git: Add support for opening git worktrees (#20164)

This adds support for [git
worktrees](https://matklad.github.io/2024/07/25/git-worktrees.html). It
fixes the errors that show up (git blame not working) and actually adds
support for detecting git changes in a `.git` folder that's outside of
our path (and not even in the ancestor chain of our root path).

(While working on this we discovered that our `.gitignore` handling is
not 100% correct. For example: we do stop processing `.gitignore` files
once we found a `.git` repository and don't go further up the ancestors,
which is correct, but then we also don't take into account the
`excludesFile` that a user might have configured, see:
https://git-scm.com/docs/gitignore)


Closes https://github.com/zed-industries/zed/issues/19842
Closes https://github.com/zed-industries/zed/issues/4670

Release Notes:

- Added support for git worktrees. Zed can now open git worktrees and
the git status in them is correctly handled.

---------

Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Bennet <bennet@zed.dev>

crates/fs/src/fs.rs

@@ -1,3 +1,9 @@
+#[cfg(target_os = "macos")]
+mod mac_watcher;
+
+#[cfg(target_os = "linux")]
+pub mod linux_watcher;
+
 use anyhow::{anyhow, Result};
 use git::GitHostingProviderRegistry;
 
@@ -530,14 +536,21 @@ impl Fs for RealFs {
         Pin<Box<dyn Send + Stream<Item = Vec<PathEvent>>>>,
         Arc<dyn Watcher>,
     ) {
-        use fsevent::{EventStream, StreamFlags};
+        use fsevent::StreamFlags;
 
-        let (tx, rx) = smol::channel::unbounded();
-        let (stream, handle) = EventStream::new(&[path], latency);
-        std::thread::spawn(move || {
-            stream.run(move |events| {
-                smol::block_on(
-                    tx.send(
+        let (events_tx, events_rx) = smol::channel::unbounded();
+        let handles = Arc::new(parking_lot::Mutex::new(collections::BTreeMap::default()));
+        let watcher = Arc::new(mac_watcher::MacWatcher::new(
+            events_tx,
+            Arc::downgrade(&handles),
+            latency,
+        ));
+        watcher.add(path).expect("handles can't be dropped");
+
+        (
+            Box::pin(
+                events_rx
+                    .map(|events| {
                         events
                             .into_iter()
                             .map(|event| {
@@ -555,19 +568,14 @@ impl Fs for RealFs {
                                     kind,
                                 }
                             })
-                            .collect(),
-                    ),
-                )
-                .is_ok()
-            });
-        });
-
-        (
-            Box::pin(rx.chain(futures::stream::once(async move {
-                drop(handle);
-                vec![]
-            }))),
-            Arc::new(RealWatcher {}),
+                            .collect()
+                    })
+                    .chain(futures::stream::once(async move {
+                        drop(handles);
+                        vec![]
+                    })),
+            ),
+            watcher,
         )
     }
 
@@ -580,81 +588,26 @@ impl Fs for RealFs {
         Pin<Box<dyn Send + Stream<Item = Vec<PathEvent>>>>,
         Arc<dyn Watcher>,
     ) {
-        use notify::EventKind;
         use parking_lot::Mutex;
 
         let (tx, rx) = smol::channel::unbounded();
         let pending_paths: Arc<Mutex<Vec<PathEvent>>> = Default::default();
-        let root_path = path.to_path_buf();
+        let watcher = Arc::new(linux_watcher::LinuxWatcher::new(tx, pending_paths.clone()));
 
-        // Check if root path is a symlink
-        let target_path = self.read_link(&path).await.ok();
-
-        watcher::global({
-            let target_path = target_path.clone();
-            |g| {
-                let tx = tx.clone();
-                let pending_paths = pending_paths.clone();
-                g.add(move |event: &notify::Event| {
-                    let kind = match event.kind {
-                        EventKind::Create(_) => Some(PathEventKind::Created),
-                        EventKind::Modify(_) => Some(PathEventKind::Changed),
-                        EventKind::Remove(_) => Some(PathEventKind::Removed),
-                        _ => None,
-                    };
-                    let mut paths = event
-                        .paths
-                        .iter()
-                        .filter_map(|path| {
-                            if let Some(target) = target_path.clone() {
-                                if path.starts_with(target) {
-                                    return Some(PathEvent {
-                                        path: path.clone(),
-                                        kind,
-                                    });
-                                }
-                            } else if path.starts_with(&root_path) {
-                                return Some(PathEvent {
-                                    path: path.clone(),
-                                    kind,
-                                });
-                            }
-                            None
-                        })
-                        .collect::<Vec<_>>();
-
-                    if !paths.is_empty() {
-                        paths.sort();
-                        let mut pending_paths = pending_paths.lock();
-                        if pending_paths.is_empty() {
-                            tx.try_send(()).ok();
-                        }
-                        util::extend_sorted(&mut *pending_paths, paths, usize::MAX, |a, b| {
-                            a.path.cmp(&b.path)
-                        });
-                    }
-                })
-            }
-        })
-        .log_err();
-
-        let watcher = Arc::new(RealWatcher {});
-
-        watcher.add(path).ok(); // Ignore "file doesn't exist error" and rely on parent watcher.
+        watcher.add(&path).ok(); // Ignore "file doesn't exist error" and rely on parent watcher.
+        if let Some(parent) = path.parent() {
+            // watch the parent dir so we can tell when settings.json is created
+            watcher.add(parent).log_err();
+        }
 
