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

Jeff King [off-list ref] writes:

But even that is a lesser breakage than taking away grep.extendedRegexp
entirely. Taking it away breaks anybody who uses it; tweaking (2) only
breaks people who set both config variables. But why would anyone do
that?

OK.  Now we have an evidence that we have thought things through
that we can point at when people later complain, I'd feel much safer
to apply that "This will break t7810" patch, together with changes
to t7810 to drop these crazy expectations ;-)