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<!DOCTYPE sect2 SYSTEM "../../../dtd/dblite.dtd">

<sect2 lang="en" id="git-gc(1)">
    <title>git-gc(1)</title>
    <date>2024-07-02</date>
<revhistory><revision><date>2024-07-02</date></revision></revhistory>
<indexterm>
<primary>git-gc(1)</primary>
</indexterm>
<simplesect id="git-gc(1)__name">
<title>NAME</title>
<simpara>git-gc - Cleanup unnecessary files and optimize the local repository</simpara>
</simplesect>
<simplesect id="git-gc(1)__synopsis">
<title>SYNOPSIS</title>
<blockquote>
<literallayout><emphasis>git gc</emphasis> [--aggressive] [--auto] [--quiet] [--prune=&lt;date&gt; | --no-prune] [--force] [--keep-largest-pack]</literallayout>
</blockquote>
</simplesect>
<simplesect id="git-gc(1)__description">
<title>DESCRIPTION</title>
<simpara>Runs a number of housekeeping tasks within the current repository,
such as compressing file revisions (to reduce disk space and increase
performance), removing unreachable objects which may have been
created from prior invocations of <emphasis>git add</emphasis>, packing refs, pruning
reflog, rerere metadata or stale working trees. May also update ancillary
indexes such as the commit-graph.</simpara>
<simpara>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 <emphasis>git gc</emphasis> automatically. See <emphasis>gc.auto</emphasis>
below for how to disable this behavior.</simpara>
<simpara>Running <emphasis>git gc</emphasis> 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
<xref linkend="git-fast-import(1)" /> for more details on the import case.</simpara>
</simplesect>
<simplesect id="git-gc(1)__options">
<title>OPTIONS</title>
<variablelist>
<varlistentry>
<term>
--aggressive
</term>
<listitem>
<simpara>
        Usually <emphasis>git gc</emphasis> runs very quickly while providing good disk
        space utilization and performance.  This option will cause
        <emphasis>git gc</emphasis> to more aggressively optimize the repository at the expense
        of taking much more time.  The effects of this optimization are
        mostly persistent. See the "AGGRESSIVE" section below for details.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--auto
</term>
<listitem>
<simpara>
        With this option, <emphasis>git gc</emphasis> checks whether any housekeeping is
        required; if not, it exits without performing any work.
</simpara>
<simpara>See the <emphasis>gc.auto</emphasis> option in the "CONFIGURATION" section below for how
this heuristic works.</simpara>
<simpara>Once housekeeping is triggered by exceeding the limits of
configuration options such as <emphasis>gc.auto</emphasis> and <emphasis>gc.autoPackLimit</emphasis>, all
other housekeeping tasks (e.g. rerere, working trees, reflog&#8230;) will
be performed as well.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--[no-]cruft
</term>
<listitem>
<simpara>
        When expiring unreachable objects, pack them separately into a
        cruft pack instead of storing them as loose objects. <emphasis>--cruft</emphasis>
        is on by default.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--max-cruft-size=&lt;n&gt;
</term>
<listitem>
<simpara>
        When packing unreachable objects into a cruft pack, limit the
        size of new cruft packs to be at most <emphasis>&lt;n&gt;</emphasis> bytes. Overrides any
        value specified via the <emphasis>gc.maxCruftSize</emphasis> configuration. See
        the <emphasis>--max-cruft-size</emphasis> option of <xref linkend="git-repack(1)" /> for
        more.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--prune=&lt;date&gt;
</term>
<listitem>
<simpara>
        Prune loose objects older than date (default is 2 weeks ago,
        overridable by the config variable <emphasis>gc.pruneExpire</emphasis>).
        --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.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--no-prune
</term>
<listitem>
<simpara>
        Do not prune any loose objects.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--quiet
</term>
<listitem>
<simpara>
        Suppress all progress reports.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--force
</term>
<listitem>
<simpara>
        Force <emphasis>git gc</emphasis> to run even if there may be another <emphasis>git gc</emphasis>
        instance running on this repository.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
--keep-largest-pack
</term>
<listitem>
<simpara>
        All packs except the largest non-cruft pack, any packs marked
        with a <emphasis>.keep</emphasis> file, and any cruft pack(s) are consolidated into
        a single pack. When this option is used, <emphasis>gc.bigPackThreshold</emphasis>
        is ignored.
