Merge pull request #24 from Duhemm/fport/inter-project-dependency-tracking

FPORT: Inter-project dependency tracking

librarymanagement/src/main/scala/sbt/librarymanagement/TrackLevel.scala

@@ -0,0 +1,33 @@
+package sbt.librarymanagement
+
+/**
+ * An enumeration defining the tracking of dependencies.  A level includes all of the levels
+ * with id larger than its own id.  For example, Warn (id=3) includes Error (id=4).
+ */
+object TrackLevel {
+  case object NoTracking extends TrackLevel {
+    override def id: Int = 0
+  }
+  case object TrackIfMissing extends TrackLevel {
+    override def id: Int = 1
+  }
+  case object TrackAlways extends TrackLevel {
+    override def id: Int = 10
+  }
+
+  private[sbt] def apply(x: Int): TrackLevel =
+    x match {
+      case 0  => NoTracking
+      case 1  => TrackIfMissing
+      case 10 => TrackAlways
+    }
+
+  def intersection(a: TrackLevel, b: TrackLevel): TrackLevel =
+    if (a.id < b.id) a
+    else b
+  def intersectionAll(vs: List[TrackLevel]): TrackLevel = vs reduceLeft intersection
+}
+
+sealed trait TrackLevel {
+  def id: Int
+}