1GIT-GC(1)                         Git Manual                         GIT-GC(1)
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NAME

6       git-gc - Cleanup unnecessary files and optimize the local repository
7

SYNOPSIS

9       git gc [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
10

DESCRIPTION

12       Runs a number of housekeeping tasks within the current repository, such
13       as compressing file revisions (to reduce disk space and increase
14       performance), removing unreachable objects which may have been created
15       from prior invocations of git add, packing refs, pruning reflog, rerere
16       metadata or stale working trees. May also update ancillary indexes such
17       as the commit-graph.
18
19       When common porcelain operations that create objects are run, they will
20       check whether the repository has grown substantially since the last
21       maintenance, and if so run git gc automatically. See gc.auto below for
22       how to disable this behavior.
23
24       Running git gc manually should only be needed when adding objects to a
25       repository without regularly running such porcelain commands, to do a
26       one-off repository optimization, or e.g. to clean up a suboptimal
27       mass-import. See the "PACKFILE OPTIMIZATION" section in git-fast-
28       import(1) for more details on the import case.
29

OPTIONS

31       --aggressive
32           Usually git gc runs very quickly while providing good disk space
33           utilization and performance. This option will cause git gc to more
34           aggressively optimize the repository at the expense of taking much
35           more time. The effects of this optimization are mostly persistent.
36           See the "AGGRESSIVE" section below for details.
37
38       --auto
39           With this option, git gc checks whether any housekeeping is
40           required; if not, it exits without performing any work.
41
42           See the gc.auto option in the "CONFIGURATION" section below for how
43           this heuristic works.
44
45           Once housekeeping is triggered by exceeding the limits of
46           configuration options such as gc.auto and gc.autoPackLimit, all
47           other housekeeping tasks (e.g. rerere, working trees, reflog...)
48           will be performed as well.
49
50       --prune=<date>
51           Prune loose objects older than date (default is 2 weeks ago,
52           overridable by the config variable gc.pruneExpire). --prune=now
53           prunes loose objects regardless of their age and increases the risk
54           of corruption if another process is writing to the repository
55           concurrently; see "NOTES" below. --prune is on by default.
56
57       --no-prune
58           Do not prune any loose objects.
59
60       --quiet
61           Suppress all progress reports.
62
63       --force
64           Force git gc to run even if there may be another git gc instance
65           running on this repository.
66
67       --keep-largest-pack
68           All packs except the largest pack and those marked with a .keep
69           files are consolidated into a single pack. When this option is
70           used, gc.bigPackThreshold is ignored.
71

AGGRESSIVE

73       When the --aggressive option is supplied, git-repack(1) will be invoked
74       with the -f flag, which in turn will pass --no-reuse-delta to git-pack-
75       objects(1). This will throw away any existing deltas and re-compute
76       them, at the expense of spending much more time on the repacking.
77
78       The effects of this are mostly persistent, e.g. when packs and loose
79       objects are coalesced into one another pack the existing deltas in that
80       pack might get re-used, but there are also various cases where we might
81       pick a sub-optimal delta from a newer pack instead.
82
83       Furthermore, supplying --aggressive will tweak the --depth and --window
84       options passed to git-repack(1). See the gc.aggressiveDepth and
85       gc.aggressiveWindow settings below. By using a larger window size we’re
86       more likely to find more optimal deltas.
87
88       It’s probably not worth it to use this option on a given repository
89       without running tailored performance benchmarks on it. It takes a lot
90       more time, and the resulting space/delta optimization may or may not be
91       worth it. Not using this at all is the right trade-off for most users
92       and their repositories.
93

