diff -r f78eadbb5769 -r f9a80054dd3c mercurial/copies.py
--- a/mercurial/copies.py	Wed May 20 00:43:23 2009 +0200
+++ b/mercurial/copies.py	Wed May 20 00:52:46 2009 +0200
@@ -106,7 +106,7 @@
         return {}, {}
 
     # avoid silly behavior for parent -> working dir
-    if c2.node() == None and c1.node() == repo.dirstate.parents()[0]:
+    if c2.node() is None and c1.node() == repo.dirstate.parents()[0]:
         return repo.dirstate.copies(), {}
 
     limit = _findlimit(repo, c1.rev(), c2.rev())