Re: git-prompt.sh incompatible with non-basic global grep.patternType

> One thing that I noticed is that there is this strange field
> in grep_opt called .extended_regexp_option; it only is set from the
> boolean configuration grep.extendedregexp and worse yet it takes
> precedence over the command line option or grep.patternType, e.g.
> t7810-grep expects crazy things like these:
> 
>  * "git -c grep.extendedregexp=true -c grep.patterntype=basic grep"
>    wants to be like "git grep -E"
> 
>  * "git -c grep.extendedregexp=false -c grep.patterntype=extended grep"
>    wants to be like "git grep -G"
> 
> This comes from b22520a3 (grep: allow -E and -n to be turned on by
> default via configuration, 2011-03-30) back when we didn't have a
> more generic grep.patternType configuration mechanism in v1.7.5
> days, and it probably need to be deprecated to maintain our sanity.
> I.e. when we see the configuration used, first we warn the user and
> set grep.patternType to extended instead, and then eventually error
> out in a backward-compatibility breaking release of Git we will make
> in some future date, together with things like other compatibility
> breaking topics like ex/deprecate-empty-pathspec-as-match-all.
> 
> But that is a separate topic after this fix goes in anyway.

> -- >8 --
> From: Junio C Hamano <gitster@pobox.com>
> Date: Fri, 22 Jul 2016 11:43:14 -0700
> Subject: [PATCH] grep: further simplify setting the pattern type
> [...]