title: dynamic docker-compose config from env
body: <p>Is there a tool to dynamically set <code>services</code>, <code>external_links</code>, etc. for container orchestration, depending on an environment variable?</p>
  <p>Tool should have convenient syntax (Python/js/bash - any clearly readable), and support conditions (if).</p>
  <p>Now I have 3 files like <code>docker-compose.local.yml</code>, and edit them all.</p>
  <pre><code>cp docker-compose.local.yml docker-compose.yml;
  docker-compose up;
  </code></pre>
  <p>I wan't one config file</p>
  <pre><code>ENV=local;
  docker-compose up; # or &quot;node start-compose.js&quot;
  </code></pre>
  <p>I know that docker-compose supports environment variables like</p>
  <pre><code>volumes:
    - ${ENV}-filename:/.../filename
  </code></pre>
  <p>But I need more.</p>