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1 | git-maintenance(1) |
2 | ================== | |
3 | ||
4 | NAME | |
5 | ---- | |
6 | git-maintenance - Run tasks to optimize Git repository data | |
7 | ||
8 | ||
9 | SYNOPSIS | |
10 | -------- | |
11 | [verse] | |
12 | 'git maintenance' run [<options>] | |
13 | ||
14 | ||
15 | DESCRIPTION | |
16 | ----------- | |
17 | Run tasks to optimize Git repository data, speeding up other Git commands | |
18 | and reducing storage requirements for the repository. | |
19 | ||
20 | Git commands that add repository data, such as `git add` or `git fetch`, | |
21 | are optimized for a responsive user experience. These commands do not take | |
22 | time to optimize the Git data, since such optimizations scale with the full | |
23 | size of the repository while these user commands each perform a relatively | |
24 | small action. | |
25 | ||
26 | The `git maintenance` command provides flexibility for how to optimize the | |
27 | Git repository. | |
28 | ||
29 | SUBCOMMANDS | |
30 | ----------- | |
31 | ||
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32 | register:: |
33 | Initialize Git config values so any scheduled maintenance will | |
34 | start running on this repository. This adds the repository to the | |
35 | `maintenance.repo` config variable in the current user's global | |
36 | config and enables some recommended configuration values for | |
37 | `maintenance.<task>.schedule`. The tasks that are enabled are safe | |
38 | for running in the background without disrupting foreground | |
39 | processes. | |
61f7a383 | 40 | + |
7efc3782 | 41 | The `register` subcommand will also set the `maintenance.strategy` config |
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42 | value to `incremental`, if this value is not previously set. The |
43 | `incremental` strategy uses the following schedule for each maintenance | |
44 | task: | |
45 | + | |
46 | -- | |
47 | * `gc`: disabled. | |
48 | * `commit-graph`: hourly. | |
49 | * `prefetch`: hourly. | |
50 | * `loose-objects`: daily. | |
51 | * `incremental-repack`: daily. | |
52 | -- | |
53 | + | |
54 | `git maintenance register` will also disable foreground maintenance by | |
55 | setting `maintenance.auto = false` in the current repository. This config | |
56 | setting will remain after a `git maintenance unregister` command. | |
0c18b700 | 57 | |
2057d750 | 58 | run:: |
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59 | Run one or more maintenance tasks. If one or more `--task` options |
60 | are specified, then those tasks are run in that order. Otherwise, | |
61 | the tasks are determined by which `maintenance.<task>.enabled` | |
62 | config options are true. By default, only `maintenance.gc.enabled` | |
63 | is true. | |
2057d750 | 64 | |
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65 | start:: |
66 | Start running maintenance on the current repository. This performs | |
67 | the same config updates as the `register` subcommand, then updates | |
68 | the background scheduler to run `git maintenance run --scheduled` | |
69 | on an hourly basis. | |
70 | ||
71 | stop:: | |
72 | Halt the background maintenance schedule. The current repository | |
73 | is not removed from the list of maintained repositories, in case | |
74 | the background maintenance is restarted later. | |
75 | ||
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76 | unregister:: |
77 | Remove the current repository from background maintenance. This | |
78 | only removes the repository from the configured list. It does not | |
79 | stop the background maintenance processes from running. | |
80 | ||
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81 | TASKS |
82 | ----- | |
83 | ||
663b2b1b DS |
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 | ||
28cb5e66 DS |
92 | prefetch:: |
93 | The `prefetch` task updates the object directory with the latest | |
94 | objects from all registered remotes. For each remote, a `git fetch` | |
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95 | command is run. The configured refspec is modified to place all |
96 | requested refs within `refs/prefetch/`. Also, tags are not updated. | |
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97 | + |
98 | This is done to avoid disrupting the remote-tracking branches. The end users | |
99 | expect these refs to stay unmoved unless they initiate a fetch. With prefetch | |
100 | task, however, the objects necessary to complete a later real fetch would | |
101 | already be obtained, so the real fetch would go faster. In the ideal case, | |
83fcadd6 | 102 | it will just become an update to a bunch of remote-tracking branches without |
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103 | any object transfer. |
104 | ||
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105 | gc:: |
