Documentation/git-maintenance.txt - jrn/git - Git at Google

 git-maintenance(1)
 ==================

 NAME
 ----
 git-maintenance - Run tasks to optimize Git repository data


 SYNOPSIS
 --------
 [verse]
 'git maintenance' run [<options>]
 'git maintenance' start [--scheduler=<scheduler>]
 'git maintenance' (stop|register|unregister) [<options>]


 DESCRIPTION
 -----------
 Run tasks to optimize Git repository data, speeding up other Git commands
 and reducing storage requirements for the repository.

 Git commands that add repository data, such as `git add` or `git fetch`,
 are optimized for a responsive user experience. These commands do not take
 time to optimize the Git data, since such optimizations scale with the full
 size of the repository while these user commands each perform a relatively
 small action.

 The `git maintenance` command provides flexibility for how to optimize the
 Git repository.

 SUBCOMMANDS
 -----------

 run::
 	Run one or more maintenance tasks. If one or more `--task` options
 	are specified, then those tasks are run in that order. Otherwise,
 	the tasks are determined by which `maintenance.<task>.enabled`
 	config options are true. By default, only `maintenance.gc.enabled`
 	is true.

 start::
 	Start running maintenance on the current repository. This performs
 	the same config updates as the `register` subcommand, then updates
 	the background scheduler to run `git maintenance run --scheduled`
 	on an hourly basis.

 stop::
 	Halt the background maintenance schedule. The current repository
 	is not removed from the list of maintained repositories, in case
 	the background maintenance is restarted later.

 register::
 	Initialize Git config values so any scheduled maintenance will start
 	running on this repository. This adds the repository to the
 	`maintenance.repo` config variable in the current user's global config,
 	or the config specified by --config-file option, and enables some
 	recommended configuration values for `maintenance.<task>.schedule`. The
 	tasks that are enabled are safe for running in the background without
 	disrupting foreground processes.
 +
 The `register` subcommand will also set the `maintenance.strategy` config
 value to `incremental`, if this value is not previously set. The
 `incremental` strategy uses the following schedule for each maintenance
 task:
 +
 --
 * `gc`: disabled.
 * `commit-graph`: hourly.
 * `prefetch`: hourly.
 * `loose-objects`: daily.
 * `incremental-repack`: daily.
 --
 +
 `git maintenance register` will also disable foreground maintenance by
 setting `maintenance.auto = false` in the current repository. This config
 setting will remain after a `git maintenance unregister` command.

 unregister::
 	Remove the current repository from background maintenance. This
 	only removes the repository from the configured list. It does not
 	stop the background maintenance processes from running.
 +
 The `unregister` subcommand will report an error if the current repository
 is not already registered. Use the `--force` option to return success even
 when the current repository is not registered.

 TASKS
 -----

 commit-graph::
 	The `commit-graph` job updates the `commit-graph` files incrementally,
 	then verifies that the written data is correct. The incremental
 	write is safe to run alongside concurrent Git processes since it
 	will not expire `.graph` files that were in the previous
 	`commit-graph-chain` file. They will be deleted by a later run based
 	on the expiration delay.

 prefetch::
 	The `prefetch` task updates the object directory with the latest
 	objects from all registered remotes. For each remote, a `git fetch`
 	command is run. The configured refspec is modified to place all
 	requested refs within `refs/prefetch/`. Also, tags are not updated.
 +
 This is done to avoid disrupting the remote-tracking branches. The end users
 expect these refs to stay unmoved unless they initiate a fetch.  However,
 with the prefetch task, the objects necessary to complete a later real fetch
 would already be obtained, making the real fetch faster.  In the ideal case,
 it will just become an update to a bunch of remote-tracking branches without
 any object transfer.

 gc::
 	Clean up unnecessary files and optimize the local repository. "GC"
 	stands for "garbage collection," but this task performs many
 	smaller tasks. This task can be expensive for large repositories,
 	as it repacks all Git objects into a single pack-file. It can also
 	be disruptive in some situations, as it deletes stale data. See
 	linkgit:git-gc[1] for more details on garbage collection in Git.

