support forcing conflicts to allow interactive editing

[Juanma Barranquero]

This is similar to "#243150 support -i flag as per git", though not identical (I think).

The idea is having a flag for rebase to force each commit (or perhaps specify which ones) to be considered a conflict, so the user can interactively edit and change it.

The use case is when a bunch of small patches are maintained in a branch and periodically rebased (without conflicts), but you just need to adjust each one once before finally pushing them to the master branch.

This could help, for example, in Emacs. The final --force-conflict (or whatever the name) would allow the developer to stop the rebase and update the dates in the ChangeLog files just before the final push.

[Jelmer Vernooij (jelmer)]

I agree this would bee a nice thing to support.

This shouldn't be an option on rebase though imho, I think it's rather something that belongs on e.g. a filter-branch (which would also be appropriate for the bzr-rewrite plugin).