Stackgo by Sibi Prabakaran

This plugin helps to automatically redirect Hackage requests to Stackage, when the request is via search engines like Google/Bing etc. For cases, where the package documentation hasn't yet been added to Stackage - it will redirect to the Hackage pages.

You can also configure the specific lts page it should be redircted to by changing it's value in preferences. By default it will always redirect to the latest lts page.