custom repositories

[christian at truelite.it (Christian Surchi)]

I'm using live-helper in sid to build a live cd based on etch. I have
some packages in our custom repositories and I'd like to use them, both
for building and the image. What is, at the moment, the method to  use
it? Old style _repo way doesn't work. I read in wiki about having
config/sources.list.build or config/sources.list.image, but they are
ignored... 

Thanks
Christian