Add support for Scoverage (#571)

* Add initial work for ScoverageModule

* style: Move package scoverage from lib to contrib

Suggested by @lefou
> I think, it would be better to add under `mill.contrib.scoverage`.

Pull request: #571

* Initial changes to non-hardcoded scoverage version

* Using task context api to specify dataDir

Now measurement data will be written to:
PROJECT_ROOT/out/MODULE/scoverage/data/

and the html report will be written to:
PROJECT_ROOT/out/MODULE/scoverage/data/htmlReport/

* Remove wild card imports in scoverage

Also remove scoverage dependency from build.sc

* Move htmlReport into worker

Based on what I've seen in
scalalib, scalajslib, scalanativelib, playlib, and twirllib modules.

Still need to add tests

* Add basic docs + tests for scoverage

I still am working on testing the actual generation of
reports.

* Use cross-module for scoverage worker

Now we can support multiple versions of scoverage
by adding them to the crossmodule list.

Also now running the local publish script succeeds.

* Add scoverage to ci tests

* Add detailed ScoverageModule documentation

* Test scoverage dataDir

* Remove <pre> tags in scaladoc

* Add scoverage dependency in less hacky way

* Modify scoverage tests to check classpaths

* Put docs in alphabetical order

* Test classpaths for scoverage runtime

* Remove abstract def test: ScoverageTests

* Construct classloader differently

* Revert "Construct classloader differently"

This reverts commit fccf9a94cc38fb9e2be58a9ff90b00b65f339db6.

* Revert "Construct classloader differently"

Also fixes unfound error in html report

This reverts commit fccf9a94cc38fb9e2be58a9ff90b00b65f339db6.

* Fix classpath for scoverage worker

1 files changed, 26 insertions, 1 deletions

diff --git a/build.sc b/build.sc
index fd5d4e29..215e8d37 100755
--- a/build.sc
+++ b/build.sc
@@ -287,6 +287,31 @@ object contrib extends MillModule {
     def moduleDeps = Seq(scalalib)
   }
 
+  object scoverage extends MillModule {
+    def moduleDeps = Seq(scalalib, scoverage.api)
+
+    def testArgs = T {
+      val mapping = Map(
+        "MILL_SCOVERAGE_REPORT_WORKER_1_3_1" -> worker("1.3.1").compile().classes.path
+      )
+      scalalib.worker.testArgs() ++
+        scalalib.backgroundwrapper.testArgs() ++
+        (for ((k, v) <- mapping) yield s"-D$k=$v")
+    }
+
+    object api extends MillApiModule {
+      def moduleDeps = Seq(scalalib)
+    }
+
+    object worker extends Cross[WorkerModule]("1.3.1")
+
+    class WorkerModule(scoverageVersion: String) extends MillApiModule {
+      def moduleDeps = Seq(scoverage.api)
+
+      def ivyDeps = Agg(ivy"org.scoverage::scalac-scoverage-plugin:${scoverageVersion}")
+    }
+  }
+
   object buildinfo extends MillModule {
     def moduleDeps = Seq(scalalib)
     // why do I need this?
@@ -436,7 +461,7 @@ def launcherScript(shellJvmArgs: Seq[String],
 }
 
 object dev extends MillModule{
-  def moduleDeps = Seq(scalalib, scalajslib, scalanativelib, contrib.scalapblib, contrib.tut)
+  def moduleDeps = Seq(scalalib, scalajslib, scalanativelib, contrib.scalapblib, contrib.tut, contrib.scoverage)
 
   def forkArgs =
     (