A good system to download and migrate issues and pull requests is important, but that doesn't require federation.

I would love to see a smaller scoped federation of:

  - Forks across instances, including for the purpose of PRs (Git)
  - Activity feeds and notifications (Activity or ATproto)
  - Authentication and some user settings (OAuth)

The attacks span from forged DMCA takedowns, to national blocking orders, to suspicion that a contributor is from a sanctioned country (whether they still live there or not), to rogue project admins, and some other more creative attacks.

Project infrastructure should be distributed, with copies of data in as many computers as possible, across as many jurisdictions as possible.

For example, the social features of GitHub, which I like (like stars, browsing repositories by tags etc..)

But also For PRs, the way to make a pull request to a repo hosted at A, from your own node hosted at B.

And like other commenters said, you can do this workflow with git over email like a lot of projects to, but the main goal of the federation here to me is the user experience, the UI being able to link all of theses separate repositories, issues, PRs, etc, like everything was hosted at the same place.