diff -r 3df0bd706c40 -r 833210fbd900 mercurial/merge.py
--- a/mercurial/merge.py	Fri Dec 27 15:14:19 2019 -0800
+++ b/mercurial/merge.py	Fri Dec 27 13:47:59 2019 -0800
@@ -2635,7 +2635,7 @@
         repo.setparents(pctx.node(), pother)
         repo.dirstate.write(repo.currenttransaction())
         # fix up dirstate for copies and renames
-        copies.graftcopies(repo, wctx, ctx, base)
+        copies.graftcopies(wctx, ctx, base)
     return stats