sbt/project/StatusPlugin.scala

import sbt._
import Keys._
import java.util.regex.Pattern

object StatusPlugin extends AutoPlugin {
  override def requires = plugins.JvmPlugin
  override def trigger = allRequirements

  object autoImport {
    lazy val publishStatus = SettingKey[String]("publish-status")
  }

  import autoImport._

  override def buildSettings: Seq[Setting[_]] = Seq(
    isSnapshot <<= version(v => v.contains("-") && snapshotQualifier(v)),
    publishStatus <<= isSnapshot { snap => if (snap) "snapshots" else "releases" },
    commands += stampVersion
  )
  def stampVersion = Command.command("stamp-version") { state =>
    val extracted = Project.extract(state)
    val status = extracted.get(publishStatus)
    // Set new version AND lock down the publishStatus to what it was, as
    // our release regexes no longer support ivy data format, due to other issues.
    extracted.append(
      (version in ThisBuild ~= stamp) ::
        (publishStatus in ThisBuild := status) ::
        Nil,
      state)
  }
  def stamp(v: String): String =
    if (v endsWith Snapshot)
      (v stripSuffix Snapshot) + "-" + timestampString(System.currentTimeMillis)
    else
      error("Release version '" + v + "' cannot be stamped")
  def timestampString(time: Long): String =
    {
      val format = new java.text.SimpleDateFormat("yyyyMMdd-HHmmss")
      format.format(new java.util.Date(time))
    }
  final val Snapshot = "-SNAPSHOT"
  // NOte: This moved into sbt itself...  But we need to add semantic knowledge of how
  // we stamp our nightlies.
  def snapshotQualifier(v: String) = Pattern.matches(""".+-.*SNAPSHOT.*""", v)
}