git-maintenance - Run tasks to optimize Git repository data
'git maintenance' run [<options>]
Run tasks to optimize Git repository data, speeding up other Git commands
and reducing storage requirements for the repository.
Git commands that add repository data, such as `git add` or `git fetch`,
are optimized for a responsive user experience. These commands do not take
time to optimize the Git data, since such optimizations scale with the full
size of the repository while these user commands each perform a relatively
The `git maintenance` command provides flexibility for how to optimize the
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`
The `commit-graph` job updates the `commit-graph` files incrementally,
then verifies that the written data is correct. If the new layer has an
issue, then the chain file is removed and the `commit-graph` is
rewritten from scratch.
The verification only checks the top layer of the `commit-graph` chain.
If the incremental write merged the new commits with at least one
existing layer, then there is potential for on-disk corruption being
carried forward into the new file. This will be noticed and the new
commit-graph file will be clean as Git reparses the commit data from
the object database.
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
This is done to avoid disrupting the remote-tracking branches. The end users
expect these refs to stay unmoved unless they initiate a fetch. With prefetch
task, however, the objects necessary to complete a later real fetch would
already be obtained, so the real fetch would go faster. In the ideal case,
it will just become an update to bunch of remote-tracking branches without
any object transfer.
Cleanup unnecessary files and optimize the local repository. "GC"
stands for "garbage collection," but this task performs many
smaller tasks. This task can be rather 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
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.
Part of the linkgit:git suite