Merge branch 'sd/cd-p-show-toplevel'

* sd/cd-p-show-toplevel:
  Use $(git rev-parse --show-toplevel) in cd_to_toplevel().
  Add 'git rev-parse --show-toplevel' option.

Documentation/git-rev-parse.txt

@@ -112,6 +112,9 @@ OPTIONS
 --remotes::
 	Show tag refs found in `$GIT_DIR/refs/remotes`.
 
+--show-toplevel::
+	Show the absolute path of the top-level directory.
+
 --show-prefix::
 	When the command is invoked from a subdirectory, show the
 	path of the current directory relative to the top-level