{{[[TODO]]}} i also realized that `new-branch-end` (or `branch-end-new`, if `ben` is good for shortname) is a little subtle -- if you're inserting a new branch (or branches) __between 2 existing ones__ (always the case here) in the same rebase, if you e.g. have normal ordering of 1., 2., 3., etc., now you'd have to add another level, e.g. if inserting between 2. and 3., it now becomes: 1., 2.1, 2.2, 3. perhaps we don't need to modify the existing 2. into 2.1, or actually, perhaps it should be 1., 2., 3.1, 3.2, because we're taking & splitting commits from 3., not from 2. (since a number marks the __end__, __not__ the beginning.). again, how do we retain e.g. github comments here? not worth to focus on right now, but good to keep in mind.