git-help: add page (#4019)

common/pages/git-help.md

@@ -0,0 +1,24 @@
+# git help
+
+> Display help information about git.
+> More information: <https://git-scm.com/docs/git-help>.
+
+- Display help about a specific git subcommand:
+
+`git help {{subcommand}}`
+
+- Display help about a specific git subcommand in a web browser: 
+
+`git help --web {{subcommand}}`
+
+- Display a list of all available git subcommands:
+
+`git help --all`
+
+- List the available guides:
+
+`git help --guide`
+
+- List all possible configuration variables:
+
+`git help --config`