rcs: Log message option

 
 2.1.5 Log message option
 ------------------------
 
 Both ‘ci’ and ‘rcs’ allow a log message to be specified with the ‘-m’
 option.  If the MSG argument to this option is empty, RCS uses the
 default ‘*** empty log message ***’.  This particular message is handled
 specially (i.e., filtered out) by ‘rlog’.