code: public JobFile track(FileStatus jobFileStatus) {
  
      String jobfileName = jobFileStatus.getPath().getName();
      JobFile jobFile = new JobFile(jobfileName);
  
      // Extra check, caller should already have taken care of this.
      if (jobFile.isJobConfFile() || jobFile.isJobHistoryFile()) {
        track(jobFile.getJobid());
  
        long modificationTimeMillis = jobFileStatus.getModificationTime();
        if (modificationTimeMillis < minModificationTimeMillis) {
          minModificationTimeMillis = modificationTimeMillis;
        }
        if (modificationTimeMillis > maxModificationTimeMillis) {
          maxModificationTimeMillis = modificationTimeMillis;
        }
      }
      return jobFile;
    }
docs: Converts a jobFileStatus to a JobFile and tracks the min and max
  modification times and JobIds.
  
  @param jobFileStatus
  of a jobfile, must be a proper JobFile. Cannot be null.
  @return a JobFile for the given jobFileStatus.