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

On Mon, Nov 16, 2020 at 11:39:35AM -0800, Junio C Hamano wrote:

Ævar Arnfjörð Bjarmason [off-list ref] writes:

quoted

On Fri, Nov 13 2020, Patrick Steinhardt wrote:

quoted

While not document, it is currently possible to specify config entries

"While not documented..."

quoted

+		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