func (f *StringFlag) IsSet() bool {
	return f.HasBeenSet
}
IsSet returns whether or not the flag has been set through env or file
package cli
import "flag"
type StringFlag struct {
	Name        string
	Aliases     []string
	Usage       string
	EnvVars     []string
	FilePath    string
	Required    bool
	Hidden      bool
	TakesFile   bool
	Value       string
	DefaultText string
	Destination *string
	HasBeenSet  bool
}