Mercurial logging to a separate file (#76)
Without this, only Mercurial operations done through hgserve do get logged in gunicorn.log, thanks to our Gunicorn configuration redirection of stderr, but Mercurial operations initiated by the Rails app or any other similar direct means don't.
For instance, if a merge initiated by the Web UI fails, its stderr would be displayed in the UI for a few seconds, and would otherwise not appear in any file.
Even worse (see #76 (closed)), anything dumped into stderr makes GitLab thinks it is an error, and this leaves MRs merged from the UI or the RESTful API in the 'open' state even though the actual merging has been made.
This is orthogonal to the Sentry subsystem.
--HG-- branch : heptapod