title: Ambiguous argument in git reset
body: <p>I recently screwed up a <code>git rebase -i</code>, and so I wanted to do a <code>git reset --hard HEAD@{5}</code>.</p>
  
  <p>However, doing a <code>git reset --hard HEAD@{5}</code> or <code>git log HEAD@{5}</code> caused the following error message to be shown:</p>
  
  <pre><code>fatal: ambiguous argument 'HEAD@{5}': unknown revision or path not in the working tree.
  </code></pre>
  
  <p>Then, I decided to specify the hash key corresponding to <code>HEAD@{5}</code> shown in <code>git reflog</code> instead.  For instance: </p>
  
  <pre><code>git reset --hard e8be841
  </code></pre>
  
  <p>In doing so, was there any risk screwing up the git repository or doing something unexpected?</p>