In order to properly deploy phabricator with scap3, `/srv/phab` needs to link to the scap3 deployment repository.
NOTE: A short downtime will be required (schedule a maintenance window)
Steps:
1. [-] {T125851} ([[ https://gerrit.wikimedia.org/r/#/c/269561/ | patch ]] submitted, pending merge)
1. [x] prepare patch to reconfigure phabricator to look for repositories in /srv/repos ^ handled by the above patch
1. [] wait for maintenance window
1. [] Stop puppet, apache2 and phd on `iridium`
1. [] merge aforementioned patch
1. [] move `/srv/phab/repos` to `/srv/repos`
1. [] rename `/srv/phab` to `/srv/old_phab`
1. [] create a symlink named `/srv/phab` pointing to `/srv/deployment/phabricator/deployment`
1. [] test-run with puppet to make sure that it behaves
1. [] double-check that /srv/phab is now pointing to a sane phabricator/deployment tree with the correct tags checked out
1. [] start puppet, phd and apache2