title: Previously merged commits keep appearing on new Pull Requests
body: <p>I am having difficulty understanding why some previously merged commits keep appearing in pull requests.</p>
  <p>We have a master branch and then an integration one against which we develop against via feature branch pull requests - so git flow type workflow.</p>
  <p>I currently have an open PR like so:</p>
  <p><a href="https://i.stack.imgur.com/8FFo8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8FFo8.png" alt="enter image description here" /></a></p>
  <p>But the first few commits on this, were already merged in an earlier PR:</p>
  <p><a href="https://i.stack.imgur.com/xCtq5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xCtq5.png" alt="enter image description here" /></a></p>
  <p>I dont get why this is happening, can someone explain?</p>