bundle: don't segfault on "git bundle <subcmd>"

Since aef7d75 (builtin/bundle.c: let parse-options parse
subcommands, 2022-08-19) we've been segfaulting if no argument was
provided.

The fix is easy, as all of the "git bundle" subcommands require a
non-option argument we can check that we have arguments left after
calling parse-options().

This makes use of code added in 73c3253 (bundle: framework for
options before bundle file, 2019-11-10), before this change that code
has always been unreachable. In 73c3253 we'd never reach it as we
already checked "argc < 2" in cmd_bundle() itself.

Then when aef7d75 (whose segfault we're fixing here) migrated this
code to the subcommand API it removed that "argc < 2" check, but we
were still checking the wrong "argc" in parse_options_cmd_bundle(), we
need to check the "newargc". The "argc" will always be >= 1, as it
will necessarily contain at least the subcommand name
itself (e.g. "create").

As an aside, this could be safely squashed into this, but let's not do
that for this minimal segfault fix, as it's an unrelated refactoring:

	--- a/builtin/bundle.c
	+++ b/builtin/bundle.c
	@@ -55,13 +55,12 @@ static int parse_options_cmd_bundle(int argc,
	 		const char * const usagestr[],
	 		const struct option options[],
	 		char **bundle_file) {
	-	int newargc;
	-	newargc = parse_options(argc, argv, NULL, options, usagestr,
	+	argc = parse_options(argc, argv, NULL, options, usagestr,
	 			     PARSE_OPT_STOP_AT_NON_OPTION);
	-	if (!newargc)
	+	if (!argc)
	 		usage_with_options(usagestr, options);
	 	*bundle_file = prefix_filename(prefix, argv[0]);
	-	return newargc;
	+	return argc;
	 }

	 static int cmd_bundle_create(int argc, const char **argv, const char *prefix) {

Reported-by: Hubert Jasudowicz <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Tested-by: Hubert Jasudowicz <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/bundle.c

@@ -48,7 +48,7 @@ static int parse_options_cmd_bundle(int argc,
 	int newargc;
 	newargc = parse_options(argc, argv, NULL, options, usagestr,
 			     PARSE_OPT_STOP_AT_NON_OPTION);
-	if (argc < 1)
+	if (!newargc)
 		usage_with_options(usagestr, options);
 	*bundle_file = prefix_filename(prefix, argv[0]);
 	return newargc;

t/t6020-bundle-misc.sh

@@ -11,6 +11,13 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-bundle.sh
 
+for cmd in create verify list-heads unbundle
+do
+	test_expect_success "usage: git bundle $cmd needs an argument" '
+		test_expect_code 129 git bundle $cmd
+	'
+done
+
 # Create a commit or tag and set the variable with the object ID.
 test_commit_setvar () {
 	notick=