That was helpful to me as well.
I also found that in a test deployment, that has been upgraded several times, it was easier to drop my postgres mattermost db and let the chef (omnibus) recipe rebuild my mattermost db, since it contained no real production history that I cared about. That sorted out a lot of weird things that I did to myself while trying to upgrade manually from older 7.x versions to the latest july 2016 version of mattermost in gitlab 8.9