git-pack-objects(1) — Linux manual page


GIT-PACK-OBJECTS(1)            Git Manual            GIT-PACK-OBJECTS(1)

NAME         top

       git-pack-objects - Create a packed archive of objects

SYNOPSIS         top

       git pack-objects [-q | --progress | --all-progress] [--all-progress-implied]
               [--no-reuse-delta] [--delta-base-offset] [--non-empty]
               [--local] [--incremental] [--window=<n>] [--depth=<n>]
               [--revs [--unpacked | --all]] [--keep-pack=<pack-name>]
               [--cruft] [--cruft-expiration=<time>]
               [--stdout [--filter=<filter-spec>] | <base-name>]
               [--shallow] [--keep-true-parents] [--[no-]sparse] < <object-list>

DESCRIPTION         top

       Reads list of objects from the standard input, and writes either
       one or more packed archives with the specified base-name to disk,
       or a packed archive to the standard output.

       A packed archive is an efficient way to transfer a set of objects
       between two repositories as well as an access efficient archival
       format. In a packed archive, an object is either stored as a
       compressed whole or as a difference from some other object. The
       latter is often called a delta.

       The packed archive format (.pack) is designed to be
       self-contained so that it can be unpacked without any further
       information. Therefore, each object that a delta depends upon
       must be present within the pack.

       A pack index file (.idx) is generated for fast, random access to
       the objects in the pack. Placing both the index file (.idx) and
       the packed archive (.pack) in the pack/ subdirectory of
       $GIT_OBJECT_DIRECTORY (or any of the directories on
       $GIT_ALTERNATE_OBJECT_DIRECTORIES) enables Git to read from the
       pack archive.

       The git unpack-objects command can read the packed archive and
       expand the objects contained in the pack into "one-file
       one-object" format; this is typically done by the smart-pull
       commands when a pack is created on-the-fly for efficient network
       transport by their peers.

OPTIONS         top

           Write into pairs of files (.pack and .idx), using <base-name>
           to determine the name of the created file. When this option
           is used, the two files in a pair are written in
           <base-name>-<SHA-1>.{pack,idx} files. <SHA-1> is a hash based
           on the pack content and is written to the standard output of
           the command.

           Write the pack contents (what would have been written to
           .pack file) out to the standard output.

           Read the revision arguments from the standard input, instead
           of individual object names. The revision arguments are
           processed the same way as git rev-list with the --objects
           flag uses its commit arguments to build the list of objects
           it outputs. The objects on the resulting list are packed.
           Besides revisions, --not or --shallow <SHA-1> lines are also

           This implies --revs. When processing the list of revision
           arguments read from the standard input, limit the objects
           packed to those that are not already packed.

           This implies --revs. In addition to the list of revision
           arguments read from the standard input, pretend as if all
           refs under refs/ are specified to be included.

           Include unasked-for annotated tags if the object they
           reference was included in the resulting packfile. This can be
           useful to send new tags to native Git clients.

           Read the basenames of packfiles (e.g., pack-1234abcd.pack)
           from the standard input, instead of object names or revision
           arguments. The resulting pack contains all objects listed in
           the included packs (those not beginning with ^), excluding
           any objects listed in the excluded packs (beginning with ^).

           Incompatible with --revs, or options that imply --revs (such
           as --all), with the exception of --unpacked, which is

           Packs unreachable objects into a separate "cruft" pack,
           denoted by the existence of a .mtimes file. Typically used by
           git repack --cruft. Callers provide a list of pack names and
           indicate which packs will remain in the repository, along
           with which packs will be deleted (indicated by the - prefix).
           The contents of the cruft pack are all objects not contained
           in the surviving packs which have not exceeded the grace
           period (see --cruft-expiration below), or which have exceeded
           the grace period, but are reachable from an other object
           which hasn’t.

           When the input lists a pack containing all reachable objects
           (and lists all other packs as pending deletion), the
           corresponding cruft pack will contain all unreachable objects
           (with mtime newer than the --cruft-expiration) along with any
           unreachable objects whose mtime is older than the
           --cruft-expiration, but are reachable from an unreachable
           object whose mtime is newer than the --cruft-expiration).

