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

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

9       git pack-objects [-q | --progress | --all-progress] [--all-progress-implied]
10               [--no-reuse-delta] [--delta-base-offset] [--non-empty]
11               [--local] [--incremental] [--window=<n>] [--depth=<n>]
12               [--revs [--unpacked | --all]] [--keep-pack=<pack-name>]
13               [--stdout [--filter=<filter-spec>] | base-name]
14               [--shallow] [--keep-true-parents] [--sparse] < object-list
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16

DESCRIPTION

18       Reads list of objects from the standard input, and writes either one or
19       more packed archives with the specified base-name to disk, or a packed
20       archive to the standard output.
21
22       A packed archive is an efficient way to transfer a set of objects
23       between two repositories as well as an access efficient archival
24       format. In a packed archive, an object is either stored as a compressed
25       whole or as a difference from some other object. The latter is often
26       called a delta.
27
28       The packed archive format (.pack) is designed to be self-contained so
29       that it can be unpacked without any further information. Therefore,
30       each object