t6120 (describe): check --long properly
t6120 (describe): check --long properly

Existing test checked --long only for exactly tagged commit.  We should
make sure it works sensibly for commits that are not tagged.

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