GIT-GC(1) Git Manual GIT-GC(1)
git-gc - Cleanup unnecessary files and optimize the local repository
git gc [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
Runs a number of housekeeping tasks within the current repository, such
as compressing file revisions (to reduce disk space and increase
performance), removing unreachable objects which may have been created
from prior invocations of git add, packing refs, pruning reflog, rerere
metadata or stale working trees. May also update ancillary indexes such
as the commit-graph.
Users are encouraged to run this task on a regular basis within each
repository to maintain good disk space utilization and good operating
Some git commands may automatically run git gc; see the --auto flag
below for details. If you know what you're doing and all you want is to
disable this behavior permanently without further considerations, just
$ git config --global gc.auto 0
Usually git gc runs very quickly while providing good disk space
utilization and performance. This option will cause git gc to more
aggressively optimize the repository at the expense of taking much
more time. The effects of this optimization are persistent, so this
option only needs to be used occasionally; every few hundred
changesets or so.
With this option, git gc checks whether any housekeeping is
required; if not, it exits without performing any work. Some git
commands run git gc --auto after performing operations that could
create many loose objects. Housekeeping is required if there are
too many loose objects or too many packs in the repository.
If the number of loose objects exceeds the value of the gc.auto
configuration variable, then all loose objects are combined into a
single pack using git repack -d -l. Setting the value of gc.auto to
0 disables automatic packing of loose objects.
If the number of packs exceeds the value of gc.autoPackLimit, then
existing packs (except those marked with a .keep file or over
gc.bigPackThreshold limit) are consolidated into a single pack by
using the -A option of git repack. If the amount of memory is
estimated not enough for git repack to run smoothly and
gc.bigPackThreshold is not set, the largest pack will also be
excluded (this is the equivalent of running git gc with
--keep-base-pack). Setting gc.autoPackLimit to 0 disables automatic
consolidation of packs.
If houskeeping is required due to many loose objects or packs, all
other housekeeping tasks (e.g. rerere, working trees, reflog...)
will be performed as well.
Prune loose objects older than date (default is 2 weeks ago,
overridable by the config variable gc.pruneExpire). --prune=all
prunes loose objects regardless of their age and increases the risk
of corruption if another process is writing to the repository
concurrently; see "NOTES" below. --prune is on by default.
Do not prune any loose objects.
Suppress all progress reports.
Force git gc to run even if there may be another git gc instance
running on this repository.
All packs except the largest pack and those marked with a .keep
files are consolidated into a single pack. When this option is
used, gc.bigPackThreshold is ignored.
The optional configuration variable gc.reflogExpire can be set to
indicate how long historical entries within each branch's reflog should
remain available in this repository. The setting is expressed as a
length of time, for example 90 days or 3 months. It defaults to 90
The optional configuration variable gc.reflogExpireUnreachable can be
set to indicate how long historical reflog entries which are not part
of the current branch should remain available in this repository. These
types of entries are generally created as a result of using git commit
--amend or git rebase and are the commits prior to the amend or rebase
occurring. Since these changes are not part of the current project most
users will want to expire them sooner. This option defaults to 30 days.
The above two configuration variables can be given to a pattern. For
example, this sets non-default expiry values only to remote-tracking
reflogExpire = never
reflogExpireUnreachable = 3 days
The optional configuration variable gc.rerereResolved indicates how
long records of conflicted merge you resolved earlier are kept. This
defaults to 60 days.
The optional configuration variable gc.rerereUnresolved indicates how
long records of conflicted merge you have not resolved are kept. This
defaults to 15 days.
The optional configuration variable gc.packRefs determines if git gc
runs git pack-refs. This can be set to "notbare" to enable it within
all non-bare repos or it can be set to a boolean value. This defaults
The optional configuration variable gc.commitGraph determines if git gc
should run git commit-graph write. This can be set to a boolean value.
This defaults to false.
The optional configuration variable gc.aggressiveWindow controls how
much time is spent optimizing the delta compression of the objects in
the repository when the --aggressive option is specified. The larger
the value, the more time is spent optimizing the delta compression. See
the documentation for the --window option in git-repack(1) for more
details. This defaults to 250.
Similarly, the optional configuration variable gc.aggressiveDepth
controls --depth option in git-repack(1). This defaults to 50.
The optional configuration variable gc.pruneExpire controls how old the
unreferenced loose objects have to be before they are pruned. The
default is "2 weeks ago".
Optional configuration variable gc.worktreePruneExpire controls how old
a stale working tree should be before git worktree prune deletes it.
Default is "3 months ago".
git gc tries very hard not to delete objects that are referenced
anywhere in your repository. In particular, it will keep not only
objects referenced by your current set of branches and tags, but also
objects referenced by the index, remote-tracking branches, refs saved
by git filter-branch in refs/original/, or reflogs (which may reference
commits in branches that were later amended or rewound). If you are
expecting some objects to be deleted and they aren't, check all of
those locations and decide whether it makes sense in your case to
remove those references.
On the other hand, when git gc runs concurrently with another process,
there is a risk of it deleting an object that the other process is
using but hasn't created a reference to. This may just cause the other
process to fail or may corrupt the repository if the other process
later adds a reference to the deleted object. Git has two features that
significantly mitigate this problem:
1. Any object with modification time newer than the --prune date is
kept, along with everything reachable from it.
2. Most operations that add an object to the database update the
modification time of the object if it is already present so that #1
However, these features fall short of a complete solution, so users who
run commands concurrently have to live with some risk of corruption
(which seems to be low in practice) unless they turn off automatic
garbage collection with git config gc.auto 0.
The git gc --auto command will run the pre-auto-gc hook. See
githooks(5) for more information.
Part of the git(1) suite
Git 2.20.1 12/17/2018 GIT-GC(1)