Re: [PATCH 2/2] ls-files: add --sparse option

[Derrick Stolee <stolee@gmail.com>]

On 12/9/2021 7:50 AM, Ævar Arnfjörð Bjarmason wrote:
> 
> On Wed, Dec 08 2021, Derrick Stolee wrote:
> 
>> On 12/8/2021 1:36 PM, Elijah Newren wrote:
>>> On Wed, Dec 8, 2021 at 10:23 AM Derrick Stolee <stolee@gmail.com> wrote:
>>>>
>>>> On 12/8/2021 12:04 PM, Elijah Newren wrote:
>>>>>
>>>>> This actually looks quite nice, though the magic '16' is kind of
>>>>> annoying.  Could we get rid of that -- perhaps using something to rip
>>>>> out the diff header, or using comm instead?
>>>>
>>>> What I really want is "remove the first two lines of this file"
>>>
>>> Is `tail -n +3` portable?  Looks like we have five uses of tail -n +N
>>> in the testsuite, so it should be okay to use.
>>
>> Ah, that's the magic incantation. Sounds good.
>>
>>>> but perhaps "tail -n $(wc -l expect)" would suffice to avoid a
>>>> magic number?
>>>
>>> That works too.
>>
>> If the "-n +X" syntax works, then I'll opt for that.
> 
> I think it should be per
> https://pubs.opengroup.org/onlinepubs/009695299/utilities/tail.html
> 
> But isn't that "diff -u" non-portable, per GIT_TEST_CMP. I.e. sometimes
> we'll fall back on "cmp" etc.

You're talking about this hunk, right?

if test -z "$GIT_TEST_CMP"
then
	if test -n "$GIT_TEST_CMP_USE_COPIED_CONTEXT"
	then
		GIT_TEST_CMP="$DIFF -c"
	else
		GIT_TEST_CMP="$DIFF -u"
	fi
fi

This only switches from "diff -u" to "diff -c" if the
GIT_TEST_CMP_USE_COPIED_CONTEXT variable is set, but it is not set
by default. Thus, we are using "diff -u" by default throughout.

Please let me know if I'm misreading this.

Thanks,
-Stolee