add proper command line options and logging

vanity/src/main.rs

@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 use clap::Parser;
 use libvanity::vanity::VanityRequest;
 
@@ -11,12 +13,20 @@ struct Args {
 
     #[clap(help = "pattern of public key")]
     pattern: String,
+
+    #[clap(short, long, default_value = "WARN")]
+    log_level: String,
 }
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let args = Args::parse();
 
+    let level = tracing::Level::from_str(&args.log_level)?;
+    tracing_subscriber::FmtSubscriber::builder()
+        .with_max_level(level)
+        .init();
+
     let mut client =
         libvanity::vanity::vanity_service_client::VanityServiceClient::connect(args.endpoint)
             .await?;