Re: [PATCH v7 0/3] maintenance: add support for systemd timers on Linux

> Hello,
> 
> Please find hereafter a new reroll of my patchset to add support for
> systemd timers on Linux for the `git maintenance start` command.
> 
> The changes compared to the previous version address the remarks
> raised during the previous review.
> ... 
> Diff-intervalle contre v6 :
> -:  ---------- > 1:  899b11ed5b cache.h: Introduce a generic "xdg_config_home_for(…)" function
> 1:  604627f347 ! 2:  f3e2f0256b maintenance: `git maintenance run` learned `--scheduler=<scheduler>`
>      @@ Documentation/git-maintenance.txt: OPTIONS
>        
>       +--scheduler=auto|crontab|launchctl|schtasks::
>       +	When combined with the `start` subcommand, specify the scheduler
>      -+	to use to run the hourly, daily and weekly executions of
>      ++	for running the hourly, daily and weekly executions of
>       +	`git maintenance run`.
>      -+	The possible values for `<scheduler>` depend on the system: `crontab`
>      -+	is available on POSIX systems, `launchctl` is available on
>      -+	MacOS and `schtasks` is available on Windows.
>      -+	By default or when `auto` is specified, a suitable scheduler for
>      -+	the system is used. On MacOS, `launchctl` is used. On Windows,
>      -+	`schtasks` is used. On all other systems, `crontab` is used.
>      ++	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
>      @@ builtin/gc.c: 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
>      ++ *   arguments unmodified.
>      ++ *
>      ++ * * If $GET_TEST_MAINT_SCHEDULER is set, return true.
>      ++ *   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 *item;
>      @@ builtin/gc.c: static int schtasks_schedule_task(const char *exec_path, enum sche
>       +	int is_available;
>       +	struct child_process child = CHILD_PROCESS_INIT;
>       +
>      -+	if (get_schedule_cmd(&cmd, &is_available) && !is_available)
>      -+		return 0;
>      ++	if (get_schedule_cmd(&cmd, &is_available))
>      ++		return is_available;

>       +
>       +	strvec_split(&child.args, cmd);
>       +	strvec_push(&child.args, "-l");
>      @@ builtin/gc.c: static int crontab_update_schedule(int run_maintenance, int fd, co
>       +	enum scheduler scheduler;
>       +};
>       +
>      -+static void resolve_auto_scheduler(enum scheduler *scheduler)
>      ++static enum scheduler resolve_scheduler(enum scheduler scheduler)
>       +{
>      -+	if (*scheduler != SCHEDULER_AUTO)
>      -+		return;
>      ++	if (scheduler != SCHEDULER_AUTO)
>      ++		return scheduler;
>       +
>        #if defined(__APPLE__)
>       -static const char platform_scheduler[] = "launchctl";
>      -+	*scheduler = SCHEDULER_LAUNCHCTL;
>      -+	return;
>      ++	return SCHEDULER_LAUNCHCTL;
>       +
>        #elif defined(GIT_WINDOWS_NATIVE)
>       -static const char platform_scheduler[] = "schtasks";
>      -+	*scheduler = SCHEDULER_SCHTASKS;
>      -+	return;
>      ++	return SCHEDULER_SCHTASKS;
>       +
>        #else
>       -static const char platform_scheduler[] = "crontab";
>      -+	*scheduler = SCHEDULER_CRON;
>      -+	return;
>      ++	return SCHEDULER_CRON;
>        #endif
>       +}

