Note: help and version output are generated by a naïve script which tries a few variants of
<command> --help, <command> -h etc. to find the command's help and version info.
Sometimes it gets lucky, sometimes it doesn't; if the output below looks wrong, it probably is.
gdal_sieve.py --version (return code: 0)
GDAL 2.2.1, released 2017/06/23
gdal_sieve.py -HELP (return code: 1)
gdal_sieve [-q] [-st threshold] [-4] [-8] [-o name=value]
srcfile [-nomask] [-mask filename] [-of format] [dstfile]