apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceBranchService.java/NamespaceBranchService/merge
class NamespaceBranchService:  public ReleaseDTO merge(String appId, Env env, String clusterName, String namespaceName,
                          String branchName, String title, String comment,
                          boolean isEmergencyPublish, boolean deleteBranch, String operator) {

    ItemChangeSets changeSets = calculateBranchChangeSet(appId, env, clusterName, namespaceName, branchName, operator);

    ReleaseDTO mergedResult =
            releaseService.updateAndPublish(appId, env, clusterName, namespaceName, title, comment,
                    branchName, isEmergencyPublish, deleteBranch, changeSets);

    Tracer.logEvent(TracerEventType.MERGE_GRAY_RELEASE,
            String.format("%s+%s+%s+%s", appId, env, clusterName, namespaceName));

    return mergedResult;
  }