[PATCH 1 of 2 V3] manifest: allow specifying the revlog filename

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1488414957 28800
#      Wed Mar 01 16:35:57 2017 -0800
# Node ID 9c89185b63f574cad1d4009f6c9dd511a2cba986
# Parent  0bb3089fe73527c64f1afc40b86ecb8dfe7fd7aa
manifest: allow specifying the revlog filename

Previously we had hardcoded the manifest filename to be 00manifest.i. In our
external treemanifest extension, we want to allow writing a treemanifest side by
side with a flat manifest, so we need to be able to store the root revisions at
a different location (in our extension we use 00manifesttree.i).

This patches moves the revlog name to a parameter so we can adjust it.

diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -1132,7 +1132,12 @@ class manifestrevlog(revlog.revlog):
     '''A revlog that stores manifest texts. This is responsible for caching the
     full-text manifest contents.
     '''
-    def __init__(self, opener, dir='', dirlogcache=None):
+    def __init__(self, opener, dir='', dirlogcache=None, indexfile=None):
+        """Constructs a new manifest revlog
+
+        `indexfile` - used by extensions to have two manifests at once, like
+        when transitioning between flatmanifeset and treemanifests.
+        """
         # During normal operations, we expect to deal with not more than four
         # revs at a time (such as during commit --amend). When rebasing large
         # stacks of commits, the number can go up, hence the config knob below.
@@ -1150,12 +1155,16 @@ class manifestrevlog(revlog.revlog):
 
         self._fulltextcache = util.lrucachedict(cachesize)
 
-        indexfile = "00manifest.i"
         if dir:
             assert self._treeondisk, 'opts is %r' % opts
             if not dir.endswith('/'):
                 dir = dir + '/'
-            indexfile = "meta/" + dir + "00manifest.i"
+
+        if indexfile is None:
+            indexfile = '00manifest.i'
+            if dir:
+                indexfile = "meta/" + dir + indexfile
+
         self._dir = dir
         # The dirlogcache is kept on the root manifest log
         if dir: