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 --[no-]cruft::
  58         When expiring unreachable objects, pack them separately into a
  59         cruft pack instead of storing them as loose objects. `--cruft`
  60         is on by default.
  61
  62 --prune=<date>::
  63         Prune loose objects older than date (default is 2 weeks ago,
  64         overridable by the config variable `gc.pruneExpire`).
  65         --prune=now prunes loose objects regardless of their age and
  66         increases the risk of corruption if another process is writing to
  67         the repository concurrently; see "NOTES" below. --prune is on by
  68         default.
  69
  70 --no-prune::
  71         Do not prune any loose objects.
  72
  73 --quiet::
  74         Suppress all progress reports.
  75
  76 --force::
  77         Force `git gc` to run even if there may be another `git gc`
  78         instance running on this repository.
  79
  80 --keep-largest-pack::
  81         All packs except the largest non-cruft pack, any packs marked
  82         with a `.keep` file, and any cruft pack(s) are consolidated into
  83         a single pack. When this option is used, `gc.bigPackThreshold`
  84         is ignored.
  85
  86 AGGRESSIVE
  87 ----------
  88
  89 When the `--aggressive` option is supplied, linkgit:git-repack[1] will
  90 be invoked with the `-f` flag, which in turn will pass
  91 `--no-reuse-delta` to linkgit:git-pack-objects[1]. This will throw
  92 away any existing deltas and re-compute them, at the expense of
  93 spending much more time on the repacking.
  94
  95 The effects of this are mostly persistent, e.g. when packs and loose
  96 objects are coalesced into one another pack the existing deltas in
  97 that pack might get re-used, but there are also various cases where we
  98 might pick a sub-optimal delta from a newer pack instead.
  99
 100 Furthermore, supplying `--aggressive` will tweak the `--depth` and
 101 `--window` options passed to linkgit:git-repack[1]. See the
 102 `gc.aggressiveDepth` and `gc.aggressiveWindow` settings below. By
 103 using a larger window size we're more likely to find more optimal
 104 deltas.
 105
 106 It's probably not worth it to use this option on a given repository
 107 without running tailored performance benchmarks on it. It takes a lot
 108 more time, and the resulting space/delta optimization may or may not
 109 be worth it. Not using this at all is the right trade-off for most
 110 users and their repositories.
 111
 112 CONFIGURATION
 113 -------------
 114
 115 include::includes/cmd-config-section-all.txt[]
 116
 117 include::config/gc.txt[]
 118
 119 NOTES
 120 -----
 121
 122 'git gc' tries very hard not to delete objects that are referenced
 123 anywhere in your repository. In particular, it will keep not only
 124 objects referenced by your current set of branches and tags, but also
 125 objects referenced by the index, remote-tracking branches, reflogs
 126 (which may reference commits in branches that were later amended or
 127 rewound), and anything else in the refs/* namespace. Note that a note
 128 (of the kind created by 'git notes') attached to an object does not
 129 contribute in keeping the object alive. If you are expecting some
 130 objects to be deleted and they aren't, check all of those locations
 131 and decide whether it makes sense in your case to remove those
 132 references.
 133
 134 On the other hand, when 'git gc' runs concurrently with another process,
 135 there is a risk of it deleting an object that the other process is using
 136 but hasn't created a reference to. This may just cause the other process
 137 to fail or may corrupt the repository if the other process later adds a
 138 reference to the deleted object. Git has two features that significantly
 139 mitigate this problem:
 140
 141 . Any object with modification time newer than the `--prune` date is kept,
 142   along with everything reachable from it.
 143
 144 . Most operations that add an object to the database update the
 145   modification time of the object if it is already present so that #1
 146   applies.
 147
 148 However, these features fall short of a complete solution, so users who
 149 run commands concurrently have to live with some risk of corruption (which
 150 seems to be low in practice).
 151
 152 HOOKS
 153 -----
 154
 155 The 'git gc --auto' command will run the 'pre-auto-gc' hook.  See
 156 linkgit:githooks[5] for more information.
 157
 158
 159 SEE ALSO
 160 --------
 161 linkgit:git-prune[1]
 162 linkgit:git-reflog[1]
 163 linkgit:git-repack[1]
 164 linkgit:git-rerere[1]
 165
 166 GIT
 167 ---
 168 Part of the linkgit:git[1] suite