Use IPC message to handle .reload command in meteor shell.

I considered using a nonzero process.exit code, but I didn't want to run
any risk of reusing a meaningful code, and the accepted range of codes
unfortunately does not include parseInt("reload", 36), or 1657112629.

Should fix #10934.

packages/shell-server/package.js

@@ -1,6 +1,6 @@
 Package.describe({
   name: "shell-server",
-  version: "0.4.0",
+  version: "0.5.0",
   summary: "Server-side component of the `meteor shell` command.",
   documentation: "README.md"
 });

packages/shell-server/shell-server.js

@@ -12,6 +12,9 @@ import {
 import { createServer } from "net";
 import { start as replStart } from "repl";
 
+// Enable process.sendMessage for communication with build process.
+import "meteor/inter-process-messaging";
+
 const INFO_FILE_MODE = parseInt("600", 8); // Only the owner can read or write.
 const EXITING_MESSAGE = "Shell exiting...";
 
@@ -308,7 +311,11 @@ class Server {
     repl.defineCommand("reload", {
       help: "Restart the server and the shell",
       action: function() {
-        process.exit(0);
+        if (process.sendMessage) {
+          process.sendMessage("shell-server", { command: "reload" });
+        } else {
+          process.exit(0);
+        }
       }
     });
   }

tools/runners/run-app.js

@@ -767,6 +767,14 @@ _.extend(AppRunner.prototype, {
     var serverWatcher;
     var clientWatcher;
 
+    appProcess.proc.onMessage("shell-server", message => {
+      if (message && message.command === "reload") {
+        self._resolvePromise("run", { outcome: "changed" });
+      } else {
+        return Promise.reject("Unsupported shell command: " + message);
+      }
+    });
+
     if (self.watchForChanges) {
       serverWatcher = new watch.Watcher({
         watchSet: serverWatchSet,