Fix revision bundling

Summary:
This fixes headless not terminating due to the `package.json` not being readable.
I instead write this to the `global` object in the same way that the version is
set.

Reviewed By: jknoxville

Differential Revision: D14579316

fbshipit-source-id: 238afe912366c423552305e120088f4abac4c20b

src/utils/packageMetadata.js

@@ -23,6 +23,10 @@ const getPackageJSON = async () => {
 
 export const readCurrentRevision: () => Promise<?string> = 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;
   },