title: Git: How to convert an existing `merge` to a `merge --squash`?
body: <p>I performed multiple <code>merge</code> commits but they should have been <code>merge --squash</code> instead. The conflict resolution took more than a day so I can't afford to redo the merging by hand.</p>
  
  <p>Is there a way to convert the <code>merge</code> to <code>merge --squash</code> ?</p>