feat(dynamo-run): improve available engines list in --help (#664)

Signed-off-by: yexiaochuan <tap91624@gmail.com>

launch/dynamo-run/src/main.rs

@@ -32,7 +32,7 @@ Example:
 
 const ZMQ_SOCKET_PREFIX: &str = "dyn";
 
-const USAGE: &str = "USAGE: dynamo-run in=[http|text|dyn://<path>|batch:<folder>|none] out=[See available engines below] [--http-port 8080] [--model-path <path>] [--model-name <served-model-name>] [--model-config <hf-repo>] [--tensor-parallel-size=1] [--num-nodes=1] [--node-rank=0] [--leader-addr=127.0.0.1:9876] [--base-gpu-id=0] [--extra-engine-args=args.json] [--router-mode random|round-robin]";
+const USAGE: &str = "USAGE: dynamo-run in=[http|text|dyn://<path>|batch:<folder>|none] out=ENGINE_LIST [--http-port 8080] [--model-path <path>] [--model-name <served-model-name>] [--model-config <hf-repo>] [--tensor-parallel-size=1] [--num-nodes=1] [--node-rank=0] [--leader-addr=127.0.0.1:9876] [--base-gpu-id=0] [--extra-engine-args=args.json] [--router-mode random|round-robin]";
 
 fn main() -> anyhow::Result<()> {
     logging::init();
@@ -117,12 +117,10 @@ async fn wrapper(runtime: dynamo_runtime::Runtime) -> anyhow::Result<()> {
     let mut out_opt = None;
     let args: Vec<String> = env::args().skip(1).collect();
     if args.is_empty() || args[0] == "-h" || args[0] == "--help" {
-        println!("{USAGE}");
+        let engine_list = Output::available_engines().join("|");
+        let usage = USAGE.replace("ENGINE_LIST", &engine_list);
+        println!("{usage}");
         println!("{HELP}");
-        println!(
-            "Available engines: {}",
-            Output::available_engines().join(", ")
-        );
 
         return Ok(());
     }