userheads
http://codereview.appspot.com/6423063/
Could not practically test the edits, because current users implementation is tied to routing middleware, and would require passing some branch-unrelated parameters to middleware.routing.store_branch
Also, not a final implementation, still not sure if all parts of the algorithm, described on 76-89 of http://etherpad.osuosl.org/moin2-bms, are present.