title: Validate pull request with jenkins in VSTS
body: <p>The only workaround we found for validating pull requests in visual studio online currently is to create a visual studio build definition that triggers our jenkins job, and create a branch policy on that build definition.</p>
  
  <p>But Visual Studio online is able to trigger the jenkins job directly when a git pull request is created / updated.</p>
  
  <p>Is it possible to create a branch policy on the outcome of that jenkins job? The TFS plugin already provides status feedback for the "normal push" build status.</p>