[PATCH 2 of 4] manifest: adds manifestctx.readfast

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1473809190 25200
#      Tue Sep 13 16:26:30 2016 -0700
# Node ID f5b0e6f84938d661ee32b2303cb17e30a3fbb9df
# Parent  f63c46ee248044f73f51a5edc9c7be419df8ff39
manifest: adds manifestctx.readfast

This adds a copy of manifest.readfast to manifestctx.readfast and adds a
consumer of it. It currently looks like duplicate code, but a future patch
causes these functions to diverge as tree concepts are added to the tree
version.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -824,7 +824,7 @@ class basefilectx(object):
         """
         repo = self._repo
         cl = repo.unfiltered().changelog
-        ma = repo.manifest
+        mfl = repo.manifestlog
         # fetch the linkrev
         fr = filelog.rev(fnode)
         lkr = filelog.linkrev(fr)
@@ -849,7 +849,7 @@ class basefilectx(object):
                 if path in ac[3]: # checking the 'files' field.
                     # The file has been touched, check if the content is
                     # similar to the one we search for.
-                    if fnode == ma.readfast(ac[0]).get(path):
+                    if fnode == mfl[ac[0]].readfast().get(path):
                         return a
             # In theory, we should never get out of that loop without a result.
             # But if manifest uses a buggy file revision (not children of the
diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -993,6 +993,14 @@ class manifestctx(object):
                 self._data = manifestdict(text)
         return self._data
 
+    def readfast(self):
+        rl = self._revlog
+        r = rl.rev(self._node)
+        deltaparent = rl.deltaparent(r)
+        if deltaparent != revlog.nullrev and deltaparent in rl.parentrevs(r):
+            return self.readdelta()
+        return self.read()
+
     def readdelta(self):
         revlog = self._revlog
         if revlog._usemanifestv2:
@@ -1066,6 +1074,14 @@ class treemanifestctx(object):
                     md.setflag(f, fl1)
         return md
 
+    def readfast(self):
+        rl = self._revlog
+        r = rl.rev(self._node)
+        deltaparent = rl.deltaparent(r)
+        if deltaparent != revlog.nullrev and deltaparent in rl.parentrevs(r):
+            return self.readdelta()
+        return self.read()
+
 class manifest(manifestrevlog):
     def __init__(self, opener, dir='', dirlogcache=None):
         '''The 'dir' and 'dirlogcache' arguments are for internal use by
@@ -1149,20 +1165,6 @@ class manifest(manifestrevlog):
         d = mdiff.patchtext(self.revdiff(self.deltaparent(r), r))
         return manifestdict(d)
 
-    def readfast(self, node):
-        '''use the faster of readdelta or read
-
-        This will return a manifest which is either only the files
-        added/modified relative to p1, or all files in the
-        manifest. Which one is returned depends on the codepath used
-        to retrieve the data.
-        '''
-        r = self.rev(node)
-        deltaparent = self.deltaparent(r)
-        if deltaparent != revlog.nullrev and deltaparent in self.parentrevs(r):
-            return self.readdelta(node)
-        return self.read(node)
-
     def readshallowfast(self, node):
         '''like readfast(), but calls readshallowdelta() instead of readdelta()
         '''