Create a sample of a script for a pre-push hook. The main purpose is to
illustrate how a script may parse the information which is supplied to
such a hook. The script may also be useful to some people as-is for
avoiding to push commits which are marked as a work in progress.
Signed-off-by: Aaron Schrab <aaron@schrab.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>