feat(iroh-cli): improve ergonomics of iroh gossip subscribe CLI cmd

iroh-cli/src/commands/gossip.rs

@@ -9,28 +9,52 @@ use iroh::{
     client::{gossip::SubscribeOpts, Iroh},
     net::NodeId,
 };
+use std::str::FromStr as _;
 use tokio::io::AsyncBufReadExt;
 
 /// Commands to manage gossiping.
 #[derive(Subcommand, Debug, Clone)]
 #[allow(clippy::large_enum_variant)]
 pub enum GossipCommands {
-    /// Subscribe to a topic
-    #[command(group(
-        ArgGroup::new("input")
-            .required(true)
-            .args(&["topic", "raw_topic"])
-    ))]
+    /// Subscribe to a gossip topic
+    #[command(
+        long_about = r#"Subscribe to a gossip topic
+
+Example usage:
+
+    $ iroh gossip subscribe --topic test --start
+
+This will print the current node's id. Open another terminal
+or another machine and you can join the same topic:
+
+    # on another machine/terminal
+    $ iroh gossip subscribe --topic test <other node_id> --start
+
+Any lines entered in stdin will be sent to the given topic
+and received messages will be printed to stdout line-by-line.
+
+The process waits for Ctrl+C to exit."#,
+        group(
+            ArgGroup::new("input")
+                .required(true)
+                .args(&["topic", "raw_topic"])
+        )
+    )]
     Subscribe {
-        /// Topic string to subscribe to.
+        /// The topic to subscribe to.
         ///
         /// This will be hashed with BLAKE3 to get the actual topic ID.
         #[clap(long)]
         topic: Option<String>,
         /// The raw topic to subscribe to as hex. Needs to be 32 bytes, i.e. 64 hex characters.
         #[clap(long)]
         raw_topic: Option<String>,
-        bootstrap: Vec<NodeId>,
+        /// The set of nodes that are also part of the gossip swarm to bootstrap with.
+        ///
+        /// If empty, this will bootstrap a new swarm. Running the command will print
+        /// the node's `NodeId`, which can be used as the bootstrap argument in other nodes.
+        bootstrap: Vec<String>,
+        /// If enabled, all gossip events will be printed, including neighbor up/down events.
         #[clap(long, short)]
         verbose: bool,
     },
@@ -46,7 +70,13 @@ impl GossipCommands {
                 bootstrap,
                 verbose,
             } => {
-                let bootstrap = bootstrap.into_iter().collect();
+                let bootstrap = bootstrap
+                    .into_iter()
+                    .map(|node_id| NodeId::from_str(&node_id).map_err(|e| {
+                        anyhow::anyhow!("Failed to parse bootstrap node id \"{node_id}\": {e}\nMust be a valid base32-encoded iroh node id.")
+                    }))
+                    .collect::<Result<_, _>>()?;
+
                 let topic = match (topic, raw_topic) {
                     (Some(topic), None) => blake3::hash(topic.as_bytes()).into(),
                     (None, Some(raw_topic)) => {
@@ -57,7 +87,7 @@ impl GossipCommands {
                     }
                     _ => anyhow::bail!("either topic or raw_topic must be provided"),
                 };
-                // blake3::hash(topic.as_ref()).into();
+
                 let opts = SubscribeOpts {
                     bootstrap,
                     subscription_capacity: 1024,