--- a/hgext3rd/evolve/compat.py	Sat Oct 14 19:14:27 2017 +0200
+++ b/hgext3rd/evolve/compat.py	Tue Oct 17 17:35:05 2017 +0200
@@ -7,6 +7,7 @@
 """
 
 from mercurial import (
+    copies,
     context,
     hg,
     obsolete,
@@ -177,3 +178,12 @@
     """function to start a pager in case ui.pager() exists"""
     if util.safehasattr(ui, 'pager'):
         ui.pager(cmd)
+
+def duplicatecopies(repo, wctx, rev, fromrev, skiprev=None):
+    # cannot use anything else until 4.3 support is dropped.
+    assert wctx.rev() is None
+    if copies.duplicatecopies.__code__.co_argcount < 5:
+        # pre 4.4 duplicatecopies compat
+        copies.duplicatecopies(repo, rev, fromrev, skiprev=skiprev)
+    else:
+        copies.duplicatecopies(repo, wctx, rev, fromrev, skiprev=skiprev)