           Incompatible with --unpack-unreachable, --keep-unreachable,
           --pack-loose-unreachable, --stdin-packs, as well as any other
           options which imply --revs.

           If specified, objects are eliminated from the cruft pack if
           they have an mtime older than <approxidate>. If unspecified
           (and given --cruft), then no objects are eliminated.

       --window=<n>, --depth=<n>
           These two options affect how the objects contained in the
           pack are stored using delta compression. The objects are
           first internally sorted by type, size and optionally names
           and compared against the other objects within --window to see
           if using delta compression saves space. --depth limits the
           maximum delta depth; making it too deep affects the
           performance on the unpacker side, because delta data needs to
           be applied that many times to get to the necessary object.

           The default value for --window is 10 and --depth is 50. The
           maximum depth is 4095.

           This option provides an additional limit on top of --window;
           the window size will dynamically scale down so as to not take
           up more than <n> bytes in memory. This is useful in
           repositories with a mix of large and small objects to not run
           out of memory with a large window, but still be able to take
           advantage of the large window for the smaller objects. The
           size can be suffixed with "k", "m", or "g".
           --window-memory=0 makes memory usage unlimited. The default
           is taken from the pack.windowMemory configuration variable.

           In unusual scenarios, you may not be able to create files
           larger than a certain size on your filesystem, and this
           option can be used to tell the command to split the output
           packfile into multiple independent packfiles, each not larger
           than the given size. The size can be suffixed with "k", "m",
           or "g". The minimum size allowed is limited to 1 MiB. The
           default is unlimited, unless the config variable
           pack.packSizeLimit is set. Note that this option may result
           in a larger and slower repository; see the discussion in

           This flag causes an object already in a local pack that has a
           .keep file to be ignored, even if it would have otherwise
           been packed.

           This flag causes an object already in the given pack to be
           ignored, even if it would have otherwise been packed.
           <pack-name> is the pack file name without leading directory
           (e.g.  pack-123.pack). The option could be specified multiple
           times to keep multiple packs.

           This flag causes an object already in a pack to be ignored
           even if it would have otherwise been packed.

           This flag causes an object that is borrowed from an alternate
           object store to be ignored even if it would have otherwise
           been packed.

           Only create a packed archive if it would contain at least one

           Progress status is reported on the standard error stream by
           default when it is attached to a terminal, unless -q is
           specified. This flag forces progress status even if the
           standard error stream is not directed to a terminal.

           When --stdout is specified then progress report is displayed
           during the object count and compression phases but inhibited
           during the write-out phase. The reason is that in some cases
           the output stream is directly linked to another command which
           may wish to display progress status of its own as it
           processes incoming pack data. This flag is like --progress
           except that it forces progress report for the write-out phase
           as well even if --stdout is used.

           This is used to imply --all-progress whenever progress
           display is activated. Unlike --all-progress this flag doesn’t
           actually force any progress display by itself.

           This flag makes the command not to report its progress on the
           standard error stream.

           When creating a packed archive in a repository that has
           existing packs, the command reuses existing deltas. This
           sometimes results in a slightly suboptimal pack. This flag
           tells the command not to reuse existing deltas but compute
           them from scratch.

           This flag tells the command not to reuse existing object data
           at all, including non deltified object, forcing recompression
           of everything. This implies --no-reuse-delta. Useful only in
           the obscure case where wholesale enforcement of a different
           compression level on the packed data is desired.

           Specifies compression level for newly-compressed data in the
           generated pack. If not specified, pack compression level is
           determined first by pack.compression, then by
           core.compression, and defaults to -1, the zlib default, if
           neither is set. Add --no-reuse-object if you want to force a
           uniform compression level on all data no matter the source.

