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Re: [PATCH 3/3] commit: add an option the reword HEAD

From
PWPhillip Wood <phillip.wood123@gmail.com>
Date
Sep 24, 2020, 09:58 UTC
Message-ID
<95cc6fb2-d1bc-11de-febe-c2b5c78a6850@gmail.com>
In-Reply-To
<nycvar.QRO.7.76.6.2009232241140.5061@tvgsbejvaqbjf.bet>
Hi Dscho
On 23/09/2020 21:42, Johannes Schindelin wrote:
Show 78 quoted lines
> Hi Phillip,
> 
> On Wed, 23 Sep 2020, Phillip Wood wrote:
> 
>> On 23/09/2020 11:22, Johannes Schindelin wrote:
>>>
>>> On Mon, 21 Sep 2020, Phillip Wood via GitGitGadget wrote:
>>>
>>>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>>>
>>>> If one notices a typo in the last commit after starting to stage
>>>> changes for the next commit it is useful to be able to reword the last
>>>> commit without changing its contents. Currently the way to do that is
>>>> by specifying --amend --only with no pathspec which is not that
>>>> obvious to new users (so much so that before beb635ca9c ("commit:
>>>> remove 'Clever' message for --only --amend", 2016-12-09) commit
>>>> printed a message to congratulate the user on figuring out how to do
>>>> it). If the last commit is empty one has to pass --allow-empty as well
>>>> even though the contents are not being changed. This commits adds a
>>>> --reword option for commit that rewords the last commit without
>>>> changing its contents.
>>>
>>> I would like to explain the idea I tried to get across when I proposed to
>>> implement support for `reword!` (and `--reword`) because I feel that it
>>> will change the design of this patch in a rather big way.
>>>
>>> First of all, let me explain the scenario in which I long for the
>>> `--reword` option: I maintain several patch thickets, the most obvious one
>>> being Git for Windows' patch thicket that is merge-rebased [*1*] onto
>>> every new Git version.
>>>
>>> At times, I need to adjust a commit message in that patch thicket. It
>>> would be quite wasteful to perform a full merge-rebase, therefore I
>>> typically call `git commit --squash <commit> -c <commit>`, copy the
>>> oneline, paste it after the `squash!` line (surrounded by empty lines), and
>>> then reword the commit message. When the next Git version comes out, I do
>>> a merging-rebase, and when the editor pops up because of that `squash!`
>>> oneline, I remove the now-obsolete version(s) of the commit message.
>>>
>>> Obviously, I have to be careful to either also pass `--only` (which I
>>> somehow managed to learn about only today) or I have to make sure that I
>>> have no staged changes. In practice, I actually specify a bogus path,
>>> which has the same effect as `--only`.
>>>
>>> What I would actually rather have is the `--reword` option: `git commit
>>> --reword <commit>`. In my mind, this would _add_ a new, "empty" commit,
>>> letting me edit the commit message of the specified commit, and using that
>>> as commit message, prefixed with the line `reword! <oneline>`.
>>>
>>> This, in turn, would need to be accompanied by support in the interactive
>>> rebase, to perform the desired reword (which is admittedly quite a bit
>>> different from what the way the todo command `reword` works).
>>>
>>> With that in mind, I would like to caution against the design of your
>>> current patch, because it would slam the door shut on the way I would like
>>> `--reword` to work.
>>
>> I'm keen to have an easy way to reword HEAD and a way to implement your
>> reword! idea.
>>
>> I posted a comment on your gitgitgadget issue about reword! and drop![1]
>> pointing to some patches[2] that implement the reword! idea as amend!. I think
>> we want to be able to  fixup a commit and reword it at the same time which is
>> way I chose the name amend! rather than reword! The implementation currently
>> changes `git commit --amend` to take an optional commit which isn't ideal. I
>> wonder if calling it revise! would be better then we could have `git commit
>> --reword` to reword HEAD and `git commit --revise <commit>` to create a commit
>> that will reword and fixup <commit> when the user runs `git rebase -i
>> --autostash`. fold! is another possibility.
>>
>> I don't think this patch series stops us implementing something for rebase but
>> it would mean we couldn't use the name reword! unless we allow `git commit
>> --reword` to take an optional commit which I'm not that keen on.
>>
>> What do you think to an alternative name?
> 
> I am really worried that the proliferation of confusingly similar options
> will increase Git's reputation for being awfully hard to use.

