On Wed, 18 Nov 2009, Stefan Sperling wrote:
> On Wed, Nov 18, 2009 at 08:47:51AM +0200, Alan Barrett wrote:
> > On Mon, 16 Nov 2009, Stefan Sperling wrote:
> > > 5) Hunks are only applied if they do not overlap with any other hunk.
> > Other patch implementations are able to deal with overlapping hunks.
[example snipped]
>
> I can see that applying overlapping hunks could be made to work in
> theory. But when do people use such patches in practice?
> Would gnu diff or svn diff ever produce anything like the example on
> the left?
I think I have seen overlapping context diffs from a very old version
of diff. Of course the overlap was only in the leading and trailing
context lines. I don't think current versions of gnu diff or svn diff
will produce them. I have created such patches by hand occasionally
(by splitting up a more conventional patch that was failing to apply).
The algorithm you presented earlier could, I think, easily be modified
to keep track of the number of lines of leading and trailing context in
each hunk, and then allow the leading context of one hunk to overlap
the trailing context of another hunk, or vice versa, but never allow
overlaps that involve the "core" of any hunk (where "core" is defined as
what's left after the leading and trailing context is removed). Whether
it's worth the effort is another question.
> > An interactive patch assistant or conflict resolution tool might
> > want to offer the option of splitting a hunk into two or more
> > smaller hunks and re-trying each smaller hunk. "git add --patch"
> > offers something like this in a different context (getting ready
> > to commit a subset of the changes to a file).
>
> Right now I'm aiming for basic, but solid, patch support. Nothing fancy.
I wasn't suggesting that you should implement any kind of interactive
patch assistant, but I was trying to show a plausible use case for
overlapping hunks.
--apb (Alan Barrett)
