title: sbt: copy resources to classpath in multi project build
body: <p>I have a sbt project with following structure:</p>
  
  <pre><code>project
  |
  |-- file.json
  |-- &lt;serverProject&gt;
  |-- &lt;clientProject&gt;
  </code></pre>
  
  <p><code>project</code> aggregates both <code>serverProject</code> and <code>clientProject</code>. Starting sbt and compiling works fine. </p>
  
  <p>When running or packaging <code>serverProject</code> I want <code>file.json</code> to end up at the classpath of <code>serverProject</code>.</p>
  
  <p>I added <code>file.json</code> to the <code>unmanagedResources in (Compile)</code> for <code>serverProject</code> but I get following error when trying to run / package:</p>
  
  <pre><code>[info] Done packaging.
  java.lang.RuntimeException: Duplicate mappings:
      project/serverProject/target/scala-2.11/classes/file.json
  from
      file.json
          project/serverProject/file.json
      at scala.sys.package$.error(package.scala:27)
      at sbt.Sync$.noDuplicateTargets(Sync.scala:67)
      ...
  </code></pre>
  
  <p>It looks like sbt finds both the project root directory and serverProject directory as candidates for <code>file.json</code> after which it fails.</p>
  
  <p>How to get around this error?</p>
  
  <p>Thanks for reading and helping out!</p>