YAML, Docker Compose, Spaces & Quotes : <p>Under what circumstances <strong>must</strong> one use quotes in a YAML file, specifically when using <code>docker-compose</code>.</p>

<p>For instance,</p>

<pre><code>service:
  image: "my-registry/repo:tag1"
  environment:
    ENV1: abc
    ENV2: "abc"
    ENV3: "a b c"
</code></pre>

<p>If spaces are required, for example, must one use quotes around the environment variable, as depicted in <code>ENV3</code>?</p>
