That way we can join forks-of-forks into the same network even if
their original source was deleted.
Consider the following:
`awesome-oss/badger` is forked to `coolstuff/badger`, which is
forked to `user-a/badger` which in turn is forked to
`user-b/badger`.
When `awesome-oss/badger` is deleted, we will now create a fork
network with `coolstuff/badger` as the root. The `user-a/badger`
and `user-b/badger` projects will be added to the network.