code: private void _appendOption (@Nonnull final StringBuilder aSB, @Nonnull final Option aOption, final boolean bRequired)
    {
      if (!bRequired)
        aSB.append ('[');
  
      if (aOption.hasShortOpt ())
        aSB.append (getOptPrefix ()).append (aOption.getShortOpt ());
      else
        aSB.append (getLongOptPrefix ()).append (aOption.getLongOpt ());
  
      // if the Option has a value and a non blank argname
      if (aOption.canHaveArgs ())
      {
        aSB.append (aOption.hasShortOpt () ? " " : getLongOptSeparator ());
        aSB.append ('<').append (aOption.hasArgName () ? aOption.getArgName () : getArgName ()).append ('>');
      }
  
      // if the Option is not a required option
      if (!bRequired)
        aSB.append (']');
    }
docs: Appends the usage clause for an Option to a StringBuilder.
  
  @param aSB
  the StringBuilder to append to
  @param aOption
  the Option to append
  @param bRequired
  whether the Option is required or not