Re: [RFC PATCH] rebase: implement --rewind

> This is fundamentally --edit-todo, except that we first prepend the
> already applied commits and reset back to `onto`. This is useful when
> one finds that a prior change needs (further) modifications.
>
> This patch implements "flat" rewind, that is, once the todo edit has
> been committed, one can abort only the complete rebase. The pre-rewind
> position is marked with a `break` command (these pile up when rewinding
> multiple times; the user is expected to clean them up as necessary).
>
> An alternative to that would be "nested" rewind, where one can return to
> the pre-rewind state even after committing the todo edit. However, this:
> - would add somewhat significant complexity due to having to maintain a
>   stack of todos and HEADs
> - would be mildly confusing to use due to needing to track the state of
>   the stack. One could simplify this somewhat by hiding the rest of the
>   previous todo before nesting, but this would be somewhat limiting in
>   turn (one might want to defer a factored out hunk, and stashing it is
>   not necessarily the most elegant way to do it).
> - would be of somewhat limited usefulness, speaking from experience
>
> This patch leaves transitive resolution of rewritten-list to the
> consumer. This is probably a bad idea.
> Somewhat related to that, --update-refs isn't properly handled yet.