The same_name() private function wants a quick-and-exact check to
see if they two names are byte-for-byte identical first and then
fall back to the slow path. Use memcmp(3) for the former to make it
clear that we do not want any "name" specific comparison.
Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>