alias_subcommand "plugins" "plugin"
+
+# remote ############################################################### remote
+
+_describe_remote() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} remote
+  ${_ME} remote branches [<url>]
+  ${_ME} remote delete <branch-name>
+  ${_ME} remote remove
+  ${_ME} remote rename [<branch-name>] <name>
+  ${_ME} remote reset <branch-name>
+  ${_ME} remote set <url> [<branch-name>]
+
+$(_color_primary "Subcommands"):
+  (default)  Print the remote URL and branch for the notebook.
+  branches   List branches on the current or given remote.
+  delete     Delete <branch-name> from the remote.
+             Caveat: only orphan branches can be deleted.
+  remove     Remove the remote URL from the notebook.
+             Alias: \`unset\`
+  rename     Rename the current orphan branch or <branch-name> to <name>.
+             Caveat: only orphan branches can be renamed.
+  reset      Reset <branch-name> on the remote to a blank initial state.
+  set        Set the remote URL and branch for the notebook.
+
+$(_color_primary "Description"):
+  Configure the remote repository URL and branch for the current notebook.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-git-sync
+  ${_README_URL}#-revision-history
+
+$(_color_primary "See Also"):
+  ${_ME} help history
+  ${_ME} help notebooks
+  ${_ME} help status
+  ${_ME} help sync
+
+$(_color_primary "Examples"):
+  ${_ME} remote set https://github.com/example/example.git
+  ${_ME} remote remove
+  ${_ME} example-notebook:remote set https://github.com/example/example.git
+HEREDOC
+}
+_remote() {
+  local _new_branch=
+  local _new_remote_url=
+  local _only_url=0
+  local _remote_branch_name=
+  local _rename_arguments=()
+  local _skip_confirmation=0
+  local _skip_preamble=0
+  local _subcommand=
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg:-}" in
+      --skip*confirm*)  _skip_confirmation=1    ;;
+      --skip*preamble)  _skip_preamble=1        ;;
+      --url|url)        _only_url=1             ;;
+      *)
+        case "${_subcommand:-}" in
+          '') _subcommand="${__arg:-}"          ;;
+          add|branches|set)
+            if [[   -z "${_new_remote_url:-}"   ]]
+            then
+              _new_remote_url="${__arg:-}"
+            elif [[ -z "${_new_branch:-}"       ]]
+            then
+              _new_branch="${__arg:-}"
+            fi
+            ;;
+          delete|reset)
+            _remote_branch_name="${__arg:-}"
+            ;;
+          rename)
+            _rename_arguments+=("${__arg:-}")
+            ;;
+        esac
+        ;;
+    esac
+  done
+
+  local _notebook_path=
+  _notebook_path="$(_notebooks current --path)"
+
+  local _current_branch=
+  _current_branch="$(
+    git -C "${_notebook_path}" rev-parse --abbrev-ref HEAD
+  )"
+
+  local _current_remote_url=
+  _current_remote_url="$(
+    git -C "${_notebook_path:-}" remote get-url origin 2>/dev/null || :
+  )"
+
+  local _remote_exists=0
+
+  if [[ -n "${_current_remote_url:-}"           ]]
+  then
+    _remote_exists=1
+  fi
+
+  case "${_subcommand:-}" in
+    branches)
+      {
+        if [[ -n "${_new_remote_url:-}"         ]]
+        then
+          git -C "${_notebook_path}" ls-remote  \
+            --heads "${_new_remote_url:-}"      \
+            2>/dev/null                         \
+            | LC_ALL=C sed "s/.*\///g"
+        elif ((_remote_exists))
+        then
+          git -C "${_notebook_path}" ls-remote  \
+            --heads                             \
+            2>/dev/null                         \
+            | LC_ALL=C sed "s/.*\///g"
+        else
+          _exit_1 printf "No remote configured.\\n"
+        fi
+      } | {
+        local _highlight_matching_branch=0
+
+        if ((_remote_exists))                   &&
+           [[ -z  "${_new_remote_url:-}"  ]]    ||
+           [[     "${_new_remote_url:-}"  ==    "${_current_remote_url:-}"  ]]
+        then
+          _highlight_matching_branch=1
+        fi
+
+        local         __line=
+        while read -r __line
+        do
+          if ((_highlight_matching_branch))     &&
+             [[   "${__line:-}"           ==    "${_current_branch:-}"      ]]
+          then
+            printf "%s\\n" "$(_color_primary "${__line}")"
+          else
+            printf "%s\\n" "${__line}"
+          fi
+        done
+      }
+
+      return 0
+      ;;
+    delete)
+      if ! ((_remote_exists))
+      then
+        _exit_1 printf "No remote configured.\\n"
+      fi
+
+      if [[ -z "${_remote_branch_name:-}"       ]]
+      then
+        _exit_1 _help "remote"
+      fi
+
+      # TODO: combine into single `ls-remote` operation
+      local _remote_branches=()
+      _remote_branches=($(
+        git -C "${_notebook_path}" ls-remote        \
+          --heads "${_current_remote_url:-}"        \
+           2>/dev/null                              \
+          | LC_ALL=C sed "s/.*\///g" || :
+      ))
+
+      local _primary_remote_branch=
+      _primary_remote_branch="$(
+        git -C "${_notebook_path}" ls-remote        \
+          --symref "${_current_remote_url:-}" HEAD  \
+          2>/dev/null                               \
+          | awk '/^ref:/ {sub(/refs\/heads\//, "", $2); print $2}' || :
+      )"
+
+      if [[ -z "${_remote_branches[*]:-}"       ]] ||
+         [[ -z "${_primary_remote_branch:-}"    ]]
+      then
+        _exit_1 printf "Unable to contact remote.\\n"
+      fi
+
+      if ! _contains "${_remote_branch_name:-}" "${_remote_branches[@]:-}"
+      then
+        _exit_1 printf "Remote branch not found: %s\\n" \
+          "${_remote_branch_name:-}"
+      fi
+
+      if [[ "${_remote_branch_name:-}" == "${_primary_remote_branch:-}" ]]
+      then
+        _remote reset "${_remote_branch_name:-}"
+      fi
+
+      printf "Deleting remote branch: %s\\n"    \
+        "$(_color_primary "${_remote_branch_name:-}")"
+
+      _print_line "-----------------------"
+
+      while true
+      do
+        local __yn=
+        IFS='' read -r -e -d $'\n' -p           \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+        case "${__yn}" in
+          [Yy]*)
+            break
+            ;;
+          *)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            exit 0
+            ;;
+        esac
+      done
+
+      git -C "${_notebook_path:-}" push origin  \
+        ":${_remote_branch_name}"  --force      \
+        &>/dev/null                             ||
+        _exit_1 printf "Unable to delete remote branch: %s\\n" \
+          "${_remote_branch_name}"
+
+      printf "Remote branch deleted.\\n"
+      ;;
+    remove|rm|unset)
+      if ((_remote_exists))
+      then
+        printf "Removing remote: %s\\n"         \
+          "$(_color_primary "${_current_remote_url:-}")"
+
+        if ! ((_skip_confirmation))
+        then
+          while true
+          do
+            local __yn=
+            IFS='' read -r -e -d $'\n' -p       \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+            case "${__yn}" in
+              [Yy]*)
+                break
+                ;;
+              *)
+                printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                exit 0
+                ;;
+            esac
+          done
+        fi
+
+        # TODO: combine into single `ls-remote` operation
+        local _remote_branches=()
+        _remote_branches=($(
+          git -C "${_notebook_path}" ls-remote        \
+            --heads "${_current_remote_url:-}"        \
+             2>/dev/null                              \
+            | LC_ALL=C sed "s/.*\///g" || :
+        ))
+
+        local _primary_remote_branch=
+        _primary_remote_branch="$(
+          git -C "${_notebook_path}" ls-remote        \
+            --symref "${_current_remote_url:-}" HEAD  \
+            2>/dev/null                               \
+            | awk '/^ref:/ {sub(/refs\/heads\//, "", $2); print $2}' || :
+        )"
+
+        if [[ -z "${_remote_branches[*]:-}"       ]] ||
+           [[ -z "${_primary_remote_branch:-}"    ]]
+        then
+          _warn printf "Unable to contact remote.\\n"
+        else
+          local _delete_remote_branch=0
+
+          if _contains "${_current_branch}" "${_remote_branches[@]:-}"
+          then
+            local _delete_action="Remove"
+
+            if [[ "${_current_branch:-}" == "${_primary_remote_branch:-}" ]]
+            then
+              _delete_action="Reset"
+            fi
+
+            local _branch_delete_prompt=
+            _branch_delete_prompt="\
+$(_color_primary "${_delete_action} branch on remote?") ($(_color_primary "${_current_branch}"))"
+
+            while true
+            do
+              local __yn=
+              IFS='' read -r -e -d $'\n' -p             \
+                "${_branch_delete_prompt} $(_color_brackets "y/N") " __yn
+
+              case "${__yn}" in
+                [Yy]*)
+                  _delete_remote_branch=1
+
+                  break
+                  ;;
+                q*|exit)
+                  printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                  exit 0
+                  ;;
+                *)
+                  break
+                  ;;
+              esac
+            done
+          fi
+
+          if ((_delete_remote_branch))
+          then
+            if [[ "${_current_branch}" == "${_primary_remote_branch}" ]]
+            then
+              _remote reset "${_current_branch}"        \
+                <<< "y${_NEWLINE}" 1>/dev/null          &&
+                printf "Remote branch reset: %s\\n"     \
+                  "$(_color_primary "${_current_branch}")"
+            else
+              _remote delete "${_current_branch}"       \
+                <<< "y${_NEWLINE}" 1>/dev/null          &&
+                printf "Remote branch deleted: %s\\n"   \
+                  "$(_color_primary "${_current_branch}")"
+            fi
+          fi
+        fi
+
+        git -C "${_notebook_path:-}" remote rm origin &&
+          printf "Remote removed.\\n"
+
+        return 0
+      else
+        _exit_1 printf "No remote configured.\\n"
+      fi
+      ;;
+    rename)
+      local _target_branch_name=
+
+      local _remote_branches=()
+
+      if ((_remote_exists))
+      then
+        _remote_branches=($(
+          git -C "${_notebook_path}" ls-remote  \
+            --heads "${_current_remote_url:-}"  \
+            | LC_ALL=C sed "s/.*\///g" || :
+        ))
+
+        if [[ -z "${_remote_branches[*]:-}"     ]]
+        then
+          _exit_1 printf "Unable to contact remote.\\n"
+        fi
+      fi
+
+      if [[ "${#_rename_arguments[@]}" -gt 1    ]]
+      then
+        if _contains "${_rename_arguments[0]:-}" "${_remote_branches[@]:-}"
+        then
+          _remote_branch_name="${_rename_arguments[0]:-}"
+          _target_branch_name="${_rename_arguments[1]:-}"
+        else
+          _exit_1 printf                        \
+            "Remote branch not found: %s\\n"    \
+            "$(_color_primary "${_rename_arguments[0]:-}")"
+        fi
+      else
+        _target_branch_name="${_rename_arguments[0]:-}"
+      fi
+
+      if [[ -z "${_target_branch_name:-}"       ]]
+      then
+        _exit_1 _help "remote"
+      fi
+
+      if _contains "${_target_branch_name:-}" "${_remote_branches[@]:-}"
+      then
+        _exit_1 printf "A remote branch with that name already exists.\\n"
+      fi
+
+      local _remote_head_branch=
+
+      if [[ -n "${_current_remote_url:-}"       ]]
+      then
+        _remote_head_branch="$(
+          git ls-remote --symref "${_current_remote_url:-}" HEAD      \
+            | awk '/^ref:/ {sub(/refs\/heads\//, "", $2); print $2}'
+        )"
+      fi
+
+      if [[ -n  "${_remote_head_branch:-}"                            ]] &&
+         [[     "${_remote_branch_name:-"${_current_branch}"}" ==     \
+                  "${_remote_head_branch:-}"                          ]]
+      then
+        _exit_1 printf "Only orphan branches can be renamed.\\n"
+      fi
+
+      if [[ -n "${_remote_branch_name:-}"                             ]] &&
+         [[    "${_remote_branch_name:-}" != "${_current_branch:-}"   ]]
+      then
+        printf      "Renaming remote branch\\n"
+        _print_line "----------------------"
+      else
+        printf      "Renaming current branch\\n"
+        _print_line "-----------------------"
+      fi
+
+      printf        "From: %s\\n" "${_remote_branch_name:-"${_current_branch:-}"}"
+      printf        "To:   %s\\n" "$(_color_primary "${_target_branch_name:-}")"
+
+      _print_line   "-----------"
+
+      while true
+      do
+        local __yn=
+        IFS='' read -r -e -d $'\n' -p                     \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+        case "${__yn}" in
+          [Yy]*)
+            break
+            ;;
+          *)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            exit 0
+            ;;
+        esac
+      done
+
+      if ((_remote_exists))
+      then
+        if [[   -z  "${_remote_branch_name:-}"                           ]] ||
+           [[       "${_remote_branch_name:-}" == "${_current_branch:-}" ]]
+        then
+          {
+            git -C "${_notebook_path}" checkout           \
+              -b "${_target_branch_name}"                 \
+              "${_current_branch}"                        &&
+              git -C "${_notebook_path}" push             \
