tag -d: print sha1 of deleted tag

tag -d: print sha1 of deleted tag

Print the sha1 of the deleted tag (in addition to the tag name) so that
one can easily recreate a mistakenly deleted tag:

git tag -d tagname
Deleted tag 'tagname' (was DEADBEEF)
git tag 'tagname' DEADBEEF

We output the previous ref also in the case of forcefully overwriting
tags.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Suggested-by: Jari Aalto <jari.aalto@cante.net>
Helped-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Zoltán Füzesi <zfuzesi@eaglet.hu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>