fetch_tar (Multiruby)

    # File lib/multiruby.rb, line 169
      def self.fetch_tar v
        in_versions_dir do
          warn "  Determining latest version for #{v}"
          ver = v[/\d+\.\d+/]
          base = extract_latest_version("#{RUBY_URL}/#{ver}/", v)
          abort "Could not determine release for #{v}" unless base
          url = File.join RUBY_URL, ver, base
          unless File.file? base then
            warn "    Fetching #{base} via HTTP... this might take a while."
            open(url) do |f|
              File.open base, 'w' do |out|
                out.write f.read
              end
            end
          end
        end
      end