Re: Aborting git rebase --edit-todo

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Junio & Victor,

On Thu, 3 Sep 2020, Junio C Hamano wrote:

> Victor Toni <victor.toni@gmail.com> writes:
>
> > When doing a commit or choosing what to do for an interactive rebase
> > one can just wipe the whole content of the editor, save and close to
> > abort the action.
> > While doing a `git rebase --edit-todo` I came to the conclusion that I
> > would like to abort the edit and did the same. The final `git rebase
> > --continue` got me rid of the rest of the commits...
> > (Fortunately the "missing" commits could be rescued by looking into
> > `.git/logs/HEAD` so thumbs up for that. )
> > Unfortunately the behaviour of `--edit-todo` was a bit surprising and
> > somehow doesn't feel consistent with the other actions involving an
> > editor.
> >
> > Can this be considered a bug?
>
> It is rather unusual (or almost always wrong) to have a totally
> empty commit log or initial todo list, so it is understandable for
> Git in these situations to stop without doing anything further.
>
> There is no other sensible interpretations of what you are telling
> Git to you by returning an empty buffer---it is extremely unlikely
> you want to create a commit with no log message (without explicitly
> allowing it with --allow-empty-message, the command is likely to
> fail anyway), and it is extremely unlikely that you wanted to just
> reset the tip of the branch to the --onto commit.
>
> Once an interactive rebase session has started and you are given the
> remainder of the steps to edit and you give an empty buffer back,
> however, there are two possible interpretations that are equally
> sensible, I would think.
>
>  - One is that you are signaling that you are done with the rebase
>    session and all the remaining commits are to be discarded.
>
>  - The other is that you botched editing the todo list, and you wish
>    Git to give you another chance to edit it again.
>
> I think the implementor chose the first interpretation.  The "drop"
> insn is a relatively recent invention, and back when it was missing
> from the vocabulary, I do not think it was possible to say " discard
> all the rest" without emptying the todo list, so that design is
> understandable.
>
> Now we have the "drop" verb, the latter interpretation becomes
> possible without making it impossible for the user to express the
> former.  It might be a good idea to
>
>  (1) save away the original before allowing --edit-todo to edit,
>
>  (2) open the editor, and
>
>  (3) when getting an empty buffer back, go back to step (2) using
>      the back-up made in step (1).
>
> Either way, the todo list editor buffer can have additional comment
> instructing what happens when the buffer is emptied.
>
> I have no strong opinion on this one myself.  Deferring to Dscho,
> who may have a lot more to say on the design issue around this
> feature than I do.

First of all, some historical background: the idea that deleting
everything in the todo list aborts the rebase *predates* `git rebase
--edit-todo` by quite a bit, in fact, that idea was implemented in either
the very first version of `git rebase -i` or at least very, very short
thereafter.

This idea came from the fact that deleting the commit message would abort
a `git commit`.

In the meantime, `--edit-todo` is a thing (where this behavior makes a lot
less sense), and `drop` is also a thing.

I agree that it may be a good time to deprecate that behavior, after
introducing a new verb `abort` or something like that.

Ciao,
Dscho