Repository redirects are here
github.com
github.com
Surprising that they didn't implement this as it seems like the easiest thing to implement and pretty damn useful.
1. Create https://github.com/beefsack/test1
2. Rename to https://github.com/beefsack/test2, redirect works
3. Create new https://github.com/beefsack/test1, link from (1) points to this new repo
So yeah, it looks like it works.