This is an example from Goswin Brederlow <brederlo@informatik.uni-tuebingen.de>
for the ListHook directive.

He describes the example as:
> attached a sample config that mirrors only packages from the debian-cd
> netinstall CD image task. I think this would make a usefull example
> for making a partial mirror by filtering.

The speciality of the example needing the ListHook and not
easer possible with FilterList is the need for different
packages in different architectured. (Though extending
FilterList to support this is on my TODO-List)