Consider a better word than "global" since it actually indicates that the option is syntactically valid on the current command and its subcommands

[jonsequitur]

        // I assume that a caller of this will understand the difference of a Global option and a non-Global option
        public void AddGlobalOption(Option option);

[KalleOlaviNiemitalo]

Add(Option option, bool inheritable) would allow initializer list syntax; but the resulting code would not be very easy to understand. The bool could be replaced with OptionOptions.ValidInSubcommands but that would mean larger API and the name looks bad.

[KalleOlaviNiemitalo]

This was done in #2060, by replacing Command.AddGlobalOption with Option.AppliesToSelfAndChildren.

[KalleOlaviNiemitalo]

"AppliesToSelfAndChildren" would have been a bit misleading if #2063 had allowed directives as children of a command.

[jonsequitur]

Thanks, @KalleOlaviNiemitalo. I'll close this one.