Remove FileManagement

This was unused.

build.sbt

@@ -903,6 +903,9 @@ lazy val mainProj = (project in file("main"))
         "sbt.internal.ReverseLookupClassLoaderHolder$ReverseLookupClassLoader"
       ),
       exclude[MissingClassProblem]("sbt.internal.LayeredClassLoaderImpl"),
+      exclude[MissingClassProblem]("sbt.internal.FileManagement"),
+      exclude[MissingClassProblem]("sbt.internal.FileManagement$"),
+      exclude[MissingClassProblem]("sbt.internal.FileManagement$CopiedFileTreeRepository"),
       // false positives
       exclude[DirectMissingMethodProblem]("sbt.plugins.IvyPlugin.requires"),
       exclude[DirectMissingMethodProblem]("sbt.plugins.JUnitXmlReportPlugin.requires"),

main/src/main/scala/sbt/internal/FileManagement.scala

@@ -1,30 +0,0 @@
-/*
- * sbt
- * Copyright 2011 - 2018, Lightbend, Inc.
- * Copyright 2008 - 2010, Mark Harrah
- * Licensed under Apache License 2.0 (see LICENSE)
- */
-
-package sbt
-package internal
-
-import java.io.IOException
-import java.nio.file.Path
-
-import sbt.internal.nio.{ FileEvent, FileTreeRepository, Observable, Observer }
-import sbt.nio.file.Glob
-
-private[sbt] object FileManagement {
-  private[sbt] def copy[T](fileTreeRepository: FileTreeRepository[T]): FileTreeRepository[T] =
-    new CopiedFileTreeRepository[T](fileTreeRepository)
-  private[this] class CopiedFileTreeRepository[T](underlying: FileTreeRepository[T])
-      extends FileTreeRepository[T] {
-    override def list(path: Path): Seq[(Path, T)] = underlying.list(path)
-    override def close(): Unit = {}
-    override def register(glob: Glob): Either[IOException, Observable[FileEvent[T]]] =
-      underlying.register(glob)
-    override def addObserver(observer: Observer[FileEvent[T]]): AutoCloseable =
-      underlying.addObserver(observer)
-    override def toString: String = s"CopiedFileTreeRepository($underlying)"
-  }
-}