parse_diff

# File lib/spec/runner/options.rb, line 200
      def parse_diff(format)
        case format
        when :context, 'context', 'c'
          @diff_format  = :context
          default_differ
        when :unified, 'unified', 'u', '', nil
          @diff_format  = :unified
          default_differ
        else
          @diff_format  = :custom
          self.differ_class = load_class(format, 'differ', '--diff')
        end
      end