An example of how to write a task that copies project dependencies to a directory.

ex-copy-plugin-dependencies-task.sbt

TaskKey[Unit]("copy-plugin-dependencies") <<= (update) map {
      (updateReport) =>
         updateReport.select(Set("compile", "runtime")) map { jar =>
            import java.util.jar.{JarFile, Manifest => JarManifest}
            val jarFile = new JarFile(jar)
            val jarAttributes = jarFile.getManifest().getMainAttributes()
            val targetdir = file("plugins")
            if (!targetdir.exists) targetdir.mkdir()
            else if (!targetdir.isDirectory) error("%s is not a directory".format(targetdir))
            for (bundleSymName <- Option(jarAttributes.getValue("Bundle-SymbolicName"));
                 version <- Option(jarAttributes.getValue("Bundle-Version"))) 
            yield { (bundleSymName, version, jar, targetdir) }
         } foreach { _ match {
            case Some((bundleSymName, version, jar, targetdir)) => {
               import java.nio.file.Files
               Files.copy(jar.toPath, targetdir.toPath.resolve("%s_%s.jar".format(bundleSymName, version)))
            }
            case None => ()
            }
         }
}