title: How to rollback the two previous commits?
body: <p>Consider this scenario:</p>
  
  <ol>
  <li>Developer A does a commit: <strong>#n</strong></li>
  <li>Dev. B does commit <strong>#n+1</strong></li>
  <li>Dev. A does commit <strong>#n+2</strong></li>
  <li>and commit <strong>#n+3</strong></li>
  </ol>
  
  <p>and then discovers that in his commit #n+2 he introduced a defect.</p>
  
  <p>How can dev. A rollback his last 2 commits and continue developing on commit <strong>#n+1</strong>?</p>
  
  <p>Tried <code>git reset --hard HEAD~2</code><a href="http://git-scm.com/docs/git-reset" rel="noreferrer">*</a>, but it's coming back to dev A's commit <strong>#n</strong>.</p>