Adjust zed -n behavior (#53346)

When there's already a workspace that matches the paths provided,
activate that workspace, otherwise create a new window. This is
different from the default behavior of always adding to the sidebar.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A

Author: eholk

crates/workspace/src/workspace.rs

@@ -9174,30 +9174,35 @@ pub async fn find_existing_workspace(
     let mut open_visible = OpenVisible::All;
     let mut best_match = None;
 
-    if open_options.open_new_workspace != Some(true) {
-        cx.update(|cx| {
-            for window in workspace_windows_for_location(location, cx) {
-                if let Ok(multi_workspace) = window.read(cx) {
-                    for workspace in multi_workspace.workspaces() {
-                        let project = workspace.read(cx).project.read(cx);
-                        let m = project.visibility_for_paths(
-                            abs_paths,
-                            open_options.open_new_workspace == None,
-                            cx,
-                        );
-                        if m > best_match {
-                            existing = Some((window, workspace.clone()));
-                            best_match = m;
-                        } else if best_match.is_none()
-                            && open_options.open_new_workspace == Some(false)
-                        {
-                            existing = Some((window, workspace.clone()))
-                        }
+    cx.update(|cx| {
+        for window in workspace_windows_for_location(location, cx) {
+            if let Ok(multi_workspace) = window.read(cx) {
+                for workspace in multi_workspace.workspaces() {
+                    let project = workspace.read(cx).project.read(cx);
+                    let m = project.visibility_for_paths(
+                        abs_paths,
+                        open_options.open_new_workspace == None,
+                        cx,
+                    );
+                    if m > best_match {
+                        existing = Some((window, workspace.clone()));
+                        best_match = m;
+                    } else if best_match.is_none() && open_options.open_new_workspace == Some(false)
+                    {
+                        existing = Some((window, workspace.clone()))
                     }
                 }
             }
-        });
+        }
+    });
+
+    // With -n, only reuse a window if the path is genuinely contained
+    // within an existing worktree (don't fall back to any arbitrary window).
+    if open_options.open_new_workspace == Some(true) && best_match.is_none() {
+        existing = None;
+    }
 
+    if open_options.open_new_workspace != Some(true) {
         let all_paths_are_files = existing
             .as_ref()
             .and_then(|(_, target_workspace)| {

crates/zed/src/zed.rs

@@ -2667,6 +2667,7 @@ mod tests {
         .unwrap();
         assert_eq!(cx.update(|cx| cx.windows().len()), 1);
 
+        // Opening a file inside the existing worktree with -n reuses the window.
         cx.update(|cx| {
             open_paths(
                 &[PathBuf::from(path!("/root/dir/c"))],
@@ -2680,6 +2681,22 @@ mod tests {
         })
         .await
         .unwrap();
+        assert_eq!(cx.update(|cx| cx.windows().len()), 1);
+
+        // Opening a path NOT in any existing worktree with -n creates a new window.
+        cx.update(|cx| {
+            open_paths(
+                &[PathBuf::from(path!("/root/b"))],
+                app_state.clone(),
+                workspace::OpenOptions {
+                    open_new_workspace: Some(true),
+                    ..Default::default()
+                },
+                cx,
+            )
+        })
+        .await
+        .unwrap();
         assert_eq!(cx.update(|cx| cx.windows().len()), 2);
     }
 
@@ -2733,7 +2750,7 @@ mod tests {
         .unwrap();
         assert_eq!(cx.update(|cx| cx.windows().len()), 1);
 
-        // Opening a directory with -n creates a new window.
+        // Opening a directory already in a worktree with -n reuses the window.
         cx.update(|cx| {
             open_paths(
                 &[PathBuf::from(path!("/root/dir2"))],
@@ -2747,6 +2764,22 @@ mod tests {
         })
         .await
         .unwrap();
+        assert_eq!(cx.update(|cx| cx.windows().len()), 1);
+
+        // Opening a directory NOT in any worktree with -n creates a new window.
+        cx.update(|cx| {
+            open_paths(
+                &[PathBuf::from(path!("/root"))],
+                app_state.clone(),
+                workspace::OpenOptions {
+                    open_new_workspace: Some(true),
+                    ..Default::default()
+                },
+                cx,
+            )
+        })
+        .await
+        .unwrap();
         assert_eq!(cx.update(|cx| cx.windows().len()), 2);
     }
 

crates/zed/src/zed/open_listener.rs

@@ -1043,7 +1043,7 @@ mod tests {
             })
             .unwrap();
 
-        // Now open a file inside that workspace, but tell Zed to open a new window
+        // Opening a file inside the existing worktree with -n reuses the window.
         open_workspace_file(
             path!("/root/dir1/file1.txt"),
             Some(true),
@@ -1052,18 +1052,7 @@ mod tests {
         )
         .await;
 
-        assert_eq!(cx.windows().len(), 2);
-
-        let multi_workspace_2 = cx.windows()[1].downcast::<MultiWorkspace>().unwrap();
-        multi_workspace_2
-            .update(cx, |multi_workspace, _, cx| {
-                multi_workspace.workspace().update(cx, |workspace, cx| {
-                    assert!(workspace.active_item_as::<Editor>(cx).is_some());
-                    let items = workspace.items(cx).collect::<Vec<_>>();
-                    assert_eq!(items.len(), 1, "Workspace should have two items");
-                });
-            })
-            .unwrap();
+        assert_eq!(cx.windows().len(), 1);
     }
 
     #[gpui::test]