Out of ideas
Well, no context available for now...

yet another
Jepeee

And another one...
Yea, I know...

Aaand another attempt
Test if svn-diff is linked correctly... sorry...

Reverted changes
Commented out svn-diff again...

And another one
Changed SVN-diff to use slash instead of backslash...

Another attempt
Changed GNU diff path...

Reverted last changes
The last attempt didn't work out for several reasons: svn:ignore was not ignored. Changes of the actual code where hidden.

Attempt to add context
Trying to make full context available by making SVN aware of where GNU diff lives.