bash-completion: Add comments to remind about required arguments
bash-completion: Add comments to remind about required arguments

Add a few simple comments above commands that take arguments. These
comments are meant to remind developers of potential problems that
can occur when the script is sourced on systems with "set -u." Any
function which requires arguments really ought to be called with
explicit arguments given.

Also adds a #!bash to the top of bash completions so that editing
software can always identify that the file is of sh type.

Signed-off-by: Ted Pavlic <46ab578353b0478abc71fa54796a76c10bbe41a8@tedpavlic.com>
Acked-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git