106 | Clean up unnecessary files and optimize the local repository. "GC" | |
107 | stands for "garbage collection," but this task performs many | |
108 | smaller tasks. This task can be expensive for large repositories, | |
109 | as it repacks all Git objects into a single pack-file. It can also | |
110 | be disruptive in some situations, as it deletes stale data. See | |
111 | linkgit:git-gc[1] for more details on garbage collection in Git. | |
112 | ||
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113 | loose-objects:: |
114 | The `loose-objects` job cleans up loose objects and places them into | |
115 | pack-files. In order to prevent race conditions with concurrent Git | |
116 | commands, it follows a two-step process. First, it deletes any loose | |
117 | objects that already exist in a pack-file; concurrent Git processes | |
118 | will examine the pack-file for the object data instead of the loose | |
119 | object. Second, it creates a new pack-file (starting with "loose-") | |
120 | containing a batch of loose objects. The batch size is limited to 50 | |
121 | thousand objects to prevent the job from taking too long on a | |
122 | repository with many loose objects. The `gc` task writes unreachable | |
123 | objects as loose objects to be cleaned up by a later step only if | |
124 | they are not re-added to a pack-file; for this reason it is not | |
125 | advisable to enable both the `loose-objects` and `gc` tasks at the | |
126 | same time. | |
127 | ||
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128 | incremental-repack:: |
129 | The `incremental-repack` job repacks the object directory | |
130 | using the `multi-pack-index` feature. In order to prevent race | |
131 | conditions with concurrent Git commands, it follows a two-step | |
132 | process. First, it calls `git multi-pack-index expire` to delete | |
133 | pack-files unreferenced by the `multi-pack-index` file. Second, it | |
134 | calls `git multi-pack-index repack` to select several small | |
135 | pack-files and repack them into a bigger one, and then update the | |
136 | `multi-pack-index` entries that refer to the small pack-files to | |
137 | refer to the new pack-file. This prepares those small pack-files | |
138 | for deletion upon the next run of `git multi-pack-index expire`. | |
139 | The selection of the small pack-files is such that the expected | |
140 | size of the big pack-file is at least the batch size; see the | |
141 | `--batch-size` option for the `repack` subcommand in | |
142 | linkgit:git-multi-pack-index[1]. The default batch-size is zero, | |
143 | which is a special case that attempts to repack all pack-files | |
144 | into a single pack-file. | |
145 | ||
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146 | pack-refs:: |
147 | The `pack-refs` task collects the loose reference files and | |
148 | collects them into a single file. This speeds up operations that | |
149 | need to iterate across many references. See linkgit:git-pack-refs[1] | |
150 | for more information. | |
151 | ||
2057d750 DS |
152 | OPTIONS |
153 | ------- | |
154 | --auto:: | |
155 | When combined with the `run` subcommand, run maintenance tasks | |
156 | only if certain thresholds are met. For example, the `gc` task | |
157 | runs when the number of loose objects exceeds the number stored | |
158 | in the `gc.auto` config setting, or when the number of pack-files | |
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159 | exceeds the `gc.autoPackLimit` config setting. Not compatible with |
160 | the `--schedule` option. | |
161 | ||
162 | --schedule:: | |
163 | When combined with the `run` subcommand, run maintenance tasks | |
164 | only if certain time conditions are met, as specified by the | |
165 | `maintenance.<task>.schedule` config value for each `<task>`. | |
166 | This config value specifies a number of seconds since the last | |
167 | time that task ran, according to the `maintenance.<task>.lastRun` | |
168 | config value. The tasks that are tested are those provided by | |
169 | the `--task=<task>` option(s) or those with | |
170 | `maintenance.<task>.enabled` set to true. | |
2057d750 | 171 | |
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172 | --quiet:: |
173 | Do not report progress or other information over `stderr`. | |
174 | ||
090511bc DS |
175 | --task=<task>:: |
176 | If this option is specified one or more times, then only run the | |
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177 | specified tasks in the specified order. If no `--task=<task>` |
178 | arguments are specified, then only the tasks with | |
179 | `maintenance.<task>.enabled` configured as `true` are considered. | |
180 | See the 'TASKS' section for the list of accepted `<task>` values. | |
090511bc | 181 | |
0016b618 DS |
182 | |
183 | TROUBLESHOOTING | |
