--- a/mercurial/copies.py	Thu Nov 01 11:24:45 2018 -0700
+++ b/mercurial/copies.py	Thu Nov 01 13:20:12 2018 -0700
@@ -219,6 +219,7 @@
 def _forwardcopies(a, b, match=None):
     """find {dst@b: src@a} copy mapping where a is an ancestor of b"""
 
+    match = a.repo().narrowmatch(match)
     # check for working copy
     if b.rev() is None:
         if a == b.p1():