Alice allows Bob to fetch this repo, but doesn't announce it, which means
that Bob needs to know to fetch it from Alice.

``` ~alice
$ rad id update --title "Allow Bob" --description "" --allow did:key:z6Mkt67GdsW7715MEfRuP4pSZxJRJh6kj6Y48WRqVv4N1tRk -q
[..]
```

First, Bob seeds the repo.

``` ~bob
$ rad seed rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu --no-fetch
[..]
```

If Bob just tries to fetch it without specifying seeds, he gets an error:

``` ~bob
$ rad sync rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu --fetch
✗ Error: no seeds found for rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu
```

If he specifies a seed that isn't in his routing table, he gets a warning and
an error:

``` ~bob
$ rad sync rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu --fetch --seed z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi
! Warning: node z6MknSL…StBU8Vi is not connected or seeding.. skipping
✗ Error: no seeds found for rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu
```

For this to work, Bob has to force the sync:

``` ~bob
$ rad sync rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu --fetch --seed z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi --force
✓ Fetching rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu from z6MknSL…StBU8Vi..
✓ Fetched repository from 1 seed(s)
```

``` ~bob
$ rad ls --private --all
╭───────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ Name        RID                                 Visibility   Head      Description                        │
├───────────────────────────────────────────────────────────────────────────────────────────────────────────┤
│ heartwood   rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu   private      f2de534   radicle heartwood protocol & stack │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────╯
```

Note that if multiple seeds are specified, the command succeeds as long as one
seed succeeds.

``` ~bob
$ rad sync rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu --fetch --seed z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi --seed z6MkwPUeUS2fJMfc2HZN1RQTQcTTuhw4HhPySB8JeUg2mVvx --force
✓ Fetching rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu from z6MknSL…StBU8Vi..
✗ Fetching rad:z2ug5mwNKZB8KGpBDRTrWHAMbvHCu from z6MkwPU…Ug2mVvx.. error: session does not exist; cannot initiate fetch
✓ Fetched repository from 1 seed(s)
```