diff --git a/mercurial/branchmap.py b/mercurial/branchmap.py
--- a/mercurial/branchmap.py
+++ b/mercurial/branchmap.py
@@ -167,6 +167,8 @@ class branchcache(dict):
             return False
 
     def _branchtip(self, heads):
+        '''Return tuple with last open head in heads and false,
+        otherwise return last closed head and true.'''
         tip = heads[-1]
         closed = True
         for h in reversed(heads):
@@ -177,6 +179,9 @@ class branchcache(dict):
         return tip, closed
 
     def branchtip(self, branch):
+        '''Return the tipmost open head on branch head, otherwise return the
+        tipmost closed head on branch.
+        Raise KeyError for unknown branch.'''
         return self._branchtip(self[branch])[0]
 
     def branchheads(self, branch, closed=False):
diff --git a/mercurial/help/revisions.txt b/mercurial/help/revisions.txt
--- a/mercurial/help/revisions.txt
+++ b/mercurial/help/revisions.txt
@@ -14,9 +14,9 @@ of exactly one full-length identifier.
 
 Any other string is treated as a bookmark, tag, or branch name. A
 bookmark is a movable pointer to a revision. A tag is a permanent name
-associated with a revision. A branch name denotes the tipmost revision
-of that branch. Bookmark, tag, and branch names must not contain the ":"
-character.
+associated with a revision. A branch name denotes the tipmost open branch head
+of that branch - or if they are all closed, the tipmost closed head of the
+branch. Bookmark, tag, and branch names must not contain the ":" character.
 
 The reserved name "tip" always identifies the most recent revision.
 
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -655,7 +655,8 @@ class localrepository(object):
         return sorted(marks)
 
     def branchmap(self):
-        '''returns a dictionary {branch: [branchheads]}'''
+        '''returns a dictionary {branch: [branchheads]} with branchheads
+        ordered by increasing revision number'''
         branchmap.updatecache(self)
         return self._branchcaches[self.filtername]
 
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -723,7 +723,8 @@ Test a help topic
   
       Any other string is treated as a bookmark, tag, or branch name. A bookmark
       is a movable pointer to a revision. A tag is a permanent name associated
-      with a revision. A branch name denotes the tipmost revision of that
+      with a revision. A branch name denotes the tipmost open branch head of
+      that branch - or if they are all closed, the tipmost closed head of the
       branch. Bookmark, tag, and branch names must not contain the ":"
       character.
   
@@ -1878,9 +1879,9 @@ Dish up an empty repo; serve it cold.
   <p>
   Any other string is treated as a bookmark, tag, or branch name. A
   bookmark is a movable pointer to a revision. A tag is a permanent name
-  associated with a revision. A branch name denotes the tipmost revision
-  of that branch. Bookmark, tag, and branch names must not contain the &quot;:&quot;
-  character.
+  associated with a revision. A branch name denotes the tipmost open branch head
+  of that branch - or if they are all closed, the tipmost closed head of the
+  branch. Bookmark, tag, and branch names must not contain the &quot;:&quot; character.
   </p>
   <p>
   The reserved name &quot;tip&quot; always identifies the most recent revision.