title: docker-compose execute command in sibling container
body: <p>I am building an end to end test suite around a number of services. Some of these services aren't really services. They are actually procedural scripts which are run in sequence. These are executed at the command line and accept arguments, as you would expect a script to do.</p>
  
  <p>We have docker images for these scripts/apps. I have compiled them into a docker-compose file. They are defined there as services which are sibling to the end to end test suite itself. So, for example:</p>
  
  <p><strong>docker-compose.yml</strong></p>
  
  <pre><code>version: '3.4'
  services:
    script:
      build: https://${GITHUB_ACCESS}:@github.com/company/script.git
      image: script:e2e
    e2e_tests:
      build: .
      image: e2e:e2e
  </code></pre>
  
  <p>Now, the e2e service needs to execute the script. Since the script isn't a service, I can't make a simple api call. How would I pass a command into the <code>script</code> container in order to execute it, from the e2e_tests container?</p>