dir: exit before wildcard fall-through if there is no wildcard

dir: exit before wildcard fall-through if there is no wildcard

The DO_MATCH_LEADING_PATHSPEC had a fall-through case for if there was a
wildcard, noting that we don't yet have enough information to determine
if a further paths under the current directory might match due to the
presence of wildcards.  But if we have no wildcards in our pathspec,
then we shouldn't get to that fall-through case.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>