+                -u origin "${_target_branch_name}"        &&
+              git -C "${_notebook_path}" branch           \
+                -d "${_current_branch}"                   &&
+              git -C "${_notebook_path}" push             \
+                --delete origin "${_current_branch}"      &&
+              git -C "${_notebook_path}" remote prune origin
+          } &>/dev/null || _exit_1 printf "Unable to rename branch.\\n"
+        elif [[ -n  "${_remote_branch_name:-}"                           ]] &&
+             [[     "${_remote_branch_name:-}" != "${_current_branch:-}" ]]
+        then
+          local _temp_repo_path="${_NB_TEMP_DIRECTORY}/${RANDOM}"
+
+          {
+            cd "${_NB_TEMP_DIRECTORY}"                    &&
+              git clone --no-local                        \
+                --single-branch                           \
+                --branch "${_remote_branch_name:-}"       \
+                "${_current_remote_url}"                  \
+                "${_temp_repo_path}"                      &&
+              git -C "${_temp_repo_path}" checkout        \
+                -b "${_target_branch_name}"               \
+                "${_remote_branch_name}"                  &&
+              git -C "${_temp_repo_path}" push            \
+                -u origin "${_target_branch_name}"        &&
+              git -C "${_temp_repo_path}" branch          \
+                -d "${_remote_branch_name}"               &&
+              git -C "${_temp_repo_path}" push            \
+                --delete origin "${_remote_branch_name}"  &&
+              git -C "${_temp_repo_path}" remote prune origin
+          } &>/dev/null || _exit_1 printf "Unable to rename branch.\\n"
+        fi
+      else
+        git -C "${_notebook_path}" branch                 \
+          -m "${_target_branch_name}"                     \
+          &>/dev/null || _exit_1 printf "Unable to rename branch.\\n"
+      fi
+
+      printf "Renamed to: %s\\n" "$(_color_primary "${_target_branch_name}")"
+      ;;
+    reset)
+      if ! ((_remote_exists))
+      then
+        _exit_1 printf "No remote configured.\\n"
+      fi
+
+      if [[ -z "${_remote_branch_name:-}"     ]]
+      then
+        _exit_1 _help "remote"
+      fi
+
+      local _remote_branches=()
+      _remote_branches=($(
+        git -C "${_notebook_path}" ls-remote  \
+          --heads "${_current_remote_url:-}"  \
+           2>/dev/null                        \
+          | LC_ALL=C sed "s/.*\///g" || :
+      ))
+
+      if [[ -z "${_remote_branches[*]:-}"     ]]
+      then
+        _exit_1 printf "Unable to contact remote.\\n"
+      fi
+
+      if ! _contains "${_remote_branch_name:-}" "${_remote_branches[@]:-}"
+      then
+        _exit_1 printf "Remote branch not found: %s\\n" \
+          "${_remote_branch_name:-}"
+      fi
+
+      printf "Resetting remote branch: %s\\n"           \
+        "$(_color_primary "${_remote_branch_name:-}")"
+
+      _print_line "------------------------"
+
+      while true
+      do
+        local __yn=
+        IFS='' read -r -e -d $'\n' -p         \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+        case "${__yn}" in
+          [Yy]*)
+            break
+            ;;
+          *)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            exit 0
+            ;;
+        esac
+      done
+
+      local _blank_repo_path="${_NB_TEMP_DIRECTORY:-/tmp}/${RANDOM}"
+
+      mkdir -p "${_blank_repo_path}"
+      cd "${_blank_repo_path}" || return 1
+
+      {
+        git -C "${_blank_repo_path}" init             \
+            --initial-branch "${_remote_branch_name}" &&
+          touch "${_blank_repo_path}/.index"          &&
+          git -C "${_blank_repo_path}" add --all      &&
+          git -C "${_blank_repo_path}" commit         \
+            -a -m "[${_ME}] Initialize"               &&
+          git -C "${_blank_repo_path}" remote add     \
+            origin "${_current_remote_url:-}"         &&
+          git -C "${_blank_repo_path}" push origin    \
+            "${_remote_branch_name}" --force
+      } &>/dev/null ||
+        _exit_1 printf "Unable to reset remote branch: %s\\n" \
+          "$(_color_primary "${_remote_branch_name}")"
+
+      printf "Remote branch reset.\\n"
+      ;;
+    set|add)
+      if [[ -z "${_new_remote_url:-}" ]]
+      then
+        _exit_1 _help "remote"
+      fi
+
+      if [[ -z "${_new_branch:-}"     ]]
+      then
+        _new_branch="${_current_branch}"
+      fi
+
+      if ! ((_skip_preamble))
+      then
+        if ((_remote_exists))
+        then
+          printf "Updating remote for: %s\\n" \
+            "$(_color_primary "$(_notebooks current --name)")"
+
+          printf "From:   %s (%s)\\n" "${_current_remote_url}" "${_current_branch}"
+
+          _print_line "Updating remote for: $(_notebooks current --name)"
+        else
+          printf "Adding remote to: %s\\n"    \
+            "$(_color_primary "$(_notebooks current --name)")"
+
+          _print_line "Adding remote to: $(_notebooks current --name)"
+        fi
+
+        printf "URL:    %s\\n" "$(_color_primary "${_new_remote_url}")"
+        printf "Branch: %s\\n" "$(_color_primary "${_new_branch}")"
+
+        _print_line "--------------"
+
+        while true
+        do
+          local __yn=
+
+          IFS='' read -r -e -d $'\n' -p                               \
+            "$(_color_primary "Proceed?") $(_color_brackets "y/N") "  \
+            __yn
+
+          case "${__yn:-}" in
+            [Yy]*)
+              break
+              ;;
+            *)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+          esac
+        done
+      fi
+
+      local _remote_branches=()
+      _remote_branches=($(
+        git -C "${_notebook_path}" ls-remote    \
+          --heads "${_new_remote_url:-}"        \
+          | LC_ALL=C sed "s/.*\///g" || :
+      ))
+
+      local _selected_push_option=
+      local _show_branch_selection_prompt=0
+      local _show_branch_name_prompt=1
+
+      if [[ "${#_remote_branches[@]}" -eq 0     ]]
+      then
+        _selected_push_option=2
+        _show_branch_name_prompt=0
+      elif ! _contains "${_new_branch}" "${_remote_branches[@]:-}"
+      then
+        _print_line "--------------"
+
+        cat <<HEREDOC
+Branch not present on remote: $(_color_primary "${_new_branch:-}")
+
+$(_color_brackets "1") Merge and sync with an existing remote branch.
+$(_color_brackets "2") Sync as a new orphan branch on the remote.
+
+HEREDOC
+
+        while true
+        do
+          IFS='' read -r -e -d $'\n' -p                                   \
+"$(_color_primary "Choose an option") or $(_color_primary "q") to quit: " \
+            _selected_push_option
+
+          case "${_selected_push_option:-}" in
+            1)
+              _show_branch_selection_prompt=1
+
+              break
+              ;;
+            2)
+              break
+              ;;
+            q*|exit)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+          esac
+        done
+      else
+        local _temp_repo_path="${_NB_TEMP_DIRECTORY}/${RANDOM}"
+
+        (
+          cd "${_NB_TEMP_DIRECTORY}"                            &&
+            git clone --no-local                                \
+              --single-branch --branch "${_new_branch:-}"       \
+              "${_new_remote_url}"                              \
+              "${_temp_repo_path}" &>/dev/null
+        )
+
+        local _local_branch_root_hash=
+        _local_branch_root_hash="$(
+          git -C "${_notebook_path}" rev-list --max-parents=0   \
+            "${_current_branch}"
+        )"
+
+        local _remote_branch_root_hash=
+        _remote_branch_root_hash="$(
+          git -C "${_temp_repo_path}" rev-list --max-parents=0  \
+            "remotes/origin/${_new_branch}"
+        )"
+
+        local _remote_branch_commit_hashes=()
+        _remote_branch_commit_hashes=($(
+          git -C "${_temp_repo_path}" rev-list                  \
+            --max-count 3 "remotes/origin/${_new_branch}"
+        ))
+
+        local _remote_branch_files=()
+        _remote_branch_files=($(
+          git -C "${_temp_repo_path}" ls-tree --name-only "origin/${_new_branch}"
+        ))
+
+        if [[ "${_local_branch_root_hash:-}"  ==  "${_remote_branch_root_hash:-}" ]]
+        then
+          _selected_push_option=1
+        else
+           if [[ "${#_remote_branch_commit_hashes[@]}"  -eq 1         ]]  &&
+              [[ "${#_remote_branch_files[@]}"          -eq 1         ]]  &&
+              [[ "${_remote_branch_files[0]}"           ==  ".index"  ]]
+          then
+            _selected_push_option=1
+          else
+            _print_line "--------------"
+
+            cat <<HEREDOC
+Remote branch has existing history: $(_color_primary "${_new_branch:-}")
+
+$(_color_brackets "1") Merge and sync with the existing remote branch: $(_color_primary "${_new_branch:-}")
+HEREDOC
+
+            if [[ "${#_remote_branches[@]}" -le 1 ]]
+            then
+              cat <<HEREDOC
+$(_color_brackets "2") Sync as a new orphan branch on the remote.
+
+HEREDOC
+            else
+              cat <<HEREDOC
+$(_color_brackets "2") Merge and sync with a different existing remote branch.
+$(_color_brackets "3") Sync as a new orphan branch on the remote.
+
+HEREDOC
+            fi
+
+            local _existing_history_prompt_option=
+
+            while true
+            do
+              IFS='' read -r -e -d $'\n' -p                               \
+"$(_color_primary "Choose an option") or $(_color_primary "q") to quit: " \
+              _existing_history_prompt_option
+
+              case "${_existing_history_prompt_option:-}" in
+                1)
+                  _selected_push_option=1
+
+                  break
+                  ;;
+                2)
+                  if [[ "${#_remote_branches[@]}" -le 1 ]]
+                  then
+                    _selected_push_option=2
+                  else
+                    _selected_push_option=1
+                    _show_branch_selection_prompt=1
+                  fi
+
+                  break
+                  ;;
+                3)
+                  _selected_push_option=2
+
+                  break
+                  ;;
+                q*|exit)
+                  printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                  exit 0
+                  ;;
+              esac
+            done
+          fi
+        fi
+      fi
+
+      if ((_show_branch_selection_prompt))
+      then
+        _print_line "------------------------------"
+
+        printf "Remote branches:\\n\\n"
+
+        local i=
+        for ((i=0; i < ${#_remote_branches[@]}; i++))
+        do
+          printf "%s %s\\n"                       \
+            "$(_color_brackets "$((i+1))")"       \
+            "${_remote_branches[${i}]:-}"
+        done
+
+        printf "\\n"
+
+        local _selected_branch=
+
+        while true
+        do
+          IFS='' read -r -e -d $'\n' -p                                               \
+            "$(_color_primary "Choose a branch") or $(_color_primary "q") to quit: "  \
+            _selected_branch
+
+          case "${_selected_branch:-}" in
+            q*|exit)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              exit 0
+              ;;
+            [0-9]*)
+              if [[ -n "${_remote_branches[$((_selected_branch - 1))]:-}" ]]
+              then
+                _new_branch="${_remote_branches[$((_selected_branch - 1))]:-}"
+
+                break
+              fi
+              ;;
+          esac
+        done
+      fi
+
+      if [[ "${_selected_push_option:-}" == "2"               ]]
+      then
+        local _target_orphan_branch_name="${_new_branch}"
+
+        if _contains "${_new_branch}" "${_remote_branches[@]:-}"
+        then
+          if [[ "${_new_branch:-}" == "${_current_branch:-}"  ]]
+          then
+            local _notebook_name_branch_name="${_notebook_path##*/}"
+            _notebook_name_branch_name="${_notebook_name_branch_name//' '/-}"
+            _notebook_name_branch_name="$(
+              printf "%s\\n" "${_notebook_name_branch_name}"  \
+                | tr '[:upper:]' '[:lower:]'
+            )"
+          fi
+
+          local _uniqueness_counter=0
+          local _unique_branch_name="${_notebook_name_branch_name}"
+
+          while _contains "${_unique_branch_name}" "${_remote_branches[@]:-}"
+          do
+            _uniqueness_counter="$((_uniqueness_counter+1))"
+
+            printf -v _unique_branch_name -- "%s-%01d"        \
+              "${_notebook_name_branch_name}"                 \
+              "${_uniqueness_counter}"
+          done
+
+          _target_orphan_branch_name="${_unique_branch_name}"
+        fi
+
+        if ! ((_show_branch_name_prompt))
+        then
+          _new_branch="${_target_orphan_branch_name}"
+        else
+          _print_line "------------------------------"
+
+          local _bk_name=  && _bk_name="$(_color_brackets "${_target_orphan_branch_name}")"
+          local _hi_enter= && _hi_enter="$(_color_primary 'enter')"
+          local _hi_q=     && _hi_q="$(_color_primary 'q')"
+          local _hi_type=  && _hi_type="$(_color_primary 'type')"
+
+          cat <<HEREDOC
+Press ${_hi_enter} to use the selected name, ${_hi_type} a new name, or press ${_hi_q} to quit.
