Black magic to tell sbt to choose the first duplicate class when resolving dependency collisions instead of just failing out.

blah.scala

  /**
   * Black magic to tell sbt to choose the first duplicate class when resolving dependency collisions instead of just
   * failing out.
    */
mergeStrategy in assembly <<= (mergeStrategy in assembly) {
  (old) => {
    case x if Assembly.isConfigFile(x) =>
      MergeStrategy.concat
    case PathList(ps@_*) if Assembly.isReadme(ps.last) || Assembly.isLicenseFile(ps.last) =>
      MergeStrategy.rename
    case PathList("META-INF", xs@_*) =>
      (xs map { _.toLowerCase}) match {
        case ("manifest.mf" :: Nil) | ("index.list" :: Nil) | ("dependencies" :: Nil) =>
          MergeStrategy.discard
        case ps@(x :: xs) if ps.last.endsWith(".sf") || ps.last.endsWith(".dsa") =>
          MergeStrategy.discard
        case "plexus" :: xs =>
          MergeStrategy.discard
        case "services" :: xs =>
          MergeStrategy.filterDistinctLines
        case ("spring.schemas" :: Nil) | ("spring.handlers" :: Nil) =>
          MergeStrategy.filterDistinctLines
        case _ => MergeStrategy.deduplicate
      }
    case _ => MergeStrategy.first // overrides the default fallback MergeStrategy of deduplicate
  }
}