Trying to get war file name from SBT

gistfile1.scala

import sbt._
import Keys._

import com.github.siasia.{WebPlugin=>WP}

object MyBuild extends Build {

  val myTask = TaskKey[Unit]("my-task")

  lazy val myProject = Project("webproject", file("."), settings =Defaults.defaultSettings ++
    WP.webSettings ++ Seq[Setting[_]](
      myTask <<= (streams, target, scalaVersion, projectID, artifact in WP.packageWar) map (
        (out, t, sv, p,  a) => "ls -la " + new File(t, Artifact.artifactName(sv, p, a)).getAbsolutePath ! out.log)
    ))
}