+
+HEREDOC
+
+          while true
+          do
+            local _orphan_branch_prompt_response=
+
+            IFS='' read -r -e -d $'\n' -p                     \
+              "Name ${_bk_name}: "                            \
+              _orphan_branch_prompt_response
+
+            case "${_orphan_branch_prompt_response:-}" in
+              '')
+                _new_branch="${_target_orphan_branch_name}"
+
+                break
+                ;;
+              q*|exit)
+                printf "Exiting%s\\n" "$(_color_muted "...")"
+
+                exit 0
+                ;;
+              *)
+                _new_branch="${_orphan_branch_prompt_response}"
+
+                break
+                ;;
+            esac
+          done
+        fi
+      fi
+
+      if [[ "${_new_branch:-}" != "${_current_branch:-}"      ]]
+      then
+        git -C "${_notebook_path}" branch -m "${_new_branch:-}"
+      fi
+
+      if ((_remote_exists))
+      then
+        _print_line "--------------"
+        _remote unset --skip-confirmation
+        _print_line "---------------"
+      fi
+
+      git -C "${_notebook_path}" remote add origin "${_new_remote_url}" ||
+        return 1
+
+      _git sync "${_notebook_path}" --skip-prompt
+
+      local _updated_current_branch=
+      _updated_current_branch="$(
+        git -C "${_notebook_path}" rev-parse --abbrev-ref HEAD
+      )"
+
+      local __local_branch=
+      for   __local_branch in $(git -C "${_notebook_path}" branch --all)
+      do
+        if [[   "${__local_branch:-}" =~ ^\ \ remotes/              ]] &&
+           [[ ! "${__local_branch:-}" =~ ^\ \ remotes/origin/HEAD   ]] &&
+           [[ ! "${__local_branch:-}" =~ ^\ \ remotes/origin/${_updated_current_branch}$ ]]
+        then
+          git -C "${_notebook_path}" branch               \
+            --delete --remotes "${__local_branch#\ \ remotes/}" &>/dev/null
+        fi
+      done
+
+      local _updated_remote_url=
+      _updated_remote_url="$(
+        git -C "${_notebook_path}" remote get-url origin 2>/dev/null
+      )"
+
+      printf "Remote set to: %s (%s)\\n"                  \
+        "$(_color_primary "${_updated_remote_url}")"      \
+        "$(_color_primary "${_updated_current_branch}")"
+
+      return 0
+      ;;
+    *)
+      if ((_remote_exists))
+      then
+        if ((_only_url))
+        then
+          printf "%s\\n" "${_current_remote_url:-}"
+        else
+          printf "%s (%s)\\n" "${_current_remote_url:-}" "${_current_branch:-}"
+        fi
+      else
+        _warn printf "No remote configured.\\n"
+
+        return 1
+      fi
+      ;;
+  esac
+}
+
+# settings ########################################################### settings
+
+_describe_settings() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} set [<name> [<value>] | <number> [<value>]]
+  ${_ME} settings colors [<number> | themes]
+  ${_ME} settings edit
+  ${_ME} settings get   (<name> | <number>)
+  ${_ME} settings list  [--long]
+  ${_ME} settings set   (<name> | <number>) <value>
+  ${_ME} settings show  (<name> | <number>)
+  ${_ME} settings unset (<name> | <number>)
+
+$(_color_primary "Subcommands"):
+  (default)  Open the settings prompt, to <name> or <number>, if present.
+             When <value> is also present, assign <value> to the setting.
+  colors     Print a table of available colors and their xterm color numbers.
+             When <number> is provided, print the number in its color.
+             \`settings colors themes\` prints a list of installed themes.
+  edit       Open the \`${_ME}\` configuration file in \`\$EDITOR\`.
+  get        Print the value of a setting.
+  list       List information about available settings.
+  set        Assign <value> to a setting.
+  show       Print the help information and current value of a setting.
+  unset      Unset a setting, returning it to the default value.
+
+$(_color_primary "Description"):
+  Configure \`${_ME}\`. Use \`${_ME} settings set\` to customize a setting and
+  \`${_ME} settings unset\` to restore the default for a setting.
+
+  Use the \`${_ME} set\` alias to quickly assign values to settings:
+
+    ${_ME} set color_theme blacklight
+    ${_ME} set limit 40
+
+$(_color_primary "Read More"):
+  ${_README_URL}#%EF%B8%8F-set--settings
+
+$(_color_primary "See Also"):
+  ${_ME} help unset
+
+$(_color_primary "Examples"):
+  ${_ME} settings
+  ${_ME} set 5 "org"
+  ${_ME} set color_primary 105
+  ${_ME} set unset color_primary
+  ${_ME} set color_secondary unset
+  ${_ME} settings colors
+  ${_ME} settings colors 105
+  ${_ME} set limit 15
+
+$(_color_primary "Alias"):
+  ${_ME} set
+HEREDOC
+}
+_settings() {
+  # Usage: _settings_colors [<number>] [themes]
+  _settings_colors() {
+    # Usage: _settings_colors_print <number>
+    _settings_colors_print() {
+      printf '\e[38;5;%dm %3d ' "${1:-}" "${1:-}"
+    }
+
+    if [[   -n  "${1:-}"              ]]
+    then
+      if [[     "${1}" == "themes"    ]]
+      then
+        printf "%s\\n" "${_NB_COLOR_THEMES[@]}"
+      else
+        if [[ ! "${1}" =~ [[:digit:]] ]]
+        then
+          _exit_1 printf "Usage: %s settings colors [<number> | themes]\\n" "${_ME}"
+        fi
+
+        _settings_colors_print "${1:-}"
+
+        printf "\\n"
+      fi
+    else
+      local i=
+      for ((i=0; i < 256; i++))
+      do
+        if ((i)) && ! ((i % 16))
+        then
+          printf "\\n"
+        fi
+
+        _settings_colors_print "${i}"
+      done
+
+      printf "\\n"
+    fi
+  }
+
+  # Usage: _settings_get_value (<number> | <name>)
+  _settings_get_value() {
+    local _setting_name=
+    _setting_name="$(_settings_identify "${1:-}")"
+
+    _env | grep "${_setting_name}" | cut -d= -f2
+  }
+
+  # Usage: _settings_identify [--id] (<number> | <name>)
+  _settings_identify() {
+    local _get_id=0
+    local _id_or_name=
+
+    case "${1:-}" in
+      '')
+        return 1
+        ;;
+      --id)
+        _get_id=1
+
+        if [[ -n "${2:-}" ]]
+        then
+          _id_or_name="${2:-}"
+        else
+          return 1
+        fi
+        ;;
+      *)
+        _id_or_name="${1}"
+        ;;
+    esac
+
+    case "${_id_or_name}" in
+      1|*auto*|*AUTO*|*sync*|*SYNC*)
+        ((_get_id)) && printf "1"   || printf "NB_AUTO_SYNC"
+
+        return 0
+        ;;
+      2|*primary*|*PRIMARY*)
+        ((_get_id)) && printf "2"   || printf "NB_COLOR_PRIMARY"
+
+        return 0
+        ;;
+      3|*secondary*|*SECONDARY*)
+        ((_get_id)) && printf "3"   || printf "NB_COLOR_SECONDARY"
+
+        return 0
+        ;;
+      4|*color*theme*|*COLOR*THEME*|*scheme*|theme*)
+        ((_get_id)) && printf "4"   || printf "NB_COLOR_THEME"
+
+        return 0
+        ;;
+      5|*ext*|*EXT*)
+        ((_get_id)) && printf "5"   || printf "NB_DEFAULT_EXTENSION"
+
+        return 0
+        ;;
+      6|*editor*|*EDITOR*)
+        ((_get_id)) && printf "6"   || printf "EDITOR"
+
+        return 0
+        ;;
+      7|*encrypt*|*ENCRYPT*)
+        ((_get_id)) && printf "7"   || printf "NB_ENCRYPTION_TOOL"
+
+        return 0
+        ;;
+      8|*footer*|*FOOTER*)
+        ((_get_id)) && printf "8"   || printf "NB_FOOTER"
+
+        return 0
+        ;;
+      9|*header*|*HEADER*)
+        ((_get_id)) && printf "9"   || printf "NB_HEADER"
+
+        return 0
+        ;;
+      10|*limit*|*LIMIT*)
+        ((_get_id)) && printf "10"  || printf "NB_LIMIT"
+
+        return 0
+        ;;
+      11|*dir*|*DIR*)
+        ((_get_id)) && printf "11"  || printf "NB_DIR"
+
+        return 0
+        ;;
+      12|*syntax*|*SYNTAX*)
+        ((_get_id)) && printf "12"  || printf "NB_SYNTAX_THEME"
+
+        return 0
+        ;;
+      *)
+        _warn                                   \
+          printf "Setting not found: %s\\n"     \
+          "$(_color_primary "${_id_or_name}")"  &&
+            return 1
+        ;;
+    esac
+  }
+
+  # Usage: _settings_prompt [<id> | <name>]
+  _settings_prompt() {
+    local _setting_name="${1:-}"
+
+    local _padding=
+    _padding="$(_print_padding "-----------" "${_COLUMNS}")"
+
+    printf "%s%s Settings\\n" "${_padding}" "$(_color_primary "${_ME}")"
+    _print_line "$(printf "%-${_COLUMNS}s" '.')"
+
+    if [[ -n "${_setting_name}" ]]
+    then
+      _setting_name="$(_settings_identify "${_setting_name}")"
+    else
+      cat <<HEREDOC
+$(_settings list)
+
+Enter the number or name of the setting to change, or $(_color_primary 'q') to quit.
+HEREDOC
+
+      while true
+      do
+        local __setting=
+        IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Number or Name: ")" __setting
+
+        if [[ -n "${__setting}" ]]
+        then
+          case "${__setting}" in
+            q|quit|exit)
+              printf "Exiting%s\\n" "$(_color_muted "...")"
+
+              return 0
+              ;;
+            *)
+              _setting_name="$(
+                _settings_identify "${__setting}"
+              )" && break
+              ;;
+          esac
+        fi
+      done
+    fi
+
+    printf "\\n"
+
+    if [[ "${_setting_name}" == "NB_COLOR_PRIMARY"    ]] ||
+       [[ "${_setting_name}" == "NB_COLOR_SECONDARY"  ]]
+    then
+      printf "%s\\n\\n" "$(_settings_colors)"
+    fi
+
+    _settings show "${_setting_name}"
+
+    local _hi_unset= && _hi_unset="$(_color_primary 'unset')"
+    local _hi_q=     && _hi_q="$(_color_primary 'q')"
+
+    cat <<HEREDOC
+
+Enter a new value, ${_hi_unset} to set to the default value, or ${_hi_q} to quit.
