Re: [PATCH v9 2/3] maintenance: `git maintenance run` learned `--scheduler=<scheduler>`

[Ramsay Jones <ramsay@ramsayjones.plus.com>]

Hi Lénaïc,

I noticed a couple of typos while tracking down a test failure
on the previous version of this series:

On 27/08/2021 22:02, Lénaïc Huard wrote:
> Depending on the system, different schedulers can be used to schedule
> the hourly, daily and weekly executions of `git maintenance run`:
> * `launchctl` for MacOS,
> * `schtasks` for Windows and
> * `crontab` for everything else.
> 
> `git maintenance run` now has an option to let the end-user explicitly
> choose which scheduler he wants to use:
> `--scheduler=auto|crontab|launchctl|schtasks`.
> 
> When `git maintenance start --scheduler=XXX` is run, it not only
> registers `git maintenance run` tasks in the scheduler XXX, it also
> removes the `git maintenance run` tasks from all the other schedulers to
> ensure we cannot have two schedulers launching concurrent identical
> tasks.
> 
> The default value is `auto` which chooses a suitable scheduler for the
> system.
> 
> `git maintenance stop` doesn't have any `--scheduler` parameter because
> this command will try to remove the `git maintenance run` tasks from all
> the available schedulers.
> 
> Signed-off-by: Lénaïc Huard <lenaic@lhuard.fr>
> ---
>  Documentation/git-maintenance.txt |   9 +
>  builtin/gc.c                      | 365 ++++++++++++++++++++++++------
>  t/t7900-maintenance.sh            |  55 ++++-
>  3 files changed, 354 insertions(+), 75 deletions(-)
> 
> diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
> index 1e738ad398..576290b5c6 100644
> --- a/Documentation/git-maintenance.txt
> +++ b/Documentation/git-maintenance.txt
> @@ -179,6 +179,15 @@ OPTIONS
>  	`maintenance.<task>.enabled` configured as `true` are considered.
>  	See the 'TASKS' section for the list of accepted `<task>` values.
>  
> +--scheduler=auto|crontab|launchctl|schtasks::
> +	When combined with the `start` subcommand, specify the scheduler
> +	for running the hourly, daily and weekly executions of
> +	`git maintenance run`.
> +	Possible values for `<scheduler>` are `auto`, `crontab` (POSIX),
> +	`launchctl` (macOS), and `schtasks` (Windows).
> +	When `auto` is specified, the appropriate platform-specific
> +	scheduler is used. Default is `auto`.
> +
>  
>  TROUBLESHOOTING
>  ---------------
> diff --git a/builtin/gc.c b/builtin/gc.c
> index f05d2f0a1a..9e464d4a10 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -1529,6 +1529,93 @@ static const char *get_frequency(enum schedule_priority schedule)
>  	}
>  }
>  
> +/*
> + * get_schedule_cmd` reads the GIT_TEST_MAINT_SCHEDULER environment variable
> + * to mock the schedulers that `git maintenance start` rely on.
> + *
> + * For test purpose, GIT_TEST_MAINT_SCHEDULER can be set to a comma-separated
> + * list of colon-separated key/value pairs where each pair contains a scheduler
> + * and its corresponding mock.
> + *
> + * * If $GET_TEST_MAINT_SCHEDULER is not set, return false and leave the

s/GET/GIT/

> + *   arguments unmodified.
> + *
> + * * If $GET_TEST_MAINT_SCHEDULER is set, return true.

s/GET/GIT/

ATB,
Ramsay Jones

> + *   In this case, the *cmd value is read as input.
> + *
> + *   * if the input value *cmd is the key of one of the comma-separated list
> + *     item, then *is_available is set to true and *cmd is modified and becomes
> + *     the mock command.
> + *
> + *   * if the input value *cmd isn’t the key of any of the comma-separated list
> + *     item, then *is_available is set to false.
