Re: Using clean/smudge filters with difftool

[John Keeping <john@keeping.me.uk>]

[Please don't top-post on this list.]

On Thu, Jun 18, 2015 at 03:15:38PM +0200, Florian Aspart wrote:
> 2015-06-18 14:31 GMT+02:00 Michael J Gruber <git@drmicha.warpmail.net>:
> > Florian Aspart venit, vidit, dixit 16.06.2015 16:11:
> >> Hi everyone,
> >>
> >> I created a clean filter to apply on some files before commiting them.
> >> The filter works correctly when I commit the file and is also applied
> >> when I usethe iff command line tool.
> >> However, when using difftool with meld, the filter is not applied and
> >> the different versions of the files are compared without any
> >> filtering.
> >>
> >> Is there a way to apply the clean/smudge filters when comparing the
> >> working copy of a file to the HEAD version in a gui diff tool?
> >>
> >> I'm using git version 2.4.3 under Ubuntu.
> >>
> >> Best,
> >> Florian
> >
> > Are you saying that "difftool" compares an uncleaned working tree file
> > with a cleaned blob? That would be a bug in either difftool or the way
> > we feed difftool.
> >
> yes in this case "difftool" compares an uncleaned working tree file
> with a cleaned blob. I did not try the smudge filter to see if it
> applied in difftool.
> 
> I think the problem comes from the way difftool is feeded, since I
> also had this problem when setting an external tool for the diff in
> the gitconfig file.
> 
> However, I'm not sure if this is a bug or it is designed to be so.
> If the external tool changes a cleaned working tree file during the
> diff, then by saving this file the result of the cleaning filter would
> also be saved in the working tree.

How is your filter configured?  Is it using a simple pattern (e.g.
"*.c") or is it using a file path?

git-difftool uses `git checkout-index --all --prefix=$dir/` and I wonder
if the prefix means that the attribute specification does not match the
temporary file that difftool produces, so no filter is applied.