CONFIGURATION

95       The below documentation is the same as what’s found in git-config(1):
96
97       gc.aggressiveDepth
98           The depth parameter used in the delta compression algorithm used by
99           git gc --aggressive. This defaults to 50, which is the default for
100           the --depth option when --aggressive isn’t in use.
101
102           See the documentation for the --depth option in git-repack(1) for
103           more details.
104
105       gc.aggressiveWindow
106           The window size parameter used in the delta compression algorithm
107           used by git gc --aggressive. This defaults to 250, which is a much
108           more aggressive window size than the default --window of 10.
109
110           See the documentation for the --window option in git-repack(1) for
111           more details.
112
113       gc.auto
114           When there are approximately more than this many loose objects in
115           the repository, git gc --auto will pack them. Some Porcelain
116           commands use this command to perform a light-weight garbage
117           collection from time to time. The default value is 6700.
118
119           Setting this to 0 disables not only automatic packing based on the
120           number of loose objects, but any other heuristic git gc --auto will
121           otherwise use to determine if there’s work to do, such as
122           gc.autoPackLimit.
123
124       gc.autoPackLimit
125           When there are more than this many packs that are not marked with
126           *.keep file in the repository, git gc --auto consolidates them into
127           one larger pack. The default value is 50. Setting this to 0
128           disables it. Setting gc.auto to 0 will also disable this.
129
130           See the gc.bigPackThreshold configuration variable below. When in
131           use, it’ll affect how the auto pack limit works.
132
133       gc.autoDetach
134           Make git gc --auto return immediately and run in background if the
135           system supports it. Default is true.
136
137       gc.bigPackThreshold
138           If non-zero, all packs larger than this limit are kept when git gc
139           is run. This is very similar to --keep-largest-pack except that all
140           packs that meet the threshold are kept, not just the largest pack.
141           Defaults to zero. Common unit suffixes of k, m, or g are supported.
142
143           Note that if the number of kept packs is more than
144           gc.autoPackLimit, this configuration variable is ignored, all packs
145           except the base pack will be repacked. After this the number of
146           packs should go below gc.autoPackLimit and gc.bigPackThreshold
147           should be respected again.
148
149           If the amount of memory estimated for git repack to run smoothly is
150           not available and gc.bigPackThreshold is not set, the largest pack
151           will also be excluded (this is the equivalent of running git gc
152           with --keep-largest-pack).
153
154       gc.writeCommitGraph
155           If true, then gc will rewrite the commit-graph file when git-gc(1)
156           is run. When using git gc --auto the commit-graph will be updated
157           if housekeeping is required. Default is true. See git-commit-
158           graph(1) for details.
159
160       gc.logExpiry
161           If the file gc.log exists, then git gc --auto will print its
162           content and exit with status zero instead of running unless that
163           file is more than gc.logExpiry old. Default is "1.day". See
164           gc.pruneExpire for more ways to specify its value.
165
166       gc.packRefs
167           Running git pack-refs in a repository renders it unclonable by Git
168           versions prior to 1.5.1.2 over dumb transports such as HTTP. This
169           variable determines whether git gc runs git pack-refs. This can be
170           set to notbare to enable it within all non-bare repos or it can be
171           set to a boolean value. The default is true.
172
173       gc.pruneExpire
174           When git gc is run, it will call prune --expire 2.weeks.ago.
175           Override the grace period with this config variable. The value
176           "now" may be used to disable this grace period and always prune
177           unreachable objects immediately, or "never" may be used to suppress
178           pruning. This feature helps prevent corruption when git gc runs
179           concurrently with another process writing to the repository; see
180           the "NOTES" section of git-gc(1).
181
182       gc.worktreePruneExpire
183           When git gc is run, it calls git worktree prune --expire
184           3.months.ago. This config variable can be used to set a different
185           grace period. The value "now" may be used to disable the grace
186           period and prune $GIT_DIR/worktrees immediately, or "never" may be
187           used to suppress pruning.
188
189       gc.reflogExpire, gc.<pattern>.reflogExpire
190           git reflog expire removes reflog entries older than this time;
191           defaults to 90 days. The value "now" expires all entries
192           immediately, and "never" suppresses expiration altogether. With
193           "<pattern>" (e.g. "refs/stash") in the middle the setting applies
194           only to the refs that match the <pattern>.
195
196       gc.reflogExpireUnreachable, gc.<pattern>.reflogExpireUnreachable
197           git reflog expire removes reflog entries older than this time and
198           are not reachable from the current tip; defaults to 30 days. The
199           value "now" expires all entries immediately, and "never" suppresses
200           expiration altogether. With "<pattern>" (e.g. "refs/stash") in the
201           middle, the setting applies only to the refs that match the
202           <pattern>.
203
204           These types of entries are generally created as a result of using
205           git commit --amend or git rebase and are the commits prior to the
206           amend or rebase occurring. Since these changes are not part of the
207           current project most users will want to expire them sooner, which
208           is why the default is more aggressive than gc.reflogExpire.
209
210       gc.rerereResolved
211           Records of conflicted merge you resolved earlier are kept for this
212           many days when git rerere gc is run. You can also use more
213           human-readable "1.month.ago", etc. The default is 60 days. See git-
214           rerere(1).
215
216       gc.rerereUnresolved
217           Records of conflicted merge you have not resolved are kept for this
218           many days when git rerere gc is run. You can also use more
219           human-readable "1.month.ago", etc. The default is 15 days. See git-
220           rerere(1).
221

NOTES

223       git gc tries very hard not to delete objects that are referenced
224       anywhere in your repository. In particular, it will keep not only
225       objects referenced by your current set of branches and tags, but also
226       objects referenced by the index, remote-tracking branches, reflogs
227       (which may reference commits in branches that were later amended or
228       rewound), and anything else in the refs/* namespace. Note that a note
229       (of the kind created by git notes) attached to an object does not
230       contribute in keeping the object alive. If you are expecting some
231       objects to be deleted and they aren’t, check all of those locations and
232       decide whether it makes sense in your case to remove those references.
233
234       On the other hand, when git gc runs concurrently with another process,
235       there is a risk of it deleting an object that the other process is
236       using but hasn’t created a reference to. This may just cause the other
237       process to fail or may corrupt the repository if the other process
238       later adds a reference to the deleted object. Git has two features that
239       significantly mitigate this problem:
240
241        1. Any object with modification time newer than the --prune date is
242           kept, along with everything reachable from it.
243
244        2. Most operations that add an object to the database update the
245           modification time of the object if it is already present so that #1
246           applies.
247
248       However, these features fall short of a complete solution, so users who
249       run commands concurrently have to live with some risk of corruption
250       (which seems to be low in practice).
251

HOOKS

253       The git gc --auto command will run the pre-auto-gc hook. See
254       githooks(5) for more information.
255

SEE ALSO

257       git-prune(1) git-reflog(1) git-repack(1) git-rerere(1)
258

GIT

260       Part of the git(1) suite
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264Git 2.33.1                        2021-10-12                         GIT-GC(1)
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