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>]
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12 Run tasks to optimize Git repository data, speeding up other Git
13 commands and reducing storage requirements for the repository.
14 Git commands that add repository data, such as git add or git fetch,
16 are optimized for a responsive user experience. These commands do not
17 take time to optimize the Git data, since such optimizations scale with
18 the full size of the repository while these user commands each perform
19 a relatively small action.
20 The git maintenance command provides flexibility for how to optimize
22 the Git repository.
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25 register
26 Initialize Git config values so any scheduled maintenance will
27 start running on this repository. This adds the repository to the
28 maintenance.repo config variable in the current user’s global
29 config and enables some recommended configuration values for
30 maintenance.<task>.schedule. The tasks that are enabled are safe
31 for running in the background without disrupting foreground
32 processes.
33 The register subcommand will also set the maintenance.strategy
35 config value to incremental, if this value is not previously set.
36 The incremental strategy uses the following schedule for each
37 maintenance task:
38 • gc: disabled.
40 • commit-graph: hourly.
42 • prefetch: hourly.
44 • loose-objects: daily.
46 • incremental-repack: daily.
48 git maintenance register will also disable foreground maintenance
50 by setting maintenance.auto = false in the current repository. This
51 config setting will remain after a git maintenance unregister
52 command.
53 run
55 Run one or more maintenance tasks. If one or more --task options
56 are specified, then those tasks are run in that order. Otherwise,
57 the tasks are determined by which maintenance.<task>.enabled config
58 options are true. By default, only maintenance.gc.enabled is true.
59 start
61 Start running maintenance on the current repository. This performs
62 the same config updates as the register subcommand, then updates
63 the background scheduler to run git maintenance run --scheduled on
64 an hourly basis.
65 stop
67 Halt the background maintenance schedule. The current repository is
68 not removed from the list of maintained repositories, in case the
69 background maintenance is restarted later.
70 unregister
72 Remove the current repository from background maintenance. This
73 only removes the repository from the configured list. It does not
74 stop the background maintenance processes from running.
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77 commit-graph
78 The commit-graph job updates the commit-graph files incrementally,
79 then verifies that the written data is correct. The incremental
80 write is safe to run alongside concurrent Git processes since it
81 will not expire .graph files that were in the previous
82 commit-graph-chain file. They will be deleted by a later run based
83 on the expiration delay.
84 prefetch
86 The prefetch task updates the object directory with the latest
87 objects from all registered remotes. For each remote, a git fetch
88 command is run. The refmap is custom to avoid updating local or
89 remote branches (those in refs/heads or refs/remotes). Instead, the
90 remote refs are stored in refs/prefetch/<remote>/. Also, tags are
91 not updated.
92 This is done to avoid disrupting the remote-tracking branches. The
94 end users expect these refs to stay unmoved unless they initiate a
95 fetch. With prefetch task, however, the objects necessary to
96 complete a later real fetch would already be obtained, so the real
97 fetch would go faster. In the ideal case, it will just become an
98 update to a bunch of remote-tracking branches without any object
99 transfer.
100 gc
102 Clean up unnecessary files and optimize the local repository. "GC"
103 stands for "garbage collection," but this task performs many
104 smaller tasks. This task can be expensive for large repositories,
105 as it repacks all Git objects into a single pack-file. It can also
106 be disruptive in some situations, as it deletes stale data. See
107 git-gc(1) for more details on garbage collection in Git.
108 loose-objects
110 The loose-objects job cleans up loose objects and places them into
111 pack-files. In order to prevent race conditions with concurrent Git
112 commands, it follows a two-step process. First, it deletes any
113 loose objects that already exist in a pack-file; concurrent Git
114 processes will examine the pack-file for the object data instead of
115 the loose object. Second, it creates a new pack-file (starting with
116 "loose-") containing a batch of loose objects. The batch size is
117 limited to 50 thousand objects to prevent the job from taking too
118 long on a repository with many loose objects. The gc task writes
119 unreachable objects as loose objects to be cleaned up by a later
120 step only if they are not re-added to a pack-file; for this reason
121 it is not advisable to enable both the loose-objects and gc tasks
122 at the same time.