 loose-objects::
 	The `loose-objects` job cleans up loose objects and places them into
 	pack-files. In order to prevent race conditions with concurrent Git
 	commands, it follows a two-step process. First, it deletes any loose
 	objects that already exist in a pack-file; concurrent Git processes
 	will examine the pack-file for the object data instead of the loose
 	object. Second, it creates a new pack-file (starting with "loose-")
 	containing a batch of loose objects. The batch size is limited to 50
 	thousand objects to prevent the job from taking too long on a
 	repository with many loose objects. The `gc` task writes unreachable
 	objects as loose objects to be cleaned up by a later step only if
 	they are not re-added to a pack-file; for this reason it is not
 	advisable to enable both the `loose-objects` and `gc` tasks at the
 	same time.

 incremental-repack::
 	The `incremental-repack` job repacks the object directory
 	using the `multi-pack-index` feature. In order to prevent race
 	conditions with concurrent Git commands, it follows a two-step
 	process. First, it calls `git multi-pack-index expire` to delete
 	pack-files unreferenced by the `multi-pack-index` file. Second, it
 	calls `git multi-pack-index repack` to select several small
 	pack-files and repack them into a bigger one, and then update the
 	`multi-pack-index` entries that refer to the small pack-files to
 	refer to the new pack-file. This prepares those small pack-files
 	for deletion upon the next run of `git multi-pack-index expire`.
 	The selection of the small pack-files is such that the expected
 	size of the big pack-file is at least the batch size; see the
 	`--batch-size` option for the `repack` subcommand in
 	linkgit:git-multi-pack-index[1]. The default batch-size is zero,
 	which is a special case that attempts to repack all pack-files
 	into a single pack-file.

 pack-refs::
 	The `pack-refs` task collects the loose reference files and
 	collects them into a single file. This speeds up operations that
 	need to iterate across many references. See linkgit:git-pack-refs[1]
 	for more information.

 OPTIONS
 -------
 --auto::
 	When combined with the `run` subcommand, run maintenance tasks
 	only if certain thresholds are met. For example, the `gc` task
 	runs when the number of loose objects exceeds the number stored
 	in the `gc.auto` config setting, or when the number of pack-files
 	exceeds the `gc.autoPackLimit` config setting. Not compatible with
 	the `--schedule` option.

 --schedule::
 	When combined with the `run` subcommand, run maintenance tasks
 	only if certain time conditions are met, as specified by the
 	`maintenance.<task>.schedule` config value for each `<task>`.
 	This config value specifies a number of seconds since the last
 	time that task ran, according to the `maintenance.<task>.lastRun`
 	config value. The tasks that are tested are those provided by
 	the `--task=<task>` option(s) or those with
 	`maintenance.<task>.enabled` set to true.

 --quiet::
 	Do not report progress or other information over `stderr`.

 --task=<task>::
 	If this option is specified one or more times, then only run the
 	specified tasks in the specified order. If no `--task=<task>`
 	arguments are specified, then only the tasks with
 	`maintenance.<task>.enabled` configured as `true` are considered.
 	See the 'TASKS' section for the list of accepted `<task>` values.

 --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`.


 TROUBLESHOOTING
 ---------------
 The `git maintenance` command is designed to simplify the repository
 maintenance patterns while minimizing user wait time during Git commands.
 A variety of configuration options are available to allow customizing this
 process. The default maintenance options focus on operations that complete
 quickly, even on large repositories.

 Users may find some cases where scheduled maintenance tasks do not run as
 frequently as intended. Each `git maintenance run` command takes a lock on
 the repository's object database, and this prevents other concurrent
 `git maintenance run` commands from running on the same repository. Without
 this safeguard, competing processes could leave the repository in an
 unpredictable state.

