title: SVN Error: "' 'x' isn't in the same repository as 'y' " during merge
body: <p>I get the error </p>
  
  <pre><code>svn: 'x' isn't in the same repository as 'y' "
  </code></pre>
  
  <p>during merge. What's the problem and how can I fix it ?</p>
  
  <p>(I actually know the answer and posting it as soon as I am allowed by the system, so that it's googleable by others. I got my share of trouble finding the answer).</p>