title: Why doesn't git allow me to safely delete a branch?
body: <p>I needed to merge two branches -- <code>second</code> into <code>first</code> and then get rid of <code>second</code>.  Here's what I did:</p>
  
  <ul>
  <li><code>git clone</code>d the project to get a fresh copy</li>
  <li><code>git checkout --track origin/second</code>, made some changes, and committed</li>
  <li><code>git checkout --track origin/first</code>, made some changes, and committed</li>
  <li><code>git merge second</code> (git says "merge made by recursive")</li>
  <li><code>git branch -d second</code></li>
  </ul>
  
  <p>Then git says:</p>
  
  <pre><code>$ git branch -d second
  warning: not deleting branch 'second' that is not yet merged to
           'refs/remotes/origin/second', even though it is merged to HEAD.
  error: The branch 'second' is not fully merged.
  If you are sure you want to delete it, run 'git branch -D second'.
  </code></pre>
  
  <p>Why is this happening?  I've never gotten this message after a merge before.  The merge worked just fine, no conflicts.  How do I safely delete the <code>second</code> branch?</p>