Add helper methods to create mappings

io/src/main/scala/sbt/io/Path.scala

@@ -85,6 +85,7 @@ object Path extends Mapper {
   val sep: Char = java.io.File.separatorChar
 
   def toURLs(files: Seq[File]): Array[URL] = files.map(_.toURI.toURL).toArray
+
 }
 
 object PathFinder {

io/src/main/scala/sbt/io/PathMapper.scala

@@ -111,6 +111,61 @@ abstract class Mapper {
   def selectSubpaths(base: File, filter: FileFilter): Traversable[(File, String)] =
     (PathFinder(base) ** filter --- PathFinder(base)) pair (relativeTo(base) | flat)
 
+  /**
+   * return a Seq of mappings which effect is to add a whole directory in the generated package
+   *
+   * @example In order to create mappings for a static directory "extra" add
+   * {{{
+   * mappings ++= directory(baseDirectory.value / "extra")
+   * }}}
+   *
+   * The resulting mappings sequence will look something like this
+   *
+   * {{{
+   * File($baseDirectory/extras) -> "extras"
+   * File($baseDirectory/extras/file1) -> "extras/file1"
+   * File($baseDirectory/extras/file2) -> "extras/file2"
+   * ...
+   * }}}
+   *
+   *
+   * @param baseDirectory The directory that should be turned into a mappings sequence.
+   * @return mappings The `baseDirectory` and all of its contents
+   */
+  def directory(baseDirectory: File): Seq[(File, String)] =
+    Option(baseDirectory.getParentFile)
+      .map(parent => PathFinder(baseDirectory).allPaths pair relativeTo(parent))
+      .getOrElse(PathFinder(baseDirectory).allPaths pair basic)
+
+  /**
+   * return a Seq of mappings  excluding the directory itself.
+   *
+   * @example In order to create mappings for a static directory "extra" add
+   * {{{
+   * mappings ++= contentOf(baseDirectory.value / "extra")
+   * }}}
+   *
+   * The resulting mappings sequence will look something like this
+   *
+   * {{{
+   * File($baseDirectory/extras/file1) -> "file1"
+   * File($baseDirectory/extras/file2) -> "file2"
+   * ...
+   * }}}
+   *
+   * @example Add a static directory "extra" and re-map the destination to a different path
+   * {{{
+   * mappings ++= contentOf(baseDirectory.value / "extra").map {
+   *   case (src, destination) => src -> s"new/path/$destination"
+   * }
+   * }}}
+   *
+   * @param baseDirectory The directory that should be turned into a mappings sequence.
+   * @return mappings - The `basicDirectory`'s contents exlcuding `basicDirectory` itself
+   */
+  def contentOf(baseDirectory: File): Seq[(File, String)] =
+    (PathFinder(baseDirectory).allPaths --- PathFinder(baseDirectory)) pair relativeTo(baseDirectory)
+
   private[this] def fold[A, B, T](zero: A => Option[B], in: Iterable[T])(f: T => A => Option[B]): A => Option[B] =
     (zero /: in)((mapper, base) => f(base) | mapper)
 }

io/src/test/scala/sbt/io/PathMapperSpec.scala

@@ -1,12 +1,17 @@
 package sbt.io
 
+import java.nio.file.{ Files, Path => NioPath }
+
 import org.scalatest._
+import Path._
+import sbt.io.syntax._
+
+class PathMapperSpec extends fixture.FlatSpec with Matchers {
 
-import Path._, sbt.io.syntax._
+  type FixtureParam = NioPath
 
-class PathMapperSpec extends FlatSpec with Matchers {
-  "PathMapper" should "create copy resource mappings correctly" in {
-    val base = file("/")
+  "rebase | flat" should "copy resource mappings correctly" in { tempDirectory =>
+    val base = tempDirectory.toFile
 
