topics: use stack.stack() instead of stack.stackdata()
stack.stackdata() also calls stack.stack() internally. Moreover if we just want
to calculate changesetcount, troubled count, it will be cheap to calculate using
stack.stack rather than stackdata().
This software was downloaded from
https://www.mercurial-scm.org/repo/evolve/
Copyright 2011 Peter Arrenbrecht <peter.arrenbrecht@gmail.com>
Logilab SA <contact@logilab.fr>
Pierre-Yves David <pierre-yves.david@ens-lyon.org>
Patrick Mezard <patrick@mezard.eu>
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