> + *
> + * Ex.:
> + *   GIT_TEST_MAINT_SCHEDULER not set
> + *     +-------+-------------------------------------------------+
> + *     | Input |                     Output                      |
> + *     | *cmd  | return code |       *cmd        | *is_available |
> + *     +-------+-------------+-------------------+---------------+
> + *     | "foo" |    false    | "foo" (unchanged) |  (unchanged)  |
> + *     +-------+-------------+-------------------+---------------+
> + *
> + *   GIT_TEST_MAINT_SCHEDULER set to “foo:./mock_foo.sh,bar:./mock_bar.sh”
> + *     +-------+-------------------------------------------------+
> + *     | Input |                     Output                      |
> + *     | *cmd  | return code |       *cmd        | *is_available |
> + *     +-------+-------------+-------------------+---------------+
> + *     | "foo" |    true     |  "./mock.foo.sh"  |     true      |
> + *     | "qux" |    true     | "qux" (unchanged) |     false     |
> + *     +-------+-------------+-------------------+---------------+
> + */
> +static int get_schedule_cmd(const char **cmd, int *is_available)
> +{
> +	char *testing = xstrdup_or_null(getenv("GIT_TEST_MAINT_SCHEDULER"));
> +	struct string_list_item *item;
> +	struct string_list list = STRING_LIST_INIT_NODUP;
> +
> +	if (!testing)
> +		return 0;
> +
> +	if (is_available)
> +		*is_available = 0;
> +
> +	string_list_split_in_place(&list, testing, ',', -1);
> +	for_each_string_list_item(item, &list) {
> +		struct string_list pair = STRING_LIST_INIT_NODUP;
> +
> +		if (string_list_split_in_place(&pair, item->string, ':', 2) != 2)
> +			continue;
> +
> +		if (!strcmp(*cmd, pair.items[0].string)) {
> +			*cmd = pair.items[1].string;
> +			if (is_available)
> +				*is_available = 1;
> +			string_list_clear(&list, 0);
> +			UNLEAK(testing);
> +			return 1;
> +		}
> +	}
> +
> +	string_list_clear(&list, 0);
> +	free(testing);
> +	return 1;
> +}
> +
> +static int is_launchctl_available(void)
> +{
> +	const char *cmd = "launchctl";
> +	int is_available;
> +	if (get_schedule_cmd(&cmd, &is_available))
> +		return is_available;
> +
> +#ifdef __APPLE__
> +	return 1;
> +#else
> +	return 0;
> +#endif
> +}
> +
>  static char *launchctl_service_name(const char *frequency)
>  {
>  	struct strbuf label = STRBUF_INIT;
> @@ -1555,19 +1642,17 @@ static char *launchctl_get_uid(void)
>  	return xstrfmt("gui/%d", getuid());
>  }
>  
> -static int launchctl_boot_plist(int enable, const char *filename, const char *cmd)
> +static int launchctl_boot_plist(int enable, const char *filename)
>  {
> +	const char *cmd = "launchctl";
>  	int result;
>  	struct child_process child = CHILD_PROCESS_INIT;
>  	char *uid = launchctl_get_uid();
>  
> +	get_schedule_cmd(&cmd, NULL);
>  	strvec_split(&child.args, cmd);
> -	if (enable)
> -		strvec_push(&child.args, "bootstrap");
> -	else
> -		strvec_push(&child.args, "bootout");
> -	strvec_push(&child.args, uid);
> -	strvec_push(&child.args, filename);
> +	strvec_pushl(&child.args, enable ? "bootstrap" : "bootout", uid,
> +		     filename, NULL);
>  
>  	child.no_stderr = 1;
>  	child.no_stdout = 1;
> @@ -1581,26 +1666,26 @@ static int launchctl_boot_plist(int enable, const char *filename, const char *cm
>  	return result;
>  }
>  
> -static int launchctl_remove_plist(enum schedule_priority schedule, const char *cmd)
> +static int launchctl_remove_plist(enum schedule_priority schedule)
>  {
>  	const char *frequency = get_frequency(schedule);
>  	char *name = launchctl_service_name(frequency);
