git gc [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
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
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 or over gc.bigPackThreshold limit) are consolidated into a single pack by using the -A option of git repack. If the amount of memory is estimated not enough for git repack to run smoothly and gc.bigPackThreshold is not set, the largest pack will also be excluded (this is the equivalent of running git gc with --keep-base-pack). Setting gc.autoPackLimit to 0 disables automatic consolidation of packs.
If houskeeping is required due to many loose objects or packs, all other housekeeping tasks (e.g. rerere, working trees, reflog...) will be performed as well.
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.writeCommitGraph determines if git gc should run git commit-graph write. This can be set to a boolean value. This defaults to false.
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".
Optional configuration variable gc.worktreePruneExpire controls how old a stale working tree should be before git worktree prune deletes it. Default is "3 months ago".
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:
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.