title: Google Cloud App Engine app.yaml for multiple environments
body: <p>I currently have my app up and running, the <code>app.yaml</code> and <code>dispatch.yaml</code> are in the root of the application and I deploy through Google Cloud CLI. </p>
  
  <p>This works well for the moment, though as I move to having a <code>dev</code>, <code>staging</code> and <code>prod</code> environment I can see that it's no longer viable. </p>
  
  <p>The main issue I see is that I have to edit the variables in the <code>app.yaml</code> file so they are appropriate for environment (for example I use <code>env_variables</code> to store mysql credentials...).</p>
  
  <p>I can't find anything in the docs that points to the correct way to manage this, any ideas? </p>
  
  <p>Also... When deploying from a GIT repo it seems that the <code>app.yaml</code> needs to be in the repo, is this correct? It doesn't seem right to me... There must be a better way! </p>