 The background maintenance schedule runs `git maintenance run` processes
 on an hourly basis. Each run executes the "hourly" tasks. At midnight,
 that process also executes the "daily" tasks. At midnight on the first day
 of the week, that process also executes the "weekly" tasks. A single
 process iterates over each registered repository, performing the scheduled
 tasks for that frequency. Depending on the number of registered
 repositories and their sizes, this process may take longer than an hour.
 In this case, multiple `git maintenance run` commands may run on the same
 repository at the same time, colliding on the object database lock. This
 results in one of the two tasks not running.

 If you find that some maintenance windows are taking longer than one hour
 to complete, then consider reducing the complexity of your maintenance
 tasks. For example, the `gc` task is much slower than the
 `incremental-repack` task. However, this comes at a cost of a slightly
 larger object database. Consider moving more expensive tasks to be run
 less frequently.

 Expert users may consider scheduling their own maintenance tasks using a
 different schedule than is available through `git maintenance start` and
 Git configuration options. These users should be aware of the object
 database lock and how concurrent `git maintenance run` commands behave.
 Further, the `git gc` command should not be combined with
 `git maintenance run` commands. `git gc` modifies the object database
 but does not take the lock in the same way as `git maintenance run`. If
 possible, use `git maintenance run --task=gc` instead of `git gc`.

 The following sections describe the mechanisms put in place to run
 background maintenance by `git maintenance start` and how to customize
 them.

 BACKGROUND MAINTENANCE ON POSIX SYSTEMS
 ---------------------------------------

 The standard mechanism for scheduling background tasks on POSIX systems
 is cron(8). This tool executes commands based on a given schedule. The
 current list of user-scheduled tasks can be found by running `crontab -l`.
 The schedule written by `git maintenance start` is similar to this:

 -----------------------------------------------------------------------
 # BEGIN GIT MAINTENANCE SCHEDULE
 # The following schedule was created by Git
 # Any edits made in this region might be
 # replaced in the future by a Git command.

 0 1-23 * * * "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=hourly
 0 0 * * 1-6 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=daily
 0 0 * * 0 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=weekly

 # END GIT MAINTENANCE SCHEDULE
 -----------------------------------------------------------------------

 The comments are used as a region to mark the schedule as written by Git.
 Any modifications within this region will be completely deleted by
 `git maintenance stop` or overwritten by `git maintenance start`.

 The `crontab` entry specifies the full path of the `git` executable to
 ensure that the executed `git` command is the same one with which
 `git maintenance start` was issued independent of `PATH`. If the same user
 runs `git maintenance start` with multiple Git executables, then only the
 latest executable is used.

 These commands use `git for-each-repo --config=maintenance.repo` to run
 `git maintenance run --schedule=<frequency>` on each repository listed in
 the multi-valued `maintenance.repo` config option. These are typically
 loaded from the user-specific global config. The `git maintenance` process
 then determines which maintenance tasks are configured to run on each
 repository with each `<frequency>` using the `maintenance.<task>.schedule`
 config options. These values are loaded from the global or repository
 config values.

 If the config values are insufficient to achieve your desired background
 maintenance schedule, then you can create your own schedule. If you run
 `crontab -e`, then an editor will load with your user-specific `cron`
 schedule. In that editor, you can add your own schedule lines. You could
 start by adapting the default schedule listed earlier, or you could read
 the crontab(5) documentation for advanced scheduling techniques. Please
 do use the full path and `--exec-path` techniques from the default
 schedule to ensure you are executing the correct binaries in your
 schedule.


 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)`.


 BACKGROUND MAINTENANCE ON MACOS SYSTEMS
 ---------------------------------------

 While macOS technically supports `cron`, using `crontab -e` requires
 elevated privileges and the executed process does not have a full user
 context. Without a full user context, Git and its credential helpers
 cannot access stored credentials, so some maintenance tasks are not
 functional.

 Instead, `git maintenance start` interacts with the `launchctl` tool,
 which is the recommended way to schedule timed jobs in macOS. Scheduling
 maintenance through `git maintenance (start|stop)` requires some
 `launchctl` features available only in macOS 10.11 or later.

