We solve the problem with rebasing. If it's not part of the main branch then it's not part of history, so rebasing to organize the pull request makes sense.
Rebase works great when you need/want to preserve he revision history. It's probably the ideal process to put in place if you can mandate it.
One thing to keep in mind is that it might lead to a number of merge conflicts that may be difficult or tedious to resolve depending of how the branches have diverged. Merging may avoid these.
One thing to keep in mind is that it might lead to a number of merge conflicts that may be difficult or tedious to resolve depending of how the branches have diverged. Merging may avoid these.