+HEREDOC
+
+    while true
+    do
+      local __value=
+      IFS='' read -r -e -d $'\n' -p "$(_color_primary "Value: ")" __value
+
+      if [[ -n "${__value}" ]]
+      then
+        case "${__value}" in
+          q|quit|exit)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            return 0
+            ;;
+          unset|default|reset)
+            _settings_unset "${_setting_name}"              || continue
+
+            break
+            ;;
+          *)
+            _settings_set   "${_setting_name}" "${__value}" || continue
+
+            break
+            ;;
+        esac
+      fi
+    done
+  }
+
+  # Usage: _settings_set (<number> | <name>) <value>
+  _settings_set() {
+    local _entry=
+    local _value="${2:-}"
+
+    local _setting_name=
+    _setting_name="$(_settings_identify "${1:-}")"
+
+    if _contains "${2:-}" "unset" "default" "reset"
+    then
+      _settings_unset "${_setting_name}"
+
+      return 0
+    fi
+
+    _settings_validate_value "${_setting_name}" "${2:-}"    || return 1
+
+    if [[ "${_value:-}"       =~ ^~       ]]
+    then
+      # shellcheck disable=SC2016
+      _value="$(printf "%s\\n" "${_value}" | LC_ALL=C sed "s|~|${HOME}|g")"
+    fi
+
+    local _attribution=
+    _attribution="# Set by \`${_ME}\` • $(date)"
+
+    if [[ "${_setting_name}"  == "EDITOR" ]]
+    then
+      _entry="export ${_setting_name}=\"${_value}\" ${_attribution}"
+    else
+      _entry="export ${_setting_name}=\"\${${_setting_name}:-${_value}}\" ${_attribution}"
+    fi
+
+    _settings_unset "${_setting_name}" > /dev/null 2>&1     || return 1
+
+    printf "\\n%s\\n" "${_entry}" >> "${NBRC_PATH}"
+
+    if [[   "${_setting_name}" == "NB_COLOR_PRIMARY"    ]]  ||
+       [[   "${_setting_name}" == "NB_COLOR_SECONDARY"  ]]
+    then
+      _setting_name="$(_tput setaf "${_value}")${_setting_name}${_TPUT_SGR0}"
+      _value="$(_tput setaf "${_value}")${_value}${_TPUT_SGR0}"
+    elif [[ "${_setting_name}" == "NB_COLOR_THEME"      ]]
+    then
+      local _new_color=
+      _new_color="$(
+        NB_COLOR_THEME="${_value}" NB_COLOR_PRIMARY=''  \
+          "${_MY_PATH}" settings get NB_COLOR_PRIMARY
+      )"
+
+      _setting_name="$(_tput setaf "${_new_color}")${_setting_name}${_TPUT_SGR0}"
+      _value="$(_tput setaf "${_new_color}")${_value}${_TPUT_SGR0}"
+    else
+      _setting_name="$(_color_primary "${_setting_name}")"
+      _value="$(_color_primary "${_value}")"
+    fi
+
+    printf "%s set to %s\\n" "${_setting_name}" "${_value}"
+  }
+
+  # Usage: _settings_unset (<number> | <name>)
+  _settings_unset() {
+    local _setting_name=
+    _setting_name="$(_settings_identify "${1:-}")"
+
+    _sed_i                                              \
+      -e "/^export ${_setting_name}.*Added by.*$/d"     \
+      -e "/^export ${_setting_name}.*Set by.*$/d"       \
+      "${NBRC_PATH}"
+
+    local _stripped=
+    _stripped=$(<"${NBRC_PATH}")
+
+    printf "%s\\n" "${_stripped}" > "${NBRC_PATH}"
+
+    local _default_value=
+    _default_value="$(
+      eval "${_setting_name}='' \"${_MY_PATH}\" settings get ${_setting_name}"
+    )"
+
+    if [[   "${_setting_name}" == "NB_COLOR_SECONDARY"  ]]
+    then
+      _setting_name="$(_color_primary "${_setting_name}")"
+      _default_value="$(_tput setaf "${_default_value}")${_default_value}${_TPUT_SGR0}"
+    elif [[ "${_setting_name}" == "NB_COLOR_PRIMARY"    ]]
+    then
+      _setting_name="$(_tput setaf "${_default_value}")${_setting_name}${_TPUT_SGR0}"
+      _default_value="$(_tput setaf "${_default_value}")${_default_value}${_TPUT_SGR0}"
+    elif [[ "${_setting_name}" == "NB_COLOR_THEME"      ]]
+    then
+      _new_hi_color="$(
+        NB_COLOR_THEME="${_ME}" NB_COLOR_PRIMARY=''     \
+          "${_MY_PATH}" settings get NB_COLOR_PRIMARY
+      )"
+
+      _setting_name="$(_tput setaf "${_new_hi_color}")${_setting_name}${_TPUT_SGR0}"
+      _default_value="$(_tput setaf "${_new_hi_color}")${_default_value}${_TPUT_SGR0}"
+    else
+      _setting_name="$(_color_primary "${_setting_name}")"
+      _default_value="$(_color_primary "${_default_value}")"
+    fi
+
+    printf "%s restored to the default: %s\\n"          \
+      "${_setting_name}"                                \
+      "${_default_value}"
+  }
+
+  # Usage: _settings_validate_value (<number> | <name>) <value>
+  _settings_validate_value() {
+    if [[ "${1:-}" == 'EDITOR'                ]]  ||
+       [[ "${1:-}" == 'NB_DEFAULT_EXTENSION'  ]]
+    then
+      if [[ -n "${2:-}"                       ]]
+      then
+        return 0
+      else
+        _warn printf                \
+          "%s requires a value.\\n" \
+          "${1:-}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_AUTO_SYNC'        ]]  ||
+         [[ "${1:-}" == 'NB_FOOTER'           ]]
+    then
+      if [[ "${2:-}" =~ (^0$|^1$)             ]]
+      then
+        return 0
+      else
+        _warn printf                              \
+          "%s must be either \"0\" or \"1\".\\n"  \
+          "${1}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_HEADER'           ]]
+    then
+      if [[ "${2:-}" =~ (^0$|^1$|^2$|^3$)     ]]
+      then
+        return 0
+      else
+        _warn printf                                      \
+          "%s must be \"0\", \"1\", \"2\", or \"3\".\\n"  \
+          "${1}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_LIMIT'            ]]
+    then
+      if [[ "${2:-}" =~ ^[0-9]+$              ]]  ||
+         [[ "${2:-}" =~ ^auto$                ]]  ||
+         [[ "${2:-}" =~ ^auto[+|-][0-9]+$     ]]
+      then
+        return 0
+      else
+        _warn printf                                                \
+          "%s must be a number, \"auto,\" or \"auto-<number>\".\\n" \
+          "${1}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_DIR'              ]]
+    then
+      if [[ -z  "${2:-}"                      ]]  ||
+         [[ "${2}"   == "/"                   ]]  ||
+         {
+           [[   -e "${2}"                     ]]  &&
+           [[ ! -w "${2}"                     ]]
+         }
+      then
+        _warn printf                                      \
+          "\"%s\" is not a valid location for NB_DIR.\\n" \
+          "${2:-}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_ENCRYPTION_TOOL'  ]]
+    then
+      if [[ "${2:-}" =~ (^openssl$|^gpg$)     ]]
+      then
+        return 0
+      else
+        _warn printf \
+          "NB_ENCRYPTION_TOOL must be either \"openssl\" or \"gpg\".\\n"
+
+          return 1
+      fi
+    elif [[ "${1:-}" == 'NB_COLOR_PRIMARY'    ]]  ||
+         [[ "${1:-}" == 'NB_COLOR_SECONDARY'  ]]
+    then
+      if [[ "${2:-}" =~ ^[0-9]                ]]
+      then
+        return 0
+      else
+        _warn printf                \
+          "%s must be a number.\\n" \
+          "${1}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_COLOR_THEME'      ]]
+    then
+      if _contains "${2:-}" "${_NB_COLOR_THEMES[@]}"
+      then
+        return 0
+      else
+        _warn printf                                    \
+          "%s must be one of the available themes.\\n"  \
+          "${1}"
+
+        return 1
+      fi
+    elif [[ "${1:-}" == 'NB_SYNTAX_THEME'     ]]
+    then
+      if ! hash bat 2>/dev/null
+      then
+        printf "bat required: https://github.com/sharkdp/bat\\n"
+      else
+        local _theme_list=
+        _theme_list=($(bat --list-themes --color never))
+
+        if _contains "${2:-}" "${_theme_list[@]}"
+        then
+          return 0
+        else
+          _warn printf                                    \
+            "%s must be one of the available themes.\\n"  \
+            "${1}"
+
+          return 1
+        fi
+      fi
+    else
+      return 0
+    fi
+  }
+
+  local _settings_list_items=()
+  local _settings_help_items=()
+
+  _settings_list_items+=("$(_color_brackets '1')  auto_sync")
+  _settings_help_items+=("\
+    $(_color_secondary " ---------")
+     By default, operations that trigger a git commit like \`add\`, \`edit\`,
+     and \`delete\` will sync notebook changes to the remote repository, if
+     one is set. To disable this behavior, set this to \"0\".
+
+     • Default Value: $(_color_primary "1")")
+
+  _settings_list_items+=("$(_color_brackets '2')  color_primary")
+  _settings_help_items+=("\
+    $(_color_secondary " -------------")
+     The primary color used to highlight identifiers and messages.
+
+     • Supported Values: xterm color numbers 0 through 255.
+     • Default Value:    $(_color_primary "68") (blue) for 256 color terminals,
+                         $(_color_primary "4")  (blue) for  8  color terminals.")
+
+  _settings_list_items+=("$(_color_brackets '3')  color_secondary")
+  _settings_help_items+=("\
+    $(_color_secondary " ---------------")
+     The color used for lines and footer elements.
+
+     • Supported Values: xterm color numbers 0 through 255.
+     • Default Value:    $(_color_primary "8")")
+
+  _settings_list_items+=("$(_color_brackets '4')  color_theme")
+  _settings_help_items+=("\
+    $(_color_secondary " -----------")
+     The color theme.
+
+     To view screenshots of the built-in themes, visit:
+
+         $(_color_primary "https://git.io/nb-docs-color-themes")
+
+     \`${_ME}\` supports custom, user-defined themes. To learn more, run:
+
+         $(_color_primary "${_ME} help --colors")
+
+     To change the syntax highlighting theme, use:
+
+         $(_color_primary "${_ME} set syntax_theme")
+
+     • Available themes:
+
+$(
+  local __theme=
+  for   __theme in "${_NB_COLOR_THEMES[@]}"
+  do
+    printf "         %s\\n" "$(_color_primary "${__theme}")"
+  done
+)
+
+     • Default Value: $(_color_primary "${_ME}")")
+
+  _settings_list_items+=("$(_color_brackets '5')  default_extension")
+  _settings_help_items+=("\
+    $(_color_secondary " -----------------")
+     The default extension to use for note files. Change to \"org\" for Emacs
+     Org mode files, \"rst\" for reStructuredText, \"txt\" for plain text, or
+     whatever you prefer.
+
+     • Default Value: $(_color_primary "md")")
+
+  _settings_list_items+=("$(_color_brackets '6')  editor")
+  _settings_help_items+=("\
+    $(_color_secondary " ------")
+     The command line text editor used by \`${_ME}\`.
+
+     • Example Values:
+
+$(
+  local __editor=
+  for   __editor in atom code emacs macdown mate micro nano pico subl vi vim
+  do
+    if _command_exists "${__editor}"
+    then
+      printf "         %s\\n" "$(_color_primary "${__editor}")"
+    fi
+  done
+)")
+
+  _settings_list_items+=("$(_color_brackets '7')  encryption_tool")
+  _settings_help_items+=("\
+    $(_color_secondary " ---------------")
+     The tool used for encrypting notes.
+
+     • Supported Values: $(_color_primary "openssl"), $(_color_primary "gpg")
+     • Default Value:    $(_color_primary "openssl")")
+
+  _settings_list_items+=("$(_color_brackets '8')  footer")
+  _settings_help_items+=("\
+    $(_color_secondary " ------")
+     By default, \`${_ME}\` and \`${_ME} ls\` include a footer with example commands.
+     To hide this footer, set this to \"0\".
+
+     • Default Value: $(_color_primary "1")")
+
+  _settings_list_items+=("$(_color_brackets '9')  header")
+  _settings_help_items+=("\
+    $(_color_secondary " ------")
+     By default, \`${_ME}\` and \`${_ME} ls\` include a header listing available notebooks.
+     Set the alignment, or hide the header with \"0\".
+
+     • Supported Values:
+
+       $(_color_primary "0")  Hide Header
+       $(_color_primary "1")  Dynamic Alignment
+            - Left justified when list is shorter than terminal width.
