diff -r a387b0390082 -r e864353f8c6b mercurial/patch.py
--- a/mercurial/patch.py	Fri Apr 18 13:33:20 2014 +0200
+++ b/mercurial/patch.py	Tue Jan 06 22:55:01 2015 -0800
@@ -1658,7 +1658,6 @@
     if not modified and not added and not removed:
         return []
 
-    revs = None
     hexfunc = repo.ui.debugflag and hex or short
     revs = [hexfunc(node) for node in [ctx1.node(), ctx2.node()] if node]