Re: Integrating wdiff into diff

[Denver Gingerich]

On 6/3/07, Karl Berry <address@hidden> wrote:
>     to wdiff's current output style to make it work properly as input to a
>     modified patch
>
> Is that important?  If I want to use patch, I use diff -u or diff -c.
> I've never missed not being to patch with wdiff.

In addition to having more readable diff output for long lines (which
we would get after implementing the wdiff functionality), it would be
nice if diff could produce patches that are similarly readable.
Patches produced by diff with the -u or -c options do not look very
pretty for files with long lines.

Another reason for doing this is reducing the file size of patches.
Currently if you have a file that has a single 10,000 character line
and you modify one word in it and create a diff, your patch will be
about 20,000 bytes.  Implementing support for wdiff output that can be
used by patch would reduce that patch's size to around 100 bytes.

> Anyway ... if you want to work on wdiff, I'd like to suggest a first
> step of making a new standalone wdiff release.  I can agree that
> integrating wdiff functionality into diff makes sense in the abstract,
> but even if you prepare the patches, reviewing and integrating them
> would require a substantial chunk of Paul's all-too-finite time.
>
> Meanwhile, the currently released wdiff on ftp.gnu.org dates from 1994.
> Updating that to current infrastructure and adding the word-context
> feature would make for a very worthy release, and probably not all that
> much effort.
>
> If you are interested in going that route, and it's ok with Paul, I
> could send you our general info about maintaining a GNU package and we
> could go from there.

I would be interested in updating the standalone wdiff as you
suggested.  I can see that this would be a much easier starting point
than trying to integrate wdiff into diff right off the bat.

> By the way, there is slightly-updated version (0.5g) from Francois
> Pinard, the original author, which fixes a bad core dump bug.  It is at
> http://wdiff.progiciels-bpi.ca/.  As far as I know that is the latest
> code, and Francois is unlikely to work on it again in the foreseeable
> future.

According to the NEWS section of that page, there is an even newer
version of wdiff (0.5h).  However, I don't see 0.5h on the download
page.  Am I missing something?

Denver