 Your user-specific scheduled tasks are stored as XML-formatted `.plist`
 files in `~/Library/LaunchAgents/`. You can see the currently-registered
 tasks using the following command:

 -----------------------------------------------------------------------
 $ ls ~/Library/LaunchAgents/org.git-scm.git*
 org.git-scm.git.daily.plist
 org.git-scm.git.hourly.plist
 org.git-scm.git.weekly.plist
 -----------------------------------------------------------------------

 One task is registered for each `--schedule=<frequency>` option. To
 inspect how the XML format describes each schedule, open one of these
 `.plist` files in an editor and inspect the `<array>` element following
 the `<key>StartCalendarInterval</key>` element.

 `git maintenance start` will overwrite these files and register the
 tasks again with `launchctl`, so any customizations should be done by
 creating your own `.plist` files with distinct names. Similarly, the
 `git maintenance stop` command will unregister the tasks with `launchctl`
 and delete the `.plist` files.

 To create more advanced customizations to your background tasks, see
 launchctl.plist(5) for more information.


 BACKGROUND MAINTENANCE ON WINDOWS SYSTEMS
 -----------------------------------------

 Windows does not support `cron` and instead has its own system for
 scheduling background tasks. The `git maintenance start` command uses
 the `schtasks` command to submit tasks to this system. You can inspect
 all background tasks using the Task Scheduler application. The tasks
 added by Git have names of the form `Git Maintenance (<frequency>)`.
 The Task Scheduler GUI has ways to inspect these tasks, but you can also
 export the tasks to XML files and view the details there.

 Note that since Git is a console application, these background tasks
 create a console window visible to the current user. This can be changed
 manually by selecting the "Run whether user is logged in or not" option
 in Task Scheduler. This change requires a password input, which is why
 `git maintenance start` does not select it by default.

 If you want to customize the background tasks, please rename the tasks
 so future calls to `git maintenance (start|stop)` do not overwrite your
 custom tasks.

 CONFIGURATION
 -------------

 include::includes/cmd-config-section-all.txt[]

 include::config/maintenance.txt[]


 GIT
 ---
 Part of the linkgit:git[1] suite
	git-maintenance(1)
	==================

	NAME
	----
	git-maintenance - Run tasks to optimize Git repository data


	SYNOPSIS
	--------
	[verse]
	'git maintenance' run [<options>]
	'git maintenance' start [--scheduler=<scheduler>]
	'git maintenance' (stop\|register\|unregister) [<options>]


	DESCRIPTION
	-----------
	Run tasks to optimize Git repository data, speeding up other Git commands
	and reducing storage requirements for the repository.

	Git commands that add repository data, such as `git add` or `git fetch`,
	are optimized for a responsive user experience. These commands do not take
	time to optimize the Git data, since such optimizations scale with the full
	size of the repository while these user commands each perform a relatively
	small action.

	The `git maintenance` command provides flexibility for how to optimize the
	Git repository.

	SUBCOMMANDS
	-----------

	run::
	Run one or more maintenance tasks. If one or more `--task` options
	are specified, then those tasks are run in that order. Otherwise,
	the tasks are determined by which `maintenance.<task>.enabled`
	config options are true. By default, only `maintenance.gc.enabled`
	is true.

	start::
	Start running maintenance on the current repository. This performs
	the same config updates as the `register` subcommand, then updates
	the background scheduler to run `git maintenance run --scheduled`
	on an hourly basis.

	stop::
	Halt the background maintenance schedule. The current repository
	is not removed from the list of maintained repositories, in case
	the background maintenance is restarted later.

