Re: [PATCH v2 1/1] advice: add --no-advice global option

> You need an environment variable if you want the command-line option to
> work consistently across commands that spawn external processes. E.g.:
>
>   git --no-advice fetch --all
>
> is going to spawn fetch sub-processes under the hood. You'd want them to
> respect --no-advice, too, so we either have to propagate the
> command-line option or use the environment. And when you consider an
> external script like git-foo that runs a bunch of underlying Git
> commands, then propagating becomes too cumbersome and error-prone.

> You should use git_env_bool() to avoid the confusing behavior that
> GIT_NO_ADVICE=false still turns off advice. ;)
>
> You can also drop the "NO", which helps avoid awkward double negation.
> For example, if you do:
>
>   if (git_env_bool("GIT_ADVICE", 1))
> 	return 0;
>
> then leaving that variable unset will act as if it is set to "1", but
> you can still do GIT_ADVICE=0 to suppress it.