Hi Ershad,
Apologies for the delayed reply. I highly appreciate you providing detailed steps based on your experience. The upgrade process definitely looks not that easy. We do not have a whole lot of user base, hardly 20 active users and around 10GB of data. If we do not care of merge requests history, but of course the commit history is very important, is it a safer option to spin up gitlab 8.5 version on a different box and port the git repositories over to the new server. I am sure if we were to port the entire old data to the newer version, system will go mad. Another reason of asking this is to implement a cleaner install using chef / ansible provisioning system, so it can make the future upgrades manageable.