Append :fmt as a separate history state

helix-term/src/commands.rs

@@ -927,6 +927,7 @@ fn format(editor: &mut Editor, args: &[&str], event: PromptEvent) {
 
             if let Ok(transaction) = transaction {
                 doc.apply(&transaction, view.id);
+                doc.append_changes_to_history(view.id);
             }
         }
     }