Re: BUG: git grep behave oddly with alternatives

[Jeff King <peff@peff.net>]

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?

-Peff