Re: [RFC PATCH 0/2] Introduce new merge-tree-ort command

From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Elijah Newren <newren@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Christian Couder <christian.couder@gmail.com>,
	Git Mailing List <git@vger.kernel.org>,
	Christian Couder <chriscool@tuxfamily.org>,
	Taylor Blau <me@ttaylorr.com>
Subject: Re: [RFC PATCH 0/2] Introduce new merge-tree-ort command
Date: Thu, 13 Jan 2022 10:26:57 +0100	[thread overview]
Message-ID: <220113.86k0f4vuz5.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <CABPp-BHQdkhAEmTrtc+XMgj5A5ASBVRw0_bXH10NSrMsyRK+oA@mail.gmail.com>

On Wed, Jan 12 2022, Elijah Newren wrote:

> On Wed, Jan 12, 2022 at 10:06 AM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Elijah Newren <newren@gmail.com> writes:
>>
> ...
>> I however suspect that Ævar didn't mean by "legacy merge plumbing
>> built-in" the strategy backends.  IOW, I had an impression that what
>> is on the chopping block is merge-tree and not merge-recursive.
>>
>> But since you brought up deprecation of recursive, let's spend a few
>> minutes on the topic.
>
> Not sure it matters, but for reference, Ævar explicitly brought up
> merge-recursive.c.  The fuller quote was:
>
>> >> I.e. is it really costing us
>> >> to just leave these "legacy merge" plumbing built-ins and
>> >> merge-recursive.c etc. in place?
>
> Because he brought it up, I decided to address it.  It was unclear to
> me whether he meant builtin/merge-recursive.c or the toplevel
> merge-recursive.c, so I just addressed both.

FWIW what I meant (but clearly didn't make clear enough) is whether we'd
deprecate the git-merge-tree(1) command, not whatever powers it under
the hood.

I.e. I took the greater discussion here to mean (but may have
misunderstood it) that we were talking about the needs for a
libgit2-replacing merge plumbing.

The existing git-merge-tree command probably gets us 5% towards that,
and I can see how being bug-for-bug compatible with it might be
inconvenient in some future on-top-of-ort rewrite and extension of it.

So we probably SHOULD keep it, but I don't think it's a MUST. I.e. if
you/someone wrote some more powerful version of it, and keeping it
became hard to support I think it would be OK to transition/deprecate
it, as presumably its existing users wouldn't be too inconvenienced, or
would be happier with the more powerful plumbing tool.