1GIT-MAINTENANCE(1) Git Manual GIT-MAINTENANCE(1)
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6 git-maintenance - Run tasks to optimize Git repository data
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9 git maintenance run [<options>]
10 git maintenance start [--scheduler=<scheduler>]
11 git maintenance (stop|register|unregister) [<options>]
12
14 Run tasks to optimize Git repository data, speeding up other Git
15 commands and reducing storage requirements for the repository.
16 Git commands that add repository data, such as git add or git fetch,
18 are optimized for a responsive user experience. These commands do not
19 take time to optimize the Git data, since such optimizations scale with
20 the full size of the repository while these user commands each perform
21 a relatively small action.
22 The git maintenance command provides flexibility for how to optimize
24 the Git repository.
25
27 run
28 Run one or more maintenance tasks. If one or more --task options
29 are specified, then those tasks are run in that order. Otherwise,
30 the tasks are determined by which maintenance.<task>.enabled config
31 options are true. By default, only maintenance.gc.enabled is true.
32 start
34 Start running maintenance on the current repository. This performs
35 the same config updates as the register subcommand, then updates
36 the background scheduler to run git maintenance run --scheduled on
37 an hourly basis.
38 stop
40 Halt the background maintenance schedule. The current repository is
41 not removed from the list of maintained repositories, in case the
42 background maintenance is restarted later.
43 register
45 Initialize Git config values so any scheduled maintenance will
46 start running on this repository. This adds the repository to the
47 maintenance.repo config variable in the current user’s global
48 config, or the config specified by --config-file option, and
49 enables some recommended configuration values for
50 maintenance.<task>.schedule. The tasks that are enabled are safe
51 for running in the background without disrupting foreground
52 processes.
53 The register subcommand will also set the maintenance.strategy
55 config value to incremental, if this value is not previously set.
56 The incremental strategy uses the following schedule for each
57 maintenance task:
58 • gc: disabled.
60 • commit-graph: hourly.
62 • prefetch: hourly.
64 • loose-objects: daily.
66 • incremental-repack: daily.
68 git maintenance register will also disable foreground maintenance
70 by setting maintenance.auto = false in the current repository. This
71 config setting will remain after a git maintenance unregister
72 command.
73 unregister
75 Remove the current repository from background maintenance. This
76 only removes the repository from the configured list. It does not
77 stop the background maintenance processes from running.
78 The unregister subcommand will report an error if the current
80 repository is not already registered. Use the --force option to
81 return success even when the current repository is not registered.
82
84 commit-graph
85 The commit-graph job updates the commit-graph files incrementally,
86 then verifies that the written data is correct. The incremental
87 write is safe to run alongside concurrent Git processes since it
88 will not expire .graph files that were in the previous
89 commit-graph-chain file. They will be deleted by a later run based
90 on the expiration delay.
91 prefetch
93 The prefetch task updates the object directory with the latest
94 objects from all registered remotes. For each remote, a git fetch
95 command is run. The configured refspec is modified to place all
96 requested refs within refs/prefetch/. Also, tags are not updated.
97 This is done to avoid disrupting the remote-tracking branches. The
99 end users expect these refs to stay unmoved unless they initiate a
100 fetch. With prefetch task, however, the objects necessary to
101 complete a later real fetch would already be obtained, so the real
102 fetch would go faster. In the ideal case, it will just become an
103 update to a bunch of remote-tracking branches without any object
104 transfer.
105 gc
107 Clean up unnecessary files and optimize the local repository. "GC"
108 stands for "garbage collection," but this task performs many
109 smaller tasks. This task can be expensive for large repositories,
110 as it repacks all Git objects into a single pack-file. It can also
111 be disruptive in some situations, as it deletes stale data. See
112 git-gc(1) for more details on garbage collection in Git.
113 loose-objects
115 The loose-objects job cleans up loose objects and places them into
116 pack-files. In order to prevent race conditions with concurrent Git
117 commands, it follows a two-step process. First, it deletes any
118 loose objects that already exist in a pack-file; concurrent Git
119 processes will examine the pack-file for the object data instead of
120 the loose object. Second, it creates a new pack-file (starting with
121 "loose-") containing a batch of loose objects. The batch size is
122 limited to 50 thousand objects to prevent the job from taking too
123 long on a repository with many loose objects. The gc task writes
124 unreachable objects as loose objects to be cleaned up by a later
125 step only if they are not re-added to a pack-file; for this reason
126 it is not advisable to enable both the loose-objects and gc tasks
127 at the same time.
