I look for a TeX package that could do the following, or anything close. I image the simpler use case as giving two text files of any kind as parameters :
\diff{file1}{file2}
and this command would compute a diff over these files and include into the produced document a visual rendering like:

with maybe the line number or any other useful information about it.
Does anyone know if such a TeX package exists?
diffon the files and uselistingsto include the result. You would have to define your own syntax highlighting scheme. – Andrey Vihrov Sep 15 '11 at 11:15difftool in TeX would be overkill and not required. The only thing you could expect is a formatting package for the result of adiffoutput. Even for this an external tool might be better suited. – Martin Scharrer Sep 15 '11 at 14:30