Method addOptName

tests/catch.h:4263–4279

        typedef CLARA_AUTO_PTR( Arg ) ArgAutoPtr;

        friend void addOptName( Arg& arg, std::string const& optName )
        {
            if( optName.empty() )
                return;
            if( Detail::startsWith( optName, "--" ) ) {
                if( !arg.longName.empty() )
                    throw std::logic_error( "Only one long opt may be specified. '"
                        + arg.longName
                        + "' already specified, now attempting to add '"
                        + optName + "'" );
                arg.longName = optName.substr( 2 );
            }
            else if( Detail::startsWith( optName, "-" ) )
                arg.shortNames.push_back( optName.substr( 1 ) );
            else
                throw std::logic_error( "option must begin with - or --. Option was: '" + optName + "'" );
        }
        friend void setPositionalArg( Arg& arg, int position )
        {
            arg.position = position;