title: How to trigger Multibranch Pipeline build with github webhook
body: <p>In freestyle job there is an option named "GitHub hook trigger for GITScm polling" on stage Build Trigger.</p>
  
  <p>screen capture here:</p>
  
  <p><img src="https://i.stack.imgur.com/qj6Px.png" alt="screen capture here">.</p>
  
  <p>Together with webhook in gitlab config "<a href="http://myjenkins/gitlab/notify_commit" rel="noreferrer">http://myjenkins/gitlab/notify_commit</a>" it works fine, meaning that the build will be triggered automatically when something is pushed to the repository. 
  But why in Multibranch Pipeline there is only one option named "Periodically if not otherwise run"? Is there some plug-in not installed? How to trigger Multibranch Pipeline build with github webhook like freestyle job</p>