commandUsage(cmd) {
    // Usage
    let cmdName = cmd._name;
    if (cmd._aliases[0]) {
      cmdName = cmdName + '|' + cmd._aliases[0];
    }
    let ancestorCmdNames = '';
    for (
      let ancestorCmd = cmd.parent;
      ancestorCmd;
      ancestorCmd = ancestorCmd.parent
    ) {
      ancestorCmdNames = ancestorCmd.name() + ' ' + ancestorCmdNames;
    }
    return ancestorCmdNames + cmdName + ' ' + cmd.usage();
  }
Get the command usage to be displayed at the top of the built-in help.

@param {Command} cmd
@returns {string}