GIT-MAINTENANCE(1)                                           Git Manual                                          GIT-MAINTENANCE(1)

       git-maintenance - Run tasks to optimize Git repository data

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

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

       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.

           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 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.

           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.

           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 = false in the current
           repository. This config setting will remain after a git maintenance unregister command.

           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.

           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.

           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. With prefetch task, however, the objects necessary to complete a later real fetch would already
           be obtained, so the real fetch would go faster. In the ideal case, it will just become an update to a bunch of
           remote-tracking branches without any object transfer.

           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 git-gc(1) for more details
           on garbage collection in Git.

           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.

           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 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.

           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 git-pack-refs(1) for more information.

           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 config setting, or when the number
           of pack-files exceeds the gc.autoPackLimit config setting. Not compatible with the --schedule option.

           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.

           Do not report progress or other information over stderr.

           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.

           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.

       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.

       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:

           # 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


       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.

       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:


       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).

       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*

       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>

       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.

       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.

       Everything below this line in this section is selectively included from the git-config(1) documentation. The content is the
       same as what’s found there:
           This boolean config option controls whether some commands run git maintenance run --auto after doing their normal work.
           Defaults to true.

           This string config option provides a way to specify one of a few recommended schedules for background maintenance. This
           only affects which tasks are run during git maintenance run --schedule=X commands, provided no --task=<task> arguments
           are provided. Further, if a maintenance.<task>.schedule config value is set, then that value is used instead of the one
           provided by maintenance.strategy. The possible strategy strings are:

           •   none: This default setting implies no task are run at any schedule.

           •   incremental: This setting optimizes for performing small maintenance activities that do not delete any data. This
               does not schedule the gc task, but runs the prefetch and commit-graph tasks hourly, the loose-objects and
               incremental-repack tasks daily, and the pack-refs task weekly.

           This boolean config option controls whether the maintenance task with name <task> is run when no --task option is
           specified to git maintenance run. These config values are ignored if a --task option exists. By default, only
           maintenance.gc.enabled is true.

           This config option controls whether or not the given <task> runs during a git maintenance run --schedule=<frequency>
           command. The value must be one of "hourly", "daily", or "weekly".
           This integer config option controls how often the commit-graph task should be run as part of git maintenance run --auto.
           If zero, then the commit-graph task will not run with the --auto option. A negative value will force the task to run
           every time. Otherwise, a positive value implies the command should run when the number of reachable commits that are not
           in the commit-graph file is at least the value of The default value is 100.
           This integer config option controls how often the loose-objects task should be run as part of git maintenance run
           --auto. If zero, then the loose-objects task will not run with the --auto option. A negative value will force the task
           to run every time. Otherwise, a positive value implies the command should run when the number of loose objects is at
           least the value of The default value is 100.
           This integer config option controls how often the incremental-repack task should be run as part of git maintenance run
           --auto. If zero, then the incremental-repack task will not run with the --auto option. A negative value will force the
           task to run every time. Otherwise, a positive value implies the command should run when the number of pack-files not in
           the multi-pack-index is at least the value of The default value is 10.

       Part of the git(1) suite

Git 2.39.2                                                   04/24/2023                                          GIT-MAINTENANCE(1)