git-stash: Make examples clearer

- Difference between a stash name and a stash message was not clear. For
  example, you cannot do:

      $ git stash save foo
      $ git stash apply foo
      fatal: ambiguous argument 'foo': unknown revision or path not in
      the working tree.

- Difference between stash `apply` and `pop` was not clear
- Make it clearer that all `apply`, `pop` and `drop` can take an
  optional stash name, and that the default name is `stash@{0}`

pages/common/git-stash.md

@@ -4,24 +4,24 @@
 
 - Stash current changes (except new files):
 
-`git stash save {{optional_stash_name}}`
+`git stash save {{optional_stash_message}}`
 
 - Include new files in the stash (leaves the index completely clean):
 
-`git stash save -u {{optional_stash_name}}`
+`git stash save -u {{optional_stash_message}}`
 
 - List all stashes:
 
 `git stash list`
 
-- Re-apply the latest stash:
+- Apply a stash (default is the latest, named stash@{0}):
 
-`git stash pop`
+`git stash apply {{optional_stash_name_or_commit}}`
 
-- Re-apply a stash by name:
+- Apply a stash (default is stash@{0}), and remove it from the list if applying doesn't cause conflicts:
 
-`git stash apply {{stash_name}}`
+`git stash pop {{optional_stash_name}}`
 
-- Drop a stash by an index:
+- Drop a stash (default is stash@{0}):
 
-`git stash drop stash@{index}`
+`git stash drop {{optional_stash_name}}`