modify default_config_paths to respect XDG_CONFIG_HOME; remove unnecessary comments; fmt

src/main.rs

@@ -5,7 +5,7 @@ use std::path::PathBuf;
 
 const CONFIG_FILENAME: &str = "bot.yml";
 const APP_NAME: &str = "deltachat-remotecontrol-bot";
-const APP_DIR: &str = APP_NAME;
+const APP_CONFIG_DIR: &str = APP_NAME;
 
 /// Delta Chat bot for remote control of local network machines.
 #[derive(Parser)]
@@ -19,21 +19,25 @@ struct Args {
     config: Option<PathBuf>,
 }
 
-/// Returns the ordered list of default config paths to try when `-c` is not given.
-/// The home-directory entry is omitted if $HOME is not set.
 fn default_config_paths() -> Vec<PathBuf> {
     let mut paths = vec![PathBuf::from(CONFIG_FILENAME)];
 
-    if let Ok(home) = std::env::var("HOME") {
+    if let Ok(config_home) = std::env::var("XDG_CONFIG_HOME")
+        .map(|c| PathBuf::from(c))
+        .or(std::env::var("HOME").map(|home| PathBuf::from(home).join(".config")))
+    {
         paths.push(
-            PathBuf::from(home)
-                .join(".config")
-                .join(APP_DIR)
+            PathBuf::from(config_home)
+                .join(APP_CONFIG_DIR)
                 .join(CONFIG_FILENAME),
         );
     }
 
-    paths.push(PathBuf::from("/etc").join(APP_DIR).join(CONFIG_FILENAME));
+    paths.push(
+        PathBuf::from("/etc")
+            .join(APP_CONFIG_DIR)
+            .join(CONFIG_FILENAME),
+    );
 
     paths
 }