184 | --------------- | |
185 | The `git maintenance` command is designed to simplify the repository | |
186 | maintenance patterns while minimizing user wait time during Git commands. | |
187 | A variety of configuration options are available to allow customizing this | |
188 | process. The default maintenance options focus on operations that complete | |
189 | quickly, even on large repositories. | |
190 | ||
191 | Users may find some cases where scheduled maintenance tasks do not run as | |
192 | frequently as intended. Each `git maintenance run` command takes a lock on | |
193 | the repository's object database, and this prevents other concurrent | |
194 | `git maintenance run` commands from running on the same repository. Without | |
195 | this safeguard, competing processes could leave the repository in an | |
196 | unpredictable state. | |
197 | ||
198 | The background maintenance schedule runs `git maintenance run` processes | |
199 | on an hourly basis. Each run executes the "hourly" tasks. At midnight, | |
200 | that process also executes the "daily" tasks. At midnight on the first day | |
201 | of the week, that process also executes the "weekly" tasks. A single | |
202 | process iterates over each registered repository, performing the scheduled | |
203 | tasks for that frequency. Depending on the number of registered | |
204 | repositories and their sizes, this process may take longer than an hour. | |
205 | In this case, multiple `git maintenance run` commands may run on the same | |
206 | repository at the same time, colliding on the object database lock. This | |
207 | results in one of the two tasks not running. | |
208 | ||
209 | If you find that some maintenance windows are taking longer than one hour | |
210 | to complete, then consider reducing the complexity of your maintenance | |
211 | tasks. For example, the `gc` task is much slower than the | |
212 | `incremental-repack` task. However, this comes at a cost of a slightly | |
213 | larger object database. Consider moving more expensive tasks to be run | |
214 | less frequently. | |
215 | ||
216 | Expert users may consider scheduling their own maintenance tasks using a | |
217 | different schedule than is available through `git maintenance start` and | |
218 | Git configuration options. These users should be aware of the object | |
219 | database lock and how concurrent `git maintenance run` commands behave. | |
220 | Further, the `git gc` command should not be combined with | |
221 | `git maintenance run` commands. `git gc` modifies the object database | |
222 | but does not take the lock in the same way as `git maintenance run`. If | |
223 | possible, use `git maintenance run --task=gc` instead of `git gc`. | |
224 | ||
16c56909 DS |
225 | The following sections describe the mechanisms put in place to run |
226 | background maintenance by `git maintenance start` and how to customize | |
227 | them. | |
228 | ||
229 | BACKGROUND MAINTENANCE ON POSIX SYSTEMS | |
230 | --------------------------------------- | |
231 | ||
232 | The standard mechanism for scheduling background tasks on POSIX systems | |
233 | is cron(8). This tool executes commands based on a given schedule. The | |
234 | current list of user-scheduled tasks can be found by running `crontab -l`. | |
235 | The schedule written by `git maintenance start` is similar to this: | |
236 | ||
237 | ----------------------------------------------------------------------- | |
238 | # BEGIN GIT MAINTENANCE SCHEDULE | |
239 | # The following schedule was created by Git | |
240 | # Any edits made in this region might be | |
241 | # replaced in the future by a Git command. | |
242 | ||
243 | 0 1-23 * * * "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=hourly | |
244 | 0 0 * * 1-6 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=daily | |
245 | 0 0 * * 0 "/<path>/git" --exec-path="/<path>" for-each-repo --config=maintenance.repo maintenance run --schedule=weekly | |
246 | ||
247 | # END GIT MAINTENANCE SCHEDULE | |
248 | ----------------------------------------------------------------------- | |
249 | ||
250 | The comments are used as a region to mark the schedule as written by Git. | |
251 | Any modifications within this region will be completely deleted by | |
252 | `git maintenance stop` or overwritten by `git maintenance start`. | |
253 | ||
254 | The `crontab` entry specifies the full path of the `git` executable to | |
255 | ensure that the executed `git` command is the same one with which | |
256 | `git maintenance start` was issued independent of `PATH`. If the same user | |
257 | runs `git maintenance start` with multiple Git executables, then only the | |
258 | latest executable is used. | |
259 | ||
260 | These commands use `git for-each-repo --config=maintenance.repo` to run | |
261 | `git maintenance run --schedule=<frequency>` on each repository listed in | |
