$ gemmi cifdiff -h
Usage:
 gemmi cifdiff [options] FILE1.cif FILE2.cif
 gemmi cifdiff [options] -n FILE.cif

Compares (or just prints) categories and tags in CIF files.
  -h, --help     Print usage and exit.
  -V, --version  Print version and exit.
  -v, --verbose  Verbose output.
  -t TAG         Compare values of TAG.
  -q             Print only categories.
  -n             No comparison, just list categories and tags.
