From: Jeff King <peff@peff.net>
To: Stefan Beller <sbeller@google.com>
Cc: Junio C Hamano <gitster@pobox.com>,
Jacob Keller <jacob.keller@gmail.com>,
git@vger.kernel.org
Subject: Re: [BUG-ish] diff compaction heuristic false positive
Date: Fri, 10 Jun 2016 04:31:02 -0400 [thread overview]
Message-ID: <20160610083102.GA14192@sigill.intra.peff.net> (raw)
In-Reply-To: <20160610075043.GA13411@sigill.intra.peff.net>
On Fri, Jun 10, 2016 at 03:50:43AM -0400, Jeff King wrote:
> I found a false positive with the new compaction heuristic in v2.9:
> [...]
And by the way, this is less "hey neat, I found a case" and more "wow,
this is a lot worse than I thought".
I diffed the old and new output for the top 10,000 commits in this
particular ruby code base. There were 45 commits with changed diffs.
Spot-checking them manually, a little over 1/3 of them featured this bad
pattern. The others looked like strict improvements.
That's a lot worse than the outcomes we saw on other code bases earlier.
1/3 bad is still a net improvement, so I dunno. Is this worth worrying
about? Should we bring back the documentation for the knob to disable
it? Should we consider making it tunable via gitattributes?
I don't think that last one really helps; the good cases _and_ the bad
ones are both in ruby code (though certainly the C code we looked at
earlier was all good).
It may also be possible to make it Just Work by using extra information
like indentation. I haven't thought hard enough about that to say.
-Peff
next prev parent reply other threads:[~2016-06-10 8:31 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-10 7:50 [BUG-ish] diff compaction heuristic false positive Jeff King
2016-06-10 8:31 ` Jeff King [this message]
2016-06-10 15:56 ` Junio C Hamano
2016-06-10 16:25 ` Stefan Beller
2016-06-10 16:29 ` Jacob Keller
2016-06-10 18:13 ` Re* " Junio C Hamano
2016-06-10 18:21 ` Stefan Beller
2016-06-10 20:30 ` Jeff King
2016-06-10 20:48 ` [PATCH v2] diff: disable compaction heuristic for now Junio C Hamano
2016-06-10 20:53 ` Jeff King
2016-06-10 20:55 ` Junio C Hamano
2016-06-10 21:05 ` Jeff King
2016-06-10 21:46 ` Junio C Hamano
2016-06-10 8:31 ` [BUG-ish] diff compaction heuristic false positive Michael Haggerty
2016-06-10 8:41 ` Jeff King
2016-06-10 11:00 ` Michael Haggerty
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