[RFC] git-rebase-rewind, nested rebases, remembering stgit

Hello there,

I often find myself doing iterative refactorings, which can lead to
long branches, and while rebasing to edit HEAD~10 realize that I first
need to edit HEAD~20 or to add more commits below that stack.

If you've used stgit when it was a thing, you probably see how it
helped doing that.  While git-rebase has grown to do much more than
stgit in most areas, this is still one area where with a pain point
for me.

Here is a small git-rebase-rewind script I've been using for a few weeks,
starting with my most common use-case: automate worklow "edit git-rebase-todo
to prepend 'pick' commands for the N previous commits, then reset --hard HEAD~N".

As you will see from the new needs revealed by using this script (see in the
script header), I believe it would be valuable to integrate such a mechanism
directly into git-rebase.  Notably, "git rebase -i" itself can be seen as a
form of rewind, and this rewind feature would benefit from all the interactive
rebase work.

Does that sound like reasonable premises ?
-- 
Yann