class Rugged::Repository

def diff(left, right, opts = {})
  left = rev_parse(left) if left.kind_of?(String)
  right = rev_parse(right) if right.kind_of?(String)
  if !left.is_a?(Rugged::Tree) && !left.is_a?(Rugged::Commit) && !left.nil?
    raise TypeError, "Expected a Rugged::Tree or Rugged::Commit instance"
  end
  if !right.is_a?(Rugged::Tree) && !right.is_a?(Rugged::Commit) && !right.nil?
    raise TypeError, "Expected a Rugged::Tree or Rugged::Commit instance"
  end
  if left
    left.diff(right, opts)
  elsif right
    right.diff(left, opts.merge(:reverse => !opts[:reverse]))
  end
end