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Diffstat (limited to 'Documentation/git-gc.txt')
| -rw-r--r-- | Documentation/git-gc.txt | 187 |
1 files changed, 93 insertions, 94 deletions
diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt index e158a3b31f..0c114ad1ca 100644 --- a/Documentation/git-gc.txt +++ b/Documentation/git-gc.txt @@ -9,26 +9,27 @@ git-gc - Cleanup unnecessary files and optimize the local repository SYNOPSIS -------- [verse] -'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] +'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack] 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 ----------------------- +performance), removing unreachable objects which may have been +created from prior invocations of 'git add', packing refs, pruning +reflog, rerere metadata or stale working trees. May also update ancillary +indexes such as the commit-graph. + +When common porcelain operations that create objects are run, they +will check whether the repository has grown substantially since the +last maintenance, and if so run `git gc` automatically. See `gc.auto` +below for how to disable this behavior. + +Running `git gc` manually should only be needed when adding objects to +a repository without regularly running such porcelain commands, to do +a one-off repository optimization, or e.g. to clean up a suboptimal +mass-import. See the "PACKFILE OPTIMIZATION" section in +linkgit:git-fast-import[1] for more details on the import case. OPTIONS ------- @@ -38,33 +39,28 @@ OPTIONS 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. + mostly persistent. See the "AGGRESSIVE" section below for details. --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. +See the `gc.auto` option in the "CONFIGURATION" section below for how +this heuristic works. + -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. +Once housekeeping is triggered by exceeding the limits of +configuration options such as `gc.auto` and `gc.autoPackLimit`, all +other housekeeping tasks (e.g. rerere, working trees, reflog...) will +be performed as well. + --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. - --prune is on by default. + --prune=now 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. @@ -76,72 +72,75 @@ automatic consolidation of packs. Force `git gc` to run even if there may be another `git gc` instance running on this repository. -Configuration +--keep-largest-pack:: + All packs except the largest pack and those marked with a + `.keep` files are consolidated into a single pack. When this + option is used, `gc.bigPackThreshold` is ignored. + +AGGRESSIVE +---------- + +When the `--aggressive` option is supplied, linkgit:git-repack[1] will +be invoked with the `-f` flag, which in turn will pass +`--no-reuse-delta` to linkgit:git-pack-objects[1]. This will throw +away any existing deltas and re-compute them, at the expense of +spending much more time on the repacking. + +The effects of this are mostly persistent, e.g. when packs and loose +objects are coalesced into one another pack the existing deltas in +that pack might get re-used, but there are also various cases where we +might pick a sub-optimal delta from a newer pack instead. + +Furthermore, supplying `--aggressive` will tweak the `--depth` and +`--window` options passed to linkgit:git-repack[1]. See the +`gc.aggressiveDepth` and `gc.aggressiveWindow` settings below. By +using a larger window size we're more likely to find more optimal +deltas. + +It's probably not worth it to use this option on a given repository +without running tailored performance benchmarks on it. It takes a lot +more time, and the resulting space/delta optimization may or may not +be worth it. Not using this at all is the right trade-off for most +users and their repositories. + +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 linkgit:git-repack[1] for -more details. This defaults to 250. - -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 ------ +The below documentation is the same as what's found in +linkgit:git-config[1]: + +include::config/gc.txt[] -'git gc' tries very hard to be safe about the garbage it collects. 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). +NOTES +----- -If you are expecting some objects to be collected and they aren't, check -all of those locations and decide whether it makes sense in your case to -remove those references. +'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, notes saved +by 'git notes' under refs/notes/, reflogs (which may reference commits +in branches that were later amended or rewound), and anything else in +the refs/* namespace. 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: + +. Any object with modification time newer than the `--prune` date is kept, + along with everything reachable from it. + +. 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). HOOKS ----- |