apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ReleaseService.java/ReleaseService/calculateChildNamespaceToPublishConfiguration
class ReleaseService:  private Map<String, String> calculateChildNamespaceToPublishConfiguration(
      Map<String, String> parentNamespaceOldConfiguration, Map<String, String> parentNamespaceNewConfiguration,
      Map<String, String> childNamespaceLatestActiveConfiguration, Collection<String> branchReleaseKeys) {
    //first. calculate child namespace modified configs

    Map<String, String> childNamespaceModifiedConfiguration = calculateBranchModifiedItemsAccordingToRelease(
        parentNamespaceOldConfiguration, childNamespaceLatestActiveConfiguration, branchReleaseKeys);

    //second. append child namespace modified configs to parent namespace new latest configuration
    return mergeConfiguration(parentNamespaceNewConfiguration, childNamespaceModifiedConfiguration);
  }