>  	char *filename = launchctl_service_filename(name);
> -	int result = launchctl_boot_plist(0, filename, cmd);
> +	int result = launchctl_boot_plist(0, filename);
>  	unlink(filename);
>  	free(filename);
>  	free(name);
>  	return result;
>  }
>  
> -static int launchctl_remove_plists(const char *cmd)
> +static int launchctl_remove_plists(void)
>  {
> -	return launchctl_remove_plist(SCHEDULE_HOURLY, cmd) ||
> -		launchctl_remove_plist(SCHEDULE_DAILY, cmd) ||
> -		launchctl_remove_plist(SCHEDULE_WEEKLY, cmd);
> +	return launchctl_remove_plist(SCHEDULE_HOURLY) ||
> +	       launchctl_remove_plist(SCHEDULE_DAILY) ||
> +	       launchctl_remove_plist(SCHEDULE_WEEKLY);
>  }
>  
> -static int launchctl_schedule_plist(const char *exec_path, enum schedule_priority schedule, const char *cmd)
> +static int launchctl_schedule_plist(const char *exec_path, enum schedule_priority schedule)
>  {
>  	FILE *plist;
>  	int i;
> @@ -1669,8 +1754,8 @@ static int launchctl_schedule_plist(const char *exec_path, enum schedule_priorit
>  	fclose(plist);
>  
>  	/* bootout might fail if not already running, so ignore */
> -	launchctl_boot_plist(0, filename, cmd);
> -	if (launchctl_boot_plist(1, filename, cmd))
> +	launchctl_boot_plist(0, filename);
> +	if (launchctl_boot_plist(1, filename))
>  		die(_("failed to bootstrap service %s"), filename);
>  
>  	free(filename);
> @@ -1678,21 +1763,35 @@ static int launchctl_schedule_plist(const char *exec_path, enum schedule_priorit
>  	return 0;
>  }
>  
> -static int launchctl_add_plists(const char *cmd)
> +static int launchctl_add_plists(void)
>  {
>  	const char *exec_path = git_exec_path();
>  
> -	return launchctl_schedule_plist(exec_path, SCHEDULE_HOURLY, cmd) ||
> -		launchctl_schedule_plist(exec_path, SCHEDULE_DAILY, cmd) ||
> -		launchctl_schedule_plist(exec_path, SCHEDULE_WEEKLY, cmd);
> +	return launchctl_schedule_plist(exec_path, SCHEDULE_HOURLY) ||
> +	       launchctl_schedule_plist(exec_path, SCHEDULE_DAILY) ||
> +	       launchctl_schedule_plist(exec_path, SCHEDULE_WEEKLY);
>  }
>  
> -static int launchctl_update_schedule(int run_maintenance, int fd, const char *cmd)
> +static int launchctl_update_schedule(int run_maintenance, int fd)
>  {
>  	if (run_maintenance)
> -		return launchctl_add_plists(cmd);
> +		return launchctl_add_plists();
>  	else
> -		return launchctl_remove_plists(cmd);
> +		return launchctl_remove_plists();
> +}
> +
> +static int is_schtasks_available(void)
> +{
> +	const char *cmd = "schtasks";
> +	int is_available;
> +	if (get_schedule_cmd(&cmd, &is_available))
> +		return is_available;
> +
> +#ifdef GIT_WINDOWS_NATIVE
> +	return 1;
> +#else
> +	return 0;
> +#endif
>  }
>  
>  static char *schtasks_task_name(const char *frequency)
> @@ -1702,13 +1801,15 @@ static char *schtasks_task_name(const char *frequency)
>  	return strbuf_detach(&label, NULL);
>  }
>  
> -static int schtasks_remove_task(enum schedule_priority schedule, const char *cmd)
> +static int schtasks_remove_task(enum schedule_priority schedule)
>  {
> +	const char *cmd = "schtasks";
>  	int result;
>  	struct strvec args = STRVEC_INIT;
>  	const char *frequency = get_frequency(schedule);
>  	char *name = schtasks_task_name(frequency);
>  
> +	get_schedule_cmd(&cmd, NULL);
>  	strvec_split(&args, cmd);
>  	strvec_pushl(&args, "/delete", "/tn", name, "/f", NULL);
>  
> @@ -1719,15 +1820,16 @@ static int schtasks_remove_task(enum schedule_priority schedule, const char *cmd
>  	return result;
>  }
>  
