Preview squash commit message before squash and merge
Commit message are very important to lots of Git users and are part of the review process. When using the squash and merge feature the resultant commit message isn't obvious to less experienced Git users that the editable merge message is the message that is used in the merge commit not the squash commit. More simply, the contributing developers may not understand that a merge commit is created which is different to the squash commit (except in fast-foward only mode).
We should make the resultant commits and commit messages clear to the merge request author, reviewer and merger so they can make sure a useful commit history is being created.
Show a preview of the commits that will be added to the target branch
What does success look like, and how can we measure that?
Success should be measured once we have editing and better defaults. LINK TODO