Documentation/git-gc.txt

   1 git-gc(1)
   2 =========
   3
   4 NAME
   5 ----
   6 git-gc - Cleanup unnecessary files and optimize the local repository
   7
   8
   9 SYNOPSIS
  10 --------
  11 [verse]
  12 'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
  13
  14 DESCRIPTION
  15 -----------
  16 Runs a number of housekeeping tasks within the current repository,
  17 such as compressing file revisions (to reduce disk space and increase
  18 performance), removing unreachable objects which may have been
  19 created from prior invocations of 'git add', packing refs, pruning
  20 reflog, rerere metadata or stale working trees. May also update ancillary
  21 indexes such as the commit-graph.
  22
  23 When common porcelain operations that create objects are run, they
  24 will check whether the repository has grown substantially since the
  25 last maintenance, and if so run `git gc` automatically. See `gc.auto`
  26 below for how to disable this behavior.
  27
  28 Running `git gc` manually should only be needed when adding objects to
  29 a repository without regularly running such porcelain commands, to do
  30 a one-off repository optimization, or e.g. to clean up a suboptimal
  31 mass-import. See the "PACKFILE OPTIMIZATION" section in
  32 linkgit:git-fast-import[1] for more details on the import case.
  33
  34 OPTIONS
  35 -------
  36
  37 --aggressive::
  38         Usually 'git gc' runs very quickly while providing good disk
  39         space utilization and performance.  This option will cause
  40         'git gc' to more aggressively optimize the repository at the expense
  41         of taking much more time.  The effects of this optimization are
  42         mostly persistent. See the "AGGRESSIVE" section below for details.
  43
  44 --auto::
  45         With this option, 'git gc' checks whether any housekeeping is
  46         required; if not, it exits without performing any work.
  47 +
  48 See the `gc.auto` option in the "CONFIGURATION" section below for how
  49 this heuristic works.
  50 +
  51 Once housekeeping is triggered by exceeding the limits of
  52 configuration options such as `gc.auto` and `gc.autoPackLimit`, all
  53 other housekeeping tasks (e.g. rerere, working trees, reflog...) will
  54 be performed as well.
  55
  56
  57 --cruft::
  58         When expiring unreachable objects, pack them separately into a
  59         cruft pack instead of storing them as loose objects.
  60
  61 --prune=<date>::
  62         Prune loose objects older than date (default is 2 weeks ago,
  63         overridable by the config variable `gc.pruneExpire`).
  64         --prune=now prunes loose objects regardless of their age and
  65         increases the risk of corruption if another process is writing to
  66         the repository concurrently; see "NOTES" below. --prune is on by
  67         default.
  68
  69 --no-prune::
  70         Do not prune any loose objects.
  71
  72 --quiet::
  73         Suppress all progress reports.
  74
  75 --force::
  76         Force `git gc` to run even if there may be another `git gc`
  77         instance running on this repository.
  78
  79 --keep-largest-pack::
  80         All packs except the largest pack and those marked with a
  81         `.keep` files are consolidated into a single pack. When this
  82         option is used, `gc.bigPackThreshold` is ignored.
  83
  84 AGGRESSIVE
  85 ----------
  86
  87 When the `--aggressive` option is supplied, linkgit:git-repack[1] will
  88 be invoked with the `-f` flag, which in turn will pass
  89 `--no-reuse-delta` to linkgit:git-pack-objects[1]. This will throw
  90 away any existing deltas and re-compute them, at the expense of
  91 spending much more time on the repacking.
  92
  93 The effects of this are mostly persistent, e.g. when packs and loose
  94 objects are coalesced into one another pack the existing deltas in
  95 that pack might get re-used, but there are also various cases where we
  96 might pick a sub-optimal delta from a newer pack instead.
  97
  98 Furthermore, supplying `--aggressive` will tweak the `--depth` and
  99 `--window` options passed to linkgit:git-repack[1]. See the
 100 `gc.aggressiveDepth` and `gc.aggressiveWindow` settings below. By
 101 using a larger window size we're more likely to find more optimal
 102 deltas.
 103
 104 It's probably not worth it to use this option on a given repository
 105 without running tailored performance benchmarks on it. It takes a lot
 106 more time, and the resulting space/delta optimization may or may not
 107 be worth it. Not using this at all is the right trade-off for most
 108 users and their repositories.
 109
 110 CONFIGURATION
 111 -------------
 112
 113 The below documentation is the same as what's found in
 114 linkgit:git-config[1]:
 115
 116 include::config/gc.txt[]
 117
 118 NOTES
 119 -----
 120
 121 'git gc' tries very hard not to delete objects that are referenced
 122 anywhere in your repository. In particular, it will keep not only
 123 objects referenced by your current set of branches and tags, but also
 124 objects referenced by the index, remote-tracking branches, reflogs
 125 (which may reference commits in branches that were later amended or
 126 rewound), and anything else in the refs/* namespace. Note that a note
 127 (of the kind created by 'git notes') attached to an object does not
 128 contribute in keeping the object alive. If you are expecting some
 129 objects to be deleted and they aren't, check all of those locations
 130 and decide whether it makes sense in your case to remove those
 131 references.
 132
 133 On the other hand, when 'git gc' runs concurrently with another process,
 134 there is a risk of it deleting an object that the other process is using
 135 but hasn't created a reference to. This may just cause the other process
 136 to fail or may corrupt the repository if the other process later adds a
 137 reference to the deleted object. Git has two features that significantly
 138 mitigate this problem:
 139
 140 . Any object with modification time newer than the `--prune` date is kept,
 141   along with everything reachable from it.
 142
 143 . Most operations that add an object to the database update the
 144   modification time of the object if it is already present so that #1
 145   applies.
 146
 147 However, these features fall short of a complete solution, so users who
 148 run commands concurrently have to live with some risk of corruption (which
 149 seems to be low in practice).
 150
 151 HOOKS
 152 -----
 153
 154 The 'git gc --auto' command will run the 'pre-auto-gc' hook.  See
 155 linkgit:githooks[5] for more information.
 156
 157
 158 SEE ALSO
 159 --------
 160 linkgit:git-prune[1]
 161 linkgit:git-reflog[1]
 162 linkgit:git-repack[1]
 163 linkgit:git-rerere[1]
 164
 165 GIT
 166 ---
 167 Part of the linkgit:git[1] suite