> -static int schtasks_remove_tasks(const char *cmd)
> +static int schtasks_remove_tasks(void)
>  {
> -	return schtasks_remove_task(SCHEDULE_HOURLY, cmd) ||
> -		schtasks_remove_task(SCHEDULE_DAILY, cmd) ||
> -		schtasks_remove_task(SCHEDULE_WEEKLY, cmd);
> +	return schtasks_remove_task(SCHEDULE_HOURLY) ||
> +	       schtasks_remove_task(SCHEDULE_DAILY) ||
> +	       schtasks_remove_task(SCHEDULE_WEEKLY);
>  }
>  
> -static int schtasks_schedule_task(const char *exec_path, enum schedule_priority schedule, const char *cmd)
> +static int schtasks_schedule_task(const char *exec_path, enum schedule_priority schedule)
>  {
> +	const char *cmd = "schtasks";
>  	int result;
>  	struct child_process child = CHILD_PROCESS_INIT;
>  	const char *xml;
> @@ -1736,6 +1838,8 @@ static int schtasks_schedule_task(const char *exec_path, enum schedule_priority
>  	char *name = schtasks_task_name(frequency);
>  	struct strbuf tfilename = STRBUF_INIT;
>  
> +	get_schedule_cmd(&cmd, NULL);
> +
>  	strbuf_addf(&tfilename, "%s/schedule_%s_XXXXXX",
>  		    get_git_common_dir(), frequency);
>  	tfile = xmks_tempfile(tfilename.buf);
> @@ -1840,28 +1944,52 @@ static int schtasks_schedule_task(const char *exec_path, enum schedule_priority
>  	return result;
>  }
>  
> -static int schtasks_schedule_tasks(const char *cmd)
> +static int schtasks_schedule_tasks(void)
>  {
>  	const char *exec_path = git_exec_path();
>  
> -	return schtasks_schedule_task(exec_path, SCHEDULE_HOURLY, cmd) ||
> -		schtasks_schedule_task(exec_path, SCHEDULE_DAILY, cmd) ||
> -		schtasks_schedule_task(exec_path, SCHEDULE_WEEKLY, cmd);
> +	return schtasks_schedule_task(exec_path, SCHEDULE_HOURLY) ||
> +	       schtasks_schedule_task(exec_path, SCHEDULE_DAILY) ||
> +	       schtasks_schedule_task(exec_path, SCHEDULE_WEEKLY);
>  }
>  
> -static int schtasks_update_schedule(int run_maintenance, int fd, const char *cmd)
> +static int schtasks_update_schedule(int run_maintenance, int fd)
>  {
>  	if (run_maintenance)
> -		return schtasks_schedule_tasks(cmd);
> +		return schtasks_schedule_tasks();
>  	else
> -		return schtasks_remove_tasks(cmd);
> +		return schtasks_remove_tasks();
> +}
> +
> +static int is_crontab_available(void)
> +{
> +	const char *cmd = "crontab";
> +	int is_available;
> +	struct child_process child = CHILD_PROCESS_INIT;
> +
> +	if (get_schedule_cmd(&cmd, &is_available))
> +		return is_available;
> +
> +	strvec_split(&child.args, cmd);
> +	strvec_push(&child.args, "-l");
> +	child.no_stdin = 1;
> +	child.no_stdout = 1;
> +	child.no_stderr = 1;
> +	child.silent_exec_failure = 1;
> +
> +	if (start_command(&child))
> +		return 0;
> +	/* Ignore exit code, as an empty crontab will return error. */
> +	finish_command(&child);
> +	return 1;
>  }
>  
>  #define BEGIN_LINE "# BEGIN GIT MAINTENANCE SCHEDULE"
>  #define END_LINE "# END GIT MAINTENANCE SCHEDULE"
>  
> -static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
> +static int crontab_update_schedule(int run_maintenance, int fd)
>  {
> +	const char *cmd = "crontab";
>  	int result = 0;
>  	int in_old_region = 0;
>  	struct child_process crontab_list = CHILD_PROCESS_INIT;
> @@ -1869,6 +1997,7 @@ static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
>  	FILE *cron_list, *cron_in;
>  	struct strbuf line = STRBUF_INIT;
>  
> +	get_schedule_cmd(&cmd, NULL);
>  	strvec_split(&crontab_list.args, cmd);
>  	strvec_push(&crontab_list.args, "-l");
>  	crontab_list.in = -1;
> @@ -1945,66 +2074,160 @@ static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
>  	return result;