That is certainly a consideration, but not having a way to easily reword the last commit without changing its contents does not to improve Git's user friendliness. If you only just discovered using --only for rewording it's a fair bet a lot of regular users are unaware of it.

The reason I'm not keen on having --amend or --reword take an optional commit is that I think it is confusing as it means sometimes that option creates a new commit and sometimes it modifies the last commit furthermore passing --reword=HEAD would not reword HEAD but creates a reword! commit.

Rewording the last commit and creating a reword! commit are two different operations so I'm not sure having different options for them is that bad. To me the real confusion is that we end up with 3 options that create different flavors of fixup commits. It would be much nicer if there was a single fixup type that reworded the message as well as fixing up the contents and users just passed `--no-edit` to avoid changing the message. I'd really like to somehow change the semantics of `git commit --fixup/--squash` and the rebase `fixup`/`squash` commands to actually reword the commit. I guess that would mean an opt-in config setting which isn't ideal.

As an aside I'd like to see a new `rewrite` command that wraps the functionality of `rebase -i` so the user does not have to deal with fixups and editing a todo list. `git rewrite amend <commit>` would be equivalent to starting a rebase and marking <commit> as `edit`, the user can then make their changes and run `git rewrite continue` which would finish the rebase or `git rewrite amend <another-commit>` which would either alter the todo list to mark <another-commit> as `edit` or create new entries to rewind the rebase if <another-commit> is not in the todo list and then run `git rebase --continue`. Additionally there would be `reword` and `drop` commands and support for blame so that the user can do all this from an editor which would run `git rewrite amend -L <current-line> <current-file>` to amend the commit that introduced the current line. I've got a nasty scheme prototype of this and I've found it really useful. For an individual developer developing a patch series it is much more convenient to just edit the history directly rather than creating fixup! commits (which often seem to have conflicts when they are applied). It would not address your use where you don't want to be rebasing all the time though.

Best Wishes
Phillip
> Ciao,
> Dscho
>
Previous: Johannes SchindelinNext: Junio C Hamano
Message 14 of 21 in “commit: add an option to reword the last commit”
  1. 0/3 commit: add an option to reword the last commitPhillip Wood via GitGitGadget, Sep 21, 2020
  2. 3/3 commit: add an option the reword HEADPhillip Wood via GitGitGadget, Sep 21, 2020
  3. Eric SunshineSep 21, 2020
  4. Phillip WoodSep 21, 2020
  5. Eric SunshineSep 21, 2020
  6. Junio C HamanoSep 21, 2020
  7. Phillip WoodSep 22, 2020
  8. Junio C HamanoSep 22, 2020
  9. Christian CouderSep 21, 2020
  10. Phillip WoodSep 21, 2020
  11. Johannes SchindelinSep 23, 2020
  12. Phillip WoodSep 23, 2020
  13. Johannes SchindelinSep 23, 2020
  14. Phillip WoodSep 24, 2020
  15. Junio C HamanoSep 24, 2020
  16. 1/3 commit docs: use backquotes when quoting optionsPhillip Wood via GitGitGadget, Sep 21, 2020
  17. 2/3 commit: reorder synopsisPhillip Wood via GitGitGadget, Sep 21, 2020
  18. Junio C HamanoSep 22, 2020
  19. Phillip WoodSep 22, 2020
  20. Junio C HamanoSep 22, 2020
  21. Junio C HamanoSep 21, 2020

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