Message-ID: <20080417135013.GA2017@fieldses.org>
Date:	Thu, 17 Apr 2008 09:50:13 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Adrian Bunk <bunk@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, sverre@...belier.nl,
	git@...r.kernel.org, linux-kernel@...r.kernel.org,
	jmorris@...ei.org, viro@...iv.linux.org.uk, w@....eu,
	david@...g.hm, sclark46@...thlink.net, johnpol@....mipt.ru,
	rjw@...k.pl, tilman@...p.cc, Valdis.Kletnieks@...edu, lkml@....ca,
	davem@...emloft.net, jesper.juhl@...il.com,
	yoshfuji@...ux-ipv6.org, jeff@...zik.org, netdev@...r.kernel.org,
	davidn@...idnewall.com
Subject: Re: Reporting bugs and bisection

On Wed, Apr 16, 2008 at 10:55:03PM +0300, Adrian Bunk wrote:
> On Wed, Apr 16, 2008 at 12:02:47PM -0700, Andrew Morton wrote:
> > On Wed, 16 Apr 2008 16:26:34 +0300
> > Adrian Bunk <bunk@...nel.org> wrote:
> > 
> > > On Wed, Apr 16, 2008 at 02:15:22PM +0200, Sverre Rabbelier wrote:
> > > > I'm not subscribed to the kernel mailing list, so please include me in
> > > > the cc if you don't reply to the git list (which I am subscribed to).
> > > > 
> > > > Git is participating in Google Summer of Code this year and I've
> > > > proposed to write a 'git statistics' command. This command would allow
> > > > the user to gather data about a repository, ranging from "how active
> > > > is dev x" to "what did x work on in the last 3 weeks". It's main
> > > > feature however, would be an algorithm that ranks commits as being
> > > > either 'buggy', 'bugfix' or 'enhancement'. (There are several clues
> > > > that can aid in determining this, a commit msg along the lines of
> > > > "fixes ..." being the most obvious.)
> > > >...
> > 
> > Sounds like an interesting project.
> > 
> > > At least with the data we have currently in git it's impossible to 
> > > figure that out automatically.
> > > 
> > > E.g. if you look at commit f743d04dcfbeda7439b78802d35305781999aa11 
> > > (ide/legacy/q40ide.c: add MODULE_LICENSE), how could you determine 
> > > automatically that it is a bugfix, and the commit that introduced
> > > the bug?
> > > 
> > > You can always get some data, but if you want to get usable statistics 
> > > you need explicit tags in the commits, not some algorithm that tries 
> > > to guess.
> > 
> > Well yes.  One outcome of the project would be to tell us what changes we'd
> > need to make to our processes to make such data gathering more effective.
> > 
> > Of course, we may not actually implement such changes.  That would depend
> > upon how useful the output is to us.
> 
> That you can add this information through tags is clear, but according
> to his SoC application that's not what he wants to do.
> 
> According to his application he wants to determine automatically whether 
> a commit was a fix or whether a commit introduced a bug by doing stuff 
> like tracking whether a changed line was modified again shortly after a 
> commit.
> 
> This plan of him will simply not result in accurate numbers.

They won't be completely accurate, but who knows, maybe they'd turn out
to have a higher rate of accuracy than we'd expect.  (I assume you could
do a closer manual study of a small random sample of the results to
estimate the accuracy.)  Seems worth a try.

> Sure, you will get some numbers, but if anyone would e.g. wrongly accuse 
> me that 2% of my commits last year introduced bugs I would get 
> ***really*** angry.

It's just an experiment; reasonable people won't take it as the final
word.

--b.
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