node-addon-lilypond/output/share/lilypond/current/scripts/build/relative.py

import os
import sys


def relative(dir, r=os.getcwd()):
    dir = os.path.normpath(dir) + '/'
    r = os.path.normpath(r) + '/'
    prefix = len(os.path.commonprefix((dir, r)))
    if prefix == len(dir):
        return './'
    if prefix > 1:
        return '../' * (len(r[prefix:].split('/')) - 1) + dir[prefix:]
    return dir


if __name__ == '__main__':
    print(relative(sys.argv[1]))