new_contents: # JN 2016-06-01
  
  """
  given dropfiles, create a common one (lines contained in all files)
  """
  
  
  def common_dropfile(fnames):
      
      sets = []
      for fname in fnames:
          with open(fname, 'r') as fid:
              sets.append(set([l.strip() for l in fid.readlines()]))
  
      return sorted(sets[0].intersection(*(sets[1:])))
  
  
  if __name__ == "__main__":
      import sys
      ret = common_dropfile(sys.argv[1:])
      for l in ret:
          print(l)
  
subject: Add simple dropfile merger