diff -r 1765ed63db40 -r 1541e1a8e87d mercurial/unionrepo.py
--- a/mercurial/unionrepo.py	Mon Apr 09 10:18:10 2018 -0700
+++ b/mercurial/unionrepo.py	Fri Apr 06 22:39:58 2018 -0700
@@ -92,7 +92,7 @@
 
         return mdiff.textdiff(self.revision(rev1), self.revision(rev2))
 
-    def revision(self, nodeorrev, raw=False):
+    def revision(self, nodeorrev, _df=None, raw=False):
         """return an uncompressed revision of a given node or revision
         number.
         """
@@ -163,13 +163,15 @@
     def baserevdiff(self, rev1, rev2):
         return manifest.manifestrevlog.revdiff(self, rev1, rev2)
 
-class unionfilelog(unionrevlog, filelog.filelog):
+class unionfilelog(filelog.filelog):
     def __init__(self, opener, path, opener2, linkmapper, repo):
         filelog.filelog.__init__(self, opener, path)
         filelog2 = filelog.filelog(opener2, path)
-        unionrevlog.__init__(self, opener, self.indexfile, filelog2,
-                             linkmapper)
+        self._revlog = unionrevlog(opener, self.indexfile,
+                                   filelog2._revlog, linkmapper)
         self._repo = repo
+        self.repotiprev = self._revlog.repotiprev
+        self.revlog2 = self._revlog.revlog2
 
     def baserevision(self, nodeorrev):
         return filelog.filelog.revision(self, nodeorrev)