title: Why can't I delete a remote git branch with git push origin :branchname?
body: <p>When I try to push to a remote git branch to delete it with <code>git push origin :branchname</code> I get the following error message:</p>
  
  <blockquote>
    <p>error: unable to push to unqualified destination: remotes/origin/branchname
    The destination refspec neither matches an existing ref on the remote nor
    begins with refs/, and we are unable to guess a prefix based on the source ref.</p>
  </blockquote>
  
  <p>But when I type <code>git branch -a</code> I still see it in <code>remotes/origin/branchname</code>. Why can't I delete it remotely?</p>