From: Jeff King <peff@peff.net>
To: phillip.wood@dunelm.org.uk
Cc: "Elijah Newren" <newren@gmail.com>,
"John Cai" <johncai86@gmail.com>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"John Cai via GitGitGadget" <gitgitgadget@gmail.com>,
git@vger.kernel.org, "Patrick Steinhardt" <ps@pks.im>
Subject: Re: [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm
Date: Wed, 15 Feb 2023 10:00:23 -0500 [thread overview]
Message-ID: <Y+zzh80fybq8Tn66@coredump.intra.peff.net> (raw)
In-Reply-To: <2ca47f26-f10a-1fae-c879-f9479f7acdb1@dunelm.org.uk>
On Wed, Feb 15, 2023 at 02:44:59PM +0000, Phillip Wood wrote:
> Indeed. Ironically as there are no unique context lines in that example the
> blank lines are being matched by patience implementation falling back to the
> myers algorithm. Normally the myers implementation tries to avoid matching
> common context lines between two blocks of changed lines but I think because
> in this case it is only called on a small part of the file the blank lines
> are not common enough to trigger that heuristic. I've got a patch[1] that
> stops the patience implementation falling back to the myers algorithm and
> just trims any leading and trailing context. On the whole it I think it
> gives more readable diffs but I've not got any systematic data to back that
> up. I also suspect there are pathological cases such as each line in the
> file being duplicated where the falling back to the myers algorithm gives a
> much better result.
Ah, I should have suspected it was something like that (since one of the
purposes of patience is trying not to key on meaningless lines).
I tried your patch on my test case, and the result is even more readable
than the myers output, because it really was effectively a complete
rewrite of the function. It is, of course, not the minimal diff. I'm not
sure if there would be cases where you'd prefer the minimal. I guess if
each stanza's change really was independent of the others. But if there
is no commonality except for blank lines, I find it hard to imagine that
it's much worse to just treat the whole thing as a block.
Anyway, thank you (and Elijah) for explaining. I'm getting more
comfortable with the idea of switching the default.
-Peff
next prev parent reply other threads:[~2023-02-15 15:00 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-05 3:46 [PATCH 0/2] Teach diff to honor diff algorithms set through git attributes John Cai via GitGitGadget
2023-02-05 3:46 ` [PATCH 1/2] diff: consolidate diff algorithm option parsing John Cai via GitGitGadget
2023-02-06 16:20 ` Phillip Wood
2023-02-05 3:46 ` [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm John Cai via GitGitGadget
2023-02-05 17:50 ` Eric Sunshine
2023-02-06 13:10 ` John Cai
2023-02-06 16:27 ` Phillip Wood
2023-02-06 18:14 ` Eric Sunshine
2023-02-06 19:50 ` John Cai
2023-02-09 8:26 ` Elijah Newren
2023-02-09 10:31 ` "bad" diffs (was: [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm) Ævar Arnfjörð Bjarmason
2023-02-09 16:37 ` [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm John Cai
2023-02-06 16:39 ` Ævar Arnfjörð Bjarmason
2023-02-06 20:37 ` John Cai
2023-02-07 14:55 ` Phillip Wood
2023-02-07 17:00 ` John Cai
