config: die on error in command-line config

The error handling for git_config is somewhat confusing. We
collect errors from running git_config_from_file on the
various config files and carefully pass them back up. But
the two odd things are:

  1. We actually die on most errors in git_config_from_file.
     In fact, the only error we actually pass back up is if
     fopen() fails on the file.

  2. Most callers of git_config do not check the error
     return at all, but will continue if git_config reports
     an error.

When the code for "git -c core.foo=bar" was added, it
dutifully passed errors up the call stack, only for them to
be eventually ignored. This makes it inconsistent with the
file-parsing code, which will die when it sees malformed
config. And it's somewhat unsafe, because it means an error
in parsing a typo like:

  git -c clean.requireforce=ture clean

will continue the command, ignoring the config the user
tried to give.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.c

@@ -858,7 +858,7 @@ int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 
 	switch (git_config_from_parameters(fn, data)) {
 	case -1: /* error */
-		ret--;
+		die("unable to parse command-line config");
 		break;
 	case 0: /* found nothing */
 		break;

t/t1300-repo-config.sh

@@ -910,4 +910,12 @@ test_expect_success 'git -c does not split values on equals' '
 	test_cmp expect actual
 '
 
+test_expect_success 'git -c dies on bogus config' '
+	test_must_fail git -c core.bare=foo rev-parse
+'
+
+test_expect_success 'git -c complains about empty key' '
+	test_must_fail git -c "=foo" rev-parse
+'
+
 test_done