</simpara>
</listitem>
</varlistentry>
</variablelist>
</simplesect>
<simplesect id="git-gc(1)__aggressive">
<title>AGGRESSIVE</title>
<simpara>When the <emphasis>--aggressive</emphasis> option is supplied, <xref linkend="git-repack(1)" /> will
be invoked with the <emphasis>-f</emphasis> flag, which in turn will pass
<emphasis>--no-reuse-delta</emphasis> to <xref linkend="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.</simpara>
<simpara>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.</simpara>
<simpara>Furthermore, supplying <emphasis>--aggressive</emphasis> will tweak the <emphasis>--depth</emphasis> and
<emphasis>--window</emphasis> options passed to <xref linkend="git-repack(1)" />. See the
<emphasis>gc.aggressiveDepth</emphasis> and <emphasis>gc.aggressiveWindow</emphasis> settings below. By
using a larger window size we're more likely to find more optimal
deltas.</simpara>
<simpara>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.</simpara>
</simplesect>
<simplesect id="git-gc(1)__configuration">
<title>CONFIGURATION</title>
<simpara>Everything below this line in this section is selectively included
from the <xref linkend="git-config(1)" /> documentation. The content is the same
as what's found there:</simpara>
<variablelist>
<varlistentry>
<term>
gc.aggressiveDepth
</term>
<listitem>
<simpara>
        The depth parameter used in the delta compression
        algorithm used by <emphasis>git gc --aggressive</emphasis>.  This defaults
        to 50, which is the default for the <emphasis>--depth</emphasis> option when
        <emphasis>--aggressive</emphasis> isn't in use.
</simpara>
<simpara>See the documentation for the <emphasis>--depth</emphasis> option in
<xref linkend="git-repack(1)" /> for more details.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.aggressiveWindow
</term>
<listitem>
<simpara>
        The window size parameter used in the delta compression
        algorithm used by <emphasis>git gc --aggressive</emphasis>.  This defaults
        to 250, which is a much more aggressive window size than
        the default <emphasis>--window</emphasis> of 10.
</simpara>
<simpara>See the documentation for the <emphasis>--window</emphasis> option in
<xref linkend="git-repack(1)" /> for more details.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.auto
</term>
<listitem>
<simpara>
        When there are approximately more than this many loose
        objects in the repository, <emphasis>git gc --auto</emphasis> will pack them.
        Some Porcelain commands use this command to perform a
        light-weight garbage collection from time to time.  The
        default value is 6700.
</simpara>
<simpara>Setting this to 0 disables not only automatic packing based on the
number of loose objects, but also any other heuristic <emphasis>git gc --auto</emphasis> will
otherwise use to determine if there's work to do, such as
<emphasis>gc.autoPackLimit</emphasis>.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.autoPackLimit
</term>
<listitem>
<simpara>
        When there are more than this many packs that are not
        marked with <emphasis>*.keep</emphasis> file in the repository, <emphasis>git gc
        --auto</emphasis> consolidates them into one larger pack.  The
        default value is 50.  Setting this to 0 disables it.
        Setting <emphasis>gc.auto</emphasis> to 0 will also disable this.
</simpara>
<simpara>See the <emphasis>gc.bigPackThreshold</emphasis> configuration variable below. When in
use, it'll affect how the auto pack limit works.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.autoDetach
</term>
<listitem>
<simpara>
        Make <emphasis>git gc --auto</emphasis> return immediately and run in the background
        if the system supports it. Default is true.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.bigPackThreshold
</term>
<listitem>
<simpara>
        If non-zero, all non-cruft packs larger than this limit are kept
        when <emphasis>git gc</emphasis> is run. This is very similar to
        <emphasis>--keep-largest-pack</emphasis> except that all non-cruft packs that meet
        the threshold are kept, not just the largest pack. Defaults to
        zero. Common unit suffixes of <emphasis>k</emphasis>, <emphasis>m</emphasis>, or <emphasis>g</emphasis> are supported.