	register::
	Initialize Git config values so any scheduled maintenance will start
	running on this repository. This adds the repository to the
	`maintenance.repo` config variable in the current user's global config,
	or the config specified by --config-file option, and enables some
	recommended configuration values for `maintenance.<task>.schedule`. The
	tasks that are enabled are safe for running in the background without
	disrupting foreground processes.
	+
	The `register` subcommand will also set the `maintenance.strategy` config
	value to `incremental`, if this value is not previously set. The
	`incremental` strategy uses the following schedule for each maintenance
	task:
	+
	--
	* `gc`: disabled.
	* `commit-graph`: hourly.
	* `prefetch`: hourly.
	* `loose-objects`: daily.
	* `incremental-repack`: daily.
	--
	+
	`git maintenance register` will also disable foreground maintenance by
	setting `maintenance.auto = false` in the current repository. This config
	setting will remain after a `git maintenance unregister` command.

	unregister::
	Remove the current repository from background maintenance. This
	only removes the repository from the configured list. It does not
	stop the background maintenance processes from running.
	+
	The `unregister` subcommand will report an error if the current repository
	is not already registered. Use the `--force` option to return success even
	when the current repository is not registered.

	TASKS
	-----

	commit-graph::
	The `commit-graph` job updates the `commit-graph` files incrementally,
	then verifies that the written data is correct. The incremental
	write is safe to run alongside concurrent Git processes since it
	will not expire `.graph` files that were in the previous
	`commit-graph-chain` file. They will be deleted by a later run based
	on the expiration delay.

	prefetch::
	The `prefetch` task updates the object directory with the latest
	objects from all registered remotes. For each remote, a `git fetch`
	command is run. The configured refspec is modified to place all
	requested refs within `refs/prefetch/`. Also, tags are not updated.
	+
	This is done to avoid disrupting the remote-tracking branches. The end users
	expect these refs to stay unmoved unless they initiate a fetch. However,
	with the prefetch task, the objects necessary to complete a later real fetch
	would already be obtained, making the real fetch faster. In the ideal case,
	it will just become an update to a bunch of remote-tracking branches without
	any object transfer.

	gc::
	Clean up unnecessary files and optimize the local repository. "GC"
	stands for "garbage collection," but this task performs many
	smaller tasks. This task can be expensive for large repositories,
	as it repacks all Git objects into a single pack-file. It can also
	be disruptive in some situations, as it deletes stale data. See
	linkgit:git-gc[1] for more details on garbage collection in Git.

	loose-objects::
	The `loose-objects` job cleans up loose objects and places them into
	pack-files. In order to prevent race conditions with concurrent Git
	commands, it follows a two-step process. First, it deletes any loose
	objects that already exist in a pack-file; concurrent Git processes
	will examine the pack-file for the object data instead of the loose
	object. Second, it creates a new pack-file (starting with "loose-")
	containing a batch of loose objects. The batch size is limited to 50
	thousand objects to prevent the job from taking too long on a
	repository with many loose objects. The `gc` task writes unreachable
	objects as loose objects to be cleaned up by a later step only if
	they are not re-added to a pack-file; for this reason it is not
	advisable to enable both the `loose-objects` and `gc` tasks at the
	same time.

	incremental-repack::
	The `incremental-repack` job repacks the object directory
	using the `multi-pack-index` feature. In order to prevent race
	conditions with concurrent Git commands, it follows a two-step
	process. First, it calls `git multi-pack-index expire` to delete
	pack-files unreferenced by the `multi-pack-index` file. Second, it
	calls `git multi-pack-index repack` to select several small
	pack-files and repack them into a bigger one, and then update the
	`multi-pack-index` entries that refer to the small pack-files to
	refer to the new pack-file. This prepares those small pack-files
	for deletion upon the next run of `git multi-pack-index expire`.
	The selection of the small pack-files is such that the expected
	size of the big pack-file is at least the batch size; see the
	`--batch-size` option for the `repack` subcommand in
	linkgit:git-multi-pack-index[1]. The default batch-size is zero,
	which is a special case that attempts to repack all pack-files
	into a single pack-file.

	pack-refs::
	The `pack-refs` task collects the loose reference files and
	collects them into a single file. This speeds up operations that
	need to iterate across many references. See linkgit:git-pack-refs[1]
	for more information.

