Re: How to implement the "amend!" commit ?

[Taylor Blau <me@ttaylorr.com>]

Hi Chavri,

On Wed, Jan 13, 2021 at 06:45:25AM +0530, Charvi Mendiratta wrote:
> Hi Everyone,
>
> Implementing "amend!" commit would be an alternative to the
> fixup!/squash! commit that addresses the issue as opened here[1]. Also
> the related patches[2], adds the options to `fixup` command in
> interactive rebase and supports the "amend!" commit upon
> `--autosquash`. Next, after discussing with Phillip and Christian,
> there could be 3 possibilities to implement the "amend!" commit (UI):

To make sure that I'm understanding correctly:

  - Your series in [2] teaches the rebase directive 'fixup' two new
    options: -C, and -c. Unlike of the option-less 'fixup' command,
    these new options use the message from the fixup commit instead of
    the original.

    If I'm understanding correctly, this old-style sequence:

        pick aaaaaaaaaa original
        fixup bbbbbbbbbb fixup! new
        exec git commit --amend -C bbbbbbbbbb --no-edit

    should be equivalent to this one:

        pick aaaaaaaaaa original
        fixup -C bbbbbbbbbb fixup! new

  - Separate from that, you are asking about how to implement an
    "amend!" commit which would behave exactly as the 'fixup -C' variant
    that you are proposing.

We should clarify what you mean by "implement". I take it from the
remainder of your message that you are really asking about how we should
_expose_ this new 'fixup -C' command to users.

> Firstly, the `--fixup=<commit>` to have option like,
> `--fixup=reword/amend:<commit>`
>
> So, `git commit --fixup` can have 3 options:
>
> a) `--fixup=<commit>`, work as of now, make fixup! commit.
> b) `--fixup=amend:<commit>`, make "amend!" commit, takes changes and
> also opens the editor for a new message (Here it adds a new message to
> amend! commit's message body and upon autosquash it will fixup up the
> content and reword the original commit message i.e replaces the
> original commit message with the "amend!" commit's message).
> c) `--fixup=reword:<commit>`, makes (empty) "amend!" commit, do not
> take changes and open the editor for a new message(Here, upon
> autosquash it will just reword the original commit message).

I think that this trio is a good path forward, but...
`--fixup` behaving as it always has, which is good. Then it makes
`--fixup=amend:<commit>` insert a 'fixup -C', and `--fixup=reword:<...>`
insert a 'fixup -c'.

> Secondly,
> As an alternative to above, we can use `--fixup=<commit> --amend` and
> `--fixup=<commit> --reword`.

...I think that this option is even better.

Here '--fixup=<commit>' with '--amend' inserts a 'fixup -C' sequencer
comamnd, and using the same instead with '--reword' inserts a 'fixup -c'
sequencer command.

This is clear to me because '--fixup' makes a commit that is interpreted
separately by the sequencer machinery, so any options that are given
with it seem to indicate that they will alter how the sequencer
interprets the resulting commit, which makes sense.

Of course, it's all somewhat confusing because you have to keep track of
which are options to 'git commit', and which are sequencer commands, but
I like the direction that you're going in here.

> Next,
> To use only, `--fixup=<commit> --edit` to make the "amend!" commit.

I don't think that this is as good a direction forward.

> Also as discussed earlier[3] we are avoiding the use of additional
> options like `git commit --amend=<commit>` inorder to avoid confusion
> of doing similar things in different ways. So, I wonder which could be
> the best way to proceed with or if any other way to implement "amend!"
> commit ?
>
> Thanks and Regards,
> Charvi
>
> [1] https://github.com/gitgitgadget/git/issues/259
> [2] https://lore.kernel.org/git/20210108092345.2178-1-charvi077@gmail.com/
> [3] https://lore.kernel.org/git/95cc6fb2-d1bc-11de-febe-c2b5c78a6850@gmail.com/

Thanks,
Taylor