$ gemmi mtz2cif -h
Usage:
  gemmi mtz2cif [options] MTZ_FILE [MTZ_FILE] CIF_FILE
Options:
  -h, --help             Print usage and exit.
  -V, --version          Print version and exit.
  -v, --verbose          Verbose output.
  --spec=FILE            Column and format specification.
  --print-spec           Print default spec and exit.
  -b NAME, --block=NAME  mmCIF block name: data_NAME (default: mtz).
  --id=ID                value for _entry.id (default: xxxx).
  --skip-empty[=COLS]    Skip reflections with no values. If COLS are given, eg.
                         'I(+),I(-)', only values in those columns are checked.
  --no-comments          Do not write comments in the mmCIF file.
  --wavelength=LAMBDA    Set wavelengths (default: from input file).
  --validate-merge       For two MTZ files: validate the intensities match.
  --trim=N               (for testing) output only reflections -N <= h,k,l <=N.

One or two MTZ files are taken as the input. If two files are given,
one must be merged and the other unmerged.
If CIF_FILE is -, the output is printed to stdout.
If spec is -, it is read from stdin.

Lines in the spec file have format:
  [FLAG] COLUMN TYPE TAG [FORMAT]
 or
  $SPECIAL TAG
for example:
  SIGF_native * SIGF_meas_au 12.5e
  FREE I pdbx_r_free_flag 3.0f
  $counter id
FLAG (optional) is either ? or &:
  ? = ignored if no column in the MTZ file has this name.
  & = ignored if the previous line was ignored.
  Example:
      ? I    J intensity_meas
      & SIGI Q intensity_sigma
COLUMN is MTZ column label. Columns H K L are added if not specified.
  Alternative labels can be separated with | (e.g. FREE|FreeR_flag).
TYPE is used for checking the columm type, unless it is '*'.
TAG does not include category name, it is only the part after _refln.
FORMAT (optional) is printf-like floating-point format:
 - one of e, f, g with optional flag, width and precision
 - flag is one of + - # _; '_' stands for ' ', for example '_.4f'
 - since all numbers in MTZ are stored as float, the integer columns use
   the same format as float. The format of _refln.status is ignored.
$SPECIAL is $counter, $dataset, $image, $. or $?, as appropriate for
  _diffrn_refln.id, _diffrn_refln.diffrn_id, image number or null (./?)