123 incremental-repack
125 The incremental-repack job repacks the object directory using the
126 multi-pack-index feature. In order to prevent race conditions with
127 concurrent Git commands, it follows a two-step process. First, it
128 calls git multi-pack-index expire to delete pack-files unreferenced
129 by the multi-pack-index file. Second, it calls git multi-pack-index
130 repack to select several small pack-files and repack them into a
131 bigger one, and then update the multi-pack-index entries that refer
132 to the small pack-files to refer to the new pack-file. This
133 prepares those small pack-files for deletion upon the next run of
134 git multi-pack-index expire. The selection of the small pack-files
135 is such that the expected size of the big pack-file is at least the
136 batch size; see the --batch-size option for the repack subcommand
137 in git-multi-pack-index(1). The default batch-size is zero, which
138 is a special case that attempts to repack all pack-files into a
139 single pack-file.
140 pack-refs
142 The pack-refs task collects the loose reference files and collects
143 them into a single file. This speeds up operations that need to
144 iterate across many references. See git-pack-refs(1) for more
145 information.
146
148 --auto
149 When combined with the run subcommand, run maintenance tasks only
150 if certain thresholds are met. For example, the gc task runs when
151 the number of loose objects exceeds the number stored in the
152 gc.auto config setting, or when the number of pack-files exceeds
153 the gc.autoPackLimit config setting. Not compatible with the
154 --schedule option.
155 --schedule
157 When combined with the run subcommand, run maintenance tasks only
158 if certain time conditions are met, as specified by the
159 maintenance.<task>.schedule config value for each <task>. This
160 config value specifies a number of seconds since the last time that
161 task ran, according to the maintenance.<task>.lastRun config value.
162 The tasks that are tested are those provided by the --task=<task>
163 option(s) or those with maintenance.<task>.enabled set to true.
164 --quiet
166 Do not report progress or other information over stderr.
167 --task=<task>
169 If this option is specified one or more times, then only run the
170 specified tasks in the specified order. If no --task=<task>
171 arguments are specified, then only the tasks with
172 maintenance.<task>.enabled configured as true are considered. See
173 the TASKS section for the list of accepted <task> values.
174
176 The git maintenance command is designed to simplify the repository
177 maintenance patterns while minimizing user wait time during Git
178 commands. A variety of configuration options are available to allow
179 customizing this process. The default maintenance options focus on
180 operations that complete quickly, even on large repositories.
181 Users may find some cases where scheduled maintenance tasks do not run
183 as frequently as intended. Each git maintenance run command takes a
184 lock on the repository’s object database, and this prevents other
185 concurrent git maintenance run commands from running on the same
186 repository. Without this safeguard, competing processes could leave the
187 repository in an unpredictable state.
188 The background maintenance schedule runs git maintenance run processes
190 on an hourly basis. Each run executes the "hourly" tasks. At midnight,
191 that process also executes the "daily" tasks. At midnight on the first
192 day of the week, that process also executes the "weekly" tasks. A
193 single process iterates over each registered repository, performing the
194 scheduled tasks for that frequency. Depending on the number of
195 registered repositories and their sizes, this process may take longer
196 than an hour. In this case, multiple git maintenance run commands may
197 run on the same repository at the same time, colliding on the object
198 database lock. This results in one of the two tasks not running.
199 If you find that some maintenance windows are taking longer than one
201 hour to complete, then consider reducing the complexity of your
202 maintenance tasks. For example, the gc task is much slower than the
203 incremental-repack task. However, this comes at a cost of a slightly
204 larger object database. Consider moving more expensive tasks to be run
205 less frequently.
206 Expert users may consider scheduling their own maintenance tasks using
208 a different schedule than is available through git maintenance start
209 and Git configuration options. These users should be aware of the
210 object database lock and how concurrent git maintenance run commands
211 behave. Further, the git gc command should not be combined with git
212 maintenance run commands. git gc modifies the object database but does
213 not take the lock in the same way as git maintenance run. If possible,
214 use git maintenance run --task=gc instead of git gc.
215 The following sections describe the mechanisms put in place to run
217 background maintenance by git maintenance start and how to customize
218 them.
