branchmap: store branchcache in a dedicated object

branchmap: store branchcache in a dedicated object

Value and key of branchcache would benefit from being hold by the same object.
Moreover some logic (update, write, validation) could be move on such object.

The creation of this object is the first step toward this move. The result will
clarify branchcache related code and hide most of the detail in the class
itself. This encapsulation will greatly helps implementation of branchcache for
filtered view of the repo.

--- a/mercurial/branchmap.py	Sat Dec 22 01:34:23 2012 +0100
+++ b/mercurial/branchmap.py	Sat Dec 22 01:44:42 2012 +0100
@@ -9,13 +9,13 @@
 import encoding
 
 def read(repo):
-    partial = {}
+    partial = branchcache()
     try:
         f = repo.opener("cache/branchheads")
         lines = f.read().split('\n')
         f.close()
     except (IOError, OSError):
-        return {}, nullid, nullrev
+        return branchcache(), nullid, nullrev
 
     try:
         last, lrev = lines.pop(0).split(" ", 1)
@@ -37,7 +37,7 @@
     except Exception, inst:
         if repo.ui.debugflag:
             repo.ui.warn(str(inst), '\n')
-        partial, last, lrev = {}, nullid, nullrev
+        partial, last, lrev =  branchcache(), nullid, nullrev
     return partial, last, lrev
 
 def write(repo, branches, tip, tiprev):
@@ -143,3 +143,7 @@
         update(repo, partial, ctxgen)
     repo._branchcache = partial
     repo._branchcachetip = tip
+
+class branchcache(dict):
+    """A dict like object that hold branches heads cache"""
+

--- a/mercurial/discovery.py	Sat Dec 22 01:34:23 2012 +0100
+++ b/mercurial/discovery.py	Sat Dec 22 01:44:42 2012 +0100
@@ -193,8 +193,9 @@
 
     # D. Update newmap with outgoing changes.
     # This will possibly add new heads and remove existing ones.
-    newmap = dict((branch, heads[1]) for branch, heads in headssum.iteritems()
-                  if heads[0] is not None)
+    newmap = branchmap.branchcache((branch, heads[1])
+                                 for branch, heads in headssum.iteritems()
+                                 if heads[0] is not None)
     branchmap.update(repo, newmap, missingctx)
     for branch, newheads in newmap.iteritems():
         headssum[branch][1][:] = newheads

--- a/mercurial/localrepo.py	Sat Dec 22 01:34:23 2012 +0100
+++ b/mercurial/localrepo.py	Sat Dec 22 01:44:42 2012 +0100
@@ -666,7 +666,7 @@
         '''returns a dictionary {branch: [branchheads]}'''
         if self.changelog.filteredrevs:
             # some changeset are excluded we can't use the cache
-            bmap = {}
+            bmap = branchmap.branchcache()
             branchmap.update(self, bmap, (self[r] for r in self))
             return bmap
         else:
@@ -2495,7 +2495,7 @@
                 if rbheads:
                     rtiprev = max((int(self.changelog.rev(node))
                             for node in rbheads))
-                    self._branchcache = rbranchmap
+                    self._branchcache = branchmap.branchcache(rbranchmap)
                     rtipnode = self._branchcachetip = self[rtiprev].node()
                     branchmap.write(self, self._branchcache, rtipnode, rtiprev)
             self.invalidate()