[PureOS] Updates to tracker.pureos.net

Hello,

Today (Friday May 24th) there has been an update to the machine that runs our Phabricator instance. It has had the OS updated to Stretch (Debian 9.9).

There also has been the installation of service files to start phabricator on boot.

I think it might be nice to update phabricator as well the version running now is kinda old: https://tracker.pureos.net/config/version/

I'm happy to upgrade phabricator if it's simply a case of 'git pull' and then launching the apps but perhaps Matthias you know of a right way to do this?

Cheers,

Jeremiah