title: In Jenkins Delarative Pipeline, how to evaluate whether a specific directory is changed
body: <p>The conditionals of Jenkins Declarative Pipeline is built around branches namely. 
  I would like to evaluate whether a specific folder is changed within any branch and then run the stages.</p>
  
  <p>Something like:</p>
  
  <pre><code>stage {
     when {
        folderX changed
     }
  }
  </code></pre>
  
  <p>To give you a better idea of why I need this feature, let me elaborate. 
  The project I am working on exists out of a few modules (let's say micro services). Although every module can have its own branch or even repository, we have chosen to put them together in their own folders, so we can always keep everything clean in the master. 
  Our Jenkins pipleine has a stage for every module. However, we do not want to rebuild every module if nothing is changed in that folder. </p>