How to know if a text file is a subset of another

I am trying to find a way to determine if a text file is a subset of another.. For example: foo bar is a subset of foo bar pluto While: foo pluto and foo bar are not a subset of each other... Is there a way to do this with a command? This check must be a cross check, and it has to return: file1 subset of file2 : True file2 subset of file1 : True otherwise : False