anchor.diff:    final documentRef = firestore.document('builds/$builder:$endIndex');
     final record = await documentRef.get();
     if (!record.exists) {
  -    await documentRef
  -        .setData(DocumentData.fromMap(
  +    await documentRef.setData(DocumentData.fromMap(
           {'builder': builder, 'build_number': buildNumber, 'index': endIndex}));
       info('Created build record: '
           'builder: $builder, build_number: $buildNumber, index: $endIndex');
  -
     } else if (record.data.getInt('index') != endIndex) {
  -      error('Build $buildNumber of $builder had commit index ${record.data.getInt('index')},'
  -          'should be $endIndex.');
  -  }
  - return {"startIndex": startIndex, "endIndex": endIndex};
  +    error(
  +        'Build $buildNumber of $builder had commit index ${record.data.getInt('index')},'
  +        'should be $endIndex.');
  +  }
  +  return {"startIndex": startIndex, "endIndex": endIndex};
   }
   
   Future<void> storeChange(Map<String, dynamic> change,
  
positive.code:   final int buildNumber = int.parse(change['build_number']);
    stats.buildNumber = buildNumber;
    final Set<String> configurations =
    results.map((change) => change['configuration'] as String)
    .toSet();
    for (final configuration in configurations) {
      final record = await firestore.document('configurations/$configuration').get();
      if (!record.exists || record.data.getString('builder') != builder) {
        await firestore.document('configurations/$configuration')
            .setData(DocumentData.fromMap({'builder': builder}));
        if (!record.exists) {
          info('Configuration document $configuration -> $builder created');
  
negative.code:       .get();
  
    // Find an existing change group with a blamelist that intersects this change.
    final startIndex = buildInfo['startIndex'];
    final endIndex = buildInfo['endIndex'];
  
    bool blamelistIncludesChange(DocumentSnapshot groupDocument) {
      var group = groupDocument.data;
  