Do not allow ".lock" at the end of any refname component
Allowing any refname component to end with ".lock" is looking for
trouble; for example,
$ git br foo.lock/bar
$ git br foo
fatal: Unable to create '[...]/.git/refs/heads/foo.lock': File exists.
Therefore, do not allow any refname component to end with ".lock".
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>