broker: upgrade and rollback keep a stopped actor stopped

A stopped actor gets the new version installed, keeps its mailbox and does
not run main until the next start. Running actors still restart on the new
version. The upgraded and rolled_back answers say whether the actor runs.

cli/src/supervisor.rs

@@ -220,17 +220,16 @@ impl Supervisor {
 
     /// Make `version` current. It is compiled first (unless `component` is
     /// given): if that fails, nothing changes. `data/` and `public/` stay as
-    /// they are.
+    /// they are. A stopped actor stays stopped.
     async fn install(&mut self, version: u64, component: Option<Component>) -> Result<()> {
         let component = match component {
             Some(c) => c,
             None => self.broker.load_version(&self.id, version)?,
         };
         self.stop().await;
-        self.broker.install(&self.id, version)?;
+        self.broker.install(&self.id, version, self.running)?;
         self.version = version;
         self.component = Some(component);
-        self.running = true;
         self.restarts = 0;
         self.restart_at = None;
         Ok(())
@@ -239,20 +238,26 @@ impl Supervisor {
     async fn upgrade(&mut self, version: u64, component: Component, requester: String) -> Result<Value> {
         let previous = self.version;
         self.install(version, Some(component)).await?;
+        if !self.running {
+            // Installed, not started: main runs and mail is read at the next `start`.
+            return Ok(json!({"type": "upgraded", "actor": self.id, "version": version, "previous": previous, "running": false}));
+        }
         self.probation = Some(Probation { previous, since: Instant::now(), crashes: 0, requester });
         if let Err(e) = self.start().await {
             self.rollback(previous).await?;
             bail!("version {version} did not start ({e:#}); rolled back to {previous}");
         }
-        Ok(json!({"type": "upgraded", "actor": self.id, "version": version, "previous": previous}))
+        Ok(json!({"type": "upgraded", "actor": self.id, "version": version, "previous": previous, "running": true}))
     }
 
     async fn rollback(&mut self, version: u64) -> Result<Value> {
         let from = self.version;
         self.install(version, None).await?;
         self.probation = None;
-        self.start().await?;
-        Ok(json!({"type": "rolled_back", "actor": self.id, "from": from, "to": version}))
+        if self.running {
+            self.start().await?;
+        }
+        Ok(json!({"type": "rolled_back", "actor": self.id, "from": from, "to": version, "running": self.running}))
     }
 
     /// Handle a control request. Returns `true` when the supervisor ends.