--scheduler=auto|crontab|systemd-timer|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), `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`.

BACKGROUND MAINTENANCE ON LINUX SYSTEMD SYSTEMS

-----------------------------------------------

While Linux supports `cron`, depending on the distribution, `cron` may

be an optional package not necessarily installed. On modern Linux

distributions, systemd timers are superseding it.

If user systemd timers are available, they will be used as a replacement

of `cron`.

In this case, `git maintenance start` will create user systemd timer units

and start the timers. The current list of user-scheduled tasks can be found

by running `systemctl --user list-timers`. The timers written by `git

maintenance start` are similar to this:

-----------------------------------------------------------------------

$ systemctl --user list-timers

NEXT LEFT LAST PASSED UNIT ACTIVATES

Thu 2021-04-29 19:00:00 CEST 42min left Thu 2021-04-29 18:00:11 CEST 17min ago git-maintenance@hourly.timer git-maintenance@hourly.service

Fri 2021-04-30 00:00:00 CEST 5h 42min left Thu 2021-04-29 00:00:11 CEST 18h ago git-maintenance@daily.timer git-maintenance@daily.service

Mon 2021-05-03 00:00:00 CEST 3 days left Mon 2021-04-26 00:00:11 CEST 3 days ago git-maintenance@weekly.timer git-maintenance@weekly.service

-----------------------------------------------------------------------

One timer is registered for each `--schedule=<frequency>` option.

The definition of the systemd units can be inspected in the following files:

-----------------------------------------------------------------------

~/.config/systemd/user/git-maintenance@.timer

~/.config/systemd/user/git-maintenance@.service

~/.config/systemd/user/timers.target.wants/git-maintenance@hourly.timer

~/.config/systemd/user/timers.target.wants/git-maintenance@daily.timer

~/.config/systemd/user/timers.target.wants/git-maintenance@weekly.timer

-----------------------------------------------------------------------

`git maintenance start` will overwrite these files and start the timer

again with `systemctl --user`, so any customization should be done by

creating a drop-in file, i.e. a `.conf` suffixed file in the

`~/.config/systemd/user/git-maintenance@.service.d` directory.

`git maintenance stop` will stop the user systemd timers and delete

the above mentioned files.

For more details, see `systemd.timer(5)`.