+            - Center aligned when list is longer than terminal width.
+       $(_color_primary "2")  Center Aligned (default)
+       $(_color_primary "3")  Left Justified
+
+     • Default Value: $(_color_primary "2")")
+
+  _settings_list_items+=("$(_color_brackets '10') limit")
+  _settings_help_items+=("\
+    $(_color_secondary " -----")
+     The maximum number of items included in the \`${_ME}\` and \`${_ME} ls\` lists.
+     Set to \`auto\` to automatically limit output to the current terminal height.
+     Subtract an auto limit offset for multiline prompts with \`auto-<number>\`.
+
+     • Example Values:
+
+       15
+       auto
+       auto-2
+
+     • Default Value: $(_color_primary "15")")
+
+  _settings_list_items+=("$(_color_brackets '11') nb_dir")
+  _settings_help_items+=("\
+    $(_color_secondary " ------")
+     The location of the directory that contains the notebooks.
+
+     For example, to sync all notebooks with Dropbox, create a folder at
+     \`~/Dropbox/Notes\` and run: \`${_ME} settings set nb_dir ~/Dropbox/Notes\`
+
+     • Default Value: $(_color_primary "~/.${_ME}")")
+
+  _settings_list_items+=("$(_color_brackets '12') syntax_theme")
+  _settings_help_items+=("\
+    $(_color_secondary " ------------")
+     The syntax highlighting theme. View examples with:
+
+         $(_color_primary 'bat --list-themes')
+
+$(
+  if ! hash "bat" 2>/dev/null
+  then
+    printf "     Install \`bat\` to enable themes: https://github.com/sharkdp/bat\\n"
+  else
+    printf "     • Available themes:\\n"
+    printf "\\n"
+
+    local __theme=
+    for   __theme in $(bat --list-themes --color never)
+    do
+      printf "         %s\\n" "$(_color_primary "${__theme}")"
+    done
+  fi
+)
+
+     • Default Value: $(_color_primary 'base16')")
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      color|colors)
+        _settings_colors "${2:-}"
+
+        return 0
+        ;;
+      edit)
+        _edit_file "${NBRC_PATH}" --no-wait
+
+        return 0
+        ;;
+      get)
+        if [[ -z  "${2:-}"              ]]
+        then
+          _exit_1 _help settings
+        fi
+
+        _settings_get_value "${2:-}"
+
+        return 0
+        ;;
+      list)
+        if [[     "${2:-}" == "--long"  ]]
+        then
+          local _counter=0
+
+          local __setting=
+          for   __setting in "${_settings_list_items[@]}"
+          do
+            ((_counter)) && printf "\\n"
+            _counter="$((_counter+1))"
+
+            _settings show "${_counter}"
+          done
+        else
+          printf "%s\\n" "${_settings_list_items[@]}"
+        fi
+
+        return 0
+        ;;
+      set)
+        if [[ -z "${2:-}" ]] || [[ -z "${3:-}" ]]
+        then
+          _exit_1 _help "settings"
+        fi
+
+        _settings_set "${2:-}" "${3:-}"
+
+        return 0
+        ;;
+      show|help|about|info|more)
+        if [[ -z "${2:-}" ]]
+        then
+          _exit_1 _help "settings"
+        fi
+
+        local _setting_id=
+        _setting_id="$(_settings_identify --id "${2:-}")"
+
+        local _setting_name=
+        _setting_name="$(_settings_identify "${2:-}")"
+
+        local _index=
+        _index="$((_setting_id-1))"
+
+        printf "%s\\n%s\\n"                       \
+          "${_settings_list_items[${_index}]}"    \
+          "${_settings_help_items[${_index}]}"
+
+        printf "\\n%s is currently set to %s\\n"  \
+          "$(_color_primary "${_setting_name}")"  \
+          "$(_color_primary "$(_settings_get_value "${_setting_name}")")"
+
+        return 0
+        ;;
+      reset|unset)
+        if [[ -z "${2:-}" ]]
+        then
+          _exit_1 _help "settings"
+        fi
+
+        _settings_unset "${2:-}"
+
+        return 0
+        ;;
+      *)
+        local _setting_name=
+
+        case "${1:-}" in
+          '')       :                                             ;;
+          remote)   shift; _remote set "${@}"; return 0           ;;
+          *)        _setting_name="$(_settings_identify "${1}")"  ;;
+        esac
+
+        if [[   -n "${_setting_name:-}" ]]
+        then
+          if [[ -n "${2:-}"             ]]
+          then
+            _settings_set "${_setting_name}" "${2}"
+          else
+            _settings_prompt "${_setting_name}"
+          fi
+        else
+          _settings_prompt
+        fi
+
+        return 0
+        ;;
+    esac
+
+    shift
+  done
+}
+_alias_subcommand "settings" "config"
+_alias_subcommand "settings" "set"
+
+# shell ################################################################# shell
+
+_describe_shell() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} shell [<subcommand> [<options>...] | --clear-history]
+
+$(_color_primary "Options"):
+  --clear-history  Clear the \`${_ME}\` shell history.
+
+$(_color_primary "Description"):
+  Start the \`${_ME}\` interactive shell. Type "exit" to exit.
+
+  \`${_ME} shell\` recognizes all \`${_ME}\` subcommands and options, providing
+  a streamlined, distraction-free approach for working with \`${_ME}\`.
+
+  When <subcommand> is present, the command will run as the shell is opened.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-interactive-shell
+
+$(_color_primary "See Also"):
+  ${_ME} help run
+
+$(_color_primary "Example"):
+  $ ${_ME} shell
+  ${_ME}> ls 3
+  [3] Example
+
+  ${_ME}> edit 3 --content "New content."
+  Updated [3] Example
+
+  ${_ME}> notebook
+  home
+
+  ${_ME}> exit
+  $
+HEREDOC
+}
+_shell() {
+  HISTFILE="${NB_HIST:-${HOME}/.${_ME}_history}"
+  set -o history
+
+  local _initial_command=
+  local _prompt=
+  _prompt="$(_color_primary "${_ME}")$(_color_secondary "${_CHEVRON_RIGHT}") "
+
+  local __arg=
+  for   __arg in "${@:-}"
+  do
+    case "${__arg}" in
+      --clear-history)
+        if [[ -e "${HISTFILE}"  ]]
+        then
+          rm "${HISTFILE:?}"
+
+          printf "History cleared.\\n"
+
+          return 0
+        fi
+        ;;
+      *)
+        if [[ -n "${__arg}"     ]]
+        then
+          _initial_command+=" ${__arg}"
+        fi
+        ;;
+    esac
+  done
+
+  printf "%s" "${_TPUT_COLOR_PRIMARY}"
+  cat <<HEREDOC
+__          _
+\ \   _ __ | |__
+ \ \ | '_ \| '_ \\
+ / / | | | | |_) |
+/_/  |_| |_|_.__/
+$(_color_secondary "------------------")
+$(_color_primary "${_ME} shell") started. Enter $(_color_primary "ls") to list notes and notebooks.
+Enter $(_color_primary "help") for usage information. Enter $(_color_primary "exit") to exit.
+HEREDOC
+
+  if [[ -n "${_initial_command:-}"            ]]
+  then
+    eval "\"${_MY_PATH}\" ${_initial_command}"
+  fi
+
+  local __input=
+  while IFS='' read -r -e -d $'\n' -p "${_prompt}" __input
+  do
+    history -s "${__input}"
+
+    if [[ "${__input}" =~ (^exit$|^quit$|^q$) ]]
+    then
+      return 0
+    elif [[ "${__input}" =~ ^clear$           ]]
+    then
+      clear
+    else
+      # Strip leading 'n', 'nb', or 'notes'.
+      local _normalized_input=
+      _normalized_input="$(
+        printf "%s\\n" "${__input}"           \
+          | LC_ALL=C sed -e 's/^n$//'         \
+          | LC_ALL=C sed -e 's/^n //'         \
+          | LC_ALL=C sed -e 's/^nb$//'        \
+          | LC_ALL=C sed -e 's/^nb //'        \
+          | LC_ALL=C sed -e 's/^notes$//'     \
+          | LC_ALL=C sed -e 's/^notes //'
+      )"
+
+      local _command_name=
+
+      if [[ "${_normalized_input}" =~ ^help   ]] ||
+         [[ "${_normalized_input}" =~ ^help\  ]] ||
+         [[ "${_normalized_input}" =~ ^h$     ]] ||
+         [[ "${_normalized_input}" =~ ^h\     ]]
+      then
+        eval "\"${_MY_PATH}\" ${_normalized_input}" --shell || :
+      elif [[ "${_normalized_input}" =~ ^echo\ .*   ]]      ||
+           [[ "${_normalized_input}" =~ ^printf\ .* ]]
+      then
+        eval "${_normalized_input}"
+      elif _command_name="$(
+        printf "%s\\n" "${_normalized_input}" \
+          | grep                              \
+              --color=never                   \
+              --only-matching                 \
+              -e '^code'                      \
+              -e '^emacs'                     \
+              -e '^gvim'                      \
+              -e '^macdown'                   \
+              -e '^mate'                      \
+              -e '^mvim'                      \
+              -e '^nano'                      \
+              -e '^nvim'                      \
+              -e '^subl'                      \
+              -e '^vim'
+      )"
+      then
+        _normalized_input="$(
+          printf "%s\\n" "${_normalized_input}"     \
+            | LC_ALL=C sed -e "s/^${_command_name} //"
+        )"
+
+        eval "\"${_MY_PATH}\" edit --editor \"${_command_name}\" ${_normalized_input}"
+      else
+        eval "\"${_MY_PATH}\" ${_normalized_input}" || :
+      fi
+    fi
+  done
+}
+
+# status ############################################################### status
+
+_describe_status() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} status [<notebook>]
+
+$(_color_primary "Description"):
+  Print archival, git, and remote status for the current notebook or <notebook>.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-git-sync
+  ${_README_URL}#-revision-history
+
+$(_color_primary "See Also"):
+  ${_ME} help archive
+  ${_ME} help history
+  ${_ME} help notebooks
+  ${_ME} help remote
+  ${_ME} help sync
+  ${_ME} help unarchive
+
+$(_color_primary "Examples"):
+  ${_ME} status
+  ${_ME} status example
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} st
+HEREDOC
+}
+_status() {
+  local _notebook_name="${1%%:*}"
+  local _notebook_path=
+
+  if [[   -n "${_notebook_name:-}" ]]
+  then
+    _notebook_path="$(
+      _notebooks show "${_notebook_name:-}" --path 2>/dev/null || :
+    )"
+
+    if [[ -z "${_notebook_path:-}" ]]
+    then
+      _warn printf "Notebook not found: %s\\n" \
+        "$(_color_primary "${_notebook_name:-}")"
+
+      return 1
+    fi
+  else
+    _notebook_name="$(_notebooks current --name)"
+    _notebook_path="$(_notebooks current --path)"
+  fi
+
+  _notebooks select "${_notebook_path}"
+
+  printf "%s\\n" "$(_color_primary "${_notebook_name}")"
+  _print_line "${_notebook_name}"
+
+  printf "status: "
+
+  if [[ "$(_notebooks status "${_notebook_name}")" =~ not\ archived ]]
+  then
+    printf "unarchived\\n"
+  else
+    printf "archived\\n"
+  fi
+
+  printf "remote: "
+
+  _remote 2>/dev/null || printf "none\\n"
+
+  printf "git:    "
+
+  local _git_status_files=
+  _git_status_files="$(git -C "${_notebook_path}" status --porcelain)"
+
+  if [[ -n "${_git_status_files:-}" ]]
+  then
+    printf "dirty\\n\\nchanges\\n"
+
+    _print_line "changes"
+
+    git -C "${_notebook_path}" status --porcelain
+  else
+    printf "clean\\n"
+  fi
+}
+_alias_subcommand "status" "st"
+_alias_subcommand "status" "stat"
+
+# sync ################################################################### sync
+
+_describe_sync() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} sync [-a | --all]
+
+$(_color_primary "Options"):
+  -a, --all   Sync all unarchived notebooks.
+
+$(_color_primary "Description"):
+  Sync the current notebook with its remote.
+
+$(_color_primary "Private Repositories and Git Credentials"):
+  Syncing with private repositories requires configuring git to not prompt
+  for credentials.
+
+  For repositories cloned over HTTPS, credentials can be cached with git.
+  For repositories cloned over SSH, keys can be added to the ssh-agent.
