Re: BUG: git grep behave oddly with alternatives

["René Scharfe" <l.s.r@web.de>]

Am 04.01.23 um 08:46 schrieb Jeff King:
> On Tue, Jan 03, 2023 at 09:52:27PM +0100, René Scharfe wrote:
>
>> diff --git a/Makefile b/Makefile
>> index db447d0738..15e7edc9d2 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -289,6 +289,10 @@ include shared.mak
>>  # Define NO_REGEX if your C library lacks regex support with REG_STARTEND
>>  # feature.
>>  #
>> +# Define GIT_GREP_USES_REG_ENHANCED if your C library provides the flag
>> +# REG_ENHANCED to enable enhanced basic regular expressions and you'd
>> +# like to use it in git grep.
>
> I didn't test, but just from looking at the patch I'd expect this to
> affect other parts of Git besides git-grep. E.g., "git log --grep".
> Which raises two questions:
>
>  - would a more generalized name be better? USE_REG_ENHANCED or
>    something? That might be _too_ general, but see below.
>
>  - should this cover other cases? Grepping for "regcomp", would people
>    want this to behave consistently for "git config --get-regexp", or
>    diff funcnames, and so on?
>
> If so, then I could envision a USE_REG_ENHANCED which just wraps the
> system regcomp and adds the REG_ENHANCED flag when REG_EXTENDED is not
> set?

Good point.  I don't know what people want, though.  re_format(7) on
macOS/BSD and regex(7) on Linux call basic REs "obsolete" and extended
REs "modern", so they seem to push people away from the old kind,
enhanced or not.

But making a consistent choice for all regex use makes sense --
platforms that use compat/regex/ get the same enhanced flavor
everywhere.

René