def full_diff
      base = compare_base_obj || head
      base.diff(repo.index).merge!(repo.diff_workdir(head))
    end
def full_diff
      base = compare_base_obj || head
      base.diff(repo.index).merge!(repo.diff_workdir(head))
    end
Diffs `head` or `head` + `compare_base` (if exists),
 as it makes sense to run Undercover with the most recent file versions