topics: take logic to parse username to a separate function In next patch we will be adding support to `hg stack` to show users, and this logic will be required there too. So let's take it out in a separate function.

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