[6.1] Issues renumbering

Created by: sashkab

With 6.1 update I was surprised, that GitLab decided to brake everything and introduce project-related ids for issues, merge requests. This broke a lot of things:

• comments in commits mention old issue numbers;
• issues mention old issue numbers, but they weren't translated to new id;
• same thing with merge requests.

From one point of view, global IDs where issue. From other, when performing upgrades, GitLab could have kept old issue/merge ids for existing projects. I don't understand, why you couldn't have kept IDs same, despite making them project related?

I «fixed» this with UPDATE issues SET iid=id;. Seems to work for me, but will this cause any issues, I'm not aware of? I didn't have to update merge_requests table, but it can be updated same way: UPDATE merge_requests SET iid=id;

Why brake what's working?