title: git-flow: why does "git-flow feature finish -S" still create a merge commit?
body: <p>I have locally developed a feature which consists of a couple of <em>"work in progress"</em> commits. When I'm going to finish this feature using <code>git-flow feature finish -S</code>, I would expect to get one clean commit in <code>develop</code>. However, I get an additional merge commit on top of the squashed commit which references my <em>"work in progress"</em> commits from the obsolete feature branch. What's the purpose of this behavior? Can this additional merge commit be skipped?</p>