submodule--helper: move "is-active" to a test-tool

Create a new "test-tool submodule" and move the "is-active" subcommand
over to it. It was added in 5c2bd8b77a (submodule--helper: add
is-active subcommand, 2017-03-16), since
a452128a36 (submodule--helper: introduce add-config subcommand,
2021-08-06) it hasn't been used by git-submodule.sh.

Since we're creating a command dispatch similar to test-tool.c itself
let's split out the "struct test_cmd" into a new test-tool-utils.h,
which both this new code and test-tool.c itself can use.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Reviewed-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-submodule.c

@@ -0,0 +1,58 @@
+#include "test-tool.h"
+#include "test-tool-utils.h"
+#include "cache.h"
+#include "parse-options.h"
+#include "submodule.h"
+
+#define TEST_TOOL_IS_ACTIVE_USAGE \
+	"test-tool submodule is-active <name>"
+static const char *submodule_is_active_usage[] = {
+	TEST_TOOL_IS_ACTIVE_USAGE,
+	NULL
+};
+
+static const char *submodule_usage[] = {
+	TEST_TOOL_IS_ACTIVE_USAGE,
+	NULL
+};
+
+static int cmd__submodule_is_active(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END()
+	};
+	argc = parse_options(argc, argv, "test-tools", options,
+			     submodule_is_active_usage, 0);
+	if (argc != 1)
+		usage_with_options(submodule_is_active_usage, options);
+
+	setup_git_directory();
+
+	return !is_submodule_active(the_repository, argv[0]);
+}
+
+static struct test_cmd cmds[] = {
+	{ "is-active", cmd__submodule_is_active },
+};
+
+int cmd__submodule(int argc, const char **argv)
+{
+	struct option options[] = {
+		OPT_END()
+	};
+	size_t i;
+
+	argc = parse_options(argc, argv, "test-tools", options, submodule_usage,
+			     PARSE_OPT_STOP_AT_NON_OPTION);
+	if (argc < 1)
+		usage_with_options(submodule_usage, options);
+
+	for (i = 0; i < ARRAY_SIZE(cmds); i++)
+		if (!strcmp(cmds[i].name, argv[0]))
+			return cmds[i].fn(argc, argv);
+
+	usage_msg_optf("unknown subcommand '%s'", submodule_usage, options,
+		       argv[0]);
+
+	return 0;
+}