Use Iterator::reduce to compose history transactions

Co-authored-by: Blaž Hrastnik <[email protected]>

helix-core/src/history.rs

@@ -126,15 +126,9 @@ impl History {
             return None;
         }
 
-        let mut transaction = self.revisions[revision].transaction.clone();
-
         // The bounds are checked in the if condition above:
         // `revision + 1` is known to be `<= self.current`.
-        for revision in &self.revisions[revision + 1..self.current] {
-            transaction = transaction.compose(revision.transaction.clone());
-        }
-
-        Some(transaction)
+        self.revisions[revision..self.current].iter().cloned().reduce(|acc, transaction| acc.compose(transaction))
     }
 
     /// Undo the last edit.