chore: add warning if yarn workspaces found (#599)

lib/workers/package-file/index.js

@@ -29,6 +29,10 @@ async function renovatePackageFile(packageFileConfig) {
     return [config];
   }
 
+  if (packageContent.workspaces) {
+    logger.warn('Found workspaces');
+  }
+
   // Check for renovate config inside the package.json
   if (packageContent.renovate) {
     logger.trace(

test/workers/package-file/index.spec.js

@@ -65,7 +65,7 @@ describe('packageFileWorker', () => {
       expect(res).toEqual([]);
     });
     it('calls depTypeWorker', async () => {
-      config.api.getFileJson.mockReturnValueOnce({});
+      config.api.getFileJson.mockReturnValueOnce({ workspaces: true });
       depTypeWorker.renovateDepType.mockReturnValueOnce([{}]);
       depTypeWorker.renovateDepType.mockReturnValueOnce([{}, {}]);
       depTypeWorker.renovateDepType.mockReturnValueOnce([]);