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Re: [RFC PATCH] parse-options: disallow double-negations of options starting with no-

On Wed, Apr 19, 2017 at 02:08:20AM -0700, Jacob Keller wrote:

> From: Jacob Keller <jacob.keller@xxxxxxxxx>
> Many options can be negated by prefixing the option with "no-", for
> example "--3way" can be prefixed with "--no-3way" to disable it. Since
> 0f1930c58754 ("parse-options: allow positivation of options
> starting, with no-", 2012-02-25) we have also had support to negate
> options which start with "no-" by using the positive wording.
> This leads to the confusing (and non-documented) case that you can still
> prefix options beginning with "no-" by a second "no-" to negate them.
> That is, we allow "no-no-hardlinks" to negate the "no-hardlinks" option.
> This can be confusing to the user so lets just disallow the
> double-negative forms. If the long_name begins with "no-" then we simply
> don't allow the regular negation format, and only allow the option to be
> negated by the positive form.
> Signed-off-by: Jacob Keller <jacob.keller@xxxxxxxxx>
> ---
> I started going about implementing an OPT_NEGBOOL as suggested by Peff,
> but realized this might just be simpler, and we already support the
> positive format for the negation, so we don't lose expressiveness. We
> *might* want to tie this to an option flag instead so that it only kicks
> in if the option specifically requests it. Thoughts?

Yeah, if we are going to do anything, this is the right thing to do.

I am on the fence on whether it actually needs addressing or not. Sure,
--no-no-foo looks silly, but if the only way it happens is that the user
typed it, it doesn't seem so bad to me to respect it. I am tempted to
say we should support arbitrary levels of "no-" parsing as an easter
egg, but that is probably silly. :)

So I am fine with this patch, or without it.