title: SBT: Exclude resource subdirectory
body: <p>I've been using Gradle for most of my Scala projects, but I want to evaluate the suitability of SBT as a replacement. One of the things I've done in Gradle is to exclude a certain resource directory from the final build (for example, using CoffeeScript to write JavaScript files that will be included as final resources).</p>
  
  <p>In Gradle, I'd do this by:</p>
  
  <pre><code>sourceSets {
      main {
          resources {
              exclude 'com/example/export/dev' // exclude development resources
          }
      }
  }
  </code></pre>
  
  <p>And this would exclude the resource package <code>com.example.export.dev</code> package from the final build.</p>
  
  <p>How would I do the same in SBT? I've tried </p>
  
  <pre><code>unmanagedResourceDirectories in Compile -= (resourceDirectory in Compile).value / "com/example/export/dev"
  </code></pre>
  
  <p>but that doesn't do a thing (I understand why, but that doesn't really help). And the documentation on the SBT web site only talks about excluding file patterns (at <a href="http://www.scala-sbt.org/0.13/docs/Classpaths.html" rel="noreferrer">Classpaths, sources, and resources</a>).</p>
  
  <p>As a more descriptive image, say we have the following resource directory structure:</p>
  
  <pre><code>com
  \---example
       \---export
           \---dev
           \---something
  </code></pre>
  
  <p>In the final output, I want:</p>
  
  <pre><code>com
  \---example
      \---export
          \---something
  </code></pre>