+
+  More Information:
+    ${_README_URL}#private-repositories-and-git-credentials
+
+$(_color_primary "Sync Conflict Resolution"):
+  When \`${_ME} sync\` encounters a conflict in a text file and can't merge
+  overlapping local and remote changes, both versions are saved in the
+  file, separated by git conflict markers. Use \`${_ME} edit\` to remove the
+  conflict markers and delete any unwanted text.
+
+  When \`${_ME} sync\` encounters a conflict in a binary file, such as an
+  encrypted note or bookmark, both versions of the file are saved in the
+  notebook as individual files, one with \`--conflicted-copy\` appended to
+  the filename.
+
+  More Information:
+    ${_README_URL}#sync-conflict-resolution
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-git-sync
+  ${_README_URL}#-revision-history
+
+$(_color_primary "See Also"):
+  ${_ME} help history
+  ${_ME} help notebooks
+  ${_ME} help remote
+  ${_ME} help status
+
+$(_color_primary "Examples"):
+  ${_ME} sync
+  ${_ME} sync --all
+HEREDOC
+}
+_sync() {
+  local _notebooks=()
+  local _sync_all=0
+
+  if [[ "${1:-}" =~ (^-a$|^--all$) ]]
+  then
+    _sync_all=1
+
+    local _notebook_names=()
+    _notebooks=($(_notebooks --names --no-color --unarchived))
+  else
+    _notebooks=($(_notebooks current))
+  fi
+
+  local _sync_successful=0
+  local _sync_started=0
+  local _syncable_count=0
+
+  local __notebook=
+  for   __notebook in "${_notebooks[@]:-}"
+  do
+    if [[ "${__notebook}" == "local"      ]] &&
+       [[ -n "${_LOCAL_NOTEBOOK_PATH:-}"  ]]
+    then
+      NB_NOTEBOOK_PATH="${_LOCAL_NOTEBOOK_PATH}"
+    else
+      NB_NOTEBOOK_PATH="${NB_DIR}/${__notebook}"
+    fi
+
+    if ((_sync_all))
+    then
+      _remote &>/dev/null || continue
+    else
+      _remote 1>/dev/null || {
+        cat <<HEREDOC
+
+Set the remote for the current notebook:
+
+  $(_color_primary "${_ME} remote set <url>")
+
+Set the remote for a notebook named "example":
+
+  $(_color_primary "${_ME} example:remote set <url>")
+
+HEREDOC
+
+        return 1
+      }
+    fi
+
+    if ! ((_sync_started))
+    then
+      printf "Syncing: "
+      _sync_started=1
+    fi
+
+    printf "%s..." "$(_color_primary "${__notebook}")"
+
+    local _notebook_sync_successful=0
+
+    _syncable_count="$((_syncable_count+1))"
+
+    if ((_sync_all))
+    then # sync without prompt in background
+      GIT_TERMINAL_PROMPT=0 NB_AUTO_SYNC=1 \
+        _git checkpoint "${NB_NOTEBOOK_PATH}" "[${_ME}] Sync" --spinner
+    else # sync with prompt in foreground
+      GIT_TERMINAL_PROMPT=1 NB_AUTO_SYNC=0 \
+        _git checkpoint "${NB_NOTEBOOK_PATH}" "[${_ME}] Sync" --spinner
+
+      _git sync "${NB_NOTEBOOK_PATH}"
+
+      if ! _index verify "${NB_NOTEBOOK_PATH}" &>/dev/null
+      then
+        _index reconcile "${NB_NOTEBOOK_PATH}" --commit
+
+        while [[ -n "$(git -C "${NB_NOTEBOOK_PATH}" status --porcelain)" ]]
+        do
+          sleep 1
+        done
+
+        _git sync "${NB_NOTEBOOK_PATH}"
+      fi
+    fi && _notebook_sync_successful=1
+
+    if ! ((_notebook_sync_successful))            ||
+       _git dirty           "${NB_NOTEBOOK_PATH}" ||
+       _git out_of_sync     "${NB_NOTEBOOK_PATH}"
+    then
+      _exit_1 cat <<HEREDOC
+Sync failed.
+
+Reason unknown, but likely one of the following:
+
+- Authentication error or credentials not configured.
+- Network unavailable.
+- Misconfigured remote URL.
+
+Configuring Git Credentials:
+  ${_README_URL}#private-repositories-and-git-credentials
+HEREDOC
+    fi
+  done && ((_syncable_count)) && _sync_successful=1
+
+  if ((_sync_successful))
+  then
+    printf "Done!\\n"
+  elif ! ((_syncable_count))
+  then
+    _exit_1 cat <<HEREDOC
+No unarchived notebooks with remotes found.
+
+Set the remote for the current notebook:
+
+  $(_color_primary "${_ME} remote set <url>")
+
+Set the remote for a notebook named "example":
+
+  $(_color_primary "${_ME} example:remote set <url>")
+
+HEREDOC
+  else
+    printf "\\n"
+
+    _exit_1 printf "Sync failed.\\n"
+  fi
+}
+
+# tasks ################################################################# tasks
+
+_describe_tasks() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} tasks ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+           [open | closed]
+
+$(_color_primary "Description"):
+  List tasks in todos, notebooks, folders, and other items.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#%EF%B8%8F-tasks
+  ${_README_URL}#-todos
+
+$(_color_primary "See Also"):
+  ${_ME} help do
+  ${_ME} help todo
+  ${_ME} help undo
+
+$(_color_primary "Examples"):
+  ${_ME} tasks
+  ${_ME} tasks open
+  ${_ME} tasks closed
+  ${_ME} tasks 123
+  ${_ME} example:tasks open
+  ${_ME} tasks closed sample/
+  ${_ME} tasks closed demo:456
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} t
+HEREDOC
+}
+_tasks() {
+  _todo "tasks" "${@:-}"
+}
+_alias_subcommand "tasks" "task"
+
+# todo ################################################################### todo
+
+_describe_todo() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} todo add [<notebook>:][<folder-path>/][<filename>] <title>
+              [--description <description>] [--due <date>]
+              [-r (<url> | <selector>) | --related (<url> | <selector>)]
+              [--tags <tag1>,<tag2>...] [--task <title>]...
+  ${_ME} todo do   ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+               [<task-number>]
+  ${_ME} todo undo ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+               [<task-number>]
+  ${_ME} todos [<notebook>:][<folder-path>/] [open | closed]
+  ${_ME} todos tasks ([<notebook>:][<folder-path>/][<id> | <filename> | <description>])
+                 [open | closed]
+
+$(_color_primary "Options"):
+  --description <description>         Description for the todo.
+  --due <date>                        Due date and / or time for the todo.
+  -r, --related (<url> | <selector>)  Related URL or selector.
+  --tags <tag1>,<tag2>...             Comma-separated list of tags.
+  --task <title>                      Task to add to the tasklist.
+
+$(_color_primary "Subcommands"):
+  (default)   List todos.
+  add         Add a new todo.
+              Shortcut Aliases: \`${_ME} todo a\`, \`${_ME} todo +\`
+  do          Mark a todo or task as done.
+  tasks       List tasks in todos, notebooks, folders, and other item.
+  undo        Unmark a todo or task as done.
+
+$(_color_primary "Description"):
+  Manage todos and tasks.
+
+$(_color_primary "Read More:"):
+  ${_README_URL}#-todos
+
+$(_color_primary "See Also"):
+  ${_ME} help do
+  ${_ME} help tasks
+  ${_ME} help undo
+
+$(_color_primary "Examples"):
+  ${_ME} todo add "Example todo title."
+  ${_ME} todo add Example todo title.
+  ${_ME} todo add "Sample title." --tags tag1,tag2 --related demo:567
+  ${_ME} todos
+  ${_ME} todos open
+  ${_ME} todos closed
+  ${_ME} example:todos open
+  ${_ME} todos closed sample/
+
+$(_color_primary "Alias"):
+  ${_ME} todos
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} t
+HEREDOC
+}
+_todo() {
+  # Usage: _todo_get_task <path> <task-number>
+  _todo_get_task() {
+    local _counter=0
+    local _item_path="${1:?}"
+    local _task_number="${2:?}"
+
+    {
+      cat "${_item_path:-}"
+    } | {
+      local         __line=
+      while read -r __line
+      do
+        if [[ "${__line}" =~ (\-\ \[\]|\-\ \[\ \]|\-\ \[\x\]) ]]
+        then
+          _counter="$((_counter+1))"
+
+          if [[ "${_counter:-}" == "${_task_number:-}" ]]
+          then
+            printf "%s\\n" "${__line}"
+
+            return 0
+          fi
+        fi
+      done
+
+      return 1
+    }
+  }
+
+  # Usage: _todo_update_task <path> <number> <action>
+  _todo_update_task() {
+    local _action="${3:?}"
+    local _counter=0
+    local _item_path="${1:?}"
+    local _task_number="${2:?}"
+
+    local _temp_file_path=
+    _temp_file_path="$(_temp file)"
+
+    case "${_action:-}" in
+      do)   local _replacement_box="- [x]" ;;
+      undo) local _replacement_box="- [ ]" ;;
+    esac
+
+    {
+      cat "${_item_path:-}"
+    } | {
+      local         __line=
+      while read -r __line
+      do
+        if [[ "${__line}" =~ (\-\ \[\]|\-\ \[\ \]|\-\ \[\x\]) ]]
+        then
+          _counter="$((_counter+1))"
+
+          if [[ "${_counter:-}" ==  "${_task_number:-}"     ]]
+          then
+            printf "%s\\n" "${__line}"                      \
+              | LC_ALL=C sed                                \
+                  -e "s/- \[\]/${_replacement_box}/"        \
+                  -e "s/- \[ \]/${_replacement_box}/"       \
+                  -e "s/- \[x\]/${_replacement_box}/"
+          else
+            printf "%s\\n" "${__line}"
+          fi
+        else
+          printf "%s\\n" "${__line}"
+        fi
+      done
+
+      if [[ "${_task_number:-}" -gt "${_counter:-}"         ]]
+      then
+        _exit_1 printf "Task not found.\\n"
+      fi
+    } | {
+      cat > "${_temp_file_path}"
+    }
+
+    cat "${_temp_file_path}"  > "${_item_path}"
+
+    [[ -f "${_temp_file_path:?}" ]] && rm -rf "${_temp_file_path:?}"
+  }
+
+  local _action=
+  local _arguments=()
+  local _description=
+  local _due_datetime=
+  local _filter=
+  local _maybe_title_arguments=()
+  local _only_todos=0
+  local _option_title=
+  local _related_identifiers=()
+  local _tag_list=
+  local _tasks=()
+
+  while ((${#}))
+  do
+    case "${1:-}" in
+      --description)
+        _description="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      --due)
+        _due_datetime="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      -r|--via|--also|--related)
+        _related_identifiers+=("$(_option_get_value "${1:-}" "${2:-}")")
+
+        shift
+        ;;
+      --tag*)
+        [[ -n "${_tag_list:-}"  ]] && _tag_list+=" "
+        _tag_list+="$(_option_get_tags "${1}" "${2:-}")"
+
+        shift
+        ;;
+      --task)
+        _tasks+=("$(_option_get_value "${1:-}" "${2:-}")")
+
+        shift
+        ;;
+      --title)
+        _option_title="$(_option_get_value "${1:-}" "${2:-}")"
+
+        shift
+        ;;
+      *)
+        if [[ "${_action:-}" == "add"       ]]
+        then
+          case "${1:-}" in
+            --edit) _arguments+=("${1:-}")  ;;
+            -*)
+              _arguments+=("${1:-}")
+
+              if _option_value_is_present "${2:-}"
+              then
+                _arguments+=("${2:-}")
+
+                shift
+              fi
+              ;;
+            *)
+              _maybe_title_arguments+=("${1:-}")
+              ;;
+          esac
+        fi
+
+        case "${1:-}" in
+          +|a|add)
+            if [[ -z "${_action:-}"     ]]  ||  [[ "${_action:-}" == "tasks" ]]
+            then
+              _action="add"
+            fi
+            ;;
+          c|closed|checked|completed|done|finished)
+            _filter="closed"
+            ;;
+          d|do|close|complete|finish|check)
+            if [[ -z "${_action:-}"     ]]  ||  [[ "${_action:-}" == "tasks" ]]
+            then
+              _action="do"
+            fi
+            ;;
+          l|list)
+            if [[ -z "${_action:-}"     ]]
+            then
+              _action="list"
+            fi
+            ;;
+          o|open|incomplete|unchecked|undone|unfinished)
+            _filter="open"
+            ;;
+          tasks)
+            if [[ -z "${_action:-}"     ]]
+            then
+              _action="tasks"
+            fi
