Listing forks

It would be very nice if we could:

1. List the forks of a given upstream
2. Maybe allow syncing the list of forks with the list of local remotes?

One challenge I would see is to figure out which repository is the blessed one in the case one works with a fork of their own. But I personally love doing `git fetch --all` to pull the code of everyone I work with, and I would love it if there was a way for me to figure out which forks to add from the command line.

The issue names no files, tests, or command entry points. Start by locating the CLI code that handles upstream repositories and local Git remotes, then clarify how forks are discovered and what syncing should do before defining completion criteria.

Written by the indexing model from the issue text.