anchor.diff:        // are no subfolders that need to be added.
       }
   
  -    File packageSpec;
  -
  -    if (ENABLE_PACKAGESPEC_SUPPORT) {
  -      // Start by looking for .packages.
  -      packageSpec = folder.getChild(PACKAGE_SPEC_NAME);
  -    }
  -
  -    // Fall back to looking for a pubspec.
  -    if (packageSpec == null || !packageSpec.exists) {
  -      packageSpec = folder.getChild(PUBSPEC_NAME);
  -    }
  -
  -    if (packageSpec.exists) {
  -      return <ContextInfo>[
  -        _createContextWithSources(folder, packageSpec, children)
  -      ];
  -    }
  -    // No packagespec? Done.
  -    if (withPackageSpecOnly) {
  -      return children;
  -    }
  -    // OK, create a context without a packagespec.
  -    return <ContextInfo>[
  -      _createContextWithSources(folder, packageSpec, children)
  -    ];
  -  }
  -
  -  /**
  -   * Create a new context associated with the given [folder]. The [pubspecFile]
  -   * is the `pubspec.yaml` file contained in the folder. Add any sources that
  -   * are not included in one of the [children] to the context.
  -   */
  -  ContextInfo _createContextWithSources(
  -      Folder folder, File pubspecFile, List<ContextInfo> children) {
  -    ContextInfo info = _createContext(folder, pubspecFile, children);
  -    ChangeSet changeSet = new ChangeSet();
  -    _addSourceFiles(changeSet, folder, info);
  -    callbacks.applyChangesToContext(folder, changeSet);
  -    return info;
  +    if (parentCreated) {
  +      // Now that the child contexts have been created, add the sources that
  +      // don't belong to the children.
  +      ChangeSet changeSet = new ChangeSet();
  +      _addSourceFiles(changeSet, folder, parent);
  +      callbacks.applyChangesToContext(folder, changeSet);
  +    }
     }
   
     /**
  
positive.code:   OptimizingPubPackageMapInfo packageMapInfo;
  
    ContextInfo(
        Folder folder, File packagespecFile, this.children, this.packageRoot)
        : folder = folder,
          pathFilter = new PathFilter(folder.path, null) {
      packageDescriptionPath = packagespecFile.path;
      for (ContextInfo child in children) {
        child.parent = this;
      }
    }
  
    /**
     * Returns `true` if this context is root folder based.
     */
    bool get isRoot => parent == null;
  
    /**
     * Returns `true` if [path] is excluded, as it is in one of the children.
  
negative.code:         return folder.isOrContains(includedFolder.path);
        });
        if (!wasIncluded) {
          _createContexts(_ancestorInfo, includedFolder, false);
        }
      }
      // remove newly excluded sources
  