message: return the value, not the ref
diff: @@ -258,7 +258,9 @@ pub trait Settings {
  /// apply the Update to the Settings
  fn apply(&mut self, update: Self::Update) -> Result<(), Self::Error>;
  - fn tip(&self) -> &<Self::Block as Block>::Id;
  + /// return the tip of the current branch
  + ///
  + fn tip(&self) -> <Self::Block as Block>::Id;
  }
  /// Define that an object can be written to a `Write` object.
  