           Toggle the "sparse" algorithm to determine which objects to
           include in the pack, when combined with the "--revs" option.
           This algorithm only walks trees that appear in paths that
           introduce new objects. This can have significant performance
           benefits when computing a pack to send a small change.
           However, it is possible that extra objects are added to the
           pack-file if the included commits contain certain types of
           direct renames. If this option is not included, it defaults
           to the value of pack.useSparse, which is true unless
           otherwise specified.

           Create a "thin" pack by omitting the common objects between a
           sender and a receiver in order to reduce network transfer.
           This option only makes sense in conjunction with --stdout.

           Note: A thin pack violates the packed archive format by
           omitting required objects and is thus unusable by Git without
           making it self-contained. Use git index-pack --fix-thin (see
           git-index-pack(1)) to restore the self-contained property.

           Optimize a pack that will be provided to a client with a
           shallow repository. This option, combined with --thin, can
           result in a smaller pack at the cost of speed.

           A packed archive can express the base object of a delta as
           either a 20-byte object name or as an offset in the stream,
           but ancient versions of Git don’t understand the latter. By
           default, git pack-objects only uses the former format for
           better compatibility. This option allows the command to use
           the latter format for compactness. Depending on the average
           delta chain length, this option typically shrinks the
           resulting packfile by 3-5 per-cent.

           Note: Porcelain commands such as git gc (see git-gc(1)), git
           repack (see git-repack(1)) pass this option by default in
           modern Git when they put objects in your repository into pack
           files. So does git bundle (see git-bundle(1)) when it creates
           a bundle.

           Specifies the number of threads to spawn when searching for
           best delta matches. This requires that pack-objects be
           compiled with pthreads otherwise this option is ignored with
           a warning. This is meant to reduce packing time on
           multiprocessor machines. The required amount of memory for
           the delta search window is however multiplied by the number
           of threads. Specifying 0 will cause Git to auto-detect the
           number of CPU’s and set the number of threads accordingly.

           This is intended to be used by the test suite only. It allows
           to force the version for the generated pack index, and to
           force 64-bit index entries on objects located above the given

           With this option, parents that are hidden by grafts are
           packed nevertheless.

           Omits certain objects (usually blobs) from the resulting
           packfile. See git-rev-list(1) for valid <filter-spec> forms.

           Turns off any previous --filter= argument.

           A debug option to help with future "partial clone"
           development. This option specifies how missing objects are

           The form --missing=error requests that pack-objects stop with
           an error if a missing object is encountered. If the
           repository is a partial clone, an attempt to fetch missing
           objects will be made before declaring them missing. This is
           the default action.

           The form --missing=allow-any will allow object traversal to
           continue if a missing object is encountered. No fetch of a
           missing object will occur. Missing objects will silently be
           omitted from the results.

           The form --missing=allow-promisor is like allow-any, but will
           only allow object traversal to continue for EXPECTED promisor
           missing objects. No fetch of a missing object will occur. An
           unexpected missing object will raise an error.

           Omit objects that are known to be in the promisor remote.
           (This option has the purpose of operating only on locally
           created objects, so that when we repack, we still maintain a
           distinction between locally created objects [without
           .promisor] and objects from the promisor remote [with
           .promisor].) This is used with partial clone.

           Objects unreachable from the refs in packs named with
           --unpacked= option are added to the resulting pack, in
           addition to the reachable objects that are not in packs
           marked with *.keep files. This implies --revs.

           Pack unreachable loose objects (and their loose counterparts
           removed). This implies --revs.

           Keep unreachable objects in loose form. This implies --revs.

           Restrict delta matches based on "islands". See DELTA ISLANDS

DELTA ISLANDS         top

       When possible, pack-objects tries to reuse existing on-disk
       deltas to avoid having to search for new ones on the fly. This is
       an important optimization for serving fetches, because it means
       the server can avoid inflating most objects at all and just send
       the bytes directly from disk. This optimization can’t work when
       an object is stored as a delta against a base which the receiver
       does not have (and which we are not already sending). In that
       case the server "breaks" the delta and has to find a new one,
       which has a high CPU cost. Therefore it’s important for
       performance that the set of objects in on-disk delta
       relationships match what a client would fetch.

