Revert "Remove yarn < 1.5 workaround."

This reverts commit e188e1e.

Author: bradfordlemley

packages/react-scripts/scripts/init.js

@@ -23,6 +23,7 @@ const { defaultBrowsers } = require('react-dev-utils/browsersHelper');
 const os = require('os');
 const resolveFrom = require('resolve-from');
 const paths = require('../config/paths');
+const { findMonorepo } = require('react-dev-utils/workspaceUtils');
 
 function isInGitRepository() {
   try {
@@ -177,10 +178,19 @@ module.exports = function(
     fs.unlinkSync(templateDependenciesPath);
   }
 
+  // yarn ws not creating app/node_modules/.bin link to hoisted react-scripts
+  // -- workaround: install react-scripts again to create link
+  // -- bug in yarn 1.3.2, fix verified in nightly 1.4.1-20180211.2236 and 1.5.1
+  // TODO: remove this workaround when CRA enforces min yarn version
+  const rerunYarn = useYarn && findMonorepo(appPath).isAppIncluded;
+  if (rerunYarn) {
+    console.log('Detected app in yarn workspace, running install again');
+  }
+
   // Install react and react-dom for backward compatibility with old CRA cli
   // which doesn't install react and react-dom along with react-scripts
   // or template is presetend (via --internal-testing-template)
-  if (!isReactInstalled(appPackage) || template) {
+  if (!isReactInstalled(appPackage) || template || rerunYarn) {
     console.log(`Installing react and react-dom using ${command}...`);
     console.log();