Merge branch 'ls/editor-waiting-message'

Git shows a message to tell the user that it is waiting for the
user to finish editing when spawning an editor, in case the editor
opens to a hidden window or somewhere obscure and the user gets
lost.

* ls/editor-waiting-message:
  launch_editor(): indicate that Git waits for user input
  refactor "dumb" terminal determination

Documentation/config.txt

@@ -354,6 +354,9 @@ advice.*::
 	ignoredHook::
 		Advice shown if an hook is ignored because the hook is not
 		set as executable.
+	waitingForEditor::
+		Print a message to the terminal whenever Git is waiting for
+		editor input from the user.
 --
 
 core.fileMode::