Show different message when PR not checked out

Let the user know they need to check out PR branch before navigating to editor.

Author: jcansdale

src/GitHub.VisualStudio.UI/Resources.Designer.cs

@@ -404,4 +404,7 @@
   <data name="NavigateToEditorStatusMessage" xml:space="preserve">
     <value>Press Enter to navigate to Editor</value>
   </data>
+  <data name="NavigateToEditorNotCheckedOutStatusMessage" xml:space="preserve">
+    <value>Checkout PR branch and press Enter to navigate to Editor</value>
+  </data>
 </root>

src/GitHub.VisualStudio.UI/Resources.resx

@@ -251,8 +251,10 @@ void EnableNavigateToEditor(IWpfTextView textView, IPullRequestFileNode file)
             var view = EditorAdaptersFactoryService.GetViewAdapter(textView);
             EnableNavigateToEditor(view, file);
 
+            var statusMessage = ViewModel.IsCheckedOut ?
+                UI.Resources.NavigateToEditorStatusMessage : UI.Resources.NavigateToEditorNotCheckedOutStatusMessage;
             textView.GotAggregateFocus += (s, e) =>
-                StatusBarNotificationService.ShowMessage(UI.Resources.NavigateToEditorStatusMessage);
+                StatusBarNotificationService.ShowMessage(statusMessage);
 
             textView.LostAggregateFocus += (s, e) =>
                 StatusBarNotificationService.ShowMessage(string.Empty);