Re: BUG: git grep behave oddly with alternatives

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 13, 2023, 17:19 UTC
Message-ID: <xmqq5yda5p4l.fsf@gitster.g>
In-Reply-To: <230113.86ilhazved.gmgdl@evledraar.gmail.com>

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

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> On Thu, Jan 12 2023, Jeff King wrote:
>
>> So it does seem like all bets are off for what people can and should
>> expect here. Which isn't to say we should make things worse. I mostly
>> wondered if REG_ENHANCED might take us closer to what glibc was doing by
>> default, but it doesn't seem like it.

I thought that René's "Use enhanced only when doing BRE" was fairly focused, but I am very tempted to accept ...

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> There's a couple of ways out of this that I don't see in this thread:
>
> - Declare it not a problem: We have -G, -E and -P to map to BRE, ERE and
>   PCRE. One view is to say the first two must match POSIX, another is
>   tha whatever the platform thinks they should do is how they should
>   act.

... this view. The story "BRE and ERE work via what system libraries provide, and 'git grep' matches what system grep' does" is an easy to understand view.

> - Just mandate PCRE for Mac OS, then map -E to -P. We could do this with
>   the pcre2convert() API and PCRE2_CONVERT_POSIX_EXTENDED flag,
>   i.e. PCRE's own "translate this to ERE".

Presumably this is to ensure -E works identically everywhere? If so, then we should do that everywhere, not just on macOS. But again it makes "git grep -E" slightly incompatible with "grep" on systems (including macOS), so...