copies: use intersectmatchers() in non-merge p1 optimization

This enables the optimization introduced by d4247c306d82 for non-rebase cases.
Before, the match couldn't be narrowed if it was e.g. alwaysmatcher.

The logic is copied from bd56bea5ecf8.

mercurial/copies.py

@@ -10,6 +10,7 b' from __future__ import absolute_import'
 import heapq
 
 from . import (
+    match as matchmod,
     node,
     pathutil,
     scmutil,
@@ -182,8 +183,9 b' def _forwardcopies(a, b, match=None):'
     # optimization, since the ctx.files() for a merge commit is not correct for
     # this comparison.
     forwardmissingmatch = match
-    if not match and b.p1() == a and b.p2().node() == node.nullid:
-        forwardmissingmatch = scmutil.matchfiles(a._repo, b.files())
+    if b.p1() == a and b.p2().node() == node.nullid:
+        filesmatcher = scmutil.matchfiles(a._repo, b.files())
+        forwardmissingmatch = matchmod.intersectmatchers(match, filesmatcher)
     missing = _computeforwardmissing(a, b, match=forwardmissingmatch)
 
     ancestrycontext = a._repo.changelog.ancestors([b.rev()], inclusive=True)