title: How to avoid checkout of sources on master node with jenkins pipeline
body: <p>I want to define my builds using the Jenkins 2 pipeline feature and I want this configuration to be loaded from sources in a <code>Jenkinsfile</code>.
  However I don't want to clutter my <code>master</code> node with workspace.</p>
  
  <p>Ideally, I could specify that a pipeline job is meant to be run a given node type but that doesn't seems possible.</p>
  
  <p>I see 2 alternatives:</p>
  
  <ul>
  <li>use a dedicated repository where the jenkins job configuration is stored.</li>
  <li>use a cleaver git checkout strategy (shallow + sparse).</li>
  </ul>
  
  <p>Did I miss something? What would be the best practice ?</p>