title: What does the Private setting do on a ProjectReference in a MSBuild project file?
body: <p>I saw this in a project file the other day:</p>
  
  <pre><code>&lt;ProjectReference Include="Foo\Bar\Baz.csproj"&gt;
      &lt;Project&gt;{A GUID HERE}&lt;/Project&gt;
      &lt;Name&gt;Baz&lt;/Name&gt;
      &lt;Private&gt;False&lt;/Private&gt; &lt;!-- ??? --&gt;
      &lt;ReferenceOutputAssembly&gt;False&lt;/ReferenceOutputAssembly&gt;
  &lt;/ProjectReference&gt;
  </code></pre>
  
  <p>Every node in a <code>ProjectReference</code> appears to be self explanatory (the referenced project file, GUID, name to show in the solution explorer, and whether or not the current project should link to the referenced project) except <code>Private</code>, and the <a href="http://msdn.microsoft.com/en-us/library/bb629388.aspx" rel="noreferrer">Common MSBuild Project Items</a> page doesn't document this value. (There's a <code>Private</code> setting documented for <code>Reference</code> rather than <code>ProjectReference</code> -- but it has <code>Never</code>, <code>Always</code>, and <code>PreserveNewest</code> settings, not true and false)</p>
  
  <p>What does this setting do?</p>