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

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

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

13       Runs a number of housekeeping tasks within the current repository, such
14       as compressing file revisions (to reduce disk space and increase
15       performance), removing unreachable objects which may have been created
16       from prior invocations of git add, packing refs, pruning reflog, rerere
17       metadata or stale working trees. May also update ancillary indexes such
18       as the commit-graph.
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20       Users are encouraged to run this task on a regular basis within each
21       repository to maintain good disk space utilization and good operating
22       performance.
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24       Some git commands may automatically run git gc; see the --auto flag
25       below for details. If you know what you’re doing and all you want is to
26       disable this behavior permanently without further considerations, just
27       do:
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29           $ git config --global gc.auto 0
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OPTIONS

33       --aggressive
34           Usually git gc runs very quickly while providing good disk space
35           utilization and performance. This option will cause git gc to more
36           aggressively optimize the repository at the expense of taking much
37           more time. The effects of this optimization are persistent, so this
38           option only needs to be used occasionally; every few hundred
39           changesets or so.
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41       --auto
42           With this option, git gc checks whether any housekeeping is
43           required; if not, it exits without performing any work. Some git
44           commands run git gc --auto after performing operations that could
45           create many loose objects. Housekeeping is required if there are
46           too many loose objects or too many packs in the repository.
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48           If the number of loose objects exceeds the value of the gc.auto
49           configuration variable, then all loose objects are combined into a
50           single pack using git repack -d -l. Setting the value of gc.auto to
51           0 disables automatic packing of loose objects.
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53           If the number of packs exceeds the value of gc.autoPackLimit, then
54           existing packs (except those marked with a .keep file or over
55           gc.bigPackThreshold limit) are consolidated into a single pack by
56           using the -A option of git repack. If the amount of memory is
57           estimated not enough for git repack to run smoothly and
58           gc.bigPackThreshold is not set, the largest pack will also be
59           excluded (this is the equivalent of running git gc with
60           --keep-base-pack). Setting gc.autoPackLimit to 0 disables automatic
61           consolidation of packs.
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63           If houskeeping is required due to many loose objects or packs, all
64           other housekeeping tasks (e.g. rerere, working trees, reflog...)
65           will be performed as well.
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67       --prune=<date>
68           Prune loose objects older than date (default is 2 weeks ago,
69           overridable by the config variable gc.pruneExpire). --prune=all
70           prunes loose objects regardless of their age and increases the risk
71           of corruption if another process is writing to the repository
72           concurrently; see "NOTES" below. --prune is on by default.
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74       --no-prune
75           Do not prune any loose objects.
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77       --quiet
78           Suppress all progress reports.
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80       --force
81           Force git gc to run even if there may be another git gc instance
82           running on this repository.
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84       --keep-largest-pack
85           All packs except the largest pack and those marked with a .keep
86           files are consolidated into a single pack. When this option is
87           used, gc.bigPackThreshold is ignored.
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CONFIGURATION

90       The optional configuration variable gc.reflogExpire can be set to
91       indicate how long historical entries within each branch’s reflog should
92       remain available in this repository. The setting is expressed as a
93       length of time, for example 90 days or 3 months. It defaults to 90
94       days.
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96       The optional configuration variable gc.reflogExpireUnreachable can be
97       set to indicate how long historical reflog entries which are not part
98       of the current branch should remain available in this repository. These
99       types of entries are generally created as a result of using git commit
100       --amend or git rebase and are the commits prior to the amend or rebase
101       occurring. Since these changes are not part of the current project most
102       users will want to expire them sooner. This option defaults to 30 days.
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104       The above two configuration variables can be given to a pattern. For
105       example, this sets non-default expiry values only to remote-tracking
106       branches:
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108           [gc "refs/remotes/*"]
109                   reflogExpire = never
110                   reflogExpireUnreachable = 3 days
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113       The optional configuration variable gc.rerereResolved indicates how
114       long records of conflicted merge you resolved earlier are kept. This
115       defaults to 60 days.
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117       The optional configuration variable gc.rerereUnresolved indicates how
118       long records of conflicted merge you have not resolved are kept. This
119       defaults to 15 days.
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121       The optional configuration variable gc.packRefs determines if git gc
122       runs git pack-refs. This can be set to "notbare" to enable it within
123       all non-bare repos or it can be set to a boolean value. This defaults
124       to true.
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126       The optional configuration variable gc.commitGraph determines if git gc
127       should run git commit-graph write. This can be set to a boolean value.
128       This defaults to false.
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130       The optional configuration variable gc.aggressiveWindow controls how
131       much time is spent optimizing the delta compression of the objects in
132       the repository when the --aggressive option is specified. The larger
133       the value, the more time is spent optimizing the delta compression. See
134       the documentation for the --window option in git-repack(1) for more
135       details. This defaults to 250.
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137       Similarly, the optional configuration variable gc.aggressiveDepth
138       controls --depth option in git-repack(1). This defaults to 50.
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140       The optional configuration variable gc.pruneExpire controls how old the
141       unreferenced loose objects have to be before they are pruned. The
142       default is "2 weeks ago".
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144       Optional configuration variable gc.worktreePruneExpire controls how old
145       a stale working tree should be before git worktree prune deletes it.
146       Default is "3 months ago".
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NOTES

149       git gc tries very hard not to delete objects that are referenced
150       anywhere in your repository. In particular, it will keep not only
151       objects referenced by your current set of branches and tags, but also
152       objects referenced by the index, remote-tracking branches, refs saved
153       by git filter-branch in refs/original/, or reflogs (which may reference
154       commits in branches that were later amended or rewound). If you are
155       expecting some objects to be deleted and they aren’t, check all of
156       those locations and decide whether it makes sense in your case to
157       remove those references.
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159       On the other hand, when git gc runs concurrently with another process,
160       there is a risk of it deleting an object that the other process is
161       using but hasn’t created a reference to. This may just cause the other
162       process to fail or may corrupt the repository if the other process
163       later adds a reference to the deleted object. Git has two features that
164       significantly mitigate this problem:
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166        1. Any object with modification time newer than the --prune date is
167           kept, along with everything reachable from it.
168
169        2. Most operations that add an object to the database update the
170           modification time of the object if it is already present so that #1
171           applies.
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173       However, these features fall short of a complete solution, so users who
174       run commands concurrently have to live with some risk of corruption
175       (which seems to be low in practice) unless they turn off automatic
176       garbage collection with git config gc.auto 0.
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HOOKS

179       The git gc --auto command will run the pre-auto-gc hook. See
180       githooks(5) for more information.
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SEE ALSO

183       git-prune(1) git-reflog(1) git-repack(1) git-rerere(1)
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GIT

186       Part of the git(1) suite
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190Git 2.20.1                        12/15/2018                         GIT-GC(1)
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