+            ;;
+          todos)
+            _only_todos=1
+            ;;
+          u|undo|uncomplete|unfinish|uncheck)
+            if [[ -z "${_action:-}"     ]]  ||  [[ "${_action:-}" == "tasks" ]]
+            then
+              _action="undo"
+            fi
+            ;;
+          *)
+            [[ "${_action:-}" != "add"  ]]  &&  _arguments+=("${1:-}")
+            ;;
+        esac
+        ;;
+    esac
+
+    shift
+  done
+
+  if [[ -z "${_action:-}" ]]
+  then
+    _action="list"
+  fi
+
+  if [[ "${_SUBCOMMAND:-}"  == "t"      ]]  &&
+     [[ "${_action:-}"      == "list"   ]]  &&
+     ! ((_only_todos))
+  then
+    _action="tasks"
+  fi
+
+  case "${_action:-}" in
+    add)
+      local _first=1
+      local _title=
+
+      local __argument=
+      for   __argument in "${_maybe_title_arguments[@]:-}"
+      do
+        if ((_first))
+        then
+          if [[ "${__argument:-}" =~ (:$|/$) ]]
+          then
+            _arguments+=("${__argument}")
+          else
+            _title+="${__argument}"
+          fi
+
+          _first=0
+        else
+          [[ -n "${_title:-}"       ]] && _title+=" "
+
+          _title+="${__argument}"
+        fi
+      done
+
+      if [[ -n "${_option_title:-}" ]]
+      then
+        if [[ -n "${_title:-}"      ]]
+        then
+          _title="${_option_title} ${_MD} ${_title}"
+        else
+          _title="${_option_title}"
+        fi
+      fi
+
+      if [[ -z "${_title:-}"        ]]
+      then
+        _exit_1 _help "todo"
+      fi
+
+      local _todo_content="# [ ] ${_title:-}${_NEWLINE}"
+
+      if [[ -n "${_due_datetime:-}" ]]
+      then
+        _todo_content+="${_NEWLINE}## Due${_NEWLINE}"
+        _todo_content+="${_NEWLINE}${_due_datetime:-}${_NEWLINE}"
+      fi
+
+      if [[ -n "${_description:-}"  ]]
+      then
+        _todo_content+="${_NEWLINE}## Description${_NEWLINE}"
+        _todo_content+="${_NEWLINE}${_description}${_NEWLINE}"
+      fi
+
+      if ((${#_tasks[@]}))
+      then
+        _todo_content+="${_NEWLINE}## Tasks${_NEWLINE}${_NEWLINE}"
+
+        local __task=
+        for   __task in "${_tasks[@]:-}"
+        do
+          _todo_content+="- [ ] ${__task}${_NEWLINE}"
+        done
+      fi
+
+      if ((${#_related_identifiers[@]}))
+      then
+        _todo_content+="${_NEWLINE}## Related${_NEWLINE}${_NEWLINE}"
+        _todo_content+="$(_build_related_list "${_related_identifiers[@]:-}")"
+        _todo_content+="${_NEWLINE}"
+      fi
+
+      if [[ -n "${_tag_list:-}"         ]]
+      then
+        _todo_content+="${_NEWLINE}## Tags${_NEWLINE}"
+        _todo_content+="${_NEWLINE}${_tag_list}${_NEWLINE}"
+      fi
+
+      _add                              \
+        --content "${_todo_content:-}"  \
+        --type    "todo.md"             \
+        "${_arguments[@]:-}"
+      ;;
+    do|undo)
+      local _selector="${_arguments[0]:-}"
+      local _task_number="${_arguments[1]:-}"
+
+      if [[ -z "${_selector:-}"         ]]
+      then
+        _exit_1 _help "todo"
+      fi
+
+      local _selector_path=
+      _selector_path="$(_show "${_selector:-}" --path 2>/dev/null || :)"
+
+      if [[ -z "${_selector_path:-}"    ]]
+      then
+        _exit_1 printf "Todo not found.\\n"
+      fi
+
+      local _notebook_path=
+      _notebook_path="$(
+        _notebooks show "${_selector:-}" --path 2>/dev/null ||
+          _notebooks current --path 2>/dev/null
+      )"
+
+      if [[ !  "${_selector_path}" =~ todo\.md$   ]]        &&
+         [[ -z "${_task_number:-}"                ]]
+      then
+        _exit_1 printf "Not a todo.\\n"
+      fi
+
+      case "${_action:-}" in
+        do)
+          if [[ -n "${_task_number:-}"  ]]
+          then
+            _todo_update_task "${_selector_path:-}" "${_task_number:-}" "do"
+
+            local _updated_task=
+            _updated_task="$(
+              _todo_get_task "${_selector_path:-}" "${_task_number:-}"
+            )"
+
+            if [[ ! "${_updated_task:-}" =~ ^[[:space:]]*-\ \[x\] ]]
+            then
+              _warn cat "${_selector_path}"
+              _exit_1 printf                      \
+                "Unable to mark done: %s\\n"      \
+                "$(_todos tasks "${_selector:-}" "${_task_number}")"
+            else
+              _todos tasks "${_selector:-}" "${_task_number}"     \
+                | LC_ALL=C sed "3s/^/Done: /"
+
+              _git checkpoint "${_notebook_path}" \
+                "[${_ME}] Task Done: $(_show "${_selector:-}" --relative-path) ${_task_number}"
+            fi
+          else
+            _sed_i -e "s/# \[ \]/# \[x\]/" "${_selector_path}"
+
+            if ! grep -q "# \[x\]" "${_selector_path}"
+            then
+              _exit_1 printf                      \
+                "Unable to mark done: %s\\n"      \
+                "$(_color_primary "${_selector:-}")"
+            else
+              printf "Done: %s\\n" "$(_list "${_selector}")"
+
+              _git checkpoint "${_notebook_path}" \
+                "[${_ME}] Done: $(_show "${_selector:-}" --relative-path)"
+            fi
+          fi
+          ;;
+        undo)
+          if [[ -n "${_task_number:-}"            ]]
+          then
+            _todo_update_task "${_selector_path}" "${_task_number:-}" "undo"
+
+            local _updated_task=
+            _updated_task="$(
+              _todo_get_task "${_selector_path:-}" "${_task_number:-}"
+            )"
+
+            if [[ ! "${_updated_task:-}" =~ ^[[:space:]]*-\ \[\ \]  ]]
+            then
+              _exit_1 printf                      \
+                "Unable to undo: %s\\n"           \
+                "$(_todos tasks "${_selector:-}" "${_task_number}")"
+            else
+              _todos tasks "${_selector:-}" "${_task_number}"       \
+                | LC_ALL=C sed "3s/^/Undone: /"
+
+              _git checkpoint "${_notebook_path}" \
+                "[${_ME}] Task Undone: $(_show "${_selector:-}" --relative-path) ${_task_number}"
+            fi
+          else
+            _sed_i -e "s/# \[x\]/# \[ \]/" "${_selector_path}"
+
+            if ! grep -q "# \[ \]" "${_selector_path}"
+            then
+              _exit_1 printf                      \
+                "Unable to undo: %s\\n"           \
+                "$(_color_primary "${_selector:-}")"
+            else
+              printf "Undone: %s\\n" "$(_list "${_selector}")"
+
+              _git checkpoint "${_notebook_path}" \
+                "[${_ME}] Undone: $(_show "${_selector:-}" --relative-path)"
+            fi
+          fi
+          ;;
+      esac
+      ;;
+    list)
+      {
+        _list "${_arguments[@]:-}" --type todo 2>/dev/null
+      } | {
+        case "${_filter:-}" in
+          closed)
+            LC_ALL=C sed -E -e "/${NB_INDICATOR_TODO:-} .*\[\ \].*/d"
+            ;;
+          open)
+            LC_ALL=C sed -E -e "/${NB_INDICATOR_TODO_DONE:-} .*\[.*x.*\].*/d"
+            ;;
+          *)
+            cat
+            ;;
+        esac
+      } | {
+        local _counter=0
+
+        local         __line=
+        while read -r __line
+        do
+          _counter+=1
+
+          printf "%s\\n" "${__line:-}"
+        done
+
+        if ! ((_counter))
+        then
+          local _empty_message="No"
+
+          if [[ -n "${_filter:-}"     ]]
+          then
+            _empty_message+=" ${_filter:-}"
+          fi
+
+          _exit_1 printf "%s todos found.\\n" "${_empty_message}"
+        fi
+      }
+      ;;
+    tasks)
+      local _selector="${_arguments[0]:-}"
+      local _task_number="${_arguments[1]:-}"
+
+      local _maybe_padded_empty_qualifier=
+
+      if [[ -n "${_filter:-}"         ]]
+      then
+        _maybe_padded_empty_qualifier="${_filter:-} "
+      elif [[ -n "${_task_number:-}"  ]]
+      then
+        _maybe_padded_empty_qualifier="matching "
+      fi
+
+      local _notebook_path=
+      local _selector_path=
+
+      if [[ -n "${_selector:-}"       ]]
+      then
+        _notebook_path="$(
+          _notebooks _show "${_selector:-}" --path 2>/dev/null ||
+            _notebooks current --path
+        )"
+
+        _selector_path="$(
+          _show "${_selector:-}" --path 2>/dev/null || :
+        )"
+      fi
+
+      if [[ -z "${_selector_path:-}"  ]]
+      then
+        _selector_path="$(_notebooks current --path)"
+      fi
+
+      local _selector_is_item=1
+
+      if [[ -d "${_selector_path:-}"  ]]
+      then
+        _selector_is_item=0
+        _selector_path="${_selector_path:-}/"
+      fi
+
+      local _task_closed_patterns=(
+        -e "- \[x\]"
+      )
+      local _task_open_patterns=(
+        -e "- \[ \]"
+        -e "^- \[\]"
+        -e "[[:space:]]- \[\]"
+      )
+
+      local _todo_closed_patterns=(
+        -e "# \[x\]"
+      )
+      local _todo_open_patterns=(
+        -e "# \[ \]"
+        -e "# \[\]"
+      )
+
+      {
+        _list "${_selector_path:-}"   \
+          --error-on-empty            \
+          --no-id                     \
+          --no-indicator              \
+          --path                      \
+          --type md                   \
+          2>/dev/null || printf ""
+      } | {
+        local _first=1
+        local _in_task_list_item=0
+
+        local         __item_path=
+        while read -r __item_path
+        do
+          [[ -z "${__item_path:-}"    ]]    && continue
+          [[ -d "${__item_path:-}"    ]]    && continue
+
+          grep -q                           \
+            "${_task_closed_patterns[@]:-}" \
+            "${_task_open_patterns[@]:-}"   \
+            "${_todo_closed_patterns[@]:-}" \
+            "${_todo_open_patterns[@]:-}"   \
+            "${__item_path}" || continue
+
+          local _item_listing_no_color=
+          _item_listing_no_color="$(
+            _list "${__item_path:-}" --no-color --no-indicator
+          )"
+
+          local _item_selector="${_item_listing_no_color#[}"
+          _item_selector="${_item_selector%%]*}"
+
+          local _is_todo=0
+          local _todo_done=0
+
+          if _file_is_todo "${__item_path:-}"
+          then
+            _is_todo=1
+
+            if [[ "${_item_listing_no_color:-}" =~ \[x\]  ]]
+            then
+              _todo_done=1
+            fi
+          fi
+
+          local _filtered_task_patterns=()
+
+          case "${_filter:-}" in
+            closed) _filtered_task_patterns=("${_task_closed_patterns[@]:-}") ;;
+            open)   _filtered_task_patterns=("${_task_open_patterns[@]:-}")   ;;
+            *)
+              _filtered_task_patterns=(
+                "${_task_closed_patterns[@]:-}"
+                "${_task_open_patterns[@]:-}"
+              )
+              ;;
+          esac
+
+          local _contains_filtered_tasks=0
+
+          if grep -q                          \
+            "${_filtered_task_patterns[@]:-}" \
+            "${__item_path}"
+          then
+            _contains_filtered_tasks=1
+          fi
+
+          local _print_listing=1
+
+          if ! ((_contains_filtered_tasks))
+          then
+            if ! ((_is_todo))
+            then
+              _print_listing=0
+            fi
+
+            case "${_filter:-}" in
+              closed) ((_todo_done)) || _print_listing=0 ;;
+              open)   ((_todo_done)) && _print_listing=0 ;;
+            esac
+
+            if ((_selector_is_item))
+            then
+              _print_listing=1
+            fi
