Re: [PATCH v2 3/3] t: add -I<regex> tests

From: "Michał Kępień" <michal@isc.org>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: git@vger.kernel.org
Subject: Re: [PATCH v2 3/3] t: add -I<regex> tests
Date: Tue, 13 Oct 2020 08:38:46 +0200	[thread overview]
Message-ID: <20201013063846.GF3278@larwa.hq.kempniu.pl> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.2010121320190.50@tvgsbejvaqbjf.bet>

Hi Johannes,

> > Exercise the new -I<regex> diff option in various scenarios to ensure it
> > behaves as expected.
> 
> Excellent. I was actually looking for a test in patch 2/3 and almost
> commented about that.

Right, I expressed my doubts in this area at the end of the cover letter
for v1:

>>   - Should tests be added in a separate commit?  This is what I did as I
>>     thought it would help with readability, but...

I will be glad to follow any guidance provided, I just picked one of the
two possible routes for v1.

> Hmm. I wonder whether we could do with a much more concise test script.
> The test suite already takes a quite long time to run, which is not a
> laughing matter: we had issues in the past where contributors would skip
> running it because it took too long, and this test is sure to exacerbate
> that problem.

First, let me say that the goal of minimizing the run time of a test
suite is close to my heart (it is an issue at my day job).  Yet, I
assumed that this new test would not be detrimental to test suite run
times as it takes about half a second to run t4069-diff-ignore-regex.sh
on my machine - and (I hope) its contents are in line with the "tests
are the best documentation" proverb.  That being said, I realize that
the hosts used in various test environments may have different
processing capabilities.  I tried preparing something exhaustive and
well-commented, so that it is clear what to expect from the new feature.
Yet, if you would rather have me cut some things out, I am certainly not
particularly attached to the tests from patch 3 and I will be glad to
rip them out if that is the recommendation :-)

> I could imagine, for example, that it would be plenty enough to do
> something like this instead:
> 
> -- snip --
> diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
> index 5c7b0122b4f..bf158be137f 100755
> --- a/t/t4013-diff-various.sh
> +++ b/t/t4013-diff-various.sh
> @@ -6,6 +6,7 @@
>  test_description='Various diff formatting options'
> 
>  . ./test-lib.sh
> +. "$TEST_DIRECTORY"/diff-lib.sh
> 
>  test_expect_success setup '
> 
> @@ -473,4 +474,24 @@ test_expect_success 'diff-tree --stdin with log formatting' '
>  	test_cmp expect actual
>  '
> 
> +test_expect_success '-I<regex>' '
> +	seq 50 >I.txt &&
> +	sed -e "s/13/ten and three/" -e "/7\$/d" <I.txt >J.txt &&
> +	test_must_fail git diff --no-index -I"ten.*e" -I"^[124-9]" I.txt J.txt >actual &&
> +	cat >expect <<-\EOF &&
> +	diff --git a/I.txt b/J.txt
> +	--- a/I.txt
> +	+++ b/J.txt
> +	@@ -34,7 +31,6 @@
> +	 34
> +	 35
> +	 36
> +	-37
> +	 38
> +	 39
> +	 40
> +	EOF
> +	compare_diff_patch expect actual
> +'
> +
>  test_done
> -- snap --
> 
> Note how it tests various things in one go?

Right, neat, though this does not (yet) test:

  - the interaction between -I and --ignore-blank-lines (this is visible
    in code coverage),

  - whether the list of hunks emitted varies for different -U<n> values,

  - diffstat with -I<regex>,

  - invalid regular expressions.

Would you like me to add these tests to your proposal or to skip them,
given that -I uses the same field for marking changes as ignored as
--ignore-blank-lines does?

> P.S.: My main interest in the `-I` option is its use case for `git
> range-diff` in Git's own context: if you want to compare your patches to
> what entered the `seen` branch, there will _always_ be a difference
> because Junio adds their DCO. Something like this can help that:
> 
> git range-diff \
> 	-I'^    Signed-off-by: Junio C Hamano <gitster@pobox.com>$' \
> 	<my-patch-range> <the-equivalent-in-seen>

Right, makes sense, I have not thought of that use case.

-- 
Best regards,
Michał Kępień