fix project/flatten

sbt/src/sbt-test/project/flatten/build.sbt

@@ -1,26 +1,23 @@
-lazy val root = (project in file(".")).
+val unpackage = TaskKey[Unit]("unpackage")
-  settings(
+
+ThisBuild / scalaVersion := "2.12.8"
+
+lazy val root = (project in file("."))
+  .settings(
     forConfig(Compile, "src"),
     forConfig(Test, "test-src"),
-    baseSettings
+    libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.14.0" % Test,
+    unmanagedSources / includeFilter := "*.java" | "*.scala"
   )
 
-def baseSettings = Seq(
-  scalaVersion := "2.11.8",
-  libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.11.4" % Test,
-  includeFilter in unmanagedSources := "*.java" | "*.scala"
-)
-
 def forConfig(conf: Configuration, name: String) = Project.inConfig(conf)( unpackageSettings(name) )
 
 def unpackageSettings(name: String) = Seq(
   unmanagedSourceDirectories := (baseDirectory.value / name) :: Nil,
-  excludeFilter in unmanagedResources := (includeFilter in unmanagedSources).value,
+  unmanagedResources / excludeFilter := (unmanagedSources / includeFilter).value,
   unmanagedResourceDirectories := unmanagedSourceDirectories.value,
   unpackage := {
-    IO.unzip(artifactPath in packageSrc value, baseDirectory.value / name)
+    IO.unzip((packageSrc / artifactPath).value, baseDirectory.value / name)
     IO.delete(baseDirectory.value / name / "META-INF")
   }
 )
-
-val unpackage = TaskKey[Unit]("unpackage")