+          fi
+
+          if ! ((_print_listing))
+          then
+            continue
+          fi
+
+          if ((_contains_filtered_tasks))
+          then
+            _in_task_list_item=1
+
+            ((_first)) || printf "\\n"
+          elif ((_in_task_list_item))
+          then
+            _in_task_list_item=0
+
+            ((_first)) || printf "\\n"
+          fi
+
+          _list "${__item_path:-}"
+
+          _first=0
+
+          if ! ((_contains_filtered_tasks)) && ! ((_selector_is_item))
+          then
+            continue
+          fi
+
+          local _info_line_no_color=
+          _info_line_no_color="$(
+            _list "${__item_path:-}" --no-color
+          ) "
+
+          local _extra_length=0
+
+          case "${_info_line_no_color:-}" in
+            *${_NB_INDICATOR_TODO_DONE}*) _extra_length="0"   ;;
+            *${_NB_INDICATOR_TODO}*)      _extra_length="-3"  ;;
+            *)                            _extra_length="-1"  ;;
+          esac
+
+          _print_line "${_info_line_no_color:-}"  \
+            --no-wrap                             \
+            --visible-length "${_extra_length:-0}"
+
+          {
+            grep --color=never          \
+              -e "- \[[[:space:]]*\] " \
+              -e "- \[x\] "            \
+              "${__item_path:-}" || :
+          } | {
+            local _counter=0
+            local _printed_task_counter=0
+
+            local         __task=
+            while read -r __task
+            do
+              _counter="$((_counter+1))"
+
+              local _print_task=0
+
+              case "${_filter:-}" in
+                closed)
+                  if [[ "${__task}" =~ \-\ \[x\]              ]]
+                  then
+                    _print_task=1
+                  fi
+                  ;;
+                open)
+                  if [[ "${__task}" =~ (\-\ \[\ \]|\-\ \[\])  ]]
+                  then
+                    _print_task=1
+                  fi
+                  ;;
+                *)
+                  _print_task=1
+                  ;;
+              esac
+
+              if [[ "${_task_number:-${_counter:-}}" != "${_counter:-}" ]]
+              then
+                _print_task=0
+              fi
+
+              if ((_print_task))
+              then
+                local _formatted_task="${__task#- }"
+                _formatted_task="${_formatted_task//\[x\]/$(_color_brackets "$(_color_primary "x")")}"
+                _formatted_task="${_formatted_task//\[\]/$(_color_brackets " ")}"
+                _formatted_task="${_formatted_task//\[ \]/$(_color_brackets " ")}"
+
+                if [[ -z "${_task_number:-}" ]]
+                then
+                  _wrap off
+                fi
+
+                printf "%s %s"                                          \
+                  "$(_color_brackets "${_item_selector} ${_counter}")"  \
+                  "${_formatted_task}"
+
+                if [[ -z "${_task_number:-}" ]]
+                then
+                  printf '\033[?7h'
+                fi
+
+                printf "\\n"
+
+                _printed_task_counter="$((_printed_task_counter+1))"
+              fi
+            done
+
+            if ! ((_printed_task_counter))
+            then
+              printf "0 %stasks.\\n" "${_maybe_padded_empty_qualifier:-}"
+            fi
+          }
+        done
+      } | {
+        local _printed_line_counter=0
+
+        local         __task_line=
+        while read -r __task_line
+        do
+          printf "%s\\n" "${__task_line:-}"
+          _printed_line_counter="$((_printed_line_counter+1))"
+        done
+
+        if ! ((_printed_line_counter))
+        then
+          _warn printf "0 %stasks.\\n" "${_maybe_padded_empty_qualifier:-}"
+
+          return 1
+        fi
+      }
+      ;;
+  esac
+}
+_alias_subcommand "todo" "t"
+_alias_subcommand "todo" "to"
+_alias_subcommand "todo" "todos"
+
+# unarchive ######################################################### unarchive
+
+_describe_unarchive() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} unarchive [<name>]
+
+$(_color_primary "Description"):
+  Remove "archived" status from the current notebook or notebook <name>.
+
+  This is an alias for \`${_ME} notebooks unarchive\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#archiving-notebooks
+
+$(_color_primary "See Also"):
+  ${_ME} help archive
+  ${_ME} help notebooks
+  ${_ME} help status
+
+$(_color_primary "Examples"):
+  ${_ME} unarchive
+  ${_ME} unarchive example
+
+$(_color_primary "Shortcut Alias"):
+  ${_ME} unar
+HEREDOC
+}
+_unarchive() {
+  _notebooks unarchive "${@:-}"
+}
+_alias_subcommand "unarchive" "unar"
+
+# undo ################################################################### undo
+
+_describe_undo() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} undo ([<notebook>:][<folder-path>/][<id> | <filename> | <title>])
+          [<task-number>]
+
+$(_color_primary "Description"):
+  Mark a todo or task as not done.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#-todos
+
+$(_color_primary "See Also"):
+  ${_ME} help do
+  ${_ME} help tasks
+  ${_ME} help todo
+
+$(_color_primary "Examples"):
+  ${_ME} undo 123
+  ${_ME} undo example:sample/321
+  ${_ME} undo 543 7
+HEREDOC
+}
+_undo() {
+  _todo "undo" "${@:-}"
+}
+_alias_subcommand "undo" "undone"
+
+# unset ################################################################# unset
+
+_describe_unset() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} unset (<name> | <number>)
+
+$(_color_primary "Description"):
+  Unset a setting, returning it to the default value.
+
+  This is an alias for \`${_ME} settings unset\`.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#%EF%B8%8F-set--settings
+
+$(_color_primary "See Also"):
+  ${_ME} help settings
+
+$(_color_primary "Examples"):
+  ${_ME} unset color_primary
+  ${_ME} unset 2
+
+$(_color_primary "Alias"):
+  ${_ME} reset
+HEREDOC
+}
+_unset() {
+  case "${1:-}" in
+    '')     _exit_1   _help "unset" ; return 1 ;;
+    remote) _remote   unset         ; return 0 ;;
+    *)      _settings unset "${@:-}"; return 0 ;;
+  esac
+}
+_alias_subcommand "unset" "reset"
+
+# update ############################################################### update
+
+_describe_update() {
+  cat <<HEREDOC
+$(_color_primary "Usage"):
+  ${_ME} update
+
+$(_color_primary "Description"):
+  Update \`${_ME}\` to the latest version. You will be prompted for
+  your password if administrator privileges are required.
+
+  If \`${_ME}\` was installed using a package manager like npm or
+  Homebrew, use the package manager's upgrade functionality instead
+  of this command.
+
+$(_color_primary "Read More"):
+  ${_README_URL}#installation
+
+$(_color_primary "See Also"):
+  ${_ME} help env
+  ${_ME} help version
+HEREDOC
+}
+_update() {
+  local _current_path=
+  _current_path="${BASH_SOURCE[0]}"
+
+  if [[ -n "${_current_path}" ]]  &&
+     [[ -L "${_current_path}" ]]
+  then
+    _current_path="$(_resolve_symlink "${_current_path}")"
+  fi
+
+  if hash npm 2>/dev/null         &&
+     npm list | grep -q notes.sh  &&
+     [[ "${_current_path}"    =~ (\/node\/|\/node_modules\/)  ]]
+  then # installed with npm
+    cat <<HEREDOC
+Installed with npm. To update, run:
+  npm update -g notes.sh
+HEREDOC
+  elif hash npm 2>/dev/null       &&
+       npm list | grep -q nb.sh   &&
+       [[ "${_current_path}"  =~ (\/node\/|\/node_modules\/)  ]]
+  then # installed with npm
+    cat <<HEREDOC
+Installed with npm. To update, run:
+  npm update -g nb.sh
+HEREDOC
+  elif [[ "${OSTYPE}"         =~ ^darwin  ]] &&
+       [[ "${_current_path}"  =~ Cellar   ]]
+  then
+    cat <<HEREDOC
+Installed with Homebrew. To update, run:
+  brew upgrade nb
+HEREDOC
+  else
+    local _nb_url="${_REPO_RAW_URL}/nb"
+
+    local _temp_file=
+    _temp_file="$(_temp file)"
+
+    if ! _download_from "${_nb_url}" "${_temp_file}"
+    then
+      _exit_1 printf "Unable to download update.\\n"
+    fi
+
+    if [[ "$(_get_hash "${_temp_file}")" != "$(_get_hash "${_current_path}")" ]]
+    then
+      while true
+      do
+        printf "Updating %s in place. " "$(_color_primary "${_ME}")"
+
+        local __yn=
+        IFS='' read -r -e -d $'\n' -p \
+"$(_color_primary "Proceed?") $(_color_brackets "y/N") " __yn
+
+        case "${__yn}" in
+          [Yy]*)
+            break
+            ;;
+          *)
+            printf "Exiting%s\\n" "$(_color_muted "...")"
+
+            exit 0
+            ;;
+        esac
+      done
+
+      if [[ -w "${_current_path}" ]]
+      then
+        cat "${_temp_file}" > "${_current_path}"
+      else
+        cat "${_temp_file}" | sudo tee "${_current_path}" > /dev/null
+      fi
+
+      printf "%s updated to the latest version.\\n" "$(_color_primary "${_ME}")"
+
+      exit 0
+    else
+      printf "Already at the latest version.\\n"
+    fi
+
+    if [[ -n "${_temp_file:-}" ]] && [[ -f "${_temp_file}" ]]
+    then
+      rm "${_temp_file:?}"
+    fi
+  fi
+}
+_alias_subcommand "update" "upgrade"
+
+###############################################################################
+# Call Deferred Command: Group 3                 Call Deferred Command: Group 3
+###############################################################################
+# --------------------------------------------------------------------------- #
+
+_call_deferred_command --group 3
+
+exit 0
diff --git a/bin/ttyper b/bin/ttyper
new file mode 100755
index 0000000..1fcfb22
Binary files /dev/null and b/bin/ttyper differ
diff --git a/fedora/.bashrc b/fedora/.bashrc
index 358fdd8..8ca9f10 100644
--- a/fedora/.bashrc
+++ b/fedora/.bashrc
@@ -32,9 +32,9 @@ unset rc
 
 # PS1=$"\w`whoami`💻`hostname`"$(tput blink)"-> "$(tput sgr0)
 
-
-alias ls='ls -Alh --color=auto'
-alias ls='exa -la'
+alias q='exit'
+# alias ls='ls -Alh  --color=auto'
+alias ls='exa -lah -snew'
 alias di='sudo dnf install'
 alias dud='sudo dnf update -y'
 alias ds='dnf search'
@@ -60,7 +60,6 @@ alias dush='du -sh'
 alias docker='sudo docker'
 alias docker-compose='sudo docker-compose'
 
-
 alias dcud='sudo docker-compose up -d'
 alias dcd='sudo docker-compuse down'
 alias dcp='sudo docker-compose pull'
@@ -77,9 +76,7 @@ downup() {
 }
 
 alias dockerkillall='sudo docker kill $(docker container ls -q)'
-alias univpn='cd ~/; ./hullvpn; cd -'
 alias fld='sudo du -ahx . | sort -rh | head -5' #finds large dirs
-alias f='fuck'
 
 alias untar='tar -zxvf' #extract files from archive
 alias ipe='curl ipinfo.io/ip' #check external ip address
@@ -245,30 +242,11 @@ eval "$(starship init bash)"
 
 export GPG_TTY=/dev/pts/2
 
-export NVM_DIR="$HOME/.nvm"
-[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm
-[ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"  # This loads nvm bash_completion
-. "$HOME/.cargo/env"
 function gi() { curl -sL https://www.toptal.com/developers/gitignore/api/$@ ;}
-source /home/ctome/.dvm/dvm.sh
 export DOTNET_ROOT=$HOME/.dotnet
 export PATH=$PATH:$DOTNET_ROOT:$DOTNET_ROOT/tools
 
-### Bashhub.com Installation.
-### This Should be at the EOF. https://bashhub.com/docs
-if [ -f ~/.bashhub/bashhub.sh ]; then
-    source ~/.bashhub/bashhub.sh
-fi
-
-
-export PYENV_ROOT="$HOME/.pyenv"
-command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"
-eval "$(pyenv init -)"
 
+export PATH=$PATH:$HOME/bin
 export EDITOR="vim"
 
-
-# cohost bot things
-export COOKIE="use the cohost cookie"
-export LENGTH="8"
-export LENGTH="9"