>      @@ builtin/gc.c: static int crontab_update_schedule(int run_maintenance, int fd, co
>       +	if (scheduler == SCHEDULER_INVALID)
>       +		BUG("invalid scheduler");
>       +	if (scheduler == SCHEDULER_AUTO)
>      -+		BUG("resolve_auto_scheduler should have been called before");
>      ++		BUG("resolve_scheduler should have been called before");
>       +
>       +	if (!scheduler_fn[scheduler].is_available())
>       +		die(_("%s scheduler is not available"),
>      @@ builtin/gc.c: static int crontab_update_schedule(int run_maintenance, int fd, co
>       +	struct option options[] = {
>       +		OPT_CALLBACK_F(
>       +			0, "scheduler", &opts.scheduler, N_("scheduler"),
>      -+			N_("scheduler to use to trigger git maintenance run"),
>      ++			N_("scheduler to trigger git maintenance run"),
>       +			PARSE_OPT_NONEG, maintenance_opt_scheduler),
>       +		OPT_END()
>       +	};
>      @@ builtin/gc.c: static int crontab_update_schedule(int run_maintenance, int fd, co
>       +	if (argc)
>       +		usage_with_options(builtin_maintenance_start_usage, options);
>       +
>      -+	resolve_auto_scheduler(&opts.scheduler);
>      ++	opts.scheduler = resolve_scheduler(opts.scheduler);
>       +	validate_scheduler(opts.scheduler);
>       +
>        	if (maintenance_register())
> 2:  29628b5a92 ! 3:  0ea5b2fc45 maintenance: add support for systemd timers on Linux
>      @@ Documentation/git-maintenance.txt: OPTIONS
>       ---scheduler=auto|crontab|launchctl|schtasks::
>       +--scheduler=auto|crontab|systemd-timer|launchctl|schtasks::
>        	When combined with the `start` subcommand, specify the scheduler
>      - 	to use to run the hourly, daily and weekly executions of
>      + 	for running the hourly, daily and weekly executions of
>        	`git maintenance run`.
>      - 	The possible values for `<scheduler>` depend on the system: `crontab`
>      --	is available on POSIX systems, `launchctl` is available on
>      --	MacOS and `schtasks` is available on Windows.
>      -+	is available on POSIX systems, `systemd-timer` is available on Linux
>      -+	systems, `launchctl` is available on MacOS and `schtasks` is available
>      -+	on Windows.
>      - 	By default or when `auto` is specified, a suitable scheduler for
>      - 	the system is used. On MacOS, `launchctl` is used. On Windows,
>      --	`schtasks` is used. On all other systems, `crontab` is used.
>      -+	`schtasks` is used. On Linux, `systemd-timer` is used if user systemd
>      -+	timers are available, otherwise, `crontab` is used. On all other systems,
>      -+	`crontab` is used.
>      +-	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`.
>      ++	Possible values for `<scheduler>` are `auto`, `crontab`
>      ++	(POSIX), `systemd-timer` (Linux), `launchctl` (macOS), and
>      ++	`schtasks` (Windows). When `auto` is specified, the
>      ++	appropriate platform-specific scheduler is used; on Linux,
>      ++	`systemd-timer` is used if available, otherwise
>      ++	`crontab`. Default is `auto`.
>        
>        
>        TROUBLESHOOTING
>      @@ builtin/gc.c: static enum scheduler parse_scheduler(const char *value)
>        	else if (!strcasecmp(value, "launchctl"))
>        		return SCHEDULER_LAUNCHCTL;
>        	else if (!strcasecmp(value, "schtasks"))
>      -@@ builtin/gc.c: static void resolve_auto_scheduler(enum scheduler *scheduler)
>      - 	*scheduler = SCHEDULER_SCHTASKS;
>      - 	return;
>      +@@ builtin/gc.c: static enum scheduler resolve_scheduler(enum scheduler scheduler)
>      + #elif defined(GIT_WINDOWS_NATIVE)
>      + 	return SCHEDULER_SCHTASKS;
>        
>       +#elif defined(__linux__)
>       +	if (is_systemd_timer_available())
>      -+		*scheduler = SCHEDULER_SYSTEMD;
>      ++		return SCHEDULER_SYSTEMD;
>       +	else if (is_crontab_available())
>      -+		*scheduler = SCHEDULER_CRON;
>      ++		return SCHEDULER_CRON;
>       +	else
>       +		die(_("neither systemd timers nor crontab are available"));
>      -+	return;
>       +
>        #else
>      - 	*scheduler = SCHEDULER_CRON;
>      - 	return;
>      + 	return SCHEDULER_CRON;
>      + #endif
>       
>        ## t/t7900-maintenance.sh ##
>       @@ t/t7900-maintenance.sh: test_xmllint () {
>