match_refs: search ref list tail internally

match_refs: search ref list tail internally

Avoid code duplication by moving list tail search to match_refs().

This does not change the semantics, except for http-push, which now inserts
to the front of the ref list in order to get rid of the global remote_tail.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>