topics: fix `hg stack` in case of split This patch fixes the behaviour of hg stack which throws an error in some cases when there are multiple successors. The case of divergence is not handled yet.

syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
^tests/.*\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes