$ cvs -H tag
Usage: cvs tag [-bcdFflR] [-r rev|-D date] tag [files...]
        -b      Make the tag a "branch" tag, allowing concurrent development.
        -B      Allows -F and -d to disturb branch tags.  Use with extreme care.
        -c      Check that working files are unmodified.
        -d      Delete the given tag.
        -F      Move tag if it already exists.
        -f      Force a head revision match if tag/date not found.
        -l      Local directory only, not recursive.
        -R      Process directories recursively.
        -r rev  Existing revision/tag.
        -D      Existing date.
(Specify the --help global option for a list of other help options)