From: Lidong Yan <yldhome2d2@gmail•com>
To: Junio C Hamano <gitster@pobox•com>
Cc: Lidong Yan via GitGitGadget <gitgitgadget@gmail•com>,
git@vger•kernel.org
Subject: Re: [PATCH] diff: stop output garbled message in dry run mode
Date: Sat, 18 Oct 2025 09:11:34 +0800 [thread overview]
Message-ID: <6C994C9C-0034-46D0-8112-FF88773B5CF5@gmail.com> (raw)
In-Reply-To: <xmqqh5vx1p0q.fsf@gitster.g>
Junio C Hamano <gitster@pobox•com> writes:
>
> "Lidong Yan via GitGitGadget" <gitgitgadget@gmail•com> writes:
>
>> From: Lidong Yan <yldhome2d2@gmail•com>
>>
>> In dry run mode, diff_flush_patch() should not produce any output.
>> However, in commit b55e6d36eb (diff: ensure consistent diff behavior
>> with ignore options, 2025-08-08), only the output during the
>> comparison of two file contents was suppressed. For file deletions
>> or mode changes, diff_flush_patch() still produces output. In
>> run_extern_diff(), set quiet to true if in dry run mode. In
>> emit_diff_symbol_from_struct(), directly return if in dry run mode.
>
> The above makes it sound as if the dry-run mode was an inherent part
> of the diff machinery that existed even before b55e6d36 came, and
> b55e6d36 somehow broke it. But that is not what you are telling us,
> I think.
>
> You may know what the "dry-run" mode is, but others don't. You
> should tell the backstory a bit better to help them. I am guessing
> that this patch is to fix a breakage introduced when the dry-run
> mode is added in b55e6d36 (diff: ensure consistent diff behavior
> with ignore options, 2025-08-08)? If so, I would expect an
> explanation like ...
>
> Earlier, b55e6d36 (diff: ensure consistent diff behavior with
> ignore options, 2025-08-08) introduced "dry-run" mode to the
> diff machinery so that content based diff filtering (like
> ignoring space changes or those that match -I<regex>) can first
> try to produce a patch without emitting any output to see if
> under the given diff filtering condition we would get any output
> lines, and a new helper function diff_flush_patch_quietly() was
> introduced to use the mode to see an individual filepair needs
> to be shown.
>
> However, the solution was not complete. IN SUCH AND SUCH CASES,
> THIS BAD THING HAPPENED BECAUSE WE OVERLOOKED THIS AND THAT
> CONDITION, AND AS A RESULT, DRY-RUN MODE WAS NOT QUIET.
>
> To fix this, DO THIS AND THAT. THIS WOULD AFFECT ONLY SUCH AND
> SUCH CASES WITHOUT AFFECTING OTHER CODE PATHS LIKE DOING X AND Y.
Thanks for explaining how to describe a problem in commit message. Will rewrite
soon.
>
> ... is given to help readers understand what we wanted to do in the
> earlier commit, what we failed to do there and why, and what we can
> do at this point to clean up the mess without making further
> damange.
>
>> Signed-off-by: Lidong Yan <yldhome2d2@gmail•com>
>> ---
>> diff: stop output garbled message in dry run mode
>>
>> In dry run mode, diff_flush_patch() should not produce any output.
>> However, in commit b55e6d36eb (diff: ensure consistent diff behavior
>> with ignore options, 2025-08-08), only the output during the comparison
>> of two file contents was suppressed. For file deletions or mode changes,
>> diff_flush_patch() still produces output. In run_extern_diff(), set
>> quiet to true if in dry run mode. In emit_diff_symbol_from_struct(),
>> directly return if in dry run mode.
>
> The "below three-dash" space is a place to explain what does not
> have to be a part of the resulting commit but would help those who
> are reading the mailing list and reviewing. Repeating the same
> thing as the proposed log message does not help readers.
I am using Github pull request for convenience. I think the bot repeat my
commit messages twice.
>
>> diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
>> index 55a06eadb3..25fa452656 100755
>> --- a/t/t4013-diff-various.sh
>> +++ b/t/t4013-diff-various.sh
>> @@ -661,6 +661,27 @@ test_expect_success 'diff -I<regex>: ignore matching file' '
>> test_grep ! "file1" actual
>> '
>>
>> +test_expect_success 'diff -I<regex>: ignore all content changes' '
>> + test_when_finished "git rm -f file1 file2" &&
>> + : >file1 &&
>> + git add file1 &&
>> + : >file2 &&
>> + git add file2 &&
>> +
>> + rm -f file1 file2 &&
>> + mkdir file2 &&
>> + test_diff_no_content_changes () {
>> + git diff $1 --ignore-blank-lines -I".*" >actual &&
>> + test_line_count = 2 actual &&
>> + test_grep "file1" actual &&
>> + test_grep "file2" actual &&
>> + test_grep ! "diff --git" actual
>> + } &&
>> + test_diff_no_content_changes "--raw" &&
>> + test_diff_no_content_changes "--name-only" &&
>> + test_diff_no_content_changes "--name-status"
>> +'
>
> Test that exercises "git diff -I<regex>" is in line with what the
> original b55e6d36eb wanted to address, but given that we saw a
> recent regression report like [*], I would have liked to see "git
> diff --quiet" in the test as well.
I will read Peff’s test and see if I should also add some similar tests
> * https://lore.kernel.org/git/CACJRbWjwOQwJB13CwTfvhV3p+Hbn4KrNM9AtBanGtUS4V_1MbQ@mail.gmail.com/
>
Thanks,
Lidong
next prev parent reply other threads:[~2025-10-18 1:11 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-17 3:17 [PATCH] diff: stop output garbled message in dry run mode Lidong Yan via GitGitGadget
2025-10-17 12:07 ` Johannes Schindelin
2025-10-17 19:15 ` Junio C Hamano
2025-10-17 20:19 ` Junio C Hamano
2025-10-17 20:17 ` Junio C Hamano
2025-10-17 16:17 ` Junio C Hamano
2025-10-18 1:11 ` Lidong Yan [this message]
2025-10-18 5:02 ` Junio C Hamano
2025-10-18 9:47 ` Jeff King
2025-10-18 9:50 ` Lidong Yan
2025-10-18 9:56 ` Jeff King
2025-10-18 15:44 ` Junio C Hamano
2025-10-19 14:31 ` Lidong Yan
2025-10-19 15:33 ` Junio C Hamano
2025-10-18 9:48 ` [PATCH v2] " Lidong Yan
2025-10-19 16:20 ` [PATCH v3] " Lidong Yan
2025-10-19 16:30 ` [PATCH v4] " Lidong Yan
2025-10-22 19:53 ` Junio C Hamano
2025-10-22 21:33 ` Junio C Hamano
2025-10-23 0:27 ` Lidong Yan
2025-10-23 12:30 ` Jeff King
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