diff -r f2f9bacf0587 -r 0db41eb0a3ac mercurial/manifest.py
--- a/mercurial/manifest.py	Wed Jul 04 12:12:49 2018 -0700
+++ b/mercurial/manifest.py	Sun Jul 01 14:25:44 2018 -0700
@@ -1351,6 +1351,9 @@
     def rev(self, node):
         return self._revlog.rev(node)
 
+    def addgroup(self, deltas, linkmapper, transaction):
+        return self._revlog.addgroup(deltas, linkmapper, transaction)
+
 @interfaceutil.implementer(repository.imanifestrevisionwritable)
 class memmanifestctx(object):
     def __init__(self, manifestlog):