title: How to squash commits on Bitbucket after they have been pushed?
body: <p>I am currently working on a project with multiple others. The problem is that we created a fork of an existed project and need to squash all our commits from after the forking process to a single commit for a pull-request on <a href="https://bitbucket.org/" rel="noreferrer">Bitbucket</a>. </p>
  
  <p>Is there any way (preferably using <a href="https://www.sourcetreeapp.com/" rel="noreferrer">SourceTree</a>, otherwise terminal) to squash already pushed commits to a single commit, such that the history within Bitbucket of all the commits are also only that one commit plus the commits which were already there before we forked the project?</p>
  
  <p>Take as example just a simple project with a few files in only a <code>master</code> branch.</p>