>  }
>  
> +enum scheduler {
> +	SCHEDULER_INVALID = -1,
> +	SCHEDULER_AUTO,
> +	SCHEDULER_CRON,
> +	SCHEDULER_LAUNCHCTL,
> +	SCHEDULER_SCHTASKS,
> +};
> +
> +static const struct {
> +	const char *name;
> +	int (*is_available)(void);
> +	int (*update_schedule)(int run_maintenance, int fd);
> +} scheduler_fn[] = {
> +	[SCHEDULER_CRON] = {
> +		.name = "crontab",
> +		.is_available = is_crontab_available,
> +		.update_schedule = crontab_update_schedule,
> +	},
> +	[SCHEDULER_LAUNCHCTL] = {
> +		.name = "launchctl",
> +		.is_available = is_launchctl_available,
> +		.update_schedule = launchctl_update_schedule,
> +	},
> +	[SCHEDULER_SCHTASKS] = {
> +		.name = "schtasks",
> +		.is_available = is_schtasks_available,
> +		.update_schedule = schtasks_update_schedule,
> +	},
> +};
> +
> +static enum scheduler parse_scheduler(const char *value)
> +{
> +	if (!value)
> +		return SCHEDULER_INVALID;
> +	else if (!strcasecmp(value, "auto"))
> +		return SCHEDULER_AUTO;
> +	else if (!strcasecmp(value, "cron") || !strcasecmp(value, "crontab"))
> +		return SCHEDULER_CRON;
> +	else if (!strcasecmp(value, "launchctl"))
> +		return SCHEDULER_LAUNCHCTL;
> +	else if (!strcasecmp(value, "schtasks"))
> +		return SCHEDULER_SCHTASKS;
> +	else
> +		return SCHEDULER_INVALID;
> +}
> +
> +static int maintenance_opt_scheduler(const struct option *opt, const char *arg,
> +				     int unset)
> +{
> +	enum scheduler *scheduler = opt->value;
> +
> +	BUG_ON_OPT_NEG(unset);
> +
> +	*scheduler = parse_scheduler(arg);
> +	if (*scheduler == SCHEDULER_INVALID)
> +		return error(_("unrecognized --scheduler argument '%s'"), arg);
> +	return 0;
> +}
> +
> +struct maintenance_start_opts {
> +	enum scheduler scheduler;
> +};
> +
> +static enum scheduler resolve_scheduler(enum scheduler scheduler)
> +{
> +	if (scheduler != SCHEDULER_AUTO)
> +		return scheduler;
> +
>  #if defined(__APPLE__)
> -static const char platform_scheduler[] = "launchctl";
> +	return SCHEDULER_LAUNCHCTL;
> +
>  #elif defined(GIT_WINDOWS_NATIVE)
> -static const char platform_scheduler[] = "schtasks";
> +	return SCHEDULER_SCHTASKS;
> +
>  #else
> -static const char platform_scheduler[] = "crontab";
> +	return SCHEDULER_CRON;
>  #endif
> +}
>  
> -static int update_background_schedule(int enable)
> +static void validate_scheduler(enum scheduler scheduler)
>  {
> -	int result;
> -	const char *scheduler = platform_scheduler;
> -	const char *cmd = scheduler;
> -	char *testing;
> +	if (scheduler == SCHEDULER_INVALID)
> +		BUG("invalid scheduler");
> +	if (scheduler == SCHEDULER_AUTO)
> +		BUG("resolve_scheduler should have been called before");
> +
> +	if (!scheduler_fn[scheduler].is_available())
> +		die(_("%s scheduler is not available"),
> +		    scheduler_fn[scheduler].name);
> +}
> +
> +static int update_background_schedule(const struct maintenance_start_opts *opts,
> +				      int enable)
> +{
> +	unsigned int i;
> +	int result = 0;
>  	struct lock_file lk;
>  	char *lock_path = xstrfmt("%s/schedule", the_repository->objects->odb->path);
>  
> -	testing = xstrdup_or_null(getenv("GIT_TEST_MAINT_SCHEDULER"));
> -	if (testing) {
> -		char *sep = strchr(testing, ':');
> -		if (!sep)
> -			die("GIT_TEST_MAINT_SCHEDULER unparseable: %s", testing);
> -		*sep = '\0';
> -		scheduler = testing;
> -		cmd = sep + 1;
> +	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0) {
> +		free(lock_path);
> +		return error(_("another process is scheduling background maintenance"));
>  	}
>  
> -	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0) {
