Well, here goes.
I really should've tested it more. Seems like cherry-picking commits from my big branch missed some important fixes later on.
Server has been moved and upgraded to a much newer gitlab version, as you see. Your ssh client will very likely complain that the host keys have changed. This is normal, they have.
I really should've tested it more. Seems like cherry-picking commits from my big branch missed some important fixes later on.