</simpara>
<simpara>Note that if the number of kept packs is more than gc.autoPackLimit,
this configuration variable is ignored, all packs except the base pack
will be repacked. After this the number of packs should go below
gc.autoPackLimit and gc.bigPackThreshold should be respected again.</simpara>
<simpara>If the amount of memory estimated for <emphasis>git repack</emphasis> to run smoothly is
not available and <emphasis>gc.bigPackThreshold</emphasis> is not set, the largest pack
will also be excluded (this is the equivalent of running <emphasis>git gc</emphasis> with
<emphasis>--keep-largest-pack</emphasis>).</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.writeCommitGraph
</term>
<listitem>
<simpara>
        If true, then gc will rewrite the commit-graph file when
        <xref linkend="git-gc(1)" /> is run. When using <emphasis>git gc --auto</emphasis>
        the commit-graph will be updated if housekeeping is
        required. Default is true. See <xref linkend="git-commit-graph(1)" />
        for details.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.logExpiry
</term>
<listitem>
<simpara>
        If the file gc.log exists, then <emphasis>git gc --auto</emphasis> will print
        its content and exit with status zero instead of running
        unless that file is more than <emphasis>gc.logExpiry</emphasis> old.  Default is
        "1.day".  See <emphasis>gc.pruneExpire</emphasis> for more ways to specify its
        value.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.packRefs
</term>
<listitem>
<simpara>
        Running <emphasis>git pack-refs</emphasis> in a repository renders it
        unclonable by Git versions prior to 1.5.1.2 over dumb
        transports such as HTTP.  This variable determines whether
        <emphasis>git gc</emphasis> runs <emphasis>git pack-refs</emphasis>. This can be set to <emphasis>notbare</emphasis>
        to enable it within all non-bare repos or it can be set to a
        boolean value.  The default is <emphasis>true</emphasis>.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.cruftPacks
</term>
<listitem>
<simpara>
        Store unreachable objects in a cruft pack (see
        <xref linkend="git-repack(1)" />) instead of as loose objects. The default
        is <emphasis>true</emphasis>.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.maxCruftSize
</term>
<listitem>
<simpara>
        Limit the size of new cruft packs when repacking. When
        specified in addition to <emphasis>--max-cruft-size</emphasis>, the command line
        option takes priority. See the <emphasis>--max-cruft-size</emphasis> option of
        <xref linkend="git-repack(1)" />.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.pruneExpire
</term>
<listitem>
<simpara>
        When <emphasis>git gc</emphasis> is run, it will call <emphasis>prune --expire 2.weeks.ago</emphasis>
        (and <emphasis>repack --cruft --cruft-expiration 2.weeks.ago</emphasis> if using
        cruft packs via <emphasis>gc.cruftPacks</emphasis> or <emphasis>--cruft</emphasis>).  Override the
        grace period with this config variable.  The value "now" may be
        used to disable this grace period and always prune unreachable
        objects immediately, or "never" may be used to suppress pruning.
        This feature helps prevent corruption when <emphasis>git gc</emphasis> runs
        concurrently with another process writing to the repository; see
        the "NOTES" section of <xref linkend="git-gc(1)" />.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.worktreePruneExpire
</term>
<listitem>
<simpara>
        When <emphasis>git gc</emphasis> is run, it calls
        <emphasis>git worktree prune --expire 3.months.ago</emphasis>.
        This config variable can be used to set a different grace
        period. The value "now" may be used to disable the grace
        period and prune <emphasis>$GIT_DIR/worktrees</emphasis> immediately, or "never"
        may be used to suppress pruning.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.reflogExpire
</term>
<term>
gc.&lt;pattern&gt;.reflogExpire
</term>
<listitem>
<simpara>
        <emphasis>git reflog expire</emphasis> removes reflog entries older than
        this time; defaults to 90 days. The value "now" expires all
        entries immediately, and "never" suppresses expiration
        altogether. With "&lt;pattern&gt;" (e.g.
        "refs/stash") in the middle the setting applies only to
        the refs that match the &lt;pattern&gt;.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.reflogExpireUnreachable
</term>
<term>
gc.&lt;pattern&gt;.reflogExpireUnreachable
</term>
<listitem>
<simpara>
        <emphasis>git reflog expire</emphasis> removes reflog entries older than
        this time and are not reachable from the current tip;
        defaults to 30 days. The value "now" expires all entries
        immediately, and "never" suppresses expiration altogether.
        With "&lt;pattern&gt;" (e.g. "refs/stash")
        in the middle, the setting applies only to the refs that
        match the &lt;pattern&gt;.
