refactor: do not clone configs Vec for unprocessed imports

Each iteration of a load only considers what is new since the last
round.

The entire configs vector does not need to be cloned for working on the
small tail slice of unprocessed configs.

swhkd/src/config.rs

@@ -103,18 +103,18 @@ impl Config {
 
     pub fn load_and_merge(config: Self) -> Result<Vec<Self>, Error> {
         let mut configs = vec![config];
-        let mut prev_count = 0;
-        let mut current_count = configs.len();
-        while prev_count != current_count {
-            prev_count = configs.len();
-            for config in configs.clone() {
-                for import in Self::load_to_configs(&config)? {
+        let mut processed = 0;
+
+        while processed != configs.len() {
+            let unprocessed_range = processed..configs.len();
+            for unprocessed in unprocessed_range {
+                for import in Self::load_to_configs(&configs[unprocessed])? {
                     if !configs.contains(&import) {
                         configs.push(import);
                     }
                 }
+                processed += 1;
             }
-            current_count = configs.len();
         }
         Ok(configs)
     }