title: Git webhook does not trigger Jenkins build when pushed from remote branch
body: <p>Jenkins build is not triggered by the git webhook when pushed changes from a remote repository branch</p>
  
  <p>I have the main git repository (upstream) and the forked git repository (origin). When I push changes to upstream/master, I expect the Jenkins build to start automatically. </p>
  
  <p>Case 1: Created Pull request and merged origin/my_branch into upstream/master using the "Merge Pull Request" button from GitHub web interface</p>
  
  <p>Case 2: Created Pull request and merged origin/my_branch into upstream/master using the command line 
  <code>git push upstream my_branch:master</code></p>
  
  <p>Firstly, I would like to know the difference between case 1 and case 2 merges</p>
  
  <p>My observation is that git webhook trigger works perfectly in case 1 but in case 2 git webhook failed to trigger the Jenkins build. 
  Did anyone face the same issue?</p>
  
  <p>Please help me understand the difference here. thanks in advance</p>