diff -r aa877860d4d7 -r 21fc747e1bc5 mercurial/unionrepo.py
--- a/mercurial/unionrepo.py	Sat Sep 16 22:55:48 2017 +0900
+++ b/mercurial/unionrepo.py	Fri Sep 15 23:58:45 2017 +0900
@@ -126,7 +126,7 @@
 
     def addrevision(self, text, transaction, link, p1=None, p2=None, d=None):
         raise NotImplementedError
-    def addgroup(self, revs, linkmapper, transaction):
+    def addgroup(self, deltas, transaction, addrevisioncb=None):
         raise NotImplementedError
     def strip(self, rev, minlink):
         raise NotImplementedError