GIT-GC(1) Git Manual GIT-GC(1)
NAME
git-gc - Cleanup unnecessary files and optimize the local repository
SYNOPSIS
git gc [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
DESCRIPTION
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.
When common porcelain operations that create objects are run, they will
check whether the repository has grown substantially since the last
maintenance, and if so run git gc automatically. See gc.auto below for
how to disable this behavior.
Running git gc manually should only be needed when adding objects to a
repository without regularly running such porcelain commands, to do a
one-off repository optimization, or e.g. to clean up a suboptimal
mass-import. See the "PACKFILE OPTIMIZATION" section in git-fast-
import(1) for more details on the import case.
OPTIONS
--aggressive
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 mostly persistent.
See the "AGGRESSIVE" section below for details.
--auto
With this option, git gc checks whether any housekeeping is
required; if not, it exits without performing any work.
See the gc.auto option in the "CONFIGURATION" section below for how
this heuristic works.
Once housekeeping is triggered by exceeding the limits of
configuration options such as gc.auto and gc.autoPackLimit, all
other housekeeping tasks (e.g. rerere, working trees, reflog...)
will be performed as well.
--prune=<date>
Prune loose objects older than date (default is 2 weeks ago,
overridable by the config variable gc.pruneExpire). --prune=now
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.
--no-prune
Do not prune any loose objects.
--quiet
Suppress all progress reports.
--force
Force git gc to run even if there may be another git gc instance
running on this repository.
--keep-largest-pack
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.
AGGRESSIVE
When the --aggressive option is supplied, git-repack(1) will be invoked
with the -f flag, which in turn will pass --no-reuse-delta to git-pack-
objects(1). This will throw away any existing deltas and re-compute
them, at the expense of spending much more time on the repacking.
The effects of this are mostly persistent, e.g. when packs and loose
objects are coalesced into one another pack the existing deltas in that
pack might get re-used, but there are also various cases where we might
pick a sub-optimal delta from a newer pack instead.
Furthermore, supplying --aggressive will tweak the --depth and --window
options passed to git-repack(1). See the gc.aggressiveDepth and
gc.aggressiveWindow settings below. By using a larger window size we're
more likely to find more optimal deltas.
It's probably not worth it to use this option on a given repository
without running tailored performance benchmarks on it. It takes a lot
more time, and the resulting space/delta optimization may or may not be
worth it. Not using this at all is the right trade-off for most users
and their repositories.
CONFIGURATION
The below documentation is the same as what's found in git-config(1):
gc.aggressiveDepth
The depth parameter used in the delta compression algorithm used by
git gc --aggressive. This defaults to 50, which is the default for
the --depth option when --aggressive isn't in use.
See the documentation for the --depth option in git-repack(1) for
more details.
gc.aggressiveWindow
The window size parameter used in the delta compression algorithm
used by git gc --aggressive. This defaults to 250, which is a much
more aggressive window size than the default --window of 10.
See the documentation for the --window option in git-repack(1) for
more details.
gc.auto
When there are approximately more than this many loose objects in
the repository, git gc --auto will pack them. Some Porcelain
commands use this command to perform a light-weight garbage
collection from time to time. The default value is 6700.
Setting this to 0 disables not only automatic packing based on the
number of loose objects, but any other heuristic git gc --auto will
otherwise use to determine if there's work to do, such as
gc.autoPackLimit.
gc.autoPackLimit
When there are more than this many packs that are not marked with
*.keep file in the repository, git gc --auto consolidates them into
one larger pack. The default value is 50. Setting this to 0
disables it. Setting gc.auto to 0 will also disable this.
See the gc.bigPackThreshold configuration variable below. When in
use, it'll affect how the auto pack limit works.
gc.autoDetach
Make git gc --auto return immediately and run in background if the
system supports it. Default is true.
gc.bigPackThreshold
If non-zero, all packs larger than this limit are kept when git gc
is run. This is very similar to --keep-base-pack except that all
packs that meet the threshold are kept, not just the base pack.
Defaults to zero. Common unit suffixes of k, m, or g are supported.
Note that if the number of kept packs is more than
gc.autoPackLimit, this configuration variable is ignored, all packs
except the base pack will be repacked. After this the number of
packs should go below gc.autoPackLimit and gc.bigPackThreshold
should be respected again.
If the amount of memory estimated for git repack to run smoothly is
not available 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).
gc.writeCommitGraph
If true, then gc will rewrite the commit-graph file when git-gc(1)
is run. When using git gc --auto the commit-graph will be updated
if housekeeping is required. Default is true. See git-commit-
graph(1) for details.
gc.logExpiry
If the file gc.log exists, then git gc --auto will print its
content and exit with status zero instead of running unless that
file is more than gc.logExpiry old. Default is "1.day". See
gc.pruneExpire for more ways to specify its value.
gc.packRefs
Running git pack-refs in a repository renders it unclonable by Git
versions prior to 1.5.1.2 over dumb transports such as HTTP. This
variable determines whether 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. The default is true.
gc.pruneExpire
When git gc is run, it will call prune --expire 2.weeks.ago.
Override the grace period with this config variable. The value
"now" may be used to disable this grace period and always prune
unreachable objects immediately, or "never" may be used to suppress
pruning. This feature helps prevent corruption when git gc runs
concurrently with another process writing to the repository; see
the "NOTES" section of git-gc(1).
gc.worktreePruneExpire
When git gc is run, it calls git worktree prune --expire
3.months.ago. This config variable can be used to set a different
grace period. The value "now" may be used to disable the grace
period and prune $GIT_DIR/worktrees immediately, or "never" may be
used to suppress pruning.
gc.reflogExpire, gc.<pattern>.reflogExpire
git reflog expire removes reflog entries older than this time;
defaults to 90 days. The value "now" expires all entries
immediately, and "never" suppresses expiration altogether. With
"<pattern>" (e.g. "refs/stash") in the middle the setting applies
only to the refs that match the <pattern>.
gc.reflogExpireUnreachable, gc.<pattern>.reflogExpireUnreachable
git reflog expire removes reflog entries older than this time and
are not reachable from the current tip; defaults to 30 days. The
value "now" expires all entries immediately, and "never" suppresses
expiration altogether. With "<pattern>" (e.g. "refs/stash") in the
middle, the setting applies only to the refs that match the
<pattern>.
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, which
is why the default is more aggressive than gc.reflogExpire.
gc.rerereResolved
Records of conflicted merge you resolved earlier are kept for this
many days when git rerere gc is run. You can also use more
human-readable "1.month.ago", etc. The default is 60 days. See git-
rerere(1).
gc.rerereUnresolved
Records of conflicted merge you have not resolved are kept for this
many days when git rerere gc is run. You can also use more
human-readable "1.month.ago", etc. The default is 15 days. See git-
rerere(1).
NOTES
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, notes saved
by git notes under refs/notes/, reflogs (which may reference commits in
branches that were later amended or rewound), and anything else in the
refs/* namespace. 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
applies.
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).
HOOKS
The git gc --auto command will run the pre-auto-gc hook. See
githooks(5) for more information.
SEE ALSO
git-prune(1)git-reflog(1)git-repack(1)git-rerere(1)
GIT
Part of the git(1) suite
Git 2.27.0 06/01/2020 GIT-GC(1)