         // Check if path is a symlink and follow the target parent
-        if let Some(target) = target_path {
+        if let Some(target) = self.read_link(&path).await.ok() {
             watcher.add(&target).ok();
             if let Some(parent) = target.parent() {
                 watcher.add(parent).log_err();
             }
         }
 
-        // watch the parent dir so we can tell when settings.json is created
-        if let Some(parent) = path.parent() {
-            watcher.add(parent).log_err();
-        }
-
         (
             Box::pin(rx.filter_map({
                 let watcher = watcher.clone();
@@ -784,23 +737,6 @@ impl Watcher for RealWatcher {
     }
 }
 
-#[cfg(target_os = "linux")]
-impl Watcher for RealWatcher {
-    fn add(&self, path: &Path) -> Result<()> {
-        use notify::Watcher;
-        Ok(watcher::global(|w| {
-            w.inotify
-                .lock()
-                .watch(path, notify::RecursiveMode::NonRecursive)
-        })??)
-    }
-
-    fn remove(&self, path: &Path) -> Result<()> {
-        use notify::Watcher;
-        Ok(watcher::global(|w| w.inotify.lock().unwatch(path))??)
-    }
-}
-
 #[cfg(any(test, feature = "test-support"))]
 pub struct FakeFs {
     // Use an unfair lock to ensure tests are deterministic.
@@ -2084,49 +2020,3 @@ mod tests {
         );
     }
 }
-
-#[cfg(target_os = "linux")]
-pub mod watcher {
-    use std::sync::OnceLock;
-
-    use parking_lot::Mutex;
-    use util::ResultExt;
-
-    pub struct GlobalWatcher {
-        // two mutexes because calling inotify.add triggers an inotify.event, which needs watchers.
-        pub(super) inotify: Mutex<notify::INotifyWatcher>,
-        pub(super) watchers: Mutex<Vec<Box<dyn Fn(&notify::Event) + Send + Sync>>>,
-    }
-
-    impl GlobalWatcher {
-        pub(super) fn add(&self, cb: impl Fn(&notify::Event) + Send + Sync + 'static) {
-            self.watchers.lock().push(Box::new(cb))
-        }
-    }
-
-    static INOTIFY_INSTANCE: OnceLock<anyhow::Result<GlobalWatcher, notify::Error>> =
-        OnceLock::new();
-
-    fn handle_event(event: Result<notify::Event, notify::Error>) {
-        let Some(event) = event.log_err() else { return };
-        global::<()>(move |watcher| {
-            for f in watcher.watchers.lock().iter() {
-                f(&event)
-            }
-        })
-        .log_err();
-    }
-
-    pub fn global<T>(f: impl FnOnce(&GlobalWatcher) -> T) -> anyhow::Result<T> {
-        let result = INOTIFY_INSTANCE.get_or_init(|| {
-            notify::recommended_watcher(handle_event).map(|file_watcher| GlobalWatcher {
-                inotify: Mutex::new(file_watcher),
-                watchers: Default::default(),
-            })
-        });
-        match result {
-            Ok(g) => Ok(f(g)),
-            Err(e) => Err(anyhow::anyhow!("{}", e)),
-        }
-    }
-}

