def reset_hard(commitish = nil, opts = {})
      opts = {:hard => true}.merge(opts)
      self.lib.reset(commitish, opts)
    end
def reset_hard(commitish = nil, opts = {})
      opts = {:hard => true}.merge(opts)
      self.lib.reset(commitish, opts)
    end
resets the working directory to the commitish with '--hard'