Re: [PATCH v7 2/8] config: add new way to pass config via `--config-env`

Patrick Steinhardt [off-list ref] writes:

+void git_config_push_env(const char *spec)
+{
+	struct strbuf buf = STRBUF_INIT;
+	const char *env_name;
+	const char *env_value;
+
+	env_name = strrchr(spec, '=');
+	if (!env_name)
+		die(_("invalid config format: %s"), spec);
+	env_name++;
+	if (!*env_name)
+		die(_("missing value for --config-env"));

If reporting the name of the configuration variable, for which we
checked an environment variable, is worth doing in the !env_value
case below, shouldn't we be doing the same here, too?  I.e.

		die(_("missing environment variable name in %s", spec));;

or something to complain against "git --config-env foo="?

+	env_value = getenv(env_name);
+	if (!env_value)
+		die(_("missing environment variable '%s' for configuration '%.*s'"),
+		    env_name, (int)(env_name - spec - 1), spec);

+test_expect_success 'git --config-env=key=envvar support' '
+	cat >expect <<-\EOF &&
+	value
+	value
+	false
+	EOF
+	{
+		env ENVVAR=value git --config-env=core.name=ENVVAR config core.name &&
+		env ENVVAR=value git --config-env=foo.CamelCase=ENVVAR config foo.camelcase &&
+		env ENVVAR= git --config-env=foo.flag=ENVVAR config --bool foo.flag

These "env " prefixes are not wrong per-se but are unnecessary.  The
same for the rest of this patch.

+	} >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'git --config-env fails with invalid parameters' '
+	test_must_fail git --config-env=foo.flag config --bool foo.flag 2>error &&
+	test_i18ngrep "invalid config format" error &&
+	test_must_fail git --config-env=foo.flag= config --bool foo.flag 2>error &&
+	test_i18ngrep "missing value for --config-env" error &&
+	test_must_fail git --config-env=foo.flag=NONEXISTENT config --bool foo.flag 2>error &&

How are we making sure 

	$ NONEXISTENT=True make test

is not what the end-user is running?

	sane_unset X &&
	test_must_fail git --config-env foo.flag=X config --bool foo.flag

or something along that line, perhaps?