Code has references to non-canonical documentation and specification

[guillemj]

The code has many links to code, documents and specifications that are not their canonical source, as they reference Ubuntu resources. This is potentially problematic as Ubuntu diverges and has diverged in the past some times in incompatible ways, so this can cause issues with Debian and other Debian-derived distributions.

I think it would be best if upstream references were used for dpkg source code (from https://git.dpkg.org/), dpkg man pages (from https://manpages.debian.org/) and from the Debian policy manual (from https://www.debian.org/doc/debian-policy/).