	OPTIONS
	-------
	--auto::
	When combined with the `run` subcommand, run maintenance tasks
	only if certain thresholds are met. For example, the `gc` task
	runs when the number of loose objects exceeds the number stored
	in the `gc.auto` config setting, or when the number of pack-files
	exceeds the `gc.autoPackLimit` config setting. Not compatible with
	the `--schedule` option.

	--schedule::
	When combined with the `run` subcommand, run maintenance tasks
	only if certain time conditions are met, as specified by the
	`maintenance.<task>.schedule` config value for each `<task>`.
	This config value specifies a number of seconds since the last
	time that task ran, according to the `maintenance.<task>.lastRun`
	config value. The tasks that are tested are those provided by
	the `--task=<task>` option(s) or those with
	`maintenance.<task>.enabled` set to true.

	--quiet::
	Do not report progress or other information over `stderr`.

	--task=<task>::
	If this option is specified one or more times, then only run the
	specified tasks in the specified order. If no `--task=<task>`
	arguments are specified, then only the tasks with
	`maintenance.<task>.enabled` configured as `true` are considered.
	See the 'TASKS' section for the list of accepted `<task>` values.

	--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`.


	TROUBLESHOOTING
	---------------
	The `git maintenance` command is designed to simplify the repository
	maintenance patterns while minimizing user wait time during Git commands.
	A variety of configuration options are available to allow customizing this
	process. The default maintenance options focus on operations that complete
	quickly, even on large repositories.

	Users may find some cases where scheduled maintenance tasks do not run as
	frequently as intended. Each `git maintenance run` command takes a lock on
	the repository's object database, and this prevents other concurrent
	`git maintenance run` commands from running on the same repository. Without
	this safeguard, competing processes could leave the repository in an
	unpredictable state.

	The background maintenance schedule runs `git maintenance run` processes
	on an hourly basis. Each run executes the "hourly" tasks. At midnight,
	that process also executes the "daily" tasks. At midnight on the first day
	of the week, that process also executes the "weekly" tasks. A single
	process iterates over each registered repository, performing the scheduled
	tasks for that frequency. Depending on the number of registered
	repositories and their sizes, this process may take longer than an hour.
	In this case, multiple `git maintenance run` commands may run on the same
	repository at the same time, colliding on the object database lock. This
	results in one of the two tasks not running.

	If you find that some maintenance windows are taking longer than one hour
	to complete, then consider reducing the complexity of your maintenance
	tasks. For example, the `gc` task is much slower than the
	`incremental-repack` task. However, this comes at a cost of a slightly
	larger object database. Consider moving more expensive tasks to be run
	less frequently.

	Expert users may consider scheduling their own maintenance tasks using a
	different schedule than is available through `git maintenance start` and
	Git configuration options. These users should be aware of the object
	database lock and how concurrent `git maintenance run` commands behave.
	Further, the `git gc` command should not be combined with
	`git maintenance run` commands. `git gc` modifies the object database
	but does not take the lock in the same way as `git maintenance run`. If
	possible, use `git maintenance run --task=gc` instead of `git gc`.

	The following sections describe the mechanisms put in place to run
	background maintenance by `git maintenance start` and how to customize
	them.

	BACKGROUND MAINTENANCE ON POSIX SYSTEMS
	---------------------------------------

	The standard mechanism for scheduling background tasks on POSIX systems
	is cron(8). This tool executes commands based on a given schedule. The
	current list of user-scheduled tasks can be found by running `crontab -l`.
	The schedule written by `git maintenance start` is similar to this:

	-----------------------------------------------------------------------
	# BEGIN GIT MAINTENANCE SCHEDULE
	# The following schedule was created by Git
	# Any edits made in this region might be
	# replaced in the future by a Git command.

	0 1-23 * * * "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=hourly
	0 0 * * 1-6 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=daily
	0 0 * * 0 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=weekly

	# END GIT MAINTENANCE SCHEDULE
	-----------------------------------------------------------------------

	The comments are used as a region to mark the schedule as written by Git.
	Any modifications within this region will be completely deleted by
	`git maintenance stop` or overwritten by `git maintenance start`.

