Re: [PATCH 2/2] config: allow specifying config entries via envvar pairs

[Patrick Steinhardt <ps@pks.im>]

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On Mon, Nov 16, 2020 at 11:39:35AM -0800, Junio C Hamano wrote:
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> 
> > On Fri, Nov 13 2020, Patrick Steinhardt wrote:
> >
> >> While not document, it is currently possible to specify config entries
> >
> > "While not documented..."
> >
> >> +		strbuf_addf(&envvar, "GIT_CONFIG_KEY_%d", i);
> >> +		if ((key = getenv(envvar.buf)) == NULL)
> >> +			break;
> >
> > The convention in git.git is to avoid explicit NULL checks. So maybe
> > something like this, which also avoids the assignment inside an "if"
> >
> >     key = getenv(envvar.buf);
> >     if (!key)
> >         break;
> 
> All good suggestions, but...
> 
> "While not documented" yes, for sure, but we do not document it for
> a good reason---it is a pure implementation detail between Git
> process that runs another one as its internal implementation detail.

Agreed

> I especially do not think we want to read from unbounded number of
> GIT_CONFIG_KEY_<N> variables like this patch does.  How would a
> script cleanse its environment to protect itself from stray such
> environment variable pair?  Count up from 1 to forever?  Run "env"
> and grep for "GIT_CONFIG_KEY_[0-9]*=" (the answer is No.  What if
> some environment variables have newline in its values?)

You only have to unset `GIT_CONFIG_KEY_1` as the parser will stop
iterating on the first missing key. More generally, if you set `n` keys,
it's sufficient to unset key `n+1`.

Patrick

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