Priority pinning in apt-preferences with different versions and architectures

I’m posting this because I’ve lost too many hours figuring it out myself, the documentation is missing several important notes and I haven’t found any forum posts that really relate to this:

Question: How do I prioritize specific package versions for multiple architectures? In particular, I have a number of different packages which I would like to download for multiple architectures, and I would like to prioritize the versions so that if they’re not explicitly provided, apt will try to get a version matching my arbitrary requirements (in my case, the current git branch name) and fall back to our develop branch versions.

eg. I would like to download package my-package for both i386 and amd64 architectures and I would like to pull the latest version that includes my-git-branch-name before falling back to the latest that includes develop.

Answer:

The official documentation is here.

1. In order to support multiple architectures, all packages being pinned must have their architecture specified, and there must be an entry for each architecture. A pinning for the package name without the architecture specified will only influence the default (platform) architecture:

Package: my-package
Pin: version /your regex here/
Pin-Priority: 1001

2. The entries are whitespace-sensitive, although no errors will be reported if you have whitespace…