hg: reimplement branch listings more efficiently

Gives a 10 x speedup - which is noticable on big slow repos where the old
implementation took several seconds.

kallithea/lib/vcs/backends/hg/repository.py

@@ -121,34 +121,16 b' class MercurialRepository(BaseRepository'
         if self._empty:
             return {}
 
-        def _branchtags(localrepo):
-            """
-            Patched version of mercurial branchtags to not return the closed
-            branches
-
-            :param localrepo: locarepository instance
-            """
+        bt = OrderedDict()
+        for bn, _heads, tip, isclosed in sorted(self._repo.branchmap().iterbranches()):
+            if isclosed:
+                if closed:
+                    bt[safe_unicode(bn)] = hex(tip)
+            else:
+                if normal:
+                    bt[safe_unicode(bn)] = hex(tip)
 
-            bt = {}
-            bt_closed = {}
-            for bn, heads in localrepo.branchmap().iteritems():
-                tip = heads[-1]
-                if 'close' in localrepo.changelog.read(tip)[5]:
-                    bt_closed[bn] = tip
-                else:
-                    bt[bn] = tip
-
-            if not normal:
-                return bt_closed
-            if closed:
-                bt.update(bt_closed)
-            return bt
-
-        sortkey = lambda ctx: ctx[0]  # sort by name
-        _branches = [(safe_unicode(n), hex(h),) for n, h in
-                     _branchtags(self._repo).items()]
-
-        return OrderedDict(sorted(_branches, key=sortkey, reverse=False))
+        return bt
 
     @LazyProperty
     def tags(self):