manifest: remove manifest.add and add memmfctx.write

This removes one more dependency on the manifest class by moving the write
functionality onto the memmanifestctx classes and changing the one consumer to
use the new API.

By moving the write path to a manifestctx, we now give the individual manifests
control over how they're read and serialized. This will be useful in developing
new manifest formats and storage systems.

mercurial/localrepo.py

@@ -1700,9 +1700,13 b' class localrepository(object):'
             trp = weakref.proxy(tr)
 
             if ctx.files():
-                m1 = p1.manifest()
-                m2 = p2.manifest()
-                m = m1.copy()
+                m1ctx = p1.manifestctx()
+                m2ctx = p2.manifestctx()
+                mctx = m1ctx.copy()
+
+                m = mctx.read()
+                m1 = m1ctx.read()
+                m2 = m2ctx.read()
 
                 # check in files
                 added = []
@@ -1736,9 +1740,9 b' class localrepository(object):'
                 drop = [f for f in removed if f in m]
                 for f in drop:
                     del m[f]
-                mn = self.manifestlog.add(m, trp, linkrev,
-                                          p1.manifestnode(), p2.manifestnode(),
-                                          added, drop)
+                mn = mctx.write(trp, linkrev,
+                                p1.manifestnode(), p2.manifestnode(),
+                                added, drop)
                 files = changed + removed
             else:
                 mn = p1.manifestnode()

mercurial/manifest.py

@@ -1320,14 +1320,14 b' class manifestlog(object):'
             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 b' class memmanifestctx(object):'
     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 b' class memtreemanifestctx(object):'
         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 b' class memtreemanifestctx(object):'
     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