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