title: How do I get TeamCity to Merge master into Pull Request before each build?
body: <p>Given TeamCity &amp; our Github repo and a CI flow matching Github Flow.</p>
  
  <p>I want to be able to start my build process by first merging master into a  Pull Request's branch.</p>
  
  <p>If that succeeds, then it can go on with the rest of the build steps.</p>
  
  <p>Can this be configured in TeamCity with builtin functionality? Or do I have to create a build step &amp; write a shell script that does this and returns success/fail as my first step?</p>