Seeking source rebuilding docs

[Neale Banks <neale@lowendale.com.au>]

Greetings,

I just unpacked ppp source package from woody (i.e. "dpkg-source -x
ppp_2.4.1-4.dsc") and was most surprised to find that this didn't unpack
the source but rather gave me a ppp-2.4.1/upstream/ directory with
tarballs/ and patches/.

Fair enough, something's changed?  Thinking positively, I searched through
dpkg-source documentation and Debian site docs but can't yet find
documentation on this (presumably I'm not looking in the right place yet;
the man page eluded that "dpkg-source -x -su" may be relevant, but that
didn't seem to help).

The crux of the matter: Where can I find documentation on unpacking a
source archive (with the intention of applying a patch and rebuilding the
binary package) and the "correct" way to handle the
<package-version>/upstream/*/ contents?

Thanks,
Neale.