Re: [PATCH 1/4] sequencer: Do not require `allow_empty` for redundant commit options

["Kristoffer Haugsbakk" <code@khaugsbakk.name>]

Initial discussion (proposal): https://lore.kernel.org/git/CAHPHrSevBdQF0BisR8VK=jM=wj1dTUYEVrv31gLerAzL9=Cd8Q@mail.gmail.com/

On Fri, Jan 19, 2024, at 06:59, brianmlyles@gmail.com wrote:
> From: Brian Lyles <brianmlyles@gmail.com>
>
> Previously, a consumer of the sequencer that wishes to take advantage of
> either the `keep_redundant_commits` or `drop_redundant_commits` feature
> must also specify `allow_empty`.

Previously to this change? It is preferred to describe what the code
currently does without this change in the present tense.[1] The change
itself uses the imperative mood.[2]

† 1: SubmittingPatches, “The problem statement that describes the status
    quo …”
† 2: SubmittingPatches, “Describe your changes in imperative mood […] as
    if you are giving orders to the codebase to change its behavior.”

> The only consumer of `drop_redundant_commits` is `git-rebase`, which
> already allows empty commits by default and simply always enables
> `allow_empty`. `keep_redundant_commits` was also consumed by
> `git-cherry-pick`, which had to specify `allow-empty` when
> `keep_redundant_commits` was specified in order for the sequencer's
> `allow_empty()` to actually respect `keep_redundant_commits`.
>
> The latter is an interesting case: As noted in the docs, this means that
> `--keep-redundant-commits` implies `--allow-empty`, despite the two
> having distinct, non-overlapping meanings:

Huh. I’m used to the git-rebase(1) behavior and I definitely would have
just assumed that git-cherry-pick(1) behaves the same. :) Nice catch.

> This implication of `--allow-empty` therefore seems incorrect: One
> should be able to keep a commit that becomes empty without also being
> forced to pick commits that start as empty. However, today, the
> following series of commands would result in both the commit that became
> empty and the commit that started empty being picked despite only
> `--keep-redundant-commits` being specified:

Nice description of the current problem. All of it.

> In a future commit, an `--empty` option will be added to
> `git-cherry-pick`, meaning that `drop_redundant_commits` will be
> available in that command. For that to be possible with the current
> implementation of the sequencer's `allow_empty()`, `git-cherry-pick`
> would need to specify `allow_empty` with `drop_redundant_commits` as
> well, which is an even less intuitive implication of `--allow-empty`: in
> order to prevent redundant commits automatically, initially-empty
> commits would need to be kept automatically.
>
> Instead, this commit rewrites the `allow_empty()` logic to remove the
> over-arching requirement that `allow_empty` be specified in order to
> reach any of the keep/drop behaviors. Only if the commit was originally
> empty will `allow_empty` have an effect.

In general, phrases like “this commit <verb>” or “this patch <verb>” can
be rewritten to the “commanding” style (see [2]).[3] But here you’re
starting a new paragraph after having talked about a future commit, so
using the commanding style might be stylistically difficult to pull off
without breaking the flow of the text.

And “this [commit][patch] <verb>” seems to be used with some regularity in
any case.

🔗 3: https://lore.kernel.org/git/xmqqedeqienh.fsf@gitster.g/

> Disclaimer: This is my first contribution to the git project, and thus
> my first attempt at submitting a patch via `git-send-email`. It is also
> the first time I've touched worked in C in over a decade, and I really
> didn't work with it much before that either. I welcome any and all
> feedback on what I may have gotten wrong regarding the patch submission
> process, the code changes, or my commit messages.

This part (after the commit message) looks like the cover letter for the
series (the four patches). `SubmittingPatches` recommends submitting that
in a dedicated email message (for series that have more than one
patch). Maybe this cover letter style is just an alternative that is
equally accepted. But most series use a separate cover letter message for
what it’s worth.

Cheers

-- 
Kristoffer Haugsbakk