     val files = Seq(base / "src" / "main" / "resources" / "scalac-plugin.xml")
     val dirs = Seq(
@@ -22,4 +27,104 @@ class PathMapperSpec extends FlatSpec with Matchers {
         base / "target" / "scala-2.11" / "classes" / "scalac-plugin.xml"
     )
   }
+
+  "directory" should "create mappings including the baseDirectory" in { tempDirectory =>
+    val nestedFile1 = Files.createFile(tempDirectory resolve "file1").toFile
+    val nestedFile2 = Files.createFile(tempDirectory resolve "file2").toFile
+    val nestedDir = Files.createDirectory(tempDirectory resolve "dir1")
+    val nestedDirFile = Files.createDirectory(nestedDir resolve "dir1-file1").toFile
+
+    IO.touch(nestedFile1)
+    IO.touch(nestedFile2)
+    IO.createDirectory(nestedDir.toFile)
+    IO.touch(nestedDirFile)
+
+    val mappings = Path.directory(tempDirectory.toFile)
+
+    mappings should contain theSameElementsAs List[(File, String)](
+      tempDirectory.toFile -> s"${tempDirectory.getFileName}",
+      nestedFile1 -> s"${tempDirectory.getFileName}/file1",
+      nestedFile2 -> s"${tempDirectory.getFileName}/file2",
+      nestedDir.toFile -> s"${tempDirectory.getFileName}/dir1",
+      nestedDirFile -> s"${tempDirectory.getFileName}/dir1/dir1-file1"
+    )
+  }
+
+  it should "create one mapping entry for an empty directory" in { tempDirectory =>
+    val mappings = Path.directory(tempDirectory.toFile)
+
+    mappings should contain theSameElementsAs List[(File, String)](
+      tempDirectory.toFile -> s"${tempDirectory.getFileName}"
+    )
+  }
+
+  it should "create an empty mappings sequence for a non-existing directory" in { tempDirectory =>
+    val nonExistingDirectory = tempDirectory.resolve("imaginary")
+    val mappings = Path.directory(nonExistingDirectory.toFile)
+
+    mappings should be(empty)
+  }
+
+  it should "create one mapping entry if the directory is a file" in { tempDirectory =>
+    val file = tempDirectory.resolve("file").toFile
+    IO.touch(file)
+    val mappings = Path.directory(file)
+
+    mappings should contain theSameElementsAs List[(File, String)](
+      file -> s"${file.getName}"
+    )
+  }
+
+  "contentOf" should "create mappings excluding the baseDirectory" in { tempDirectory =>
+
+    val nestedFile1 = Files.createFile(tempDirectory resolve "file1").toFile
+    val nestedFile2 = Files.createFile(tempDirectory resolve "file2").toFile
+    val nestedDir = Files.createDirectory(tempDirectory resolve "dir1")
+    val nestedDirFile = Files.createDirectory(nestedDir resolve "dir1-file1").toFile
+
+    IO.touch(nestedFile1)
+    IO.touch(nestedFile2)
+    IO.createDirectory(nestedDir.toFile)
+    IO.touch(nestedDirFile)
+
+
+    val mappings = Path.contentOf(tempDirectory.toFile)
+
+    mappings should contain theSameElementsAs List[(File, String)](
+      nestedFile1 -> s"file1",
+      nestedFile2 -> s"file2",
+      nestedDir.toFile -> s"dir1",
+      nestedDirFile -> s"dir1/dir1-file1"
+    )
+  }
+
+  it should "create an empty mappings sequence for an empty directory" in { tempDirectory =>
+    val mappings = Path.contentOf(tempDirectory.toFile)
+
+    mappings should be(empty)
+  }
+
+  it should "create an empty mappings sequence for a non-existing directory" in { tempDirectory =>
+    val nonExistingDirectory = tempDirectory.resolve("imaginary")
+    val mappings = Path.contentOf(nonExistingDirectory.toFile)
+
+    mappings should be(empty)
+  }
+
+  it should "create an empty mappings sequence if the directory is a file" in { tempDirectory =>
+    val file = tempDirectory.resolve("file").toFile
+    val mappings = Path.contentOf(file)
+
+    mappings should be(empty)
+  }
+
+  override protected def withFixture(test: OneArgTest): Outcome = {
+    val tmpDir = Files.createTempDirectory("path-mappings")
+    try {
+      withFixture(test.toNoArgTest(tmpDir))
+    } finally {
+      // cleanup an delete the temp directory
+      IO.delete(tmpDir.toFile)
+    }
+  }
 }