       In a normal repository, this tends to work automatically. The
       objects are mostly reachable from the branches and tags, and
       that’s what clients fetch. Any deltas we find on the server are
       likely to be between objects the client has or will have.

       But in some repository setups, you may have several related but
       separate groups of ref tips, with clients tending to fetch those
       groups independently. For example, imagine that you are hosting
       several "forks" of a repository in a single shared object store,
       and letting clients view them as separate repositories through
       GIT_NAMESPACE or separate repos using the alternates mechanism. A
       naive repack may find that the optimal delta for an object is
       against a base that is only found in another fork. But when a
       client fetches, they will not have the base object, and we’ll
       have to find a new delta on the fly.

       A similar situation may exist if you have many refs outside of
       refs/heads/ and refs/tags/ that point to related objects (e.g.,
       refs/pull or refs/changes used by some hosting providers). By
       default, clients fetch only heads and tags, and deltas against
       objects found only in those other groups cannot be sent as-is.

       Delta islands solve this problem by allowing you to group your
       refs into distinct "islands". Pack-objects computes which objects
       are reachable from which islands, and refuses to make a delta
       from an object A against a base which is not present in all of
       A's islands. This results in slightly larger packs (because we
       miss some delta opportunities), but guarantees that a fetch of
       one island will not have to recompute deltas on the fly due to
       crossing island boundaries.

       When repacking with delta islands the delta window tends to get
       clogged with candidates that are forbidden by the config.
       Repacking with a big --window helps (and doesn’t take as long as
       it otherwise might because we can reject some object pairs based
       on islands before doing any computation on the content).

       Islands are configured via the pack.island option, which can be
       specified multiple times. Each value is a left-anchored regular
       expressions matching refnames. For example:

           island = refs/heads/
           island = refs/tags/

       puts heads and tags into an island (whose name is the empty
       string; see below for more on naming). Any refs which do not
       match those regular expressions (e.g., refs/pull/123) is not in
       any island. Any object which is reachable only from refs/pull/
       (but not heads or tags) is therefore not a candidate to be used
       as a base for refs/heads/.

       Refs are grouped into islands based on their "names", and two
       regexes that produce the same name are considered to be in the
       same island. The names are computed from the regexes by
       concatenating any capture groups from the regex, with a - dash in
       between. (And if there are no capture groups, then the name is
       the empty string, as in the above example.) This allows you to
       create arbitrary numbers of islands. Only up to 14 such capture
       groups are supported though.

       For example, imagine you store the refs for each fork in
       refs/virtual/ID, where ID is a numeric identifier. You might then

           island = refs/virtual/([0-9]+)/heads/
           island = refs/virtual/([0-9]+)/tags/
           island = refs/virtual/([0-9]+)/(pull)/

       That puts the heads and tags for each fork in their own island
       (named "1234" or similar), and the pull refs for each go into
       their own "1234-pull".

       Note that we pick a single island for each regex to go into,
       using "last one wins" ordering (which allows repo-specific config
       to take precedence over user-wide config, and so forth).


       Various configuration variables affect packing, see git-config(1)
       (search for "pack" and "delta").

       Notably, delta compression is not used on objects larger than the
       core.bigFileThreshold configuration variable and on files with
       the attribute delta set to false.

SEE ALSO         top

       git-rev-list(1) git-repack(1) git-prune-packed(1)

GIT         top

       Part of the git(1) suite

COLOPHON         top

       This page is part of the git (Git distributed version control
       system) project.  Information about the project can be found at
       ⟨⟩.  If you have a bug report for this manual
       page, see ⟨⟩.  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2023-12-20.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Git         2023-12-20            GIT-PACK-OBJECTS(1)

Pages that refer to this page: git(1)git-bundle(1)git-config(1)git-gc(1)git-index-pack(1)git-pack-redundant(1)git-prune-packed(1)git-repack(1)git-rev-list(1)git-show-index(1)gitformat-pack(5)