function command( repl ) {
	return onCommand;

	/**
	* Renames a syntax highlighting color theme.
	*
	* @private
	* @param {string} oldName - old theme name
	* @param {string} newName - new theme name
	* @returns {void}
	*/
	function onCommand( oldName, newName ) {
		try {
			repl.renameTheme( oldName, newName );
		} catch ( err ) {
			repl._ostream.write( format( 'Error: %s\n', err.message ) );
			return;
		}
		log( repl, format( '\nSuccessfully renamed theme from `%s` to `%s`.', oldName, newName ) );
	}
}
Returns a callback to be invoked upon calling the `renameTheme` command.

@private
@param {REPL} repl - REPL instance
@returns {Function} callback