docker3.scala

val stageDir = target.value / "native-docker" / "stage"
stageDir.mkdirs()

// copy all jars to the staging directory
val cpDir = stageDir / "cp"
cpDir.mkdirs()

val classpathJars = Seq((packageBin in Compile).value) ++ 
  (dependencyClasspath in Compile).value.map(_.data)
classpathJars.foreach(cpJar => Files.copy(
  cpJar.toPath, 
  (cpDir / cpJar.name).toPath, 
  StandardCopyOption.REPLACE_EXISTING))

val resultDir = stageDir / "result"
resultDir.mkdirs()
val resultName = "out"

val className = (mainClass in Compile).value
  .getOrElse(sys.error("Could not find a main class."))