Add public asset with app version (Play Framework)

build.sbt

resourceGenerators in Compile <+= (WebKeys.public in Assets, version).map {
  case (dir, v) =>
    val file = dir / "version.txt"
    val gitCommit = Process("git rev-parse HEAD").lines.head
    val content = "version=%s git-commit=%s".format(v, gitCommit)
    IO.write(file, content)
    Seq(file)
}