DefaultGroupingFunction.scala

dockerLayerGrouping := {
      val dockerBaseDirectory = (defaultLinuxInstallLocation in Docker).value
      (path: String) =>
        {
          val pathInWorkdir = path.stripPrefix(dockerBaseDirectory)
          if (pathInWorkdir.startsWith(s"/lib/${organization.value}"))
            Some(2)
          else if (pathInWorkdir.startsWith("/lib/"))
            Some(1)
          else if (pathInWorkdir.startsWith("/bin/"))
            Some(1)
          else None
        }
    }