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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Đoàn Trần Công Danh" <congdanhqx@gmail.com>, git@vger.kernel.org
Subject: Re: [RFC PATCH 0/2] extend --abbrev support to diff-patch format
Date: Mon, 10 Aug 2020 11:27:05 -0400	[thread overview]
Message-ID: <20200810152705.GA61606@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqqy2mmcz1e.fsf@gitster.c.googlers.com>

On Mon, Aug 10, 2020 at 08:15:41AM -0700, Junio C Hamano wrote:

> > 	A lot of those patches couldn't be applied cleanly to old
> > 	versions of said software, thus requires some changes from
> > 	developer and they needs to be regenerated from their trimmed
> > 	tree. Because the archive tree has significantly fewer
> > 	objects, the abbreviation in the index line is usually shorter
> > 	than the original patch. Thus, it generates some noise when
> > 	said developers try to compare the new patch with the original
> > 	patch if there's an exact file-hunk match.
> >
> > 	Make the object name's abbreviation length configurable to
> > 	lower those noise.
> 
> I agree with Peff that with the above as the sole motivating use
> case, the "--full-index" option is the right approach.  It is a much
> more robust solution than "--abbrev=16 would be long enough for all
> project participants to avoid length drift".  IOW these four
> paragraphs do not argue _for_ this change, at least to me.

Yeah, that's what I was getting at: if you care about robust
machine-readability, then the full index is the best solution. Reading
between the lines, I think the argument may be "using --full-index is
too long and therefore ugly, so people like the short-ish names but with
a bit of extra safety".

There's an extra challenge here, which is that you have to convince the
sender to use the extra --abbrev option, even though they themselves
won't be the ones running into the problem when applying. But I don't
think there's an elegant solution to that (we could just bump the
default abbrev everywhere to 12+, which is enough in practice).

Though I'm not 100% sure that "git apply" is smart enough to only look
at blobs (i.e., if "1234abcd" is ambiguous between a tree and a blob,
ignore the tree since patches always apply to blobs). That might be
another avenue that would make things more likely to work without
anybody having to configure anything.

> On the other hand, I think you could argue that "--full-index" is
> merely a synonym for "--abbrev=40", and the patch fixes the
> inconsistency between the object names on the "index" line, which
> can choose only between the default abbrev length and the full
> abbrev length, and all the other places we show object names, which
> uniformly honor the "--abbrev" option.

Yeah, I certainly don't mind the extra flexibility between "full" and
"default" for "index" lines. I do wonder if people want to configure the
abbreviations for those lines separately from other parts. I don't know
that I've ever particularly cared about that flexibility, but the fact
that they were set up separately all those years ago makes me think
somebody might.

-Peff

  reply	other threads:[~2020-08-10 15:37 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-09  2:19 Đoàn Trần Công Danh
2020-08-09  2:19 ` [RFC PATCH 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-09  2:19 ` [RFC PATCH 2/2] diff: extend --abbrev support to diff-patch format Đoàn Trần Công Danh
2020-08-09 19:01 ` [RFC PATCH 0/2] " Junio C Hamano
2020-08-10 10:00   ` Jeff King
2020-08-10 12:31     ` Đoàn Trần Công Danh
2020-08-10 15:15       ` Junio C Hamano
2020-08-10 15:27         ` Jeff King [this message]
2020-08-11  0:33           ` Đoàn Trần Công Danh
2020-08-11  5:22             ` Jeff King
2020-08-11 12:07               ` Đoàn Trần Công Danh
2020-08-10 15:06     ` Junio C Hamano
2020-08-11 11:49 ` [PATCH v2 0/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-11 11:49   ` [PATCH v2 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-11 18:54     ` Junio C Hamano
2020-08-11 11:49   ` [PATCH v2 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-14  0:23 ` [PATCH v3 0/2] " Đoàn Trần Công Danh
2020-08-14  0:23   ` [PATCH v3 1/2] revision: differentiate if --no-abbrev asked explicitly Đoàn Trần Công Danh
2020-08-14  0:50     ` Junio C Hamano
2020-08-14  0:59       ` Đoàn Trần Công Danh
2020-08-14  1:06         ` Junio C Hamano
2020-08-14 14:50           ` Đoàn Trần Công Danh
2020-08-19 22:50             ` Junio C Hamano
2020-08-14  0:23   ` [PATCH v3 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-14 15:18     ` SZEDER Gábor
2020-08-14 17:00       ` Junio C Hamano
2020-08-14 18:59         ` Junio C Hamano
2020-08-15  0:21           ` brian m. carlson
2020-08-15  2:27             ` Đoàn Trần Công Danh
2020-08-17 16:17               ` Junio C Hamano
2020-08-20  4:56               ` Junio C Hamano
2020-08-20 12:35 ` [PATCH v4 0/2] " Đoàn Trần Công Danh
2020-08-20 12:35   ` [PATCH v4 1/2] t4013: improve diff-post-processor logic Đoàn Trần Công Danh
2020-08-20 19:49     ` Junio C Hamano
2020-08-21 12:05       ` Đoàn Trần Công Danh
2020-08-21 15:44         ` Junio C Hamano
2020-08-20 12:35   ` [PATCH v4 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh
2020-08-20 19:58     ` Junio C Hamano
2020-08-21 11:51 ` [PATCH v5 0/2] " Đoàn Trần Công Danh
2020-08-21 11:51   ` [PATCH v5 1/2] t4013: improve diff-post-processor logic Đoàn Trần Công Danh
2020-08-21 11:51   ` [PATCH v5 2/2] diff: index-line: respect --abbrev in object's name Đoàn Trần Công Danh

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