RetroLogger - Bringing old school log level commands to sbt-0.10.x

RetroLogger.scala

/* RetroLogger.scala
 * 
 * A handy sbt-0.10.x plugin that allows you to set the log level like in the
 * old days (AKA sbt-0.7.x).
 *
 * It works by creating aliases of this form:
 * "set logLevel := Level.Debug"  ====> "debug"
 *
 * Installation:
 * - mkdir -p ~/.sbt/plugins/
 * - cp path/to/RetroLogger.scala ~/.sbt/plugins/
 * - touch ~/.sbt/plugins/build.sbt
 * - add "sbtPlugin := true" to ~/.sbt/plugins/build.sbt
 *
 * Author: Gerolf Seitz
 * Original: https://gist.github.com/1100428
 */

import sbt._
import Keys._

object RetroLogger extends Plugin {

  private def log(level: String) = (state: State) =>
    BuiltinCommands.addAlias (
      state, level,
      "set logLevel := Level.%s%s" format (level.head.toUpper, level.tail)
    )

  // The workaround from above.
  override lazy val settings: Seq[Setting[_]] = Seq[Setting[_]] (
    onLoad in Global <<= (onLoad in Global) ?? identity[State],
    onLoad in Global ~= { oldState =>
      log("error") compose
      log("warn") compose
      log("info") compose
      log("debug") compose
      oldState
    }
  )
}