crates/fs/src/linux_watcher.rs

@@ -0,0 +1,121 @@
+use notify::EventKind;
+use parking_lot::Mutex;
+use std::sync::{Arc, OnceLock};
+use util::ResultExt;
+
+use crate::{PathEvent, PathEventKind, Watcher};
+
+pub struct LinuxWatcher {
+    tx: smol::channel::Sender<()>,
+    pending_path_events: Arc<Mutex<Vec<PathEvent>>>,
+}
+
+impl LinuxWatcher {
+    pub fn new(
+        tx: smol::channel::Sender<()>,
+        pending_path_events: Arc<Mutex<Vec<PathEvent>>>,
+    ) -> Self {
+        Self {
+            tx,
+            pending_path_events,
+        }
+    }
+}
+
+impl Watcher for LinuxWatcher {
+    fn add(&self, path: &std::path::Path) -> gpui::Result<()> {
+        let root_path = path.to_path_buf();
+
+        let tx = self.tx.clone();
+        let pending_paths = self.pending_path_events.clone();
+
+        use notify::Watcher;
+
+        global({
+            |g| {
+                g.add(move |event: &notify::Event| {
+                    let kind = match event.kind {
+                        EventKind::Create(_) => Some(PathEventKind::Created),
+                        EventKind::Modify(_) => Some(PathEventKind::Changed),
+                        EventKind::Remove(_) => Some(PathEventKind::Removed),
+                        _ => None,
+                    };
+                    let mut path_events = event
+                        .paths
+                        .iter()
+                        .filter_map(|event_path| {
+                            event_path.starts_with(&root_path).then(|| PathEvent {
+                                path: event_path.clone(),
+                                kind,
+                            })
+                        })
+                        .collect::<Vec<_>>();
+
+                    if !path_events.is_empty() {
+                        path_events.sort();
+                        let mut pending_paths = pending_paths.lock();
+                        if pending_paths.is_empty() {
+                            tx.try_send(()).ok();
+                        }
+                        util::extend_sorted(
+                            &mut *pending_paths,
+                            path_events,
+                            usize::MAX,
+                            |a, b| a.path.cmp(&b.path),
+                        );
+                    }
+                })
+            }
+        })?;
+
+        global(|g| {
+            g.inotify
+                .lock()
+                .watch(path, notify::RecursiveMode::NonRecursive)
+        })??;
+
+        Ok(())
+    }
+
+    fn remove(&self, path: &std::path::Path) -> gpui::Result<()> {
+        use notify::Watcher;
+        Ok(global(|w| w.inotify.lock().unwatch(path))??)
+    }
+}
+
+pub struct GlobalWatcher {
+    // two mutexes because calling inotify.add triggers an inotify.event, which needs watchers.
+    pub(super) inotify: Mutex<notify::INotifyWatcher>,
+    pub(super) watchers: Mutex<Vec<Box<dyn Fn(&notify::Event) + Send + Sync>>>,
+}
+
+impl GlobalWatcher {
+    pub(super) fn add(&self, cb: impl Fn(&notify::Event) + Send + Sync + 'static) {
+        self.watchers.lock().push(Box::new(cb))
+    }
+}
+
+static INOTIFY_INSTANCE: OnceLock<anyhow::Result<GlobalWatcher, notify::Error>> = OnceLock::new();
+
+fn handle_event(event: Result<notify::Event, notify::Error>) {
+    let Some(event) = event.log_err() else { return };
+    global::<()>(move |watcher| {
+        for f in watcher.watchers.lock().iter() {
+            f(&event)
+        }
+    })
+    .log_err();
+}
+
+pub fn global<T>(f: impl FnOnce(&GlobalWatcher) -> T) -> anyhow::Result<T> {
+    let result = INOTIFY_INSTANCE.get_or_init(|| {
+        notify::recommended_watcher(handle_event).map(|file_watcher| GlobalWatcher {
+            inotify: Mutex::new(file_watcher),
+            watchers: Default::default(),
+        })
+    });
+    match result {
+        Ok(g) => Ok(f(g)),
+        Err(e) => Err(anyhow::anyhow!("{}", e)),
+    }
+}

crates/fs/src/mac_watcher.rs

@@ -0,0 +1,70 @@
+use crate::Watcher;
+use anyhow::{Context as _, Result};
+use collections::{BTreeMap, Bound};
+use fsevent::EventStream;
+use parking_lot::Mutex;
+use std::{
+    path::{Path, PathBuf},
+    sync::Weak,
+    time::Duration,
+};
+
+pub struct MacWatcher {
+    events_tx: smol::channel::Sender<Vec<fsevent::Event>>,
+    handles: Weak<Mutex<BTreeMap<PathBuf, fsevent::Handle>>>,
+    latency: Duration,
+}
+
+impl MacWatcher {
+    pub fn new(
+        events_tx: smol::channel::Sender<Vec<fsevent::Event>>,
+        handles: Weak<Mutex<BTreeMap<PathBuf, fsevent::Handle>>>,
+        latency: Duration,
+    ) -> Self {
+        Self {
+            events_tx,
+            handles,
+            latency,
+        }
+    }
+}
+
+impl Watcher for MacWatcher {
+    fn add(&self, path: &Path) -> Result<()> {
+        let handles = self
+            .handles
+            .upgrade()
+            .context("unable to watch path, receiver dropped")?;
+        let mut handles = handles.lock();
+
+        // Return early if an ancestor of this path was already being watched.
+        if let Some((watched_path, _)) = handles
+            .range::<Path, _>((Bound::Unbounded, Bound::Included(path)))
+            .next_back()
+        {
+            if path.starts_with(watched_path) {
+                return Ok(());
+            }
+        }
+
+        let (stream, handle) = EventStream::new(&[path], self.latency);
+        let tx = self.events_tx.clone();
+        std::thread::spawn(move || {
+            stream.run(move |events| smol::block_on(tx.send(events)).is_ok());
+        });
+        handles.insert(path.into(), handle);
+
+        Ok(())
+    }
+
+    fn remove(&self, path: &Path) -> gpui::Result<()> {
+        let handles = self
+            .handles
+            .upgrade()
+            .context("unable to remove path, receiver dropped")?;
+
+        let mut handles = handles.lock();
+        handles.remove(path);
+        Ok(())
+    }
+}