Return copied filed/folder when calling copy() (#91)

This patch fixes a regression that would cause a copied file or folder
not to be returned as part of that operation. A test has also been
added to make sure that this feature stays intact in the future.

Sources/Files.swift

@@ -165,8 +165,12 @@ public extension Location {
     /// Copy the contents of this location to a given folder
     /// - parameter newParent: The folder to copy this item to.
     /// - throws: `LocationError` if the location couldn't be copied.
-    func copy(to folder: Folder) throws {
-        try storage.copy(to: folder.path + name)
+    /// - returns: The new, copied location.
+    @discardableResult
+    func copy(to folder: Folder) throws -> Self {
+        let path = folder.path + name
+        try storage.copy(to: path)
+        return try Self(path: path)
     }
 
     /// Delete this location. It will be permanently deleted. Use with caution.

Tests/FilesTests/FilesTests.swift

@@ -332,10 +332,11 @@ class FilesTests: XCTestCase {
             try file.write("content")
 
             let subfolder = try folder.createSubfolder(named: "folder")
-            try file.copy(to: subfolder)
+            let copiedFile = try file.copy(to: subfolder)
             try XCTAssertNotNil(folder.file(named: "A"))
             try XCTAssertNotNil(subfolder.file(named: "A"))
             try XCTAssertEqual(file.read(), subfolder.file(named: "A").read())
+            try XCTAssertEqual(copiedFile, subfolder.file(named: "A"))
             XCTAssertEqual(folder.files.count(), 1)
         }
     }
@@ -357,9 +358,10 @@ class FilesTests: XCTestCase {
             let copyingFolder = try folder.createSubfolder(named: "A")
 
             let subfolder = try folder.createSubfolder(named: "folder")
-            try copyingFolder.copy(to: subfolder)
+            let copiedFolder = try copyingFolder.copy(to: subfolder)
             XCTAssertTrue(folder.containsSubfolder(named: "A"))
             XCTAssertTrue(subfolder.containsSubfolder(named: "A"))
+            XCTAssertEqual(copiedFolder, try subfolder.subfolder(named: "A"))
             XCTAssertEqual(folder.subfolders.count(), 2)
             XCTAssertEqual(subfolder.subfolders.count(), 1)
         }