219
221 The standard mechanism for scheduling background tasks on POSIX systems
222 is cron(8). This tool executes commands based on a given schedule. The
223 current list of user-scheduled tasks can be found by running crontab
224 -l. The schedule written by git maintenance start is similar to this:
225 # BEGIN GIT MAINTENANCE SCHEDULE
227 # The following schedule was created by Git
228 # Any edits made in this region might be
229 # replaced in the future by a Git command.
230 0 1-23 * * * "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=hourly
232 0 0 * * 1-6 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=daily
233 0 0 * * 0 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=weekly
234 # END GIT MAINTENANCE SCHEDULE
236 The comments are used as a region to mark the schedule as written by
238 Git. Any modifications within this region will be completely deleted by
239 git maintenance stop or overwritten by git maintenance start.
240 The crontab entry specifies the full path of the git executable to
242 ensure that the executed git command is the same one with which git
243 maintenance start was issued independent of PATH. If the same user runs
244 git maintenance start with multiple Git executables, then only the
245 latest executable is used.
246 These commands use git for-each-repo --config=maintenance.repo to run
248 git maintenance run --schedule=<frequency> on each repository listed in
249 the multi-valued maintenance.repo config option. These are typically
250 loaded from the user-specific global config. The git maintenance
251 process then determines which maintenance tasks are configured to run
252 on each repository with each <frequency> using the
253 maintenance.<task>.schedule config options. These values are loaded
254 from the global or repository config values.
255 If the config values are insufficient to achieve your desired
257 background maintenance schedule, then you can create your own schedule.
258 If you run crontab -e, then an editor will load with your user-specific
259 cron schedule. In that editor, you can add your own schedule lines. You
260 could start by adapting the default schedule listed earlier, or you
261 could read the crontab(5) documentation for advanced scheduling
262 techniques. Please do use the full path and --exec-path techniques from
263 the default schedule to ensure you are executing the correct binaries
264 in your schedule.
265
267 While macOS technically supports cron, using crontab -e requires
268 elevated privileges and the executed process does not have a full user
269 context. Without a full user context, Git and its credential helpers
270 cannot access stored credentials, so some maintenance tasks are not
271 functional.
272 Instead, git maintenance start interacts with the launchctl tool, which
274 is the recommended way to schedule timed jobs in macOS. Scheduling
275 maintenance through git maintenance (start|stop) requires some
276 launchctl features available only in macOS 10.11 or later.
277 Your user-specific scheduled tasks are stored as XML-formatted .plist
279 files in ~/Library/LaunchAgents/. You can see the currently-registered
280 tasks using the following command:
281 $ ls ~/Library/LaunchAgents/org.git-scm.git*
283 org.git-scm.git.daily.plist
284 org.git-scm.git.hourly.plist
285 org.git-scm.git.weekly.plist
286 One task is registered for each --schedule=<frequency> option. To
288 inspect how the XML format describes each schedule, open one of these
289 .plist files in an editor and inspect the <array> element following the
290 <key>StartCalendarInterval</key> element.
291 git maintenance start will overwrite these files and register the tasks
293 again with launchctl, so any customizations should be done by creating
294 your own .plist files with distinct names. Similarly, the git
295 maintenance stop command will unregister the tasks with launchctl and
296 delete the .plist files.
297 To create more advanced customizations to your background tasks, see
299 launchctl.plist(5) for more information.
300
302 Windows does not support cron and instead has its own system for
303 scheduling background tasks. The git maintenance start command uses the
304 schtasks command to submit tasks to this system. You can inspect all
305 background tasks using the Task Scheduler application. The tasks added
306 by Git have names of the form Git Maintenance (<frequency>). The Task
307 Scheduler GUI has ways to inspect these tasks, but you can also export
308 the tasks to XML files and view the details there.
309 Note that since Git is a console application, these background tasks
311 create a console window visible to the current user. This can be
312 changed manually by selecting the "Run whether user is logged in or
313 not" option in Task Scheduler. This change requires a password input,
314 which is why git maintenance start does not select it by default.
315 If you want to customize the background tasks, please rename the tasks
317 so future calls to git maintenance (start|stop) do not overwrite your
318 custom tasks.
319
321 Part of the git(1) suite
322Git 2.31.1 2021-03-26 GIT-MAINTENANCE(1)