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