code: public static List<DependencyNode> getExtraDependencies(List<DependencyNode> nodes) {
          ExtraArtifactsHandler fetcher = new ExtraArtifactsHandler(nodes);
  
          if (isSet("thorntail.download.sources")) {
              fetcher.addWithClassifier("sources");
          }
  
          if (isSet("thorntail.download.poms")) {
              fetcher.addWithExtension("pom");
          }
  
          if (isSet("thorntail.download.javadocs")) {
              fetcher.addWithClassifier("javadoc");
          }
  
          return fetcher.output;
      }
docs: Takes a list of dependencies and creates a list of extras (poms, javadocs and/or sources) for those dependencies.
  <p/>
  Set one or more of the following system properties to make the method return artifacts of a specified type:
  <ul>
  <li><code>thorntail.download.sources</code> for sources</li>
  <li><code>thorntail.download.poms</code> for pom files</li>
  <li><code>thorntail.download.javadocs</code> for javadocs</li>
  </ul>
  <p/>
  
  @param nodes list of dependencies
  @return list of extra artifacts