anchor.diff:  /// The age the browser should cache the static file if there is a hash provided
   /// and it matches the etag.
   const staticLongCache = const Duration(hours: 24);
  +
  +final _logger = new Logger('pub.shared.handler');
   
   shelf.Response redirectResponse(String url) => new shelf.Response.seeOther(url);
   
  
positive.code: }
  
  bool isNotModified(shelf.Request request, DateTime lastModified, String etag) {
    final ifModifiedSince = request.ifModifiedSince;
    if (ifModifiedSince != null &&
        lastModified != null &&
        !lastModified.isAfter(ifModifiedSince)) {
      return true;
    }
  
    final ifNoneMatch = request.headers[HttpHeaders.ifNoneMatchHeader];
    if (ifNoneMatch != null && ifNoneMatch == etag) {
      return true;
    }
  
    return false;
  
negative.code: import 'dart:convert';
  import 'dart:io';
  
  import 'package:logging/logging.dart';
  import 'package:shelf/shelf.dart' as shelf;
  
  import 'popularity_storage.dart';
  