are diffs available for .orig.tar.gz files

["Tshepang Lekhonkhobe" <tshepang@gmail.com>]

Hi,

In my great attempts to minimise bandwidth usage, I download Debian
source packages since they contain only Debian changes (.diff.gz and
perhaps the .dsc files). But then, are .orig.tar diffs for upstream
changes available? I'm thinking of monsters like Linux and OOo, that I
could just apply diffs between upstream (.orig) diffs instead of
downloading the entire thing when only a 1000 SLOC changed. Would this
be too complex a set-up if it's not already available...

thanks