diff -r 0e0ac8f09048 -r 6330df9d6393 mercurial/simplemerge.py
--- a/mercurial/simplemerge.py	Tue Aug 29 18:24:51 2017 +0200
+++ b/mercurial/simplemerge.py	Fri Sep 01 10:35:43 2017 -0700
@@ -413,7 +413,7 @@
         result[i] = override
     return result
 
-def simplemerge(ui, localctx, basectx, otherctx, repo=None, **opts):
+def simplemerge(ui, localctx, basectx, otherctx, **opts):
     """Performs the simplemerge algorithm.
 
     The merged result is written into `localctx`.