project_panel: Fix worktree root rename (#24487)

Closes #7923

This PR fixes root worktree renaming by:  

1. Handling the case where `new_path` is the new root name instead of a
relative path from the root.
2. [#20313](https://github.com/zed-industries/zed/pull/20313) added
functionality to watch for root worktree renames made externally, e.g.,
via Finder. This PR avoids relying on that watcher because, when
renaming explicitly from Zed, we can eagerly perform the necessary work
(of course after fs rename) instead of waiting for the watcher to detect
the rename. This prevents UI glitches during renaming root.

Todo:

- [x] Fix wrong abs paths when root is renamed
- [x] Fix explicit scan entry func to handle renamed root dir
- [x] Tests
- [x] Test on Linux
- [x] Tested with single and multipe worktrees
- [x] Tested when single file is root file

Release Notes:

- Fixed an issue where worktree root name couldn't be renamed in project
panel.

crates/worktree/src/worktree.rs

@@ -1432,16 +1432,7 @@ impl LocalWorktree {
                             drop(barrier);
                         }
                         ScanState::RootUpdated { new_path } => {
-                            if let Some(new_path) = new_path {
-                                this.snapshot.git_repositories = Default::default();
-                                this.snapshot.ignores_by_parent_abs_path = Default::default();
-                                let root_name = new_path
-                                    .as_path()
-                                    .file_name()
-                                    .map_or(String::new(), |f| f.to_string_lossy().to_string());
-                                this.snapshot.update_abs_path(new_path, root_name);
-                            }
-                            this.restart_background_scanners(cx);
+                            this.update_abs_path_and_refresh(new_path, cx);
                         }
                     }
                     cx.notify();
@@ -1881,6 +1872,10 @@ impl LocalWorktree {
         }))
     }
 
+    /// Rename an entry.
+    ///
+    /// `new_path` is the new relative path to the worktree root.
+    /// If the root entry is renamed then `new_path` is the new root name instead.
     fn rename_entry(
         &self,
         entry_id: ProjectEntryId,
@@ -1893,8 +1888,18 @@ impl LocalWorktree {
         };
         let new_path = new_path.into();
         let abs_old_path = self.absolutize(&old_path);
-        let Ok(abs_new_path) = self.absolutize(&new_path) else {
-            return Task::ready(Err(anyhow!("absolutizing path {new_path:?}")));
+
+        let is_root_entry = self.root_entry().is_some_and(|e| e.id == entry_id);
+        let abs_new_path = if is_root_entry {
+            let Some(root_parent_path) = self.abs_path().parent() else {
+                return Task::ready(Err(anyhow!("no parent for path {:?}", self.abs_path)));
+            };
+            root_parent_path.join(&new_path)
+        } else {
+            let Ok(absolutize_path) = self.absolutize(&new_path) else {
+                return Task::ready(Err(anyhow!("absolutizing path {new_path:?}")));
+            };
+            absolutize_path
         };
         let abs_path = abs_new_path.clone();
         let fs = self.fs.clone();
@@ -1928,9 +1933,19 @@ impl LocalWorktree {
             rename.await?;
             Ok(this
                 .update(&mut cx, |this, cx| {
-                    this.as_local_mut()
-                        .unwrap()
-                        .refresh_entry(new_path.clone(), Some(old_path), cx)
+                    let local = this.as_local_mut().unwrap();
+                    if is_root_entry {
+                        // We eagerly update `abs_path` and refresh this worktree.
+                        // Otherwise, the FS watcher would do it on the `RootUpdated` event,
+                        // but with a noticeable delay, so we handle it proactively.
+                        local.update_abs_path_and_refresh(
+                            Some(SanitizedPath::from(abs_path.clone())),
+                            cx,
+                        );
+                        Task::ready(Ok(this.root_entry().cloned()))
+                    } else {
+                        local.refresh_entry(new_path.clone(), Some(old_path), cx)
+                    }
                 })?
                 .await?
                 .map(CreatedEntry::Included)
@@ -2195,6 +2210,23 @@ impl LocalWorktree {
         self.share_private_files = true;
         self.restart_background_scanners(cx);
     }
+
+    fn update_abs_path_and_refresh(
+        &mut self,
+        new_path: Option<SanitizedPath>,
+        cx: &Context<Worktree>,
+    ) {
+        if let Some(new_path) = new_path {
+            self.snapshot.git_repositories = Default::default();
+            self.snapshot.ignores_by_parent_abs_path = Default::default();
+            let root_name = new_path
+                .as_path()
+                .file_name()
+                .map_or(String::new(), |f| f.to_string_lossy().to_string());
+            self.snapshot.update_abs_path(new_path, root_name);
+        }
+        self.restart_background_scanners(cx);
+    }
 }
 
 impl RemoteWorktree {