mq: use exact matching in the second dirstate walking for efficiency of 'qnew'

'hg qnew' with pattern/-I/-X creates matching object with them, and
uses it twice for 'dirstate.walk()': via 'repo.status()' and
'repo.commit()'.

this may cause full manifest scan in the second 'dirstate.walk()',
even though mq already knows complete target filenames at the first
'dirstate.walk()'.

this patch creates exact matching object also in this case, and use it
at 'repo.commit()' invocation to avoid full manifest scan in the
second 'dirstate.walk()'.

even though 'inclsubs' is added to 'pats' for original matching
object, it is also passed to exact matching object, because
subrepositories are deleted from result of 'dirstate.walk()' at the
end of it.

hgext/mq.py

@@ -962,7 +962,7 b' class queue(object):'
             m, a, r, d = repo.status(match=match)[:4]
         else:
             m, a, r, d = self.checklocalchanges(repo, force=True)
-            match = scmutil.matchfiles(repo, m + a + r + inclsubs)
+        match = scmutil.matchfiles(repo, m + a + r + inclsubs)
         if len(repo[None].parents()) > 1:
             raise util.Abort(_('cannot manage merge changesets'))
         commitfiles = m + a + r