brought up to speed with main

crates/zed/src/main.rs

@@ -57,8 +57,9 @@ use staff_mode::StaffMode;
 use util::{channel::RELEASE_CHANNEL, paths, ResultExt, TryFutureExt};
 use workspace::{item::ItemHandle, notifications::NotifyResultExt, AppState, Workspace};
 use zed::{
-    assets::Assets, build_window_options, handle_keymap_file_changes, initialize_workspace,
-    languages, menus,
+    assets::Assets,
+    build_window_options, handle_keymap_file_changes, initialize_workspace, languages, menus,
+    only_instance::{ensure_only_instance, IsOnlyInstance},
 };
 
 fn main() {
@@ -66,6 +67,10 @@ fn main() {
     init_paths();
     init_logger();
 
+    if ensure_only_instance() != IsOnlyInstance::Yes {
+        return;
+    }
+
     log::info!("========== starting zed ==========");
     let mut app = gpui::App::new(Assets).unwrap();