Dependency resolution is a complex task with a lot of research to back it up. Doing it simply, however, is complex.
The idea I had was to rely on the remote repository to do it. When syncing the repo locally, you just fetch a list files with a format like so:


Then when calling the "repo" command to download a pack, you could ask it to fetch all dependencies using a -d flag, and it would print all resolved packs to stdout rsther than just you pack. It could also be a totally different tool ! After all, repo is responsible for fetching remote packs. A tool could build dependency graph when given a name. This would be easy to do.

The hardest part is documenting these dependencies... But here we reach the package building part of the problem, which is also interesting, but way more complex !