rev-parse: add test script for "--verify"

rev-parse: add test script for "--verify"

This patch documents the current behavior of "git rev-parse --verify".

This command is tested both with and without the "--quiet" and
"--default" options.

This shows some problems with the current behavior that will be fixed
in latter patches:

	- in case of errors, there should be no good rev output on
	stdout,
	- with "--default" one test case is broken

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>