title: Get the commit id of merged Pull Requests
body: <p>Over the development process, there are many commits to a code repository.
  Some of them are merge commits, in other words, they carry the 'signal' to merge a particular Pull Request to master.</p>
  <p>You can see the IDs of these commits easily using an online code repository, such as Github, Bitbucket etc...</p>
  <p>However, can this be done locally?
  Is there a way to get a list of the ids of the merge commits, and see which branch each one corresponds to ?</p>