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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Taylor Blau <me@ttaylorr.com>
Cc: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>,
	git@vger.kernel.org, "René Scharfe" <l.s.r@web.de>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH v4 2/2] tests(mingw): avoid very slow `mingw_test_cmp`
Date: Fri, 18 Nov 2022 14:32:28 +0100 (CET)	[thread overview]
Message-ID: <qp0556o2-6q18-8556-0n8s-p28831qr6qs6@tzk.qr> (raw)
In-Reply-To: <Y3LD1CtKBoDhPdSZ@nand.local>

Hi Taylor,

On Mon, 14 Nov 2022, Taylor Blau wrote:

> On Mon, Nov 14, 2022 at 02:06:52PM +0000, Johannes Schindelin via GitGitGadget wrote:
> > From: Johannes Schindelin <johannes.schindelin@gmx.de>
> >
> > It is more performant to run `git diff --no-index` than running the
> > `mingw_test_cmp` code with MSYS2's Bash, i.e. the Bash that Git for
> > Windows uses. And a lot more readable.
> >
> > The original reason why Git's test suite needs the `mingw_test_cmp`
> > function at all (and why `cmp` is not good enough) is that Git's test
> > suite is not actually trying to compare binary files when it calls
> > `test_cmp`, but it compares text files. And those text files can contain
> > CR/LF line endings depending on the circumstances.
> >
> > Note: The original fix in the Git for Windows project implemented a test
> > helper that avoids the overhead of the diff machinery, in favor of
> > implementing a behavior that is more in line with what `mingw_test_cmp`
> > does now. This was done to minimize the risk in using something as
> > complex as the diff machinery to perform something as simple as
> > determining whether text output is identical to the expected output or
> > not. This approach has served Git for Windows well for years, but the
> > attempt to upstream this saw a lot of backlash and distractions during
> > the review, was disliked by the Git maintainer and was therefore
> > abandoned. For full details, see the thread at
> > https://lore.kernel.org/git/pull.1309.git.1659106382128.gitgitgadget@gmail.com/t
>
> In the previous round, you wrote that this paragraph:
>
>     It explains why we replace a relatively simple logic with a relatively
>     complex one.

Yes. And I obviously got myself misunderstood.

The simple logic I refer to is the `t/helper/test-cmp.c` that I abandoned.

The complex logic is the diff machinery we now call, which is a lot more
involved and goes through a lot more code paths.

> But I'm not sure the rewritten version does what you claim, at least in
> my own personal opinion.
>
> It is not helpful to say the original approach "saw a lot of backlash".

It is the nicest thing I can say about it.

And I want people who are curious what happened to Git for Windows' custom
code to have an explanation in the commit messages.

> It is helpful, on the other hand, to say what about the original
> approach gave reviewers pause, and why that alternative approach isn't
> pursued here.
>
> Maybe I'm splitting hairs here, but I really do stand by my original
> suggestion from back in [1].

We can also keep hitting a dead horse, but I don't think that will make
anything any better.

Thanks,
Johannes

>
> Thanks,
> Taylor
>
> [1]: https://lore.kernel.org/git/Y3B36HjDJhIY5jNz@nand.local/
>

