title: In WiX files, what does Name="SourceDir" refer to?
body: <p>WiX files always seem to include this line:</p>
  
  <pre><code>&lt;Directory Id="TARGETDIR" Name="SourceDir"&gt;
  </code></pre>
  
  <p>What is "SourceDir"? What is it used for? It's not a real directory name. Is it some kind of magical value?</p>