Function pd::testnet::join::testnet_join

pub async fn testnet_join(
    output_dir: PathBuf,
    node: Url,
    node_name: &str,
    external_address: Option<Address>,
    tm_rpc_bind: SocketAddr,
    tm_p2p_bind: SocketAddr
) -> Result<()>

Bootstrap a connection to a testnet, via a node on that testnet. Look up network peer info from the target node, and seed the tendermint p2p settings with that peer info.