feat: prefer installed config file location

data/defaults.json

@@ -1,5 +1,5 @@
 {
-  "deployments_base": "/sls/mx/applications/aaredaq",
+  "deployments_base": "/sls/mx/applications/AareDAQ",
   "default_venv_name": ".venv",
   "default_gui_file": "src/aare/gui/gui.py",
   "default_server_file": "src/aare/daq/server.py",

src/main.rs

@@ -10,17 +10,37 @@ use clap::{Parser, Subcommand};
 use config::{Config, LauncherEntry, load_config};
 use detect::detect_beamline;
 
+/// Config file installed by the RPM, preferred when it exists.
+const INSTALLED_CONFIG: &str = "/etc/aarel/defaults.json";
+/// Config file shipped in the source tree, used as a fallback.
+const LOCAL_CONFIG: &str = "data/defaults.json";
+
 #[derive(Parser)]
 #[command(name = "aarel")]
 struct Cli {
-    /// Path to the launcher config file.
-    #[arg(long, default_value = "data/defaults.json")]
-    config: PathBuf,
+    /// Path to the launcher config file. Defaults to /etc/aarel/defaults.json,
+    /// falling back to ./data/defaults.json.
+    #[arg(long)]
+    config: Option<PathBuf>,
 
     #[command(subcommand)]
     command: Command,
 }
 
+/// Resolve the config path: the explicit `--config`, else the installed config
+/// if present, else the local one.
+fn resolve_config_path(config: Option<PathBuf>) -> PathBuf {
+    if let Some(path) = config {
+        return path;
+    }
+    let installed = PathBuf::from(INSTALLED_CONFIG);
+    if installed.is_file() {
+        installed
+    } else {
+        PathBuf::from(LOCAL_CONFIG)
+    }
+}
+
 #[derive(Subcommand)]
 enum Command {
     /// Enter the TUI to choose what to launch
@@ -45,12 +65,13 @@ enum Command {
 fn main() -> Result<()> {
     let cli = Cli::parse();
 
-    let json = std::fs::read_to_string(&cli.config)
-        .with_context(|| format!("failed to read config file {}", cli.config.display()))?;
+    let config_path = resolve_config_path(cli.config);
+    let json = std::fs::read_to_string(&config_path)
+        .with_context(|| format!("failed to read config file {}", config_path.display()))?;
     let config = load_config(&json)?;
 
-    check_base_exists("deployments_base", &config.deployments_base, &cli.config)?;
-    check_base_exists("venvs_base", &config.deployments_base, &cli.config)?;
+    check_base_exists("deployments_base", &config.deployments_base, &config_path)?;
+    check_base_exists("venvs_base", &config.deployments_base, &config_path)?;
 
     match cli.command {
         Command::Pick => {