git-maintenance(1) Manual Page

Run one or more maintenance tasks. If one or more --task options are specified, then those tasks are run in that order. Otherwise, the tasks are determined by which maintenance.<task>.enabled config options are true. By default, only maintenance.gc.enabled is true.

The commit-graph job updates the commit-graph files incrementally, then verifies that the written data is correct. The incremental write is safe to run alongside concurrent Git processes since it will not expire .graph files that were in the previous commit-graph-chain file. They will be deleted by a later run based on the expiration delay.

The prefetch task updates the object directory with the latest objects from all registered remotes. For each remote, a git fetch command is run. The refmap is custom to avoid updating local or remote branches (those in refs/heads or refs/remotes). Instead, the remote refs are stored in refs/prefetch/<remote>/. Also, tags are not updated.

Clean up unnecessary files and optimize the local repository. "GC" stands for "garbage collection," but this task performs many smaller tasks. This task can be expensive for large repositories, as it repacks all Git objects into a single pack-file. It can also be disruptive in some situations, as it deletes stale data. See git-gc(1) for more details on garbage collection in Git.

The loose-objects job cleans up loose objects and places them into pack-files. In order to prevent race conditions with concurrent Git commands, it follows a two-step process. First, it deletes any loose objects that already exist in a pack-file; concurrent Git processes will examine the pack-file for the object data instead of the loose object. Second, it creates a new pack-file (starting with "loose-") containing a batch of loose objects. The batch size is limited to 50 thousand objects to prevent the job from taking too long on a repository with many loose objects. The gc task writes unreachable objects as loose objects to be cleaned up by a later step only if they are not re-added to a pack-file; for this reason it is not advisable to enable both the loose-objects and gc tasks at the same time.

The incremental-repack job repacks the object directory using the multi-pack-index feature. In order to prevent race conditions with concurrent Git commands, it follows a two-step process. First, it calls git multi-pack-index expire to delete pack-files unreferenced by the multi-pack-index file. Second, it calls git multi-pack-index repack to select several small pack-files and repack them into a bigger one, and then update the multi-pack-index entries that refer to the small pack-files to refer to the new pack-file. This prepares those small pack-files for deletion upon the next run of git multi-pack-index expire. The selection of the small pack-files is such that the expected size of the big pack-file is at least the batch size; see the --batch-size option for the repack subcommand in git-multi-pack-index(1). The default batch-size is zero, which is a special case that attempts to repack all pack-files into a single pack-file.

When combined with the run subcommand, run maintenance tasks only if certain thresholds are met. For example, the gc task runs when the number of loose objects exceeds the number stored in the gc.auto config setting, or when the number of pack-files exceeds the gc.autoPackLimit config setting.

Do not report progress or other information over stderr.

If this option is specified one or more times, then only run the specified tasks in the specified order. If no --task=<task> arguments are specified, then only the tasks with maintenance.<task>.enabled configured as true are considered. See the TASKS section for the list of accepted <task> values.