class RailsEnvironment

def externals=(items)
  unless items.is_a? String
    items = items.map{|name,uri| "#{name.ljust(29)} #{uri.chomp('/')}"}.join("\n")
  end
  Tempfile.open("svn-set-prop") do |file|
    file.write(items)
    file.flush
    system("svn propset -q svn:externals -F \"#{file.path}\" \"#{root}/vendor/plugins\"")
  end
end