copies: always respect matcher arg to _forwardcopies()

The function would ignore the matcher if the dirstate copies were
requested. It doesn't matter in practice because all callers used the
returned map only for looking up specific files from and those files
had already been filtered by the matcher (AFACT). Still, it's a little
confusing, so let's make it clearer by respecting the matcher in this
case too.

Differential Revision: https://phab.mercurial-scm.org/D1695

mercurial/copies.py

@@ -139,11 +139,11 b' def _tracefile(fctx, am, limit=-1):'
         if limit >= 0 and f.linkrev() < limit and f.rev() < limit:
             return None
 
-def _dirstatecopies(d):
+def _dirstatecopies(d, match=None):
     ds = d._repo.dirstate
     c = ds.copies().copy()
     for k in list(c):
-        if ds[k] not in 'anm':
+        if ds[k] not in 'anm' or (match and not match(k)):
             del c[k]
     return c
 
@@ -166,7 +166,7 b' def _forwardcopies(a, b, match=None):'
         b = w.p1()
         if a == b:
             # short-circuit to avoid issues with merge states
-            return _dirstatecopies(w)
+            return _dirstatecopies(w, match)
 
     # files might have to be traced back to the fctx parent of the last
     # one-side-only changeset, but not further back than that
@@ -202,7 +202,7 b' def _forwardcopies(a, b, match=None):'
 
     # combine copies from dirstate if necessary
     if w is not None:
-        cm = _chain(a, w, cm, _dirstatecopies(w))
+        cm = _chain(a, w, cm, _dirstatecopies(w, match))
 
     return cm