stash: recognize "--help" for subcommands
stash: recognize "--help" for subcommands

If you run "git stash --help", you get the help for stash
(this magic is done by the git wrapper itself). But if you
run "git stash drop --help", you get an error. We
cannot show help specific to "stash drop", of course, but we
can at least give the user the normal stash manpage.

Signed-off-by: Jeff King <696e3fbcf235d40b6ea1ebd61c87cbea79d444e7@peff.net>
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