Manual: git-pack-objects

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

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

SYNOPSIS
       git pack-objects [-q | --progress | --all-progress] [--all-progress-implied]
			  [--no-reuse-delta] [--delta-base-offset] [--non-empty]
			  [--local] [--incremental] [--window=] [--depth=]
			  [--revs [--unpacked | --all]] [--keep-pack=]
			  [--cruft] [--cruft-expiration=]
			  [--stdout [--filter=] | ]
			  [--shallow] [--keep-true-parents] [--[no-]sparse]
			  [--name-hash-version=] [--path-walk] < 

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

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

       --revs
	   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  lines are also accepted.

       --unpacked
	   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.

       --all
	   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-tag
	   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.

       --stdin-packs[=]
	   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 ^).

	   When mode is "follow", objects from packs not listed on stdin receive special treatment. Objects
	   within unlisted packs will be included if those objects are (1) reachable from the included
	   packs, and (2) not found in any excluded packs. This mode is useful, for example, to resurrect
	   once-unreachable objects found in cruft packs to generate packs which are closed under
	   reachability up to the boundary set by the excluded packs.

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

       --cruft
	   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.

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

       --window=, --depth=
	   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.

       --window-memory=
	   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  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.

       --max-pack-size=
	   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 pack.packSizeLimit.

       --honor-pack-keep
	   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.

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

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

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

       --non-empty
	   Only create a packed archive if it would contain at least one object.

       --progress
	   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.

       --all-progress
	   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.

       --all-progress-implied
	   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.

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

       --no-reuse-delta
	   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.

       --no-reuse-object
	   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.

       --compression=
	   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.

       --sparse, --no-sparse
	   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.

       --thin
	   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.

       --shallow
	   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.

       --delta-base-offset
	   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.

       --threads=
	   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.

       --index-version=[,]
	   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
	   offset.

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

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

       --no-filter
	   Turns off any previous --filter= argument.

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

	   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.

       --exclude-promisor-objects
	   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.

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

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

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

       --name-hash-version=
	   While performing delta compression, Git groups objects that may be similar based on heuristics
	   using the path to that object. While grouping objects by an exact path match is good for paths
	   with many versions, there are benefits for finding delta pairs across different full paths. Git
	   collects objects by type and then by a "name hash" of the path and then by size, hoping to group
	   objects that will compress well together.

	   The default name hash version is 1, which prioritizes hash locality by considering the final
	   bytes of the path as providing the maximum magnitude to the hash function. This version excels at
	   distinguishing short paths and finding renames across directories. However, the hash function
	   depends primarily on the final 16 bytes of the path. If there are many paths in the repo that
	   have the same final 16 bytes and differ only by parent directory, then this name-hash may lead to
	   too many collisions and cause poor results. At the moment, this version is required when writing
	   reachability bitmap files with --write-bitmap-index.

	   The name hash version 2 has similar locality features as version 1, except it considers each path
	   component separately and overlays the hashes with a shift. This still prioritizes the final bytes
	   of the path, but also "salts" the lower bits of the hash using the parent directory names. This
	   method allows for some of the locality benefits of version 1 while breaking most of the
	   collisions from a similarly-named file appearing in many different directories. At the moment,
	   this version is not allowed when writing reachability bitmap files with --write-bitmap-index and
	   it will be automatically changed to version 1.

       --path-walk
	   Perform compression by first organizing objects by path, then a second pass that compresses
	   across paths as normal. This has the potential to improve delta compression especially in the
	   presence of filenames that cause collisions in Git’s default name-hash algorithm.

	   Incompatible with --delta-islands, --shallow, or --filter. The --use-bitmap-index option will be
	   ignored in the presence of --path-walk.

DELTA ISLANDS
       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:

	   [pack]
	   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 configure:

	   [pack]
	   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).

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

GIT
       Part of the git(1) suite

Git 2.53.0					 03/02/2026				 GIT-PACK-OBJECTS(1)