bug#60690: -P '\d' in GNU and git grep

[Junio C Hamano]

Paul Eggert <eggert@cs.ucla.edu> writes:

> Here are two ways forward to fix this incompatibility (there are other
> possibilities of course):
>
> (A) GNU grep adds a --no-ucp option that acts like 10.43 pcre2grep
> --no-ucp, and git grep -P follows suit. That is, both GNU and git grep
> act like 10.43 pcre2grep -u, in that they enable PCRE2_UTF, and also
> enable PCRE2_UCP unless --no-ucp is given. This would cause \d to
> match non-ASCII digits unless --no-ucp is given.
>
> (B) GNU grep -P and git grep -P mimic pcre2grep in both -u and
> --no-ucp. That is, they would both do 8-bit-only by default, and use
> PCRE2_UTF only when -u or --utf is given, and use PCRE2_UCP only when
> --no-ucp is absent. This would cause \d to match non-ASCII digits only
> when -u is given but --no-ucp is not.
>
> Under either (A) or (B), future pcre2grep -u, GNU grep -P, and git
> grep -P would be consistent.
>
> I mildly prefer (B) but (A) would also work. (One advantage of (B) is
> that it should be faster....)

For "git grep -P", I would like to hear from Carlo and Ævar; I agree
both (A) and (B) would be workable solutions, and have a slight
preference on a solution that does not add more options that take
only in effect when -P is given, simply because these options are
cumbersome to document and explain, but that is a very minor point.

Thanks.