Merge branch 'v3' into v3-t29

# Conflicts:
#	host/Cargo.toml
#	host/src/harness/mod.rs

host/src/process/mod.rs

@@ -41,6 +41,7 @@ mod bindings {
         with: {
             "wasi:io": wasmtime_wasi::p2::bindings::io,
             "sausage:process/host.child": super::Child,
+            "sausage:process/host.watcher": super::Watcher,
         },
     });
 }
@@ -55,6 +56,8 @@ pub fn default_script() -> Arc<dyn crate::cred::script::Script> {
 }
 pub use cache::configure as configure_cache;
 mod services;
+mod watcher;
+pub use watcher::Watcher;
 mod stdio;
 pub use services::supervise;
 use stdio::Io;
@@ -567,7 +570,23 @@ impl Host for State {
         Ok(self.runtime.kill_pid(pid).map_err(|e| e.to_string()))
     }
 }
+#[async_trait::async_trait]
+impl wasmtime_wasi::p2::Pollable for Child {
+    async fn ready(&mut self) {
+        while self.code.borrow_and_update().is_none() {
+            if self.code.changed().await.is_err() {
+                break;
+            }
+        }
+    }
+}
 impl HostChild for State {
+    async fn subscribe(
+        &mut self,
+        child: Resource<Child>,
+    ) -> wasmtime::Result<Resource<wasmtime_wasi::p2::DynPollable>> {
+        wasmtime_wasi::p2::subscribe(&mut self.table, child)
+    }
     async fn pid(&mut self, child: Resource<Child>) -> wasmtime::Result<u32> {
         Ok(self.table.get(&child)?.pid)
     }