title: jenkins multi-branch pipeline not triggering branch changes
body: <p>I have 3 branches on github. I set up a jenkins multi branch pipeline. I included only 2 branches out of my 3 branches on github in jenkins GUI. ON both of those 2 branches on github, I have a jenkinsfile in which I have a logic something like this.</p>
  
  <pre><code>if(env.branch_name == 'master'){
     build for production
  }else if(env.branch_name == 'stage'){
     build for stage.
  }
  </code></pre>
  
  <p><strong>The problem: when pushing new changes to master or stage branch, multi-branch pipeline doesn't start new build. it's like it has no idea that I pushed it or not.</strong> </p>
  
  <p>I have set up github webhook correctly. it works for single pipeline, but not for multibranch. Any ideas how to fix this?</p>