rebase and merge

Our engineering team has recently migrated our codebase from gerrit to gitlab. So far we have been very pleased with gitlab, but there is one loss of functionality that has been very painful for our team and productivity.

Gerrit defaults enable "rebase and merge" with fast-forward merges when there are no conflicts.

This is not available in gitlab, any change to master since feature branch created/rebased requires another rebase (with another pipeline run). Some of our pipelines for legacy projects run quite long, over 30-45 minutes. Some of those same legacy projects are also quite busy resulting in a situations where a merge request can require several rebases (waiting hours) before it can be merged.

We would be thrilled (!!!) if something like what is being discussed in #895 would be made available.