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.

       --[no-]cruft
           When expiring unreachable objects, pack them separately into a cruft pack instead of
           storing them as loose objects.  --cruft is on by default.

       --max-cruft-size=<n>
           When packing unreachable objects into a cruft pack, limit the size of new cruft packs
           to be at most <n> bytes. Overrides any value specified via the gc.maxCruftSize
           configuration. See the --max-cruft-size option of git-repack(1) for more.

       --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 non-cruft pack, any packs marked with a .keep file, and
           any cruft pack(s) 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

       Everything below this line in this section is selectively included from the git-config(1)
       documentation. The content is the same as what’s found there:

       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 also 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 the background if the system supports
           it. Default is true.

       gc.bigPackThreshold
           If non-zero, all non-cruft packs larger than this limit are kept when git gc is run.
           This is very similar to --keep-largest-pack except that all non-cruft packs that meet
           the threshold are kept, not just the largest 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-largest-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.cruftPacks
           Store unreachable objects in a cruft pack (see git-repack(1)) instead of as loose
           objects. The default is true.

       gc.maxCruftSize
           Limit the size of new cruft packs when repacking. When specified in addition to
           --max-cruft-size, the command line option takes priority. See the --max-cruft-size
           option of git-repack(1).

       gc.pruneExpire
           When git gc is run, it will call prune --expire 2.weeks.ago (and repack --cruft
           --cruft-expiration 2.weeks.ago if using cruft packs via gc.cruftPacks or --cruft).
           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.recentObjectsHook
           When considering whether or not to remove an object (either when generating a cruft
           pack or storing unreachable objects as loose), use the shell to execute the specified
           command(s). Interpret their output as object IDs which Git will consider as "recent",
           regardless of their age. By treating their mtimes as "now", any objects (and their
           descendants) mentioned in the output will be kept regardless of their true age.

           Output must contain exactly one hex object ID per line, and nothing else. Objects
           which cannot be found in the repository are ignored. Multiple hooks are supported, but
           all must exit successfully, else the operation (either generating a cruft pack or
           unpacking unreachable objects) will be halted.

       gc.repackFilter
           When repacking, use the specified filter to move certain objects into a separate
           packfile. See the --filter=<filter-spec> option of git-repack(1).

       gc.repackFilterTo
           When repacking and using a filter, see gc.repackFilter, the specified location will be
           used to create the packfile containing the filtered out objects.  WARNING: The
           specified location should be accessible, using for example the Git alternates
           mechanism, otherwise the repo could be considered corrupt by Git as it migh not be
           able to access the objects in that packfile. See the --filter-to=<dir> option of git-
           repack(1) and the objects/info/alternates section of gitrepository-layout(5).

       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,
       reflogs (which may reference commits in branches that were later amended or rewound), and
       anything else in the refs/* namespace. Note that a note (of the kind created by git notes)
       attached to an object does not contribute in keeping the object alive. 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