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.

       --cruft
	   When expiring unreachable objects, pack them separately into a
	   cruft pack instead of storing them as loose objects.

       --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
       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 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-largest-pack except that all
	   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 false.

       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.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



Git 2.38.4			  02/20/2023			     GIT-GC(1)