git-gc(1)



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]

DESCRIPTION
       Runs a number of housekeeping tasks within the current repository, such
       as compressing file revisions (to reduce disk space and increase
       performance) and removing unreachable objects which may have been
       created from prior invocations of git add.

       Users are encouraged to run this task on a regular basis within each
       repository to maintain good disk space utilization and good operating
       performance.

       Some git commands may automatically run git gc; see the --auto flag
       below for details. If you know what you're doing and all you want is to
       disable this behavior permanently without further considerations, just
       do:

           $ git config --global gc.auto 0

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 persistent, so this
           option only needs to be used occasionally; every few hundred
           changesets or so.

       --auto
           With this option, git gc checks whether any housekeeping is
           required; if not, it exits without performing any work. Some git
           commands run git gc --auto after performing operations that could
           create many loose objects.

           Housekeeping is required if there are too many loose objects or too
           many packs in the repository. If the number of loose objects
           exceeds the value of the gc.auto configuration variable, then all
           loose objects are combined into a single pack using git repack -d
           -l. Setting the value of gc.auto to 0 disables automatic packing of
           loose objects.

           If the number of packs exceeds the value of gc.autoPackLimit, then
           existing packs (except those marked with a .keep file) are
           consolidated into a single pack by using the -A option of git
           repack. Setting gc.autoPackLimit to 0 disables automatic
           consolidation of packs.

       --prune=<date>
           Prune loose objects older than date (default is 2 weeks ago,
           overridable by the config variable gc.pruneExpire). --prune=all
           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.

CONFIGURATION
       The optional configuration variable gc.reflogExpire can be set to
       indicate how long historical entries within each branch's reflog should
       remain available in this repository. The setting is expressed as a
       length of time, for example 90 days or 3 months. It defaults to 90
       days.

       The optional configuration variable gc.reflogExpireUnreachable can be
       set to indicate how long historical reflog entries which are not part
       of the current branch should remain available in this repository. 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. This option defaults to 30 days.

       The above two configuration variables can be given to a pattern. For
       example, this sets non-default expiry values only to remote-tracking
       branches:

           [gc "refs/remotes/*"]
                   reflogExpire = never
                   reflogExpireUnreachable = 3 days

       The optional configuration variable gc.rerereResolved indicates how
       long records of conflicted merge you resolved earlier are kept. This
       defaults to 60 days.

       The optional configuration variable gc.rerereUnresolved indicates how
       long records of conflicted merge you have not resolved are kept. This
       defaults to 15 days.

       The optional configuration variable gc.packRefs determines if 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. This defaults
       to true.

       The optional configuration variable 'gc.aggressiveWindow` controls how
       much time is spent optimizing the delta compression of the objects in
       the repository when the --aggressive option is specified. The larger
       the value, the more time is spent optimizing the delta compression. See
       the documentation for the --window' option in git-repack(1) for more
       details. This defaults to 250.

       Similarly, the optional configuration variable gc.aggressiveDepth
       controls --depth option in git-repack(1). This defaults to 50.

       The optional configuration variable gc.pruneExpire controls how old the
       unreferenced loose objects have to be before they are pruned. The
       default is "2 weeks ago".

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, refs saved
       by git filter-branch in refs/original/, or reflogs (which may reference
       commits in branches that were later amended or rewound). 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) unless they turn off automatic
       garbage collection with git config gc.auto 0.

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 2.14.2                        09/26/2017                         GIT-GC(1)

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