update

# File lib/bundler/compact_index_client/updater.rb, line 28
      def update(local_path, remote_path, retrying = nil)
        headers = {}

        Dir.mktmpdir("bundler-compact-index-") do |local_temp_dir|
          local_temp_path = Pathname.new(local_temp_dir).join(local_path.basename)

          # first try to fetch any new bytes on the existing file
          if retrying.nil? && local_path.file?
            SharedHelpers.filesystem_access(local_temp_path) do
              FileUtils.cp local_path, local_temp_path
            end
            headers["If-None-Match"] = etag_for(local_temp_path)
            headers["Range"] =
              if local_temp_path.size.nonzero?
                # Subtract a byte to ensure the range won't be empty.
                # Avoids 416 (Range Not Satisfiable) responses.
                "bytes=#{local_temp_path.size - 1}-"
              else
                "bytes=#{local_temp_path.size}-"
              end
          else
            # Fastly ignores Range when Accept-Encoding: gzip is set
            headers["Accept-Encoding"] = "gzip"
          end

          response = @fetcher.call(remote_path, headers)
          return nil if response.is_a?(Net::HTTPNotModified)

          content = response.body
          if response["Content-Encoding"] == "gzip"
            content = Zlib::GzipReader.new(StringIO.new(content)).read
          end

          SharedHelpers.filesystem_access(local_temp_path) do
            if response.is_a?(Net::HTTPPartialContent) && local_temp_path.size.nonzero?
              local_temp_path.open("a") {|f| f << slice_body(content, 1..-1) }
            else
              local_temp_path.open("w") {|f| f << content }
            end
          end

          response_etag = (response["ETag"] || "").gsub(%{\AW/}, "")
          if etag_for(local_temp_path) == response_etag
            SharedHelpers.filesystem_access(local_path) do
              FileUtils.mv(local_temp_path, local_path)
            end
            return nil
          end

          if retrying
            raise MisMatchedChecksumError.new(remote_path, response_etag, etag_for(local_temp_path))
          end

          update(local_path, remote_path, :retrying)
        end
      rescue Errno::EACCES
        raise Bundler::PermissionError,
          "Bundler does not have write access to create a temp directory "            "within #{Dir.tmpdir}. Bundler must have write access to your "            "systems temp directory to function properly. "
      rescue Zlib::GzipFile::Error
        raise Bundler::HTTPError
      end