</simpara>
<simpara>These types of entries are generally created as a result of using <emphasis>git
commit --amend</emphasis> or <emphasis>git rebase</emphasis> 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, which is why the
default is more aggressive than <emphasis>gc.reflogExpire</emphasis>.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.recentObjectsHook
</term>
<listitem>
<simpara>
        When considering whether or not to remove an object (either when
        generating a cruft pack or storing unreachable objects as
        loose), use the shell to execute the specified command(s).
        Interpret their output as object IDs which Git will consider as
        "recent", regardless of their age. By treating their mtimes as
        "now", any objects (and their descendants) mentioned in the
        output will be kept regardless of their true age.
</simpara>
<simpara>Output must contain exactly one hex object ID per line, and nothing
else. Objects which cannot be found in the repository are ignored.
Multiple hooks are supported, but all must exit successfully, else the
operation (either generating a cruft pack or unpacking unreachable
objects) will be halted.</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.repackFilter
</term>
<listitem>
<simpara>
        When repacking, use the specified filter to move certain
        objects into a separate packfile.  See the
        <emphasis>--filter=&lt;filter-spec&gt;</emphasis> option of <xref linkend="git-repack(1)" />.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.repackFilterTo
</term>
<listitem>
<simpara>
        When repacking and using a filter, see <emphasis>gc.repackFilter</emphasis>, the
        specified location will be used to create the packfile
        containing the filtered out objects. <emphasis role="strong">WARNING:</emphasis> The
        specified location should be accessible, using for example the
        Git alternates mechanism, otherwise the repo could be
        considered corrupt by Git as it migh not be able to access the
        objects in that packfile. See the <emphasis>--filter-to=&lt;dir&gt;</emphasis> option
        of <xref linkend="git-repack(1)" /> and the <emphasis>objects/info/alternates</emphasis>
        section of <xref linkend="gitrepository-layout(5)" />.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.rerereResolved
</term>
<listitem>
<simpara>
        Records of conflicted merge you resolved earlier are
        kept for this many days when <emphasis>git rerere gc</emphasis> is run.
        You can also use more human-readable "1.month.ago", etc.
        The default is 60 days.  See <xref linkend="git-rerere(1)" />.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term>
gc.rerereUnresolved
</term>
<listitem>
<simpara>
        Records of conflicted merge you have not resolved are
        kept for this many days when <emphasis>git rerere gc</emphasis> is run.
        You can also use more human-readable "1.month.ago", etc.
        The default is 15 days.  See <xref linkend="git-rerere(1)" />.
</simpara>
</listitem>
</varlistentry>
</variablelist>
</simplesect>
<simplesect id="git-gc(1)__notes">
<title>NOTES</title>
<simpara><emphasis>git gc</emphasis> 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, reflogs
(which may reference commits in branches that were later amended or
rewound), and anything else in the refs/* namespace. Note that a note
(of the kind created by <emphasis>git notes</emphasis>) attached to an object does not
contribute in keeping the object alive. 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.</simpara>
<simpara>On the other hand, when <emphasis>git gc</emphasis> 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:</simpara>
<orderedlist numeration="arabic">
<listitem>
<simpara>
Any object with modification time newer than the <emphasis>--prune</emphasis> date is kept,
  along with everything reachable from it.
</simpara>
</listitem>
<listitem>
<simpara>
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.
</simpara>
</listitem>
</orderedlist>
<simpara>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).</simpara>
</simplesect>
<simplesect id="git-gc(1)__hooks">
<title>HOOKS</title>
<simpara>The <emphasis>git gc --auto</emphasis> command will run the <emphasis>pre-auto-gc</emphasis> hook.  See
<xref linkend="githooks(5)" /> for more information.</simpara>
</simplesect>
<simplesect id="git-gc(1)__see_also">
<title>SEE ALSO</title>
<simpara><xref linkend="git-prune(1)" />
<xref linkend="git-reflog(1)" />
<xref linkend="git-repack(1)" />
<xref linkend="git-rerere(1)" /></simpara>
</simplesect>
<simplesect id="git-gc(1)__git">
<title>GIT</title>
<simpara>Part of the <xref linkend="git(1)" /> suite</simpara>
</simplesect>
</sect2>
