maintenance: add prefetch task

[thirdparty/git.git] / Documentation / git-maintenance.txt

git-maintenance(1)
==================

NAME
----
git-maintenance - Run tasks to optimize Git repository data


SYNOPSIS
--------
[verse]
'git maintenance' run [<options>]


DESCRIPTION
-----------
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
small action.

The `git maintenance` command provides flexibility for how to optimize the
Git repository.

SUBCOMMANDS
-----------

run::
	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.

TASKS
-----

commit-graph::
	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.

prefetch::
	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.
+
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.

gc::
	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
	linkgit:git-gc[1] for more details on garbage collection in Git.

OPTIONS
-------
--auto::
	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.

--quiet::
	Do not report progress or other information over `stderr`.

--task=<task>::
	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.

GIT
---
Part of the linkgit:git[1] suite