title: Jenkins pipeline - add regex in checkout step
body: <p>I have a Jenkins pipeline trigerred by Post-receive Hook sent from git.  Push hook is configured receiving standard syntax from git plugin doc (<a href="https://wiki.jenkins.io/display/JENKINS/Git+Plugin#GitPlugin-Pushnotificationfromrepository" rel="nofollow noreferrer">https://wiki.jenkins.io/display/JENKINS/Git+Plugin#GitPlugin-Pushnotificationfromrepository</a>):
  <code>
  curl http://yourserver/git/notifyCommit?url=&lt;URL of the Git repository&gt;[&amp;branches=branch1[,branch2]*][&amp;sha1=&lt;commit ID&gt;]
  </code></p>
  
  <p>Then in my Jenkins pipeline I have a checkout step as follows:
  <code>
   checkout([$class: 'GitSCM', branches: [[name: '*/feature/jenkins_test']], doGenerateSubmoduleConfigurations: false, extensions: [], submoduleCfg: [], userRemoteConfigs: [[credentialsId: '76d7653e-2657-4d6c-a5e3-e3d40a82c321', url: 'ssh://git@git.mydomain.ch:7999/sbvd/my-framework.git']]])
  </code></p>
  
  <p>The above line gets properly triggered only when anyone pushes to <code>feature/jenkins_test</code>. I want to take it one step further though and trigger build only when files in specific directory in repo is touched. Normally with SCM plugin polling the repo this is possible be specifying a regular expression to match certain files only. </p>
  
  <p>Can I somehow get this filter to work with the described configuration and Jenkins pipeline?</p>