2023-02-09 9:09 ` Elijah Newren
2023-02-09 14:44 ` Phillip Wood
2023-02-10 9:57 ` Elijah Newren
2023-02-11 17:39 ` Phillip Wood
2023-02-11 1:59 ` Jeff King
2023-02-15 2:35 ` Elijah Newren
2023-02-15 4:21 ` Jeff King
2023-02-15 5:20 ` Junio C Hamano
2023-02-15 14:44 ` Phillip Wood
2023-02-15 15:00 ` Jeff King [this message]
2023-02-07 17:27 ` Ævar Arnfjörð Bjarmason
2023-02-15 14:47 ` Phillip Wood
2023-02-09 8:44 ` Elijah Newren
2023-02-14 21:16 ` John Cai
2023-02-15 3:41 ` Elijah Newren
2023-02-09 7:50 ` Elijah Newren
2023-02-09 9:41 ` Ævar Arnfjörð Bjarmason
2023-02-11 2:04 ` Jeff King
2023-02-07 17:56 ` Jeff King
2023-02-07 20:18 ` Ævar Arnfjörð Bjarmason
2023-02-07 20:47 ` Junio C Hamano
2023-02-07 21:05 ` Ævar Arnfjörð Bjarmason
2023-02-07 21:28 ` Junio C Hamano
2023-02-07 21:44 ` Ævar Arnfjörð Bjarmason
2023-02-09 16:34 ` John Cai
2023-02-11 1:39 ` Jeff King
2023-02-14 21:40 ` [PATCH v2 0/2] Teach diff to honor diff algorithms set through git attributes John Cai via GitGitGadget
2023-02-14 21:40 ` [PATCH v2 1/2] diff: consolidate diff algorithm option parsing John Cai via GitGitGadget
2023-02-15 2:38 ` Junio C Hamano
2023-02-15 23:34 ` John Cai
2023-02-15 23:42 ` Junio C Hamano
2023-02-16 2:14 ` Jeff King
2023-02-16 2:57 ` Junio C Hamano
2023-02-16 20:34 ` John Cai
2023-02-14 21:40 ` [PATCH v2 2/2] diff: teach diff to read gitattribute diff-algorithm John Cai via GitGitGadget
2023-02-15 2:56 ` Junio C Hamano
2023-02-15 3:20 ` Junio C Hamano
2023-02-16 20:37 ` John Cai
2023-02-17 20:21 ` [PATCH v3 0/2] Teach diff to honor diff algorithms set through git attributes John Cai via GitGitGadget
2023-02-17 20:21 ` [PATCH v3 1/2] diff: consolidate diff algorithm option parsing John Cai via GitGitGadget
2023-02-17 21:27 ` Junio C Hamano
2023-02-18 1:36 ` Elijah Newren
2023-02-17 20:21 ` [PATCH v3 2/2] diff: teach diff to read algorithm from diff driver John Cai via GitGitGadget
2023-02-17 21:50 ` Junio C Hamano
2023-02-18 2:56 ` Elijah Newren
2023-02-20 15:32 ` John Cai
2023-02-20 16:21 ` Elijah Newren
2023-02-20 16:49 ` John Cai
2023-02-20 17:32 ` Elijah Newren
2023-02-20 20:53 ` John Cai
2023-02-22 19:47 ` Jeff King
2023-02-24 17:44 ` John Cai
2023-02-18 1:16 ` [PATCH v3 0/2] Teach diff to honor diff algorithms set through git attributes Elijah Newren
2023-02-20 13:37 ` John Cai
2023-02-20 21:04 ` [PATCH v4 " John Cai via GitGitGadget
2023-02-20 21:04 ` [PATCH v4 1/2] diff: consolidate diff algorithm option parsing John Cai via GitGitGadget
2023-02-20 21:04 ` [PATCH v4 2/2] diff: teach diff to read algorithm from diff driver John Cai via GitGitGadget
2023-02-21 17:34 ` [PATCH v4 0/2] Teach diff to honor diff algorithms set through git attributes Junio C Hamano
2023-02-21 18:05 ` Elijah Newren
2023-02-21 18:51 ` Junio C Hamano
2023-02-21 19:36 ` John Cai
2023-02-21 20:16 ` Elijah Newren
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y+zzh80fybq8Tn66@coredump.intra.peff.net \
--to=peff@peff.net \
--cc=avarab@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitgitgadget@gmail.com \
--cc=johncai86@gmail.com \
--cc=newren@gmail.com \
--cc=phillip.wood@dunelm.org.uk \
--cc=ps@pks.im \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).