Make further progress on the rename sheet.

Evergreen/Base.lproj/RenameSheet.xib

@@ -41,6 +41,9 @@
                             <color key="textColor" name="textColor" catalog="System" colorSpace="catalog"/>
                             <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
                         </textFieldCell>
+                        <connections>
+                            <outlet property="delegate" destination="-2" id="5Oi-0v-kuj"/>
+                        </connections>
                     </textField>
                     <button verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="RI3-Rg-htY">
                         <rect key="frame" x="321" y="13" width="89" height="32"/>

Evergreen/MainWindow/Sidebar/Renaming/RenameWindowController.swift

@@ -16,9 +16,32 @@ final class RenameWindowController: NSWindowController {
 	
 	private var originalTitle: String!
 
-	public convenience init(originalTitle: String) {
+	convenience init(originalTitle: String) {
 
 		self.init(windowNibName: NSNib.Name(rawValue: "RenameSheet"))
 		self.originalTitle = originalTitle
 	}
+
+	override func windowDidLoad() {
+
+		newTitleTextField.stringValue = originalTitle
+		updateUI()
+	}
+}
+
+extension RenameWindowController: NSTextFieldDelegate {
+
+	override func controlTextDidChange(_ obj: Notification) {
+
+		updateUI()
+	}
+}
+
+private extension RenameWindowController {
+
+	func updateUI() {
+
+		let newTitle = newTitleTextField.stringValue
+		renameButton.isEnabled = !newTitle.isEmpty && newTitle != originalTitle
+	}
 }