Allow to mirror branches with different names
Problem to solve
Sometimes you want to have a branch synced up to some remote repository but you can't have it named the same for one reason or another. For example you may want to map GitHub-repo/master to your GitLab-repo/upstream branch.
Currently there is not much control over what and how gets mirrored.
Further details
There is a limited way to control mirrored branches via protected functionality but it's more like a hack and wouldn't help in the situation described above, where the local branch and mirrored remote branch' names differ.
This can be done trivially with git and only lacks GitLab support.
Proposal
Add a way to specify the desired mapping of branches from the remote repository to the local GitLab one.
What does success look like, and how can we measure that?
One can setup the mirroring of some specific branch A to "local"/downstream branch B without the disruption to the rest of the repo.