Fork, MR and maintainer contributions


I maintain a repository where I enforce a linear history: I need my contributors to rebase their MR.

If the MR origins from a branch of the project itself, I have access to a nice green “Rebase” button to make it easy. But when the MR origins from a fork, even when a contributor checks the “Allow commits from maintainers” option, it seems that I can’t rebase their merge request.

Is this because it is not only pushing new commit but also rewriting history ?

I really like both enforcing a linear history and using forks but it seems hard to use both right now.

Does anyone have a solution for this ?