Ely Office: six offline-first desktop apps in Rust and GPUI

ElyDoc, ElyTable, ElyShow (LibreOfficeKit), ElyPDF (MuPDF), ElyTree (Git),
ElyMark (Milkdown and CodeMirror in CEF). ElyMail and ElyAgent follow.

apps/ely-tree/src/watch.rs

@@ -0,0 +1,47 @@
+//! Rereads after outside changes (TREE-02, §13.3).
+
+use std::time::Duration;
+
+use futures::{StreamExt as _, channel::mpsc};
+use gpui::Context;
+use notify::{RecommendedWatcher, RecursiveMode, Watcher as _};
+
+use crate::{repo::Repo, tree::Tree};
+
+/// Bursts, such as a checkout, settle into one read.
+const SETTLE: Duration = Duration::from_millis(250);
+
+/// Watches work tree and Git directory until dropped.
+pub fn start(id: u64, repo: &Repo, cx: &mut Context<Tree>) -> notify::Result<RecommendedWatcher> {
+    let (sender, mut changes) = mpsc::unbounded();
+    let root = repo.root.display().to_string();
+    let mut watcher =
+        notify::recommended_watcher(move |event: notify::Result<notify::Event>| match event {
+            Ok(_) => {
+                let _ = sender.unbounded_send(());
+            }
+            Err(error) => log::warn!("tree: watching {root} failed: {error}"),
+        })?;
+    let mut watched = vec![repo.root.clone()];
+    // A linked worktree's Git directories lie elsewhere.
+    for dir in [&repo.common_dir, &repo.git_dir] {
+        if !watched.iter().any(|top| dir.starts_with(top)) {
+            watched.push(dir.clone());
+        }
+    }
+    for dir in &watched {
+        watcher.watch(dir, RecursiveMode::Recursive)?;
+    }
+    cx.spawn(async move |this, cx| {
+        while changes.next().await.is_some() {
+            cx.background_executor().timer(SETTLE).await;
+            while changes.try_recv().is_ok() {}
+            if this.update(cx, |tree, cx| tree.read(id, cx)).is_err() {
+                break;
+            }
+        }
+    })
+    .detach();
+    log::info!("tree: watching {}", repo.root.display());
+    Ok(watcher)
+}