--- a/src/topic/__init__.py	Mon Mar 14 20:18:09 2016 -0400
+++ b/src/topic/__init__.py	Sat Mar 12 15:36:17 2016 +0000
@@ -26,10 +26,12 @@
 from mercurial import patch
 from mercurial import phases
 from mercurial import util
+from mercurial import branchmap
 
 from . import constants
 from . import revset as topicrevset
 from . import destination
+from . import topicmap
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
@@ -92,6 +94,29 @@
         def currenttopic(self):
             return self.vfs.tryread('topic')
 
+        def branchmap(self, topic=True):
+            if not topic:
+                super(topicrepo, self).branchmap()
+            oldbranchcache = branchmap.branchcache
+            oldfilename = branchmap._filename
+            oldcaches =  getattr(self, '_branchcaches', {})
+            try:
+                branchmap.branchcache = topicmap.topiccache
+                branchmap._filename = topicmap._filename
+                self._branchcaches = getattr(self, '_topiccaches', {})
+                branchmap.updatecache(self)
+                self._topiccaches = self._branchcaches
+                return self._topiccaches[self.filtername]
+            finally:
+                self._branchcaches = oldcaches
+                branchmap.branchcache = oldbranchcache
+                branchmap._filename = oldfilename
+
+        def invalidatecaches(self):
+            super(topicrepo, self).invalidatecaches()
+            if '_topiccaches' in vars(self.unfiltered()):
+                self.unfiltered()._topiccaches.clear()
+
     repo.__class__ = topicrepo
     if util.safehasattr(repo, 'names'):
         repo.names.addnamespace(namespaces.namespace(

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/topic/topicmap.py	Sat Mar 12 15:36:17 2016 +0000
@@ -0,0 +1,61 @@
+from mercurial import branchmap
+
+def _filename(repo):
+    """name of a branchcache file for a given repo or repoview"""
+    filename = "cache/topicmap"
+    if repo.filtername:
+        filename = '%s-%s' % (filename, repo.filtername)
+    return filename
+
+oldbranchcache = branchmap.branchcache
+
+class topiccache(oldbranchcache):
+
+    def __init__(self, *args, **kwargs):
+        otherbranchcache = branchmap.branchcache
+        try:
+            # super() call may fail otherwise
+            branchmap.branchcache = oldbranchcache
+            return super(topiccache, self).__init__(*args, **kwargs)
+        finally:
+            branchmap.branchcache = otherbranchcache
+
+    def branchtip(self, branch, topic=''):
+        '''Return the tipmost open head on branch head, otherwise return the
+        tipmost closed head on branch.
+        Raise KeyError for unknown branch.'''
+        if topic:
+            branch = '%s:%s' % (branch, topic)
+        return super(topiccache, self).branchtip(branch)
+
+    def branchheads(self, branch, closed=False, topic=''):
+        if topic:
+            branch = '%s:%s' % (branch, topic)
+        return super(topiccache, self).branchheads(branch, closed=closed)
+
+    def write(self, repo):
+        # The cache key needs to take phase root in account because change to
+        # what is public affect topics. We can't write on disk until we have this.
+        return
+
+    def update(self, repo, revgen):
+        """Given a branchhead cache, self, that may have extra nodes or be
+        missing heads, and a generator of nodes that are strictly a superset of
+        heads missing, this function updates self to be correct.
+        """
+        oldgetbranchinfo = repo.revbranchcache().branchinfo
+        try:
+            def branchinfo(r):
+                info = oldgetbranchinfo(r)
+                topic = ''
+                ctx = repo[r]
+                if ctx.mutable():
+                    topic = ctx.topic()
+                branch = info[0]
+                if topic:
+                    branch = '%s:%s' % (branch, topic)
+                return (branch, info[1])
+            repo.revbranchcache().branchinfo = branchinfo
+            return super(topiccache, self).update(repo, revgen)
+        finally:
+            repo.revbranchcache().branchinfo = oldgetbranchinfo

--- a/tests/test-topic-dest.t	Mon Mar 14 20:18:09 2016 -0400
+++ b/tests/test-topic-dest.t	Sat Mar 12 15:36:17 2016 +0000
@@ -39,6 +39,8 @@
   
   $ hg log -r 'ngtip(.)'
   3 () c_delta
+  $ hg log -r 'default'
+  3 () c_delta
 
 
 multiple heads with topic
@@ -64,6 +66,8 @@
   
   $ hg log -r 'ngtip(.)'
   3 () c_delta
+  $ hg log -r 'default'
+  3 () c_delta
 
 one of the head is a valid tip
 
@@ -72,7 +76,6 @@
   $ echo epsilon >> epsilon
   $ hg add epsilon
   $ hg ci -m "c_epsilon"
-  created new head
   $ hg log -G
   @  6 () c_epsilon
   |
@@ -90,12 +93,16 @@
   
   $ hg log -r 'ngtip(.)'
   6 () c_epsilon
+  $ hg log -r 'default'
+  6 () c_epsilon
 
 merge destination
 =================
 
   $ hg up 'ngtip(default)'
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg up default
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo zeta >> zeta
   $ hg add zeta
   $ hg ci -m "c_zeta"

--- a/tests/test-topic.t	Mon Mar 14 20:18:09 2016 -0400
+++ b/tests/test-topic.t	Sat Mar 12 15:36:17 2016 +0000
@@ -75,7 +75,6 @@
      narf
   $ echo >> fran work >> beta
   $ hg ci -m 'start on fran'
-  created new head
   $ hg co narf
   switching to topic narf
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
@@ -86,6 +85,7 @@
   narf
   $ echo 'narf!!!' >> alpha
   $ hg ci -m 'narf!'
+  created new head
   $ hg log -G
   @  changeset:   6:7c34953036d6
   |  tag:         tip
@@ -287,6 +287,7 @@
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo answer >> alpha
   $ hg ci -m 'Narf is like `zort` or `poit`!'
+  created new head
   $ hg merge narf
   merging alpha
   warning: conflicts while merging alpha! (edit, then use 'hg resolve --mark')
@@ -298,12 +299,16 @@
   (no more unresolved files)
   $ hg topic narf
   $ hg ci -m 'Finish narf'
+  created new head
   $ hg topics
      fran
    * narf
      query
-  $ hg debugnamecomplete
+  $ hg debugnamecomplete # branch:topic here is a buggy side effect
   default
+  default:fran
+  default:narf
+  default:query
   fran
   narf
   query
@@ -381,7 +386,7 @@
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)
-  (run 'hg heads' to see heads, 'hg merge' to merge)
+  (run 'hg heads' to see heads)
   $ hg topics
      fran
    * query
@@ -513,6 +518,7 @@
   $ hg topics --clear
   $ echo fran? >> beta
   $ hg ci -m 'fran?'
+  created new head
   $ hg log -Gr 'draft()'
   @  changeset:   10:4073470c35e1
   |  tag:         tip