code: func (c *Context) IsSet(name string) bool {
  	if c.setFlags == nil {
  		c.setFlags = make(map[string]bool)
  		c.flagSet.Visit(func(f *flag.Flag) {
  			c.setFlags[f.Name] = true
  		})
  	}
  	return c.setFlags[name] == true
  }
docs: // Determines if the flag was actually set exists