> -		result = error(_("another process is scheduling background maintenance"));
> -		goto cleanup;
> +	for (i = 1; i < ARRAY_SIZE(scheduler_fn); i++) {
> +		if (enable && opts->scheduler == i)
> +			continue;
> +		if (!scheduler_fn[i].is_available())
> +			continue;
> +		scheduler_fn[i].update_schedule(0, get_lock_file_fd(&lk));
>  	}
>  
> -	if (!strcmp(scheduler, "launchctl"))
> -		result = launchctl_update_schedule(enable, get_lock_file_fd(&lk), cmd);
> -	else if (!strcmp(scheduler, "schtasks"))
> -		result = schtasks_update_schedule(enable, get_lock_file_fd(&lk), cmd);
> -	else if (!strcmp(scheduler, "crontab"))
> -		result = crontab_update_schedule(enable, get_lock_file_fd(&lk), cmd);
> -	else
> -		die("unknown background scheduler: %s", scheduler);
> +	if (enable)
> +		result = scheduler_fn[opts->scheduler].update_schedule(
> +			1, get_lock_file_fd(&lk));
>  
>  	rollback_lock_file(&lk);
>  
> -cleanup:
>  	free(lock_path);
> -	free(testing);
>  	return result;
>  }
>  
> -static int maintenance_start(void)
> +static const char *const builtin_maintenance_start_usage[] = {
> +	N_("git maintenance start [--scheduler=<scheduler>]"),
> +	NULL
> +};
> +
> +static int maintenance_start(int argc, const char **argv, const char *prefix)
>  {
> +	struct maintenance_start_opts opts = { 0 };
> +	struct option options[] = {
> +		OPT_CALLBACK_F(
> +			0, "scheduler", &opts.scheduler, N_("scheduler"),
> +			N_("scheduler to trigger git maintenance run"),
> +			PARSE_OPT_NONEG, maintenance_opt_scheduler),
> +		OPT_END()
> +	};
> +
> +	argc = parse_options(argc, argv, prefix, options,
> +			     builtin_maintenance_start_usage, 0);
> +	if (argc)
> +		usage_with_options(builtin_maintenance_start_usage, options);
> +
> +	opts.scheduler = resolve_scheduler(opts.scheduler);
> +	validate_scheduler(opts.scheduler);
> +
>  	if (maintenance_register())
>  		warning(_("failed to add repo to global config"));
> -
> -	return update_background_schedule(1);
> +	return update_background_schedule(&opts, 1);
>  }
>  
>  static int maintenance_stop(void)
>  {
> -	return update_background_schedule(0);
> +	return update_background_schedule(NULL, 0);
>  }
>  
>  static const char builtin_maintenance_usage[] =	N_("git maintenance <subcommand> [<options>]");
> @@ -2018,7 +2241,7 @@ int cmd_maintenance(int argc, const char **argv, const char *prefix)
>  	if (!strcmp(argv[1], "run"))
>  		return maintenance_run(argc - 1, argv + 1, prefix);
>  	if (!strcmp(argv[1], "start"))
> -		return maintenance_start();
> +		return maintenance_start(argc - 1, argv + 1, prefix);
>  	if (!strcmp(argv[1], "stop"))
>  		return maintenance_stop();
>  	if (!strcmp(argv[1], "register"))
> diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
> index 58f46c77e6..27bce7992c 100755
> --- a/t/t7900-maintenance.sh
> +++ b/t/t7900-maintenance.sh
> @@ -492,8 +492,21 @@ test_expect_success !MINGW 'register and unregister with regex metacharacters' '
>  		maintenance.repo "$(pwd)/$META"
>  '
>  
> +test_expect_success 'start --scheduler=<scheduler>' '
> +	test_expect_code 129 git maintenance start --scheduler=foo 2>err &&
> +	test_i18ngrep "unrecognized --scheduler argument" err &&
> +
> +	test_expect_code 129 git maintenance start --no-scheduler 2>err &&
> +	test_i18ngrep "unknown option" err &&
> +
> +	test_expect_code 128 \
> +		env GIT_TEST_MAINT_SCHEDULER="launchctl:true,schtasks:true" \
> +		git maintenance start --scheduler=crontab 2>err &&
> +	test_i18ngrep "fatal: crontab scheduler is not available" err
