# git-gc

## NAME



           git-gc - Cleanup unnecessary files and optimize the local
           repository
    


## SYNOPSIS



           _git gc_ [--aggressive] [--auto] [--[no-]detach] [--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-]detach
               Run in the background if the system supports it. This option
               overrides the **gc.autoDetach** config.
    
           --[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.
    
           --expire-to=<dir>
               When packing unreachable objects into a cruft pack, write a
               cruft pack containing pruned objects (if any) to the directory
               _< dir>_. This option only has an effect when used together with
               **--cruft**. See the **--expire-to** option of git-repack(1) for more
               information.
    
           --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. This
               config variable acts as a fallback in case
               **maintenance.autoDetach** is not set.
    
           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 might 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.
    


## GIT



           Part of the git(1) suite
    


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