Only show _log_ output if the user passes `--debug`

If the user doesn't pass `--debug`, we only show `INFO` logs but
without time and level to make it clearer that it is meant to be
read by the user.

Without `--debug`, the user sees:

 Still got 0.00009235 BTC left in wallet, swapping ...

With `--debug`, they see:

2021-03-01 12:21:07  DEBUG Database and seed will be stored in /home/thomas/.local/share/xmr-btc-swap
2021-03-01 12:21:07  DEBUG Starting monero-wallet-rpc on port 40779
2021-03-01 12:21:11   INFO Still got 0.00009235 BTC left in wallet, swapping ...
2021-03-01 12:21:11  DEBUG Dialing alice at 12D3KooWCdMKjesXMJz1SiZ7HgotrxuqhQJbP5sgBm2BwP1cqThi
2021-03-01 12:21:12  DEBUG Requesting quote for 0.00008795 BTC

swap/src/bin/swap_cli.rs

@@ -35,7 +35,7 @@ use swap::{
     },
     seed::Seed,
 };
-use tracing::{debug, error, warn, Level};
+use tracing::{debug, error, info, warn, Level};
 use tracing_subscriber::FmtSubscriber;
 use uuid::Uuid;
 
@@ -46,20 +46,33 @@ const MONERO_BLOCKCHAIN_MONITORING_WALLET_NAME: &str = "swap-tool-blockchain-mon
 
 #[tokio::main]
 async fn main() -> Result<()> {
+    let args = Arguments::from_args();
+
     let is_terminal = atty::is(atty::Stream::Stderr);
-    let subscriber = FmtSubscriber::builder()
-        .with_env_filter(format!("swap={}", Level::DEBUG))
-        .with_writer(std::io::stderr)
-        .with_ansi(is_terminal)
-        .with_target(false)
-        .with_timer(tracing_subscriber::fmt::time::ChronoLocal::with_format(
-            "%F %T".to_owned(),
-        ))
-        .finish();
-
-    tracing::subscriber::set_global_default(subscriber)?;
+    let base_subscriber = |level| {
+        FmtSubscriber::builder()
+            .with_writer(std::io::stderr)
+            .with_ansi(is_terminal)
+            .with_target(false)
+            .with_env_filter(format!("swap={}", level))
+    };
 
-    let args = Arguments::from_args();
+    if args.debug {
+        let subscriber = base_subscriber(Level::DEBUG)
+            .with_timer(tracing_subscriber::fmt::time::ChronoLocal::with_format(
+                "%F %T".to_owned(),
+            ))
+            .finish();
+
+        tracing::subscriber::set_global_default(subscriber)?;
+    } else {
+        let subscriber = base_subscriber(Level::INFO)
+            .without_time()
+            .with_level(false)
+            .finish();
+
+        tracing::subscriber::set_global_default(subscriber)?;
+    }
 
     let config = match args.config {
         Some(config_path) => read_config(config_path)??,
@@ -108,8 +121,8 @@ async fn main() -> Result<()> {
 
             // TODO: Also wait for more funds if balance < dust
             if bitcoin_wallet.balance().await? == Amount::ZERO {
-                debug!(
-                    "Waiting for BTC at address {}",
+                info!(
+                    "Please deposit BTC to {}",
                     bitcoin_wallet.new_address().await?
                 );
 
@@ -121,7 +134,7 @@ async fn main() -> Result<()> {
 
                 debug!("Received {}", bitcoin_wallet.balance().await?);
             } else {
-                debug!(
+                info!(
                     "Still got {} left in wallet, swapping ...",
                     bitcoin_wallet.balance().await?
                 );

swap/src/cli/command.rs

@@ -14,6 +14,9 @@ pub struct Arguments {
     )]
     pub config: Option<PathBuf>,
 
+    #[structopt(long, help = "Activate debug logging.")]
+    pub debug: bool,
+
     #[structopt(subcommand)]
     pub cmd: Option<Command>,
 }