[darcs-users] Doubts about commuteFilepatches

Iago Abal iago.abal at gmail.com
Mon Nov 22 11:48:58 UTC 2010


On Mon, Nov 22, 2010 at 11:00 AM, Eric Kow <kowey at darcs.net> wrote:

> On Wed, Nov 17, 2010 at 16:32:54 +0000, Iago Abal wrote:
> > Question 1: Darcs diff could generate non-sensible hunks? That will be a
> > bug, I think.
>
> It might not come from the differ.  I wonder what else might generate
> hunks. Could this somehow result from operations like patch coalescing,
> or maybe generating the primitives used during conflict marking?  There
> may be other sources still.
>
> If so, it seems like a quick&dirty fix (instead of fix what produces
stupid-hunks just check for them in commute). Would be interesting to know
what was the comment of the author when s/he record that patch.

> > Let me call Hunk f l [] [] "stupid-hunk": A stupid-hunk h is almost
> > equivalent to the Identity patch (but it requires h.file to exist, and
> line
> > h.line to be in "in bounds"). I think could be easily proved that a
> > stupid-hunk will always commute with another Hunk.
>
> Well I can see that the stupid hunks always commute past. I guess I'm
> vaguely concerned that there's some sort of patch theory property that
> gets violated by these odd indices, or that one day we'll be trying to
> apply a stupid hunk to line 42 of a now 10 line file.  Sure we could
> catch the stupid hunk case and systematically no-op (need to check if
> we do), but it does look weird.
>
Are you worried because this stupid-hunks are created (e.g. by colesce) with
invalid line numbers? Or are you worried because the use of commute could
lead to invalid (out of range) line numbers?

>
> --
> Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow>
> For a faster response, try +44 (0)1273 64 2905 or
> xmpp:kowey at jabber.fr <xmpp%3Akowey at jabber.fr> (Jabber or Google Talk only)
>
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-- 
Iago Abal Rivas
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