It is possible to use the `rad seed` command to specify multiple RIDs at the
same time, where each repository specified will be fetched (unless `--no-fetch`
is used):

```
$ rad seed rad:z3Rry7rpdWuGpfjPYGzdJKQADsoNW rad:z3zTnCfi6cVSZG8eCGn6AMDypgAPm
✓ Seeding policy updated for rad:z3Rry7rpdWuGpfjPYGzdJKQADsoNW with scope 'all'
✓ Fetching rad:z3Rry7rpdWuGpfjPYGzdJKQADsoNW from z6Mkt67…v4N1tRk@[..]
✓ Seeding policy updated for rad:z3zTnCfi6cVSZG8eCGn6AMDypgAPm with scope 'all'
✓ Fetching rad:z3zTnCfi6cVSZG8eCGn6AMDypgAPm from z6Mkt67…v4N1tRk@[..]
```