send-pack: remove remote reference limit

send-pack: remove remote reference limit

When build a pack for a push we query the remote copy for existant
heads.  These are used to prune unnecessary objects from the pack.
As we receive the remote references in get_remote_heads() we validate
the reference names via check_ref() which includes a length check;
rejecting those >45 characters in size.

This is a miss converted change, it was originally designed to reject
messages which were less than 45 characters in length (a 40 character
sha1 and refs/) to prevent comparing unitialised memory.  check_ref()
now gets the raw length so check for at least 5 characters.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>