262 | the multi-valued `maintenance.repo` config option. These are typically | |
263 | loaded from the user-specific global config. The `git maintenance` process | |
264 | then determines which maintenance tasks are configured to run on each | |
265 | repository with each `<frequency>` using the `maintenance.<task>.schedule` | |
266 | config options. These values are loaded from the global or repository | |
267 | config values. | |
268 | ||
269 | If the config values are insufficient to achieve your desired background | |
270 | maintenance schedule, then you can create your own schedule. If you run | |
271 | `crontab -e`, then an editor will load with your user-specific `cron` | |
272 | schedule. In that editor, you can add your own schedule lines. You could | |
273 | start by adapting the default schedule listed earlier, or you could read | |
274 | the crontab(5) documentation for advanced scheduling techniques. Please | |
275 | do use the full path and `--exec-path` techniques from the default | |
276 | schedule to ensure you are executing the correct binaries in your | |
277 | schedule. | |
278 | ||
0016b618 | 279 | |
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280 | BACKGROUND MAINTENANCE ON MACOS SYSTEMS |
281 | --------------------------------------- | |
282 | ||
283 | While macOS technically supports `cron`, using `crontab -e` requires | |
284 | elevated privileges and the executed process does not have a full user | |
285 | context. Without a full user context, Git and its credential helpers | |
286 | cannot access stored credentials, so some maintenance tasks are not | |
287 | functional. | |
288 | ||
289 | Instead, `git maintenance start` interacts with the `launchctl` tool, | |
290 | which is the recommended way to schedule timed jobs in macOS. Scheduling | |
291 | maintenance through `git maintenance (start|stop)` requires some | |
292 | `launchctl` features available only in macOS 10.11 or later. | |
293 | ||
294 | Your user-specific scheduled tasks are stored as XML-formatted `.plist` | |
295 | files in `~/Library/LaunchAgents/`. You can see the currently-registered | |
296 | tasks using the following command: | |
297 | ||
298 | ----------------------------------------------------------------------- | |
299 | $ ls ~/Library/LaunchAgents/org.git-scm.git* | |
300 | org.git-scm.git.daily.plist | |
301 | org.git-scm.git.hourly.plist | |
302 | org.git-scm.git.weekly.plist | |
303 | ----------------------------------------------------------------------- | |
304 | ||
305 | One task is registered for each `--schedule=<frequency>` option. To | |
306 | inspect how the XML format describes each schedule, open one of these | |
307 | `.plist` files in an editor and inspect the `<array>` element following | |
308 | the `<key>StartCalendarInterval</key>` element. | |
309 | ||
310 | `git maintenance start` will overwrite these files and register the | |
311 | tasks again with `launchctl`, so any customizations should be done by | |
312 | creating your own `.plist` files with distinct names. Similarly, the | |
313 | `git maintenance stop` command will unregister the tasks with `launchctl` | |
314 | and delete the `.plist` files. | |
315 | ||
316 | To create more advanced customizations to your background tasks, see | |
317 | launchctl.plist(5) for more information. | |
318 | ||
319 | ||
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320 | BACKGROUND MAINTENANCE ON WINDOWS SYSTEMS |
321 | ----------------------------------------- | |
322 | ||
323 | Windows does not support `cron` and instead has its own system for | |
324 | scheduling background tasks. The `git maintenance start` command uses | |
325 | the `schtasks` command to submit tasks to this system. You can inspect | |
326 | all background tasks using the Task Scheduler application. The tasks | |
327 | added by Git have names of the form `Git Maintenance (<frequency>)`. | |
328 | The Task Scheduler GUI has ways to inspect these tasks, but you can also | |
329 | export the tasks to XML files and view the details there. | |
330 | ||
331 | Note that since Git is a console application, these background tasks | |
332 | create a console window visible to the current user. This can be changed | |
333 | manually by selecting the "Run whether user is logged in or not" option | |
334 | in Task Scheduler. This change requires a password input, which is why | |
335 | `git maintenance start` does not select it by default. | |
336 | ||
337 | If you want to customize the background tasks, please rename the tasks | |
338 | so future calls to `git maintenance (start|stop)` do not overwrite your | |
339 | custom tasks. | |
340 | ||
0016b618 | 341 | |
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342 | GIT |
343 | --- | |
344 | Part of the linkgit:git[1] suite |