Add support for Attributed

Fixes sbt#112

src/main/scala/sbtbuildinfo/ScalaRenderer.scala

@@ -23,6 +23,8 @@ abstract class ScalaRenderer extends BuildInfoRenderer {
         case TypeExpression("sbt.librarymanagement.ModuleID", Nil) => Some("String")
         case TypeExpression("sbt.librarymanagement.Resolver", Nil) => Some("String")
 
+        case TypeExpression("sbt.internal.util.Attributed", Seq(TypeExpression("java.io.File", Nil))) => Some("java.io.File")
+
         case TypeExpression("scala.Option", Seq(arg)) =>
           tpeToReturnType(arg) map { x => s"scala.Option[$x]" }
         case TypeExpression("scala.collection.Seq", Seq(arg)) =>
@@ -52,6 +54,7 @@ abstract class ScalaRenderer extends BuildInfoRenderer {
     case op: Option[_]      => op map { x => "scala.Some(" + quote(x) + ")" } getOrElse {"scala.None"}
     case url: java.net.URL  => "new java.net.URL(%s)" format quote(url.toString)
     case file: java.io.File => "new java.io.File(%s)" format quote(file.toString)
+    case attr: sbt.Attributed[_] => quote(attr.data)
     case s                  => "\"%s\"" format encodeStringLiteral(s.toString)
   }
 

src/sbt-test/sbt-buildinfo/simple/build.sbt

@@ -6,6 +6,7 @@ lazy val root = (project in file(".")).
     name := "helloworld",
     version := "0.1",
     scalaVersion := "2.11.8",
+    TaskKey[Classpath]("someCp") := Seq(Attributed.blank(file("/tmp/f.txt"))),
     buildInfoKeys := BuildInfoKey.ofN(
       name,
       BuildInfoKey.map(version) { case (n, v) => "projectVersion" -> v.toDouble },
@@ -18,6 +19,7 @@ lazy val root = (project in file(".")).
       "year" -> 2012,
       "sym" -> 'Foo,
       BuildInfoKey.action("buildTime") { 1234L },
+      TaskKey[Classpath]("someCp"),
       target
     ),
     buildInfoPackage := "hello",
@@ -57,6 +59,8 @@ lazy val root = (project in file(".")).
              """  val sym: scala.Symbol = 'Foo""" ::
              """  /** The value is 1234L. */""" ::
              """  val buildTime: scala.Long = 1234L""" ::
+             """  /** The value is scala.collection.Seq(new java.io.File("/tmp/f.txt")). */""" ::
+             """  val someCp: scala.collection.Seq[java.io.File] = scala.collection.Seq(new java.io.File("/tmp/f.txt"))""" ::
              targetInfoComment ::
              targetInfo :: // """
              """  override val toString: String = {""" ::