title: "ambiguous merge - picked m action" - what does it mean?
body: <p>I try to merge:</p>
  
  <pre><code>hg me -r &lt;some-revision&gt;
  </code></pre>
  
  <p>and get:</p>
  
  <pre><code>&lt;some-file&gt;: ambiguous merge - picked m action
  </code></pre>
  
  <p>What does it mean?</p>