title: Amend username for a pushed commit on Github
body: <p>I made a push to a newly forked git repo on <strong>Github</strong> but after committing i noticed that my username was incorrect. The username I pushed was "Brock Woolf" but it should have been <code>brockwoolf</code> which is my username on github.</p>
  
  <p>I already changed the default locally like this:</p>
  
  <pre><code>git config --global user.name "brockwoolf"
  </code></pre>
  
  <p>But how can I change the username on the already pushed change?</p>