title: Azure DevOps - require PR re-approval if PR is updated after initial approval
body: <p>In Azure DevOps, consider the following sequence of events</p>
  <ol>
  <li>PR is created by developer, not marked as auto-complete</li>
  <li>PR is reviewed and approved by the reviewer (requrired policy is atleast 1 reviewer)</li>
  <li>Additional changes are made by the developer, PR gets updated automatically</li>
  <li>PR is completed and includes the changes made in (3) above, which are not reviewed by anyone</li>
  </ol>
  <p>How do we ensure that any additional changes done to an already approved PR needs to be re-approved?</p>
  <p>Thanks</p>