Possible regression in `git grep --untracked` pathspec matching in v2.27.0

>
> In v2.26.2 and earlier, `git grep --untracked` with negative pathspec patterns
> would filter out paths matching those patterns. In v2.27.0, this no longer works
> as expected.
>
> Example output:
>
> # v2.26.2 (good)
> $ ./git grep --untracked --files-with-matches -e '.' -- 'quote.*' ':!quote.c'
> quote.h
> $
>
> # v2.27.0 (bad)
> $ ./git grep --untracked --files-with-matches -e '.' -- 'quote.*' ':!quote.c'
> quote.c
> quote.h
> $
>
> I've bisected the change to commit 95c11ecc73f286e0a95d9591ae98f1221efe4633,
> which changed the handling of path matches in callers of `fill_directory()`.
>
> It's not clear from git-grep(1) whether the old or new behavior is "correct",
> so I request that the fix include a clarification of expected semantics.
>
> Thanks,
> - John Millikin

>
> Hi,
>
> On Tue, Jun 2, 2020 at 8:30 PM John Millikin <jmillikin@stripe.com> wrote:
> >
> > In v2.26.2 and earlier, `git grep --untracked` with negative pathspec patterns
> > would filter out paths matching those patterns. In v2.27.0, this no longer works
> > as expected.
> >
> > Example output:
> >
> > # v2.26.2 (good)
> > $ ./git grep --untracked --files-with-matches -e '.' -- 'quote.*' ':!quote.c'
> > quote.h
> > $
> >
> > # v2.27.0 (bad)
> > $ ./git grep --untracked --files-with-matches -e '.' -- 'quote.*' ':!quote.c'
> > quote.c
> > quote.h
> > $
> >
> > I've bisected the change to commit 95c11ecc73f286e0a95d9591ae98f1221efe4633,
> > which changed the handling of path matches in callers of `fill_directory()`.
> >
> > It's not clear from git-grep(1) whether the old or new behavior is "correct",
> > so I request that the fix include a clarification of expected semantics.
> >
> > Thanks,
> > - John Millikin
>
> Oh, fun, an issue from _that_ series.  At least the commit you
> bisected to wasn't 8d92fb292706 (dir: replace exponential algorithm
> with a linear one, 2020-04-01), though.
>
> Thanks for the detailed report.  I'll try to get some time to take a
> look later this week.