title: Passing a list of arguments to docker at build / run time
body: <p>I am writing a dockerfile where i want to download a <strong>changing</strong> set of git repos: repo1, repo2, repo3.
  How should I supply these urls/strings to the dockerfile at image build or container run times?</p>
  
  <p>I know one can pass an argument using the <code>ARG</code> instruction and using </p>
  
  <p><code>docker build --build-arg &lt;var-name&gt;=&lt;value&gt;</code></p>
  
  <p>But what happens when I have a list of args of arbitrary length?</p>
  
  <p>Thanks a lot.</p>