--- a/mercurial/copies.py	Mon May 29 05:57:03 2017 -0700
+++ b/mercurial/copies.py	Mon May 29 05:57:25 2017 -0700
@@ -414,10 +414,10 @@
                                       baselabel='topological common ancestor')
 
     for f in u1u:
-        _checkcopies(c1, c2, f, m1, m2, base, tca, dirtyc1, limit, data1)
+        _checkcopies(c1, c2, f, base, tca, dirtyc1, limit, data1)
 
     for f in u2u:
-        _checkcopies(c2, c1, f, m2, m1, base, tca, dirtyc2, limit, data2)
+        _checkcopies(c2, c1, f, base, tca, dirtyc2, limit, data2)
 
     copy = dict(data1['copy'].items() + data2['copy'].items())
     fullcopy = dict(data1['fullcopy'].items() + data2['fullcopy'].items())
@@ -462,8 +462,8 @@
              'incompletediverge': bothincompletediverge
             }
     for f in bothnew:
-        _checkcopies(c1, c2, f, m1, m2, base, tca, dirtyc1, limit, both1)
-        _checkcopies(c2, c1, f, m2, m1, base, tca, dirtyc2, limit, both2)
+        _checkcopies(c1, c2, f, base, tca, dirtyc1, limit, both1)
+        _checkcopies(c2, c1, f, base, tca, dirtyc2, limit, both2)
     if dirtyc1:
         # incomplete copies may only be found on the "dirty" side for bothnew
         assert not both2['incomplete']
@@ -598,16 +598,13 @@
     except StopIteration:
         return False
 
-def _checkcopies(srcctx, dstctx, f, msrc, mdst, base, tca, remotebase,
-                 limit, data):
+def _checkcopies(srcctx, dstctx, f, base, tca, remotebase, limit, data):
     """
     check possible copies of f from msrc to mdst
 
     srcctx = starting context for f in msrc
     dstctx = destination context for f in mdst
     f = the filename to check (as in msrc)
-    msrc = the source manifest
-    mdst = the destination manifest
     base = the changectx used as a merge base
     tca = topological common ancestor for graft-like scenarios
     remotebase = True if base is outside tca::srcctx, False otherwise
@@ -620,6 +617,8 @@
     once it "goes behind a certain revision".
     """
 
+    msrc = srcctx.manifest()
+    mdst = dstctx.manifest()
     mb = base.manifest()
     mta = tca.manifest()
     # Might be true if this call is about finding backward renames,