fix: use parallel config value from configuration file (#18)

Previously, the parallel setting in config files was completely ignored.
This fix implements proper config support for the parallel option:

- Add get_parallel() method to Config struct (follows same pattern as get_timeout)
- Add parallel field to ClusterDefaults struct
- Check if user explicitly specified -p/--parallel in CLI args
- Use config value when CLI option not explicitly provided
- Priority: CLI (if explicit) > Cluster config > Global defaults > CLI default (10)

Now users can set parallel in their config files:
  defaults:
    parallel: 50
  clusters:
    production:
      parallel: 100

Fixes the issue where config parallel values were defined but never used.

Author: inureyes

src/config.rs

@@ -133,6 +133,7 @@ pub struct ClusterDefaults {
     pub user: Option<String>,
     pub port: Option<u16>,
     pub ssh_key: Option<String>,
+    pub parallel: Option<usize>,
     pub timeout: Option<u64>,
 }
 
@@ -422,6 +423,18 @@ impl Config {
         self.defaults.timeout
     }
 
+    pub fn get_parallel(&self, cluster_name: Option<&str>) -> Option<usize> {
+        if let Some(cluster_name) = cluster_name {
+            if let Some(cluster) = self.get_cluster(cluster_name) {
+                if let Some(parallel) = cluster.defaults.parallel {
+                    return Some(parallel);
+                }
+            }
+        }
+
+        self.defaults.parallel
+    }
+
     /// Get interactive configuration for a cluster (with fallback to global)
     pub fn get_interactive_config(&self, cluster_name: Option<&str>) -> InteractiveConfig {
         let mut config = self.interactive.clone();

src/main.rs

@@ -66,9 +66,15 @@ async fn main() -> Result<()> {
     // Initialize logging
     init_logging(cli.verbose);
 
-    // Check if user explicitly specified --config option
+    // Check if user explicitly specified options
     let args: Vec<String> = std::env::args().collect();
     let has_explicit_config = args.iter().any(|arg| arg == "--config");
+    let has_explicit_parallel = args.iter().any(|arg| {
+        arg == "-p"
+            || arg == "--parallel"
+            || arg.starts_with("-p=")
+            || arg.starts_with("--parallel=")
+    });
 
     // If user explicitly specified --config, ensure the file exists
     if has_explicit_config {
@@ -100,6 +106,15 @@ async fn main() -> Result<()> {
     // Determine nodes to execute on
     let (nodes, actual_cluster_name) = resolve_nodes(&cli, &config).await?;
 
+    // Determine max_parallel: CLI argument takes precedence over config
+    let max_parallel = if has_explicit_parallel {
+        cli.parallel
+    } else {
+        config
+            .get_parallel(actual_cluster_name.as_deref().or(cli.cluster.as_deref()))
+            .unwrap_or(cli.parallel) // Fall back to CLI default (10)
+    };
+
     if nodes.is_empty() {
         anyhow::bail!(
             "No hosts specified. Please use one of the following options:\n  -H <hosts>    Specify comma-separated hosts (e.g., -H user@host1,user@host2)\n  -c <cluster>  Use a cluster from your configuration file"
@@ -135,7 +150,7 @@ async fn main() -> Result<()> {
 
             ping_nodes(
                 nodes,
-                cli.parallel,
+                max_parallel,
                 key_path.as_deref(),
                 strict_mode,
                 cli.use_agent,
@@ -159,7 +174,7 @@ async fn main() -> Result<()> {
 
             let params = FileTransferParams {
                 nodes,
-                max_parallel: cli.parallel,
+                max_parallel,
                 key_path: key_path.as_deref(),
                 strict_mode,
                 use_agent: cli.use_agent,
@@ -184,7 +199,7 @@ async fn main() -> Result<()> {
 
             let params = FileTransferParams {
                 nodes,
-                max_parallel: cli.parallel,
+                max_parallel,
                 key_path: key_path.as_deref(),
                 strict_mode,
                 use_agent: cli.use_agent,
@@ -293,7 +308,7 @@ async fn main() -> Result<()> {
             let params = ExecuteCommandParams {
                 nodes,
                 command: &command,
-                max_parallel: cli.parallel,
+                max_parallel,
                 key_path: key_path.as_deref(),
                 verbose: cli.verbose > 0,
                 strict_mode,