Re: [PATCH v2 3/4] doc: document the special handling of -l0

From: Elijah Newren <newren@gmail.com>
To: Jeff King <peff@peff.net>
Cc: "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Eric Sunshine" <sunshine@sunshineco.com>,
	"Derrick Stolee" <stolee@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH v2 3/4] doc: document the special handling of -l0
Date: Wed, 14 Jul 2021 10:17:21 -0700	[thread overview]
Message-ID: <CABPp-BFu4-SJrGbeSQTum_JOq4PHAGwGPPLQA+sHZMP4wvqA1w@mail.gmail.com> (raw)
In-Reply-To: <YO8Ut9b+6D/wR6uf@coredump.intra.peff.net>

On Wed, Jul 14, 2021 at 9:45 AM Jeff King <peff@peff.net> wrote:
>
> On Wed, Jul 14, 2021 at 01:12:32AM +0000, Elijah Newren via GitGitGadget wrote:
>
> > From: Elijah Newren <newren@gmail.com>
> >
> > As noted in commit 89973554b52c (diffcore-rename: make diff-tree -l0
> > mean -l<large>, 2017-11-29), -l0 has had a magical special "large"
> > historical value associated with it.  Document this value, particularly
> > since it is not large enough for some uses -- see commit 9f7e4bfa3b6d
> > (diff: remove silent clamp of renameLimit, 2017-11-13).
> >
> > Signed-off-by: Elijah Newren <newren@gmail.com>
> > ---
> >  Documentation/diff-options.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
> > index 11e08c3fd36..ba40ac66cc9 100644
> > --- a/Documentation/diff-options.txt
> > +++ b/Documentation/diff-options.txt
> > @@ -594,6 +594,9 @@ of a delete/create pair.
> >       exhaustive portion of rename/copy detection from running if
> >       the number of rename/copy targets exceeds the specified
> >       number.  Defaults to diff.renameLimit.
> > ++
> > +Note that for backward compatibility reasons, a value of 0 is treated
> > +the same as if a large value was passed (currently, 32767).
>
> Given the confusion around what "32767" even means to users, I wonder if
> we could just say: a value of 0 removes any artificial limits (but Git
> still has some internal limits which real-world cases are not likely to
> hit).

32767 is not an internal limit; and as such, it is absolutely an
artificial limit.  I had to use 48941 just a few years ago, and that
value (and others larger than 32767) are fully supported.

> Removing limits is after all the point of "0". I'm also not sure if it
> is simply for backwards compatibility. We commonly let "0" or "-1" mean
> "no limit" for convenience. It seems like something we'd want to
> support.

Making 0 mean unlimited could be done, and I think it'd be a one-line
change, but that's not what commit 89973554b52c (diffcore-rename: make
diff-tree -l0 mean -l<large>, 2017-11-29) tried to do.

I'm not opposed to such a change in the meaning of "0", but I am
opposed to documenting this value as unlimited unless we make it so.