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+git-pack-objects(1)
+===================
+
+NAME
+----
+git-pack-objects - Create a packed archive of objects
+
+
+SYNOPSIS
+--------
+[verse]
+'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>]
+	[--stdout [--filter=<filter-spec>] | base-name]
+	[--shallow] [--keep-true-parents] [--sparse] < object-list
+
+
+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
+	<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.
+
+--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 <SHA-1>` 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.
+
+--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.
+
+--window-memory=<n>::
+	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.
+
+--max-pack-size=<n>::
+	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.
+	This option
+	prevents the creation of a bitmap index.
+	The default is unlimited, unless the config variable
+	`pack.packSizeLimit` is set.
+
+--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=<pack-name>::
+	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.
+
+--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=<n>::
+	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::
+	Use 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.
+
+--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 linkgit: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 linkgit:git-gc[1]),
+`git repack` (see linkgit: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 linkgit:git-bundle[1]) when it creates a bundle.
+
+--threads=<n>::
+	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=<version>[,<offset>]::
+	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=<filter-spec>::
+	Requires `--stdout`.  Omits certain objects (usually blobs) from
+	the resulting packfile.  See linkgit:git-rev-list[1] for valid
+	`<filter-spec>` forms.
+
+--no-filter::
+	Turns off any previous `--filter=` argument.
+
+--missing=<missing-action>::
+	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.  This is the default action.
++
+The form '--missing=allow-any' will allow object traversal to continue
+if a missing object is encountered.  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.
+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.
+
+
+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).
+
+SEE ALSO
+--------
+linkgit:git-rev-list[1]
+linkgit:git-repack[1]
+linkgit:git-prune-packed[1]
+
+GIT
+---
+Part of the linkgit:git[1] suite