Merge branch 'ls/editor-waiting-message'

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