ee-specific-lines-check failed to rebase due to schema conflicts

This is similar to https://gitlab.com/gitlab-org/gitlab-ee/issues/6038 but a different issue. For #6038 (closed) it's something that Git might be able to solve for us, but I am not sure if this one could be technically possible at all.

It won't just happen on schema conflicts, but I put it in the title because that's what we hit into right now and it's the most likely conflict we'll hit into.

This is detailed in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7072#note_99644197

• I think this is what happened. In both cases, CE MR is ahead of EE MR (i.e. CE MR contains commits from CE master which aren't landed on EE MRs yet), thus the script is trying to perform rebase --onto in order to cut off those CE commits. So far everything is expected, but unfortunately, those CE MRs updated the schema version line, and the commits we want to cut off, also updated the schema version line. In other words, the CE MRs are actually based on CE commits which weren't on EE yet. When this happened, indeed it will conflict and there doesn't seem to have a way to resolve this in an automatic way.
• The only way I could think of to solve this will be either resolve the conflict manually (can't do in a script), or port those CE commits to EE MRs. Fortunately, it seems they're already landed on EE master, therefore in this case, we could just update both EE MR with EE master.

I don't think there's anything we could really do (besides making this clear in the job error message), but an issue describing it when we still have this issue should be nice.