Subject: Re: [PATCH v8] ls-files: introduce "--format" option

From: Junio C Hamano <[email-masked]>
Date: Sat, 23 Jul 2022 11:40:06 -0700

ZheNing Hu <[email-masked]> writes:

>> But is this testing the right thing?
>
> Yes, I am sure about that cut can do the same thing as awk, and it can
> specify its delimiter.

That is not an answer to "is this testing the right thing?"
question, though ;-)

>> > +test_expect_success 'git ls-files --format objectmode v.s. -s' '
>> > +     git ls-files -s >files &&
>> > +     cut -d" " -f1 files >expect &&
>> > +     git ls-files --format="%(objectmode)" >actual &&
>> > +     test_cmp expect actual
>> > +'
>>
>> It only looks at the first column of the "-s" output, and we are
>> implicitly assuming that the order of output does not change between
>> the "-s" output and "--format=<format>" output.  I wonder if it is
>> more useful and less error prone to come up with a format string
>> that 100% reproduces the "ls-files -s" output and compare the two,
>> e.g.
>>
>>         format="%(objectmode) %(objectname) %(stage)    %(path)" &&
>>         git ls-files -s >expect &&
>>         git ls-files --format="$format" >actual &&
>>         test_cmp expect actual
>>
>
> See test case: 'git ls-files --format imitate --stage' which just do such thing,

That was not the point.  By extracting only "%(objectmode)" without
having any other clues (like "%(path)") on the same line, the test
is assuming that ls-files will always sort its output in the same
order regardless of the output format, whether it is "--stage" or
"--format=<spec>", and that was what the "is this testing the right
thing?" question was about.

The other test that makes sure --format=<spec> can recreate --stage
output is fine.  If some future developer breaks the output order by
mistake for --format=<spec>, we will catch such a mistake with it.

> maybe I should change its name to 'git ls-files --format v.s. -s'?

I do not think you should.  "A v.s. B" does not imply "A and B
should create identical result".  The original title describes what
it does much more clearly.