Yarn workspaces

Summary:
1) moved "sonar/desktop/src" to "sonar/desktop/app/src", so "app" is now a separate package containing the core Flipper app code
2) Configured yarn workspaces with the root in "sonar/desktop": app, static, pkg, doctor, headless-tests. Plugins are not included for now, I plan to do this later.

Reviewed By: jknoxville

Differential Revision: D20535782

fbshipit-source-id: 600b2301960f37c7d72166e0d04eba462bec9fc1

desktop/app/src/utils/packageMetadata.tsx

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import electron from 'electron';
+import lodash from 'lodash';
+import isProduction from './isProduction';
+import path from 'path';
+import fs from 'fs';
+import {promisify} from 'util';
+
+const getPackageJSON = async () => {
+  const base =
+    isProduction() && electron.remote
+      ? electron.remote.app.getAppPath()
+      : process.cwd();
+  const content = await promisify(fs.readFile)(
+    path.join(base, 'package.json'),
+    'utf-8',
+  );
+  return JSON.parse(content);
+};
+
+export const readCurrentRevision: () => Promise<
+  string | undefined
+> = lodash.memoize(async () => {
+  // This is provided as part of the bundling process for headless.
+  if (global.__REVISION__) {
+    return global.__REVISION__;
+  }
+  const json = await getPackageJSON();
+  return json.revision;
+});