Add coverageScalacPluginVersion setting key

Make it easier to change version of scalac-scoverage-plugin dependency

Author: lustefaniak

src/main/scala/scoverage/ScoverageKeys.scala

@@ -17,4 +17,5 @@ object ScoverageKeys {
   lazy val coverageOutputDebug = settingKey[Boolean]("turn on the debug report")
   lazy val coverageCleanSubprojectFiles = settingKey[Boolean]("removes subproject data after an aggregation")
   lazy val coverageOutputTeamCity = settingKey[Boolean]("turn on teamcity reporting")
+  lazy val coverageScalacPluginVersion = settingKey[String]("version of scalac-scoverage-plugin to use")
 }

src/main/scala/scoverage/ScoverageSbtPlugin.scala

@@ -30,10 +30,11 @@ object ScoverageSbtPlugin extends AutoPlugin {
     coverageReport <<= coverageReport0,
     coverageAggregate <<= coverageAggregate0,
     ivyConfigurations := ivyConfigurations.value :+ ScoveragePluginConfig,
+    coverageScalacPluginVersion := DefaultScoverageVersion,
     libraryDependencies ++= {
       if (coverageEnabled.value) Seq(
-        OrgScoverage % (ScalacRuntimeArtifact + "_" + scalaBinaryVersion.value) % DefaultScoverageVersion,
-        OrgScoverage % (ScalacPluginArtifact + "_" + scalaBinaryVersion.value) % DefaultScoverageVersion % "scoveragePlugin->default(compile)"
+        OrgScoverage % (ScalacRuntimeArtifact + "_" + scalaBinaryVersion.value) % coverageScalacPluginVersion.value,
+        OrgScoverage % (ScalacPluginArtifact + "_" + scalaBinaryVersion.value) % coverageScalacPluginVersion.value % "scoveragePlugin->default(compile)"
       ) else Nil
     },
     scalacOptions in(Compile, compile) ++= scoverageScalacOptions.value,