Report git-hash used to package the distribution - Closes scala#1319

Author: Bartosz Krasiński

project/Build.scala

@@ -6,6 +6,7 @@ import scala.reflect.io.Path
 
 import org.scalajs.sbtplugin.ScalaJSPlugin
 import org.scalajs.sbtplugin.ScalaJSPlugin.autoImport._
+import sbt.Package.ManifestAttributes
 
 object DottyBuild extends Build {
 
@@ -172,6 +173,9 @@ object DottyBuild extends Build {
       fork in Test := true,
       parallelExecution in Test := false,
 
+      // Add git-hash used to package the distribution to the manifest to know it in runtime and report it in REPL
+      packageOptions += ManifestAttributes(("Git-Hash", VersionUtil.gitHash)),
+
       // http://grokbase.com/t/gg/simple-build-tool/135ke5y90p/sbt-setting-jvm-boot-paramaters-for-scala
       javaOptions <++= (dependencyClasspath in Runtime, packageBin in Compile) map { (attList, bin) =>
         // put the Scala {library, reflect} in the classpath

src/dotty/tools/dotc/repl/InterpreterLoop.scala

@@ -66,7 +66,8 @@ class InterpreterLoop(compiler: Compiler, config: REPL.Config)(implicit ctx: Con
     output.flush()
   }
 
-  val version = ".next (pre-alpha)"
+  val gitHash = ManifestInfo.attributes.getOrElse("Git-Hash", "unknown")
+  val version = s".next (pre-alpha, git-hash: $gitHash)"
 
   /** The main read-eval-print loop for the interpreter.  It calls
    *  `command()` for each line of input.

src/dotty/tools/dotc/repl/ManifestInfo.scala

@@ -0,0 +1,20 @@
+package dotty.tools.dotc.repl
+
+import java.net.JarURLConnection
+import scala.collection.JavaConversions._
+
+object ManifestInfo {
+
+  val attributes: Map[String, String] = {
+    for {
+      resourceUrl <- Option(getClass.getResource(getClass.getSimpleName + ".class"))
+      urlConnection = resourceUrl.openConnection() if urlConnection.isInstanceOf[JarURLConnection]
+      manifest <- Option(urlConnection.asInstanceOf[JarURLConnection].getManifest)
+    } yield {
+      manifest.getMainAttributes.foldLeft(Map[String, String]())(
+        (map, attribute) => map + (attribute._1.toString -> attribute._2.toString)
+      )
+    }
+  }.getOrElse(Map())
+
+}