Set default artifact type to empty value

Add non regression test for
https://github.com/alexarchambault/coursier/issues/322

A dirty hack is lying in this commit.

cli/src/main/scala-2.11/coursier/cli/Options.scala

@@ -61,10 +61,10 @@ case class CommonOptions(
   @Value("configuration")
   @Short("c")
     defaultConfiguration: String = "default(compile)",
-  @Help("Default artifact type (make it empty to follow POM packaging - default: jar)")
+  @Help("Default artifact type (default: follow packaging infos, else default to jar)")
   @Value("type")
   @Short("a")
-    defaultArtifactType: String = "jar",
+    defaultArtifactType: String = "",
   @Help("Maximum number of parallel downloads (default: 6)")
   @Short("n")
     parallel: Int = 6,

core/shared/src/main/scala/coursier/maven/MavenRepository.scala

@@ -69,6 +69,10 @@ object MavenRepository {
     } else
       module.name
 
+  val ignorePackaging = Set(
+    Module("org.apache.zookeeper", "zookeeper", Map.empty)
+  )
+
 }
 
 case class MavenRepository(
@@ -76,7 +80,8 @@ case class MavenRepository(
   changing: Option[Boolean] = None,
   /** Hackish hack for sbt plugins mainly - what this does really sucks */
   sbtAttrStub: Boolean = false,
-  authentication: Option[Authentication] = None
+  authentication: Option[Authentication] = None,
+  packagingBlacklist: Set[Module] = MavenRepository.ignorePackaging
 ) extends Repository {
 
   import Repository._
@@ -260,7 +265,11 @@ case class MavenRepository(
             _ <- if (xml.label == "project") \/-(()) else -\/("Project definition not found")
             proj <- Pom.project(xml)
           } yield {
-            val packagingOpt = Pom.packagingOpt(xml)
+            val packagingOpt =
+              if (packagingBlacklist(module))
+                None
+              else
+                Pom.packagingOpt(xml)
 
             proj.copy(
               configurations = defaultConfigurations,

plugin/src/main/scala-2.10/coursier/CoursierPlugin.scala

@@ -59,7 +59,7 @@ object CoursierPlugin extends AutoPlugin {
   override lazy val projectSettings = Seq(
     coursierParallelDownloads := 6,
     coursierMaxIterations := 50,
-    coursierDefaultArtifactType := "jar",
+    coursierDefaultArtifactType := "",
     coursierChecksums := Seq(Some("SHA-1"), None),
     coursierArtifactsChecksums := Seq(None),
     coursierCachePolicies := CachePolicy.default,

plugin/src/sbt-test/sbt-coursier/aar-packaging/build.sbt

@@ -0,0 +1,13 @@
+scalaVersion := "2.11.8"
+
+libraryDependencies += ("com.rengwuxian.materialedittext" % "library" % "2.1.4")
+  .exclude("com.android.support", "support-v4")
+  .exclude("com.android.support", "support-annotations")
+  .exclude("com.android.support", "appcompat-v7")
+
+coursierCachePolicies := {
+  if (sys.props("os.name").startsWith("Windows"))
+    coursierCachePolicies.value
+  else
+    Seq(coursier.CachePolicy.ForceDownload)
+}

plugin/src/sbt-test/sbt-coursier/aar-packaging/project/plugins.sbt

@@ -0,0 +1,11 @@
+{
+  val pluginVersion = sys.props.getOrElse(
+    "plugin.version",
+    throw new RuntimeException(
+      """|The system property 'plugin.version' is not defined.
+         |Specify this property using the scriptedLaunchOpts -D.""".stripMargin
+    )
+  )
+
+  addSbtPlugin("io.get-coursier" % "sbt-coursier" % pluginVersion)
+}

plugin/src/sbt-test/sbt-coursier/aar-packaging/src/main/scala/Main.scala

@@ -0,0 +1,6 @@
+import java.io.File
+import java.nio.file.Files
+
+object Main extends App {
+  Files.write(new File("output").toPath, "OK".getBytes("UTF-8"))
+}

plugin/src/sbt-test/sbt-coursier/aar-packaging/test

@@ -0,0 +1,3 @@
+$ delete output
+> run
+$ exists output