add config sourcing

src/cli.rs

@@ -176,6 +176,12 @@ pub struct RunArgs {
     /// which they will be tried. Multiple backends can be supplied as a comma-separated list.
     #[clap(value_enum, use_value_delimiter = true, long)]
     pub backends: Vec<CliBackend>,
+    /// Override the config directory.
+    ///
+    /// If not specified, JAY_CONFIG_DIR is checked, then XDG_CONFIG_HOME/jay, then
+    /// ~/.config/jay.
+    #[clap(long, value_hint = ValueHint::DirPath)]
+    pub config_dir: Option<String>,
 }
 
 #[derive(Args, Debug)]

src/compositor.rs

@@ -226,6 +226,7 @@ fn start_compositor2(
     let color_manager = ColorManager::new();
     let crit_ids = Rc::new(CritMatcherIds::default());
     let eventfd_cache = EventfdCache::new(&ring, &engine);
+    let explicit_config_dir = run_args.config_dir.clone();
     let state = Rc::new(State {
         pid,
         kb_ctx,
@@ -305,7 +306,7 @@ fn start_compositor2(
         serial: Default::default(),
         idle_inhibitor_ids: Default::default(),
         run_toplevel,
-        config_dir: config_dir(),
+        config_dir: explicit_config_dir.or_else(config_dir),
         config_file_id: NumCell::new(1),
         tracker: Default::default(),
         data_offer_ids: Default::default(),
@@ -820,6 +821,9 @@ fn create_dummy_output(state: &Rc<State>) {
 }
 
 pub fn config_dir() -> Option<String> {
+    if let Ok(dir) = env::var("JAY_CONFIG_DIR") {
+        return Some(dir);
+    }
     if let Ok(xdg) = env::var("XDG_CONFIG_HOME") {
         Some(format!("{}/jay", xdg))
     } else if let Ok(home) = env::var("HOME") {