diff -r 362f6f651b2e -r fa54f7ade491 mercurial/manifest.py
--- a/mercurial/manifest.py	Tue Nov 08 08:03:43 2016 -0800
+++ b/mercurial/manifest.py	Tue Nov 08 08:03:43 2016 -0800
@@ -1320,14 +1320,14 @@
             mancache[node] = m
         return m
 
-    def add(self, m, transaction, link, p1, p2, added, removed):
-        return self._revlog.add(m, transaction, link, p1, p2, added, removed)
-
 class memmanifestctx(object):
     def __init__(self, repo):
         self._repo = repo
         self._manifestdict = manifestdict()
 
+    def _revlog(self):
+        return self._repo.manifestlog._revlog
+
     def new(self):
         return memmanifestctx(self._repo)
 
@@ -1339,6 +1339,10 @@
     def read(self):
         return self._manifestdict
 
+    def write(self, transaction, link, p1, p2, added, removed):
+        return self._revlog().add(self._manifestdict, transaction, link, p1, p2,
+                                  added, removed)
+
 class manifestctx(object):
     """A class representing a single revision of a manifest, including its
     contents, its parent revs, and its linkrev.
@@ -1430,6 +1434,9 @@
         self._dir = dir
         self._treemanifest = treemanifest()
 
+    def _revlog(self):
+        return self._repo.manifestlog._revlog
+
     def new(self, dir=''):
         return memtreemanifestctx(self._repo, dir=dir)
 
@@ -1441,6 +1448,10 @@
     def read(self):
         return self._treemanifest
 
+    def write(self, transaction, link, p1, p2, added, removed):
+        return self._revlog().add(self._treemanifest, transaction, link, p1, p2,
+                                  added, removed)
+
 class treemanifestctx(object):
     def __init__(self, repo, dir, node):
         self._repo = repo