	The `crontab` entry specifies the full path of the `git` executable to
	ensure that the executed `git` command is the same one with which
	`git maintenance start` was issued independent of `PATH`. If the same user
	runs `git maintenance start` with multiple Git executables, then only the
	latest executable is used.

	These commands use `git for-each-repo --config=maintenance.repo` to run
	`git maintenance run --schedule=<frequency>` on each repository listed in
	the multi-valued `maintenance.repo` config option. These are typically
	loaded from the user-specific global config. The `git maintenance` process
	then determines which maintenance tasks are configured to run on each
	repository with each `<frequency>` using the `maintenance.<task>.schedule`
	config options. These values are loaded from the global or repository
	config values.

	If the config values are insufficient to achieve your desired background
	maintenance schedule, then you can create your own schedule. If you run
	`crontab -e`, then an editor will load with your user-specific `cron`
	schedule. In that editor, you can add your own schedule lines. You could
	start by adapting the default schedule listed earlier, or you could read
	the crontab(5) documentation for advanced scheduling techniques. Please
	do use the full path and `--exec-path` techniques from the default
	schedule to ensure you are executing the correct binaries in your
	schedule.


	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)`.


	BACKGROUND MAINTENANCE ON MACOS SYSTEMS
	---------------------------------------

	While macOS technically supports `cron`, using `crontab -e` requires
	elevated privileges and the executed process does not have a full user
	context. Without a full user context, Git and its credential helpers
	cannot access stored credentials, so some maintenance tasks are not
	functional.

	Instead, `git maintenance start` interacts with the `launchctl` tool,
	which is the recommended way to schedule timed jobs in macOS. Scheduling
	maintenance through `git maintenance (start\|stop)` requires some
	`launchctl` features available only in macOS 10.11 or later.

	Your user-specific scheduled tasks are stored as XML-formatted `.plist`
	files in `~/Library/LaunchAgents/`. You can see the currently-registered
	tasks using the following command:

	-----------------------------------------------------------------------
	$ ls ~/Library/LaunchAgents/org.git-scm.git*
	org.git-scm.git.daily.plist
	org.git-scm.git.hourly.plist
	org.git-scm.git.weekly.plist
	-----------------------------------------------------------------------

	One task is registered for each `--schedule=<frequency>` option. To
	inspect how the XML format describes each schedule, open one of these
	`.plist` files in an editor and inspect the `<array>` element following
	the `<key>StartCalendarInterval</key>` element.

	`git maintenance start` will overwrite these files and register the
	tasks again with `launchctl`, so any customizations should be done by
	creating your own `.plist` files with distinct names. Similarly, the
	`git maintenance stop` command will unregister the tasks with `launchctl`
	and delete the `.plist` files.

	To create more advanced customizations to your background tasks, see
	launchctl.plist(5) for more information.


	BACKGROUND MAINTENANCE ON WINDOWS SYSTEMS
	-----------------------------------------

	Windows does not support `cron` and instead has its own system for
	scheduling background tasks. The `git maintenance start` command uses
	the `schtasks` command to submit tasks to this system. You can inspect
	all background tasks using the Task Scheduler application. The tasks
	added by Git have names of the form `Git Maintenance (<frequency>)`.
	The Task Scheduler GUI has ways to inspect these tasks, but you can also
	export the tasks to XML files and view the details there.

	Note that since Git is a console application, these background tasks
	create a console window visible to the current user. This can be changed
	manually by selecting the "Run whether user is logged in or not" option
	in Task Scheduler. This change requires a password input, which is why
	`git maintenance start` does not select it by default.

	If you want to customize the background tasks, please rename the tasks
	so future calls to `git maintenance (start\|stop)` do not overwrite your
	custom tasks.

	CONFIGURATION
	-------------

	include::includes/cmd-config-section-all.txt[]

	include::config/maintenance.txt[]


	GIT
	---
	Part of the linkgit:git[1] suite