Re: Possible bug: identical lines added/removed in git diff

From: Stefan Beller <sbeller@google.com>
Date: Aug 30, 2018, 19:16 UTC
Message-ID: <CAGZ79kZNVw4-q9KYAi9G3axb7-Ggpc2EAK8ZxAZoPEnZvEL-DQ@mail.gmail.com>
In-Reply-To: <20180830025457.GA665@sigill.intra.peff.net>

On Wed, Aug 29, 2018 at 7:54 PM Jeff King <peff@peff.net> wrote:

Show 17 quoted lines

>
> On Wed, Aug 29, 2018 at 10:10:25PM -0400, Gabriel Holodak wrote:
>
> > > Could you cut down to a real minimal reproduction, i.e. just these 20
> > > lines or so?
> >
> > I'm working on getting down to a minimal reproduction, a few lines at
> > a time. One thing that seems strange: as I've removed lines, there are
> > a bunch of lines that don't matter. Then I'll find some lines that, if
> > removed, completely fix the issue. But the ordering for these
> > apparently important lines doesn't matter. They just have to be
> > somewhere in the file to cause the duplicated diffs.
> >
> > I'll upload again when I've figured out all the unimportant lines to remove.
>
> Yeah, I reproduced based on your initial post, but noticed that when I
> cut it down the problem went away.

Oh, I had to look further down than I did initially. Now I can reproduce it from the initial data as well.

Note that it goes away with --minimal.

I have a patch cooking (which was sent out as https://public-inbox.org/git/20180810221857.87399-1-sbeller@google.com/)

and one of the weaknesses in that patch is the lack of explanation on when the heuristic is applied as I have not fully understood it yet.