Currently sl import in --partial mode only saves conflicting hunks to .rej files.

It would be great to have something similar to the -3 flag for git am, where the vcs will interactively pop up EDITOR to do 3-way merge resolution of any conflicts that come up when applying a patchset.

This would be similar to what happens if you rebase a stack that conflicts with new changes in trunk, so I don't think it'll be too hard to support. But would be really nice to have when working with patch files and not github.