128 incremental-repack
130 The incremental-repack job repacks the object directory using the
131 multi-pack-index feature. In order to prevent race conditions with
132 concurrent Git commands, it follows a two-step process. First, it
133 calls git multi-pack-index expire to delete pack-files unreferenced
134 by the multi-pack-index file. Second, it calls git multi-pack-index
135 repack to select several small pack-files and repack them into a
136 bigger one, and then update the multi-pack-index entries that refer
137 to the small pack-files to refer to the new pack-file. This
138 prepares those small pack-files for deletion upon the next run of
139 git multi-pack-index expire. The selection of the small pack-files
140 is such that the expected size of the big pack-file is at least the
141 batch size; see the --batch-size option for the repack subcommand
142 in git-multi-pack-index(1). The default batch-size is zero, which
143 is a special case that attempts to repack all pack-files into a
144 single pack-file.
145 pack-refs
147 The pack-refs task collects the loose reference files and collects
148 them into a single file. This speeds up operations that need to
149 iterate across many references. See git-pack-refs(1) for more
150 information.
151
153 --auto
154 When combined with the run subcommand, run maintenance tasks only
155 if certain thresholds are met. For example, the gc task runs when
156 the number of loose objects exceeds the number stored in the
157 gc.auto config setting, or when the number of pack-files exceeds
158 the gc.autoPackLimit config setting. Not compatible with the
159 --schedule option.
160 --schedule
162 When combined with the run subcommand, run maintenance tasks only
163 if certain time conditions are met, as specified by the
164 maintenance.<task>.schedule config value for each <task>. This
165 config value specifies a number of seconds since the last time that
166 task ran, according to the maintenance.<task>.lastRun config value.
167 The tasks that are tested are those provided by the --task=<task>
168 option(s) or those with maintenance.<task>.enabled set to true.
169 --quiet
171 Do not report progress or other information over stderr.
172 --task=<task>
174 If this option is specified one or more times, then only run the
175 specified tasks in the specified order. If no --task=<task>
176 arguments are specified, then only the tasks with
177 maintenance.<task>.enabled configured as true are considered. See
178 the TASKS section for the list of accepted <task> values.
179 --scheduler=auto|crontab|systemd-timer|launchctl|schtasks
181 When combined with the start subcommand, specify the scheduler for
182 running the hourly, daily and weekly executions of git maintenance
183 run. Possible values for <scheduler> are auto, crontab (POSIX),
184 systemd-timer (Linux), launchctl (macOS), and schtasks (Windows).
185 When auto is specified, the appropriate platform-specific scheduler
186 is used; on Linux, systemd-timer is used if available, otherwise
187 crontab. Default is auto.
188
190 The git maintenance command is designed to simplify the repository
191 maintenance patterns while minimizing user wait time during Git
192 commands. A variety of configuration options are available to allow
193 customizing this process. The default maintenance options focus on
194 operations that complete quickly, even on large repositories.
195 Users may find some cases where scheduled maintenance tasks do not run
197 as frequently as intended. Each git maintenance run command takes a
198 lock on the repository’s object database, and this prevents other
199 concurrent git maintenance run commands from running on the same
200 repository. Without this safeguard, competing processes could leave the
201 repository in an unpredictable state.
202 The background maintenance schedule runs git maintenance run processes
204 on an hourly basis. Each run executes the "hourly" tasks. At midnight,
205 that process also executes the "daily" tasks. At midnight on the first
206 day of the week, that process also executes the "weekly" tasks. A
207 single process iterates over each registered repository, performing the
208 scheduled tasks for that frequency. Depending on the number of
209 registered repositories and their sizes, this process may take longer
210 than an hour. In this case, multiple git maintenance run commands may
211 run on the same repository at the same time, colliding on the object
212 database lock. This results in one of the two tasks not running.
213 If you find that some maintenance windows are taking longer than one
215 hour to complete, then consider reducing the complexity of your
216 maintenance tasks. For example, the gc task is much slower than the
217 incremental-repack task. However, this comes at a cost of a slightly
218 larger object database. Consider moving more expensive tasks to be run
219 less frequently.
