1. Deploy the app.

   To deploy tip.golang.org:
       $ gcloud --project golang-org preview app deploy --no-promote godoc.yaml

   To deploy talks.golang.org:
       $ gcloud --project golang-org preview app deploy --no-promote talks.yaml

2. Wait until the deployed version is serving requests.

3. Go to the developer console and upgrade the default version.
   https://console.developers.google.com/appengine/versions?project=golang-org&moduleId=tip

4. Clean up any old versions (they continue to use at least one instance).