brew/Library/Homebrew/extend/os/mac/dependency_collector.rb

class DependencyCollector
  undef git_dep_if_needed, subversion_dep_if_needed, cvs_dep_if_needed,
        xz_dep_if_needed, unzip_dep_if_needed, bzip2_dep_if_needed

  def git_dep_if_needed(tags); end

  def subversion_dep_if_needed(tags); end

  def cvs_dep_if_needed(tags)
    Dependency.new("cvs", tags)
  end

  def xz_dep_if_needed(tags); end

  def unzip_dep_if_needed(tags); end

  def bzip2_dep_if_needed(tags); end
end