220 Expert users may consider scheduling their own maintenance tasks using
222 a different schedule than is available through git maintenance start
223 and Git configuration options. These users should be aware of the
224 object database lock and how concurrent git maintenance run commands
225 behave. Further, the git gc command should not be combined with git
226 maintenance run commands. git gc modifies the object database but does
227 not take the lock in the same way as git maintenance run. If possible,
228 use git maintenance run --task=gc instead of git gc.
229 The following sections describe the mechanisms put in place to run
231 background maintenance by git maintenance start and how to customize
232 them.
233
235 The standard mechanism for scheduling background tasks on POSIX systems
236 is cron(8). This tool executes commands based on a given schedule. The
237 current list of user-scheduled tasks can be found by running crontab
238 -l. The schedule written by git maintenance start is similar to this:
239 # BEGIN GIT MAINTENANCE SCHEDULE
241 # The following schedule was created by Git
242 # Any edits made in this region might be
243 # replaced in the future by a Git command.
244 0 1-23 * * * "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=hourly
246 0 0 * * 1-6 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=daily
247 0 0 * * 0 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=weekly
248 # END GIT MAINTENANCE SCHEDULE
250 The comments are used as a region to mark the schedule as written by
252 Git. Any modifications within this region will be completely deleted by
253 git maintenance stop or overwritten by git maintenance start.
254 The crontab entry specifies the full path of the git executable to
256 ensure that the executed git command is the same one with which git
257 maintenance start was issued independent of PATH. If the same user runs
258 git maintenance start with multiple Git executables, then only the
259 latest executable is used.
260 These commands use git for-each-repo --config=maintenance.repo to run
262 git maintenance run --schedule=<frequency> on each repository listed in
263 the multi-valued maintenance.repo config option. These are typically
264 loaded from the user-specific global config. The git maintenance
265 process then determines which maintenance tasks are configured to run
266 on each repository with each <frequency> using the
267 maintenance.<task>.schedule config options. These values are loaded
268 from the global or repository config values.
269 If the config values are insufficient to achieve your desired
271 background maintenance schedule, then you can create your own schedule.
272 If you run crontab -e, then an editor will load with your user-specific
273 cron schedule. In that editor, you can add your own schedule lines. You
274 could start by adapting the default schedule listed earlier, or you
275 could read the crontab(5) documentation for advanced scheduling
276 techniques. Please do use the full path and --exec-path techniques from
277 the default schedule to ensure you are executing the correct binaries
278 in your schedule.
279
281 While Linux supports cron, depending on the distribution, cron may be
282 an optional package not necessarily installed. On modern Linux
283 distributions, systemd timers are superseding it.
284 If user systemd timers are available, they will be used as a
286 replacement of cron.
287 In this case, git maintenance start will create user systemd timer
289 units and start the timers. The current list of user-scheduled tasks
290 can be found by running systemctl --user list-timers. The timers
291 written by git maintenance start are similar to this:
292 $ systemctl --user list-timers
294 NEXT LEFT LAST PASSED UNIT ACTIVATES
295 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
296 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
297 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
298 One timer is registered for each --schedule=<frequency> option.
300 The definition of the systemd units can be inspected in the following
302 files:
303 ~/.config/systemd/user/git-maintenance@.timer
305 ~/.config/systemd/user/git-maintenance@.service
306 ~/.config/systemd/user/timers.target.wants/git-maintenance@hourly.timer
307 ~/.config/systemd/user/timers.target.wants/git-maintenance@daily.timer
308 ~/.config/systemd/user/timers.target.wants/git-maintenance@weekly.timer
309 git maintenance start will overwrite these files and start the timer
311 again with systemctl --user, so any customization should be done by
312 creating a drop-in file, i.e. a .conf suffixed file in the
313 ~/.config/systemd/user/git-maintenance@.service.d directory.
314 git maintenance stop will stop the user systemd timers and delete the
316 above mentioned files.
317 For more details, see systemd.timer(5).
319
321 While macOS technically supports cron, using crontab -e requires
322 elevated privileges and the executed process does not have a full user
323 context. Without a full user context, Git and its credential helpers
324 cannot access stored credentials, so some maintenance tasks are not
325 functional.
326 Instead, git maintenance start interacts with the launchctl tool, which
328 is the recommended way to schedule timed jobs in macOS. Scheduling
329 maintenance through git maintenance (start|stop) requires some
330 launchctl features available only in macOS 10.11 or later.
