class Bundler::Dsl

def git_source(name, &block)
  unless block_given?
    raise InvalidOption, "You need to pass a block to #git_source"
  end
  if valid_keys.include?(name.to_s)
    raise InvalidOption, "You cannot use #{name} as a git source. It " \
      "is a reserved key. Reserved keys are: #{valid_keys.join(", ")}"
  end
  @git_sources[name.to_s] = block
end