Fix pane deduplication for unsaved buffers that have no path (#30834)

For example, running `zed some-new-path` multiple times would open
multiple tabs.

Release Notes:

- N/A

Co-authored-by: Max <max@zed.dev>

crates/workspace/src/pane.rs

@@ -791,6 +791,7 @@ impl Pane {
     pub(crate) fn open_item(
         &mut self,
         project_entry_id: Option<ProjectEntryId>,
+        project_path: ProjectPath,
         focus_item: bool,
         allow_preview: bool,
         activate: bool,
@@ -810,6 +811,14 @@ impl Pane {
                     break;
                 }
             }
+        } else {
+            for (index, item) in self.items.iter().enumerate() {
+                if item.is_singleton(cx) && item.project_path(cx).as_ref() == Some(&project_path) {
+                    let item = item.boxed_clone();
+                    existing_item = Some((index, item));
+                    break;
+                }
+            }
         }
         if let Some((index, existing_item)) = existing_item {
             // If the item is already open, and the item is a preview item
@@ -2914,12 +2923,12 @@ impl Pane {
         self.workspace
             .update(cx, |_, cx| {
                 cx.defer_in(window, move |workspace, window, cx| {
-                    if let Some(path) = workspace
+                    if let Some(project_path) = workspace
                         .project()
                         .read(cx)
                         .path_for_entry(project_entry_id, cx)
                     {
-                        let load_path_task = workspace.load_path(path, window, cx);
+                        let load_path_task = workspace.load_path(project_path.clone(), window, cx);
                         cx.spawn_in(window, async move |workspace, cx| {
                             if let Some((project_entry_id, build_item)) =
                                 load_path_task.await.notify_async_err(cx)
@@ -2937,6 +2946,7 @@ impl Pane {
                                         let new_item_handle = to_pane.update(cx, |pane, cx| {
                                             pane.open_item(
                                                 project_entry_id,
+                                                project_path,
                                                 true,
                                                 false,
                                                 true,

crates/workspace/src/workspace.rs

@@ -1707,6 +1707,7 @@ impl Workspace {
                         pane.update_in(cx, |pane, window, cx| {
                             let item = pane.open_item(
                                 project_entry_id,
+                                project_path,
                                 true,
                                 entry.is_preview,
                                 true,
@@ -3091,12 +3092,14 @@ impl Workspace {
             })
         });
 
-        let task = self.load_path(path.into(), window, cx);
+        let project_path = path.into();
+        let task = self.load_path(project_path.clone(), window, cx);
         window.spawn(cx, async move |cx| {
             let (project_entry_id, build_item) = task.await?;
             let result = pane.update_in(cx, |pane, window, cx| {
                 let result = pane.open_item(
                     project_entry_id,
+                    project_path,
                     focus_item,
                     allow_preview,
                     activate,
@@ -3142,7 +3145,8 @@ impl Workspace {
             }
         }
 
-        let task = self.load_path(path.into(), window, cx);
+        let project_path = path.into();
+        let task = self.load_path(project_path.clone(), window, cx);
         cx.spawn_in(window, async move |this, cx| {
             let (project_entry_id, build_item) = task.await?;
             this.update_in(cx, move |this, window, cx| -> Option<_> {
@@ -3156,6 +3160,7 @@ impl Workspace {
                 new_pane.update(cx, |new_pane, cx| {
                     Some(new_pane.open_item(
                         project_entry_id,
+                        project_path,
                         true,
                         allow_preview,
                         true,