331 Your user-specific scheduled tasks are stored as XML-formatted .plist
333 files in ~/Library/LaunchAgents/. You can see the currently-registered
334 tasks using the following command:
335 $ ls ~/Library/LaunchAgents/org.git-scm.git*
337 org.git-scm.git.daily.plist
338 org.git-scm.git.hourly.plist
339 org.git-scm.git.weekly.plist
340 One task is registered for each --schedule=<frequency> option. To
342 inspect how the XML format describes each schedule, open one of these
343 .plist files in an editor and inspect the <array> element following the
344 <key>StartCalendarInterval</key> element.
345 git maintenance start will overwrite these files and register the tasks
347 again with launchctl, so any customizations should be done by creating
348 your own .plist files with distinct names. Similarly, the git
349 maintenance stop command will unregister the tasks with launchctl and
350 delete the .plist files.
351 To create more advanced customizations to your background tasks, see
353 launchctl.plist(5) for more information.
354
356 Windows does not support cron and instead has its own system for
357 scheduling background tasks. The git maintenance start command uses the
358 schtasks command to submit tasks to this system. You can inspect all
359 background tasks using the Task Scheduler application. The tasks added
360 by Git have names of the form Git Maintenance (<frequency>). The Task
361 Scheduler GUI has ways to inspect these tasks, but you can also export
362 the tasks to XML files and view the details there.
363 Note that since Git is a console application, these background tasks
365 create a console window visible to the current user. This can be
366 changed manually by selecting the "Run whether user is logged in or
367 not" option in Task Scheduler. This change requires a password input,
368 which is why git maintenance start does not select it by default.
369 If you want to customize the background tasks, please rename the tasks
371 so future calls to git maintenance (start|stop) do not overwrite your
372 custom tasks.
373
375 Everything below this line in this section is selectively included from
376 the git-config(1) documentation. The content is the same as what’s
377 found there:
378 maintenance.auto
380 This boolean config option controls whether some commands run git
381 maintenance run --auto after doing their normal work. Defaults to
382 true.
383 maintenance.strategy
385 This string config option provides a way to specify one of a few
386 recommended schedules for background maintenance. This only affects
387 which tasks are run during git maintenance run --schedule=X
388 commands, provided no --task=<task> arguments are provided.
389 Further, if a maintenance.<task>.schedule config value is set, then
390 that value is used instead of the one provided by
391 maintenance.strategy. The possible strategy strings are:
392 • none: This default setting implies no task are run at any
394 schedule.
395 • incremental: This setting optimizes for performing small
397 maintenance activities that do not delete any data. This does
398 not schedule the gc task, but runs the prefetch and
399 commit-graph tasks hourly, the loose-objects and
400 incremental-repack tasks daily, and the pack-refs task weekly.
401 maintenance.<task>.enabled
403 This boolean config option controls whether the maintenance task
404 with name <task> is run when no --task option is specified to git
405 maintenance run. These config values are ignored if a --task option
406 exists. By default, only maintenance.gc.enabled is true.
407 maintenance.<task>.schedule
409 This config option controls whether or not the given <task> runs
410 during a git maintenance run --schedule=<frequency> command. The
411 value must be one of "hourly", "daily", or "weekly".
412 maintenance.commit-graph.auto
414 This integer config option controls how often the commit-graph task
415 should be run as part of git maintenance run --auto. If zero, then
416 the commit-graph task will not run with the --auto option. A
417 negative value will force the task to run every time. Otherwise, a
418 positive value implies the command should run when the number of
419 reachable commits that are not in the commit-graph file is at least
420 the value of maintenance.commit-graph.auto. The default value is
421 100.
422 maintenance.loose-objects.auto
424 This integer config option controls how often the loose-objects
425 task should be run as part of git maintenance run --auto. If zero,
426 then the loose-objects task will not run with the --auto option. A
427 negative value will force the task to run every time. Otherwise, a
428 positive value implies the command should run when the number of
429 loose objects is at least the value of
430 maintenance.loose-objects.auto. The default value is 100.
431 maintenance.incremental-repack.auto
433 This integer config option controls how often the
434 incremental-repack task should be run as part of git maintenance
435 run --auto. If zero, then the incremental-repack task will not run
436 with the --auto option. A negative value will force the task to run
437 every time. Otherwise, a positive value implies the command should
438 run when the number of pack-files not in the multi-pack-index is at
439 least the value of maintenance.incremental-repack.auto. The default
440 value is 10.
441
443 Part of the git(1) suite
444Git 2.39.1 2023-01-13 GIT-MAINTENANCE(1)