> +'
> +
>  test_expect_success 'start from empty cron table' '
> -	GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab cron.txt" git maintenance start &&
> +	GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab cron.txt" git maintenance start --scheduler=crontab &&
>  
>  	# start registers the repo
>  	git config --get --global --fixed-value maintenance.repo "$(pwd)" &&
> @@ -516,7 +529,7 @@ test_expect_success 'stop from existing schedule' '
>  
>  test_expect_success 'start preserves existing schedule' '
>  	echo "Important information!" >cron.txt &&
> -	GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab cron.txt" git maintenance start &&
> +	GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab cron.txt" git maintenance start --scheduler=crontab &&
>  	grep "Important information!" cron.txt
>  '
>  
> @@ -545,7 +558,7 @@ test_expect_success 'start and stop macOS maintenance' '
>  	EOF
>  
>  	rm -f args &&
> -	GIT_TEST_MAINT_SCHEDULER=launchctl:./print-args git maintenance start &&
> +	GIT_TEST_MAINT_SCHEDULER=launchctl:./print-args git maintenance start --scheduler=launchctl &&
>  
>  	# start registers the repo
>  	git config --get --global --fixed-value maintenance.repo "$(pwd)" &&
> @@ -596,7 +609,7 @@ test_expect_success 'start and stop Windows maintenance' '
>  	EOF
>  
>  	rm -f args &&
> -	GIT_TEST_MAINT_SCHEDULER="schtasks:./print-args" git maintenance start &&
> +	GIT_TEST_MAINT_SCHEDULER="schtasks:./print-args" git maintenance start --scheduler=schtasks &&
>  
>  	# start registers the repo
>  	git config --get --global --fixed-value maintenance.repo "$(pwd)" &&
> @@ -619,6 +632,40 @@ test_expect_success 'start and stop Windows maintenance' '
>  	test_cmp expect args
>  '
>  
> +test_expect_success 'start and stop when several schedulers are available' '
> +	write_script print-args <<-\EOF &&
> +	printf "%s\n" "$*" | sed "s:gui/[0-9][0-9]*:gui/[UID]:; s:\(schtasks /create .* /xml\).*:\1:;" >>args
> +	EOF
> +
> +	rm -f args &&
> +	GIT_TEST_MAINT_SCHEDULER="launchctl:./print-args launchctl,schtasks:./print-args schtasks" git maintenance start --scheduler=launchctl &&
> +	printf "schtasks /delete /tn Git Maintenance (%s) /f\n" \
> +		hourly daily weekly >expect &&
> +	for frequency in hourly daily weekly
> +	do
> +		PLIST="$pfx/Library/LaunchAgents/org.git-scm.git.$frequency.plist" &&
> +		echo "launchctl bootout gui/[UID] $PLIST" >>expect &&
> +		echo "launchctl bootstrap gui/[UID] $PLIST" >>expect || return 1
> +	done &&
> +	test_cmp expect args &&
> +
> +	rm -f args &&
> +	GIT_TEST_MAINT_SCHEDULER="launchctl:./print-args launchctl,schtasks:./print-args schtasks" git maintenance start --scheduler=schtasks &&
> +	printf "launchctl bootout gui/[UID] $pfx/Library/LaunchAgents/org.git-scm.git.%s.plist\n" \
> +		hourly daily weekly >expect &&
> +	printf "schtasks /create /tn Git Maintenance (%s) /f /xml\n" \
> +		hourly daily weekly >>expect &&
> +	test_cmp expect args &&
> +
> +	rm -f args &&
> +	GIT_TEST_MAINT_SCHEDULER="launchctl:./print-args launchctl,schtasks:./print-args schtasks" git maintenance stop &&
> +	printf "launchctl bootout gui/[UID] $pfx/Library/LaunchAgents/org.git-scm.git.%s.plist\n" \
> +		hourly daily weekly >expect &&
> +	printf "schtasks /delete /tn Git Maintenance (%s) /f\n" \
> +		hourly daily weekly >>expect &&
> +	test_cmp expect args
> +'
> +
>  test_expect_success 'register preserves existing strategy' '
>  	git config maintenance.strategy none &&
>  	git maintenance register &&
>