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From: Junio C Hamano <gitster@pobox.com>
To: "Michał Kępień" <michal@isc.org>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 1/2] diff: add -I<regex> that ignores matching changes
Date: Wed, 07 Oct 2020 13:08:12 -0700	[thread overview]
Message-ID: <xmqqft6p240j.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <20201007194821.GA20549@larwa.hq.kempniu.pl> (=?utf-8?B?Ik1p?= =?utf-8?B?Y2hhxYIgS8SZcGllxYQiJ3M=?= message of "Wed, 7 Oct 2020 21:48:21 +0200")

Michał Kępień <michal@isc.org> writes:

>> cannot be memset(0) before use?  It seems like a much better
>> approach to ensure that we clear the structure.
>
> I do not know of any reason for xpparam_t structures to not be
> zero-initialized.  In fact, they _are_ zero-initialized most of the
> time; AFAICT, there are just three places in the tree in which they are
> not.
>
> Would you like me to address that in a separate patch in this patch
> series?

Yes, as a preliminary clean-up patch before the real/fun stuff ;-)

>> > +-I<regex>::
>> > +	Ignore changes whose all lines match <regex>.
>> > +
>> 
>> The implementation seems to allow only one regex, but I suspect we'd
>> want to mimic
>> 
>>     $ printf "%s\n" a a a >test_a
>>     $ printf "%s\n" b b b >test_b
>>     $ diff -Ia     test_a test_b
>>     $ diff     -Ib test_a test_b
>>     $ diff -Ia -Ib test_a test_b
>
> Ah, sure.  After skimming through various man pages available online, I
> was not sure whether all standalone versions of diff which support -I
> allow that switch to be used multiple times and I thought it would be
> better to start with the simplest thing possible.  If you would rather
> have the above implemented immediately, I can sure try that in v2.
>
>> and until that happens, the explanation needs to say something about
>> earlier <regex> being discarded when this option is given more than
>> once.
>
> Sorry, where do I look for that explanation? 

You wrote "Ignore changes whose all lines match <regex>"; I was
suggesting that we also need "when given more than once, all but the
last <regex> are ignored" after that sentence, because that is not
what people who know how -I works in versions of "diff" that support
it expect.

But I think it should be trivial to make it a list of patterns and
try to match against them in a loop.  So let's support multiple
patterns from the get-go.

> I have not thought about this approach before, but it sounds elegant to
> me, at least at first glance - option parsing code sounds like the right
> place for sanitizing user-provided parameters.  Doubly so if we take the
> multiple -I options approach.  I will try this in v2.

Sounds good.

>> I agree with what you said in the cover letter that it would be a
>> good idea to name the existing xdl_mark_ignorable() and the new one
>> in such a way that they look similar and parallel, by renaming the
>> former to xdl_mark_ignorable_lines or something.
>
> Then I will do that in v2.  Separate patch?

Given that the function has only one caller, I think it is better
done within the same patch.  xdl_mark_ignorable() as the name of the
function is not wrong per-se, so it does not deserve to be renamed
standalone in a preliminary clean-up patch---there is nothing to be
cleaned up.  The fact that we introduce a similarly tasked function
makes its current name less desirable, so adjusting to the new world
order is better done as part of the same patch.

> My pleasure ;-)  And thanks for taking a look.  Sorry about the long
> turnaround time, but unfortunately this is the best I can do at the
> moment.

Pleasure is mutual ;-)

We've survived without -I for 15 years.  Even a few more months
would not hurt anybody.  Take time, aim for a quality job, and most
importantly, have fun.

Thanks.

  reply	other threads:[~2020-10-07 20:08 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01 12:06 [PATCH 0/2] " Michał Kępień
2020-10-01 12:06 ` [PATCH 1/2] " Michał Kępień
2020-10-01 18:21   ` Junio C Hamano
2020-10-07 19:48     ` Michał Kępień
2020-10-07 20:08       ` Junio C Hamano [this message]
2020-10-01 12:06 ` [PATCH 2/2] t: add -I<regex> tests Michał Kępień
2020-10-01 17:02 ` [PATCH 0/2] diff: add -I<regex> that ignores matching changes Junio C Hamano
2020-10-12  9:17 ` [PATCH v2 0/3] " Michał Kępień
2020-10-12  9:17   ` [PATCH v2 1/3] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-12 11:14     ` Johannes Schindelin
2020-10-12 17:09       ` Junio C Hamano
2020-10-12 19:52     ` Junio C Hamano
2020-10-13  6:35       ` Michał Kępień
2020-10-12  9:17   ` [PATCH v2 2/3] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-12 11:20     ` Johannes Schindelin
2020-10-12 20:00       ` Junio C Hamano
2020-10-12 20:39         ` Johannes Schindelin
2020-10-12 21:43           ` Junio C Hamano
2020-10-13  6:37             ` Michał Kępień
2020-10-13 15:49               ` Junio C Hamano
2020-10-13  6:36       ` Michał Kępień
2020-10-13 12:02         ` Johannes Schindelin
2020-10-13 15:53           ` Junio C Hamano
2020-10-13 18:45           ` Michał Kępień
2020-10-12 18:01     ` Junio C Hamano
2020-10-13  6:38       ` Michał Kępień
2020-10-12 20:04     ` Junio C Hamano
2020-10-13  6:38       ` Michał Kępień
2020-10-12  9:17   ` [PATCH v2 3/3] t: add -I<regex> tests Michał Kępień
2020-10-12 11:49     ` Johannes Schindelin
2020-10-13  6:38       ` Michał Kępień
2020-10-13 12:00         ` Johannes Schindelin
2020-10-13 16:00           ` Junio C Hamano
2020-10-13 19:01           ` Michał Kępień
2020-10-15 11:45             ` Johannes Schindelin
2020-10-15  7:24   ` [PATCH v3 0/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-15  7:24     ` [PATCH v3 1/2] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-15  7:24     ` [PATCH v3 2/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2020-10-16 15:32       ` Phillip Wood
2020-10-16 18:04         ` Junio C Hamano
2020-10-19  9:48           ` Michał Kępień
2020-10-16 18:16       ` Junio C Hamano
2020-10-19  9:55         ` Michał Kępień
2020-10-19 17:29           ` Junio C Hamano
2020-10-16 10:00     ` [PATCH v3 0/2] " Johannes Schindelin
2020-10-20  6:48     ` [PATCH v4 " Michał Kępień
2020-10-20  6:48       ` [PATCH v4 1/2] merge-base, xdiff: zero out xpparam_t structures Michał Kępień
2020-10-20  6:48       ` [PATCH v4 2/2] diff: add -I<regex> that ignores matching changes Michał Kępień
2021-02-05 14:13       ` [PATCH 1/2] diff: add an API for deferred freeing Ævar Arnfjörð Bjarmason
2021-02-10 16:00         ` Johannes Schindelin
2021-02-11  3:00           ` Ævar Arnfjörð Bjarmason
2021-02-11  9:40             ` Johannes Schindelin
2021-02-11 10:21               ` Jeff King
2021-02-11 10:45                 ` [PATCH v2 0/2] " Ævar Arnfjörð Bjarmason
2021-02-11 10:45                 ` [PATCH v2 1/2] " Ævar Arnfjörð Bjarmason
2021-02-11 10:45                 ` [PATCH v2 2/2] diff: plug memory leak from regcomp() on {log,diff} -I Ævar Arnfjörð Bjarmason
2021-02-05 14:13       ` [PATCH " Ævar Arnfjörð Bjarmason

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