Re: [PATCH] Document the textconv filter.

Johannes Sixt [off-list ref] writes:

On Sonntag, 28. September 2008, Matthieu Moy wrote:

quoted

+Converting files to text before a diff
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The attribute `textconv` affects 'git diff' in a way similar to the
+`diff` attribute, but with `textconv`, the user provides only a way to
+convert the file into text, and git takes care of doing the diff as
+usual (i.e. other options of 'git diff' such as '--color' remain
+available).
+
+The value of `textconv` must be a string, which is the textconv
+driver.

Wouldn't it be much more useful to have git parse stdout of the custom diff 
tool in order to colorize it?

That would do it for --color, but not --color-words for example. The
problem with the GIT_EXTERNAL_DIFF is that the diff tool has to
re-implement everything that "git diff" already do.

Take my opendocument diff script :

http://www-verimag.imag.fr/~moy/opendocument/git-oodiff

That's 77 lines of code as a wrapper to odt2txt and diff. With the
"textconv" attribute, it's one line in .gitattributes, and two in
~/.gitconfig.

Of course, this would mean that external diff tools are more
complicated and their stdout has to conform mostly to the git diff
syntax. But:

quoted

+To tell git to use the `exif` filter for jpeg images, use:
+
+----------------------------------------------------------------
+*.jpg   textconv=exif
+----------------------------------------------------------------

In this very example it would be possible that the external diff driver shows 
the differences in the image in a window and also produces EXIF information 
on stdout.

Yes, but that's really a specific example. Having git colorize the
diff would be a little extra, but that wouldn't reduce the effort to
write the external diff tool itself, and doesn't give you _all_ of
git-diff, just --color.

-- 
Matthieu