Shade jarjar into sbt-shading

build.sbt

@@ -376,13 +376,37 @@ lazy val `sbt-coursier` = project
 
 // Don't try to compile that if you're not in 2.10
 lazy val `sbt-shading` = project
+  .enablePlugins(_root_.coursier.ShadingPlugin)
   .dependsOn(`sbt-coursier`)
   .settings(pluginSettings)
   .settings(
-    // Warning: this version doesn't handle well class names with '$'s
-    // (so basically any Scala library)
-    // See https://github.com/shevek/jarjar/pull/4
-    libraryDependencies += "org.anarres.jarjar" % "jarjar-core" % "1.0.0"
+    shadingNamespace := "coursier.shaded",
+    resolvers += Resolver.mavenLocal,
+    libraryDependencies += {
+      val coursierJarjarVersion = "1.0.1-coursier-SNAPSHOT"
+      def coursierJarjarFoundInM2 = (file(sys.props("user.home")) / s".m2/repository/org/anarres/jarjar/jarjar-core/$coursierJarjarVersion").exists()
+
+      val jarjarVersion =
+        if (sys.env.contains("CI") || coursierJarjarFoundInM2 || !isSnapshot.value)
+          coursierJarjarVersion
+        else {
+          val fallback = "1.0.0"
+
+          // streams.value.log.warn( // "a setting cannot depend on a task"
+          scala.Console.err.println(
+           s"""Warning: using jarjar $fallback, which doesn't properly shade Scala JARs (classes with '$$' aren't shaded).
+              |See the instructions around
+              |https://github.com/alexarchambault/coursier/blob/630a780487d662dd994ed1c3246895a22c00cf21/scripts/travis.sh#L40
+              |to use a version fine with Scala JARs.""".stripMargin
+          )
+
+          fallback
+        }
+
+      "org.anarres.jarjar" % "jarjar-core" % jarjarVersion % "shaded"
+    },
+    publish := publish.in(Shading).value,
+    publishLocal := publishLocal.in(Shading).value
   )
 
 lazy val `sbt-launcher` = project

project/plugins.sbt

@@ -4,6 +4,7 @@ addSbtPlugin("com.jsuereth" % "sbt-pgp" % "1.0.0")
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.4.0")
 addSbtPlugin("org.tpolecat" % "tut-plugin" % "0.4.8")
 addSbtPlugin("io.get-coursier" % "sbt-coursier" % "1.0.0-M15-2")
+addSbtPlugin("io.get-coursier" % "sbt-shading" % "1.0.0-M15-2")
 addSbtPlugin("com.typesafe.sbt" % "sbt-proguard" % "0.2.2")
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.1.13")
 libraryDependencies += "org.scala-sbt" % "scripted-plugin" % sbtVersion.value

sbt.properties

@@ -2,6 +2,7 @@ sbt.version=0.13.8
 
 plugins = [
   "io.get-coursier:sbt-coursier:1.0.0-M15-2"
+  "io.get-coursier:sbt-shading:1.0.0-M15-2"
   "org.xerial.sbt:sbt-pack:0.8.2"
   "org.scala-js:sbt-scalajs:0.6.14"
   "com.jsuereth:sbt-pgp:1.0.0"