[CLI] Fix config option for when a file or folder is passed. (#18469)

## Description 

Prior to #18204, `sui start` accepted a network config file when using
`--network.config`, and `sui-test-validator` accepted a config directory
when using the `--config-dir`, so we need to support both. That PR
introduces a bug as in it accepts only directories.

This PR fixes this issue and should close  #18468.

## Test plan 

How did you test the new or updated feature?

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

crates/sui/src/sui_commands.rs

@@ -601,21 +601,31 @@ async fn start(
         let epoch_duration_ms = epoch_duration_ms.unwrap_or(DEFAULT_EPOCH_DURATION_MS);
         swarm_builder = swarm_builder.with_epoch_duration_ms(epoch_duration_ms);
     } else {
-        // load from config dir that was passed, or generate a new genesis if there is no config
-        // dir passed and there is no config_dir in the default location
-        // and if a dir exists, then use that one
-        if let Some(config) = config.clone() {
-            swarm_builder = swarm_builder.dir(config);
-        } else if config.is_none() && !sui_config_dir()?.join(SUI_NETWORK_CONFIG).exists() {
+        if config.is_none() && !sui_config_dir()?.join(SUI_NETWORK_CONFIG).exists() {
             genesis(None, None, None, false, epoch_duration_ms, None, false).await?;
-            swarm_builder = swarm_builder.dir(sui_config_dir()?);
-        } else {
-            swarm_builder = swarm_builder.dir(sui_config_dir()?);
         }
+
         // Load the config of the Sui authority.
-        let network_config_path = config
-            .clone()
-            .unwrap_or(sui_config_dir()?.join(SUI_NETWORK_CONFIG));
+        // To keep compatibility with sui-test-validator where the user can pass a config
+        // directory, this checks if the config is a file or a directory
+        let network_config_path = if let Some(ref config) = config {
+            if config.is_dir() {
+                config.join(SUI_NETWORK_CONFIG)
+            } else if config.is_file()
+                && config
+                    .extension()
+                    .is_some_and(|ext| (ext == "yml" || ext == "yaml"))
+            {
+                config.clone()
+            } else {
+                config.join(SUI_NETWORK_CONFIG)
+            }
+        } else {
+            config
+                .clone()
+                .unwrap_or(sui_config_dir()?)
+                .join(SUI_NETWORK_CONFIG)
+        };
         let network_config: NetworkConfig =
             PersistedConfig::read(&network_config_path).map_err(|err| {
                 err.context(format!(
@@ -624,7 +634,9 @@ async fn start(
                 ))
             })?;
 
-        swarm_builder = swarm_builder.with_network_config(network_config);
+        swarm_builder = swarm_builder
+            .dir(sui_config_dir()?)
+            .with_network_config(network_config);
     }
 
     #[cfg(feature = "indexer")]