  reply	other threads:[~2022-11-18 13:33 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-29 14:53 [PATCH] tests: replace mingw_test_cmp with a helper in C Johannes Schindelin via GitGitGadget
2022-07-29 14:54 ` Johannes Schindelin
2022-07-29 16:44 ` Junio C Hamano
2022-09-06 13:10   ` Johannes Schindelin
2022-09-07 12:09     ` René Scharfe
2022-09-07 16:25       ` Junio C Hamano
2022-09-07 21:45         ` Re* " Junio C Hamano
2022-09-07 22:39           ` René Scharfe
2022-09-08  0:03             ` Junio C Hamano
2022-09-08  8:59         ` René Scharfe
2022-09-08 15:26           ` Ævar Arnfjörð Bjarmason
2022-09-08 20:54         ` Johannes Schindelin
2022-09-08 21:09           ` Junio C Hamano
2022-09-06 13:10 ` [PATCH v2 0/2] " Johannes Schindelin via GitGitGadget
2022-09-06 13:10   ` [PATCH v2 1/2] t0021: use Windows-friendly `pwd` Johannes Schindelin via GitGitGadget
2022-09-06 13:10   ` [PATCH v2 2/2] tests: replace mingw_test_cmp with a helper in C Johannes Schindelin via GitGitGadget
2022-09-07 11:57     ` Ævar Arnfjörð Bjarmason
2022-09-07 12:24       ` Ævar Arnfjörð Bjarmason
2022-09-07 19:45         ` Junio C Hamano
2022-09-07  9:04   ` [PATCH v2 0/2] " Johannes Schindelin
2022-11-12 22:07   ` [PATCH v3 " Johannes Schindelin via GitGitGadget
2022-11-12 22:07     ` [PATCH v3 1/2] t0021: use Windows-friendly `pwd` Johannes Schindelin via GitGitGadget
2022-11-12 22:07     ` [PATCH v3 2/2] tests(mingw): avoid very slow `mingw_test_cmp` Johannes Schindelin via GitGitGadget
2022-11-13  4:51       ` Taylor Blau
2022-11-14 13:34         ` Johannes Schindelin
2022-11-18 23:15         ` Junio C Hamano
2022-11-19  2:53           ` Taylor Blau
2022-11-19 12:03             ` Ævar Arnfjörð Bjarmason
2022-11-19  8:18           ` Johannes Sixt
2022-11-19 17:50             ` René Scharfe
2022-11-20  9:29               ` Torsten Bögershausen
2022-11-21 17:49               ` Johannes Sixt
2022-11-21  3:13             ` Junio C Hamano
2022-11-14  9:53       ` Phillip Wood
2022-11-14 13:47         ` Johannes Schindelin
2022-11-14 11:55       ` Ævar Arnfjörð Bjarmason
2022-11-14 14:02         ` Johannes Schindelin
2022-11-14 15:23           ` Ævar Arnfjörð Bjarmason
2022-11-18 23:19             ` Junio C Hamano
2022-11-19  2:56               ` Taylor Blau
2022-11-19 11:54                 ` Ævar Arnfjörð Bjarmason
2022-11-21  3:17                   ` Junio C Hamano
2022-11-14 14:06     ` [PATCH v4 0/2] tests(mingw): avoid super-slow mingw_test_cmp Johannes Schindelin via GitGitGadget
2022-11-14 14:06       ` [PATCH v4 1/2] t0021: use Windows-friendly `pwd` Johannes Schindelin via GitGitGadget
2022-11-14 14:06       ` [PATCH v4 2/2] tests(mingw): avoid very slow `mingw_test_cmp` Johannes Schindelin via GitGitGadget
2022-11-14 22:40         ` Taylor Blau
2022-11-18 13:32           ` Johannes Schindelin [this message]
2022-11-18 18:14             ` Taylor Blau
2022-11-20 23:36               ` Johannes Schindelin
2022-11-21  0:07                 ` Taylor Blau
2022-12-06 15:07       ` [PATCH v5 0/2] tests(mingw): avoid super-slow mingw_test_cmp Johannes Schindelin via GitGitGadget
2022-12-06 15:07         ` [PATCH v5 1/2] t0021: use Windows-friendly `pwd` Johannes Schindelin via GitGitGadget
2022-12-06 15:07         ` [PATCH v5 2/2] tests(mingw): avoid very slow `mingw_test_cmp` Johannes Schindelin via GitGitGadget
2022-12-06 18:55           ` Ævar Arnfjörð Bjarmason
2022-12-06 21:52           ` Johannes Sixt
2022-12-06 21:54           ` René Scharfe
2022-12-07  4:33             ` Junio C Hamano
2022-12-07  1:31           ` Taylor Blau

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