bookmarks: introduce listbinbookmarks()

`bookmarks` bundle2 part will work with binary nodes. To avoid unnecessary
conversions between binary and hex nodes let's add `listbinbookmarks()` that
returns binary nodes. For now this function is a copy-paste of
listbookmarks(). In the next patch this copy-paste will be removed.

mercurial/bookmarks.py

@@ -284,6 +284,17 b' def update(repo, parents, node):'
             lockmod.release(tr, lock)
     return update
 
+def listbinbookmarks(repo):
+    # We may try to list bookmarks on a repo type that does not
+    # support it (e.g., statichttprepository).
+    marks = getattr(repo, '_bookmarks', {})
+
+    hasnode = repo.changelog.hasnode
+    for k, v in marks.iteritems():
+        # don't expose local divergent bookmarks
+        if hasnode(v) and ('@' not in k or k.endswith('@')):
+            yield k, v
+
 def listbookmarks(repo):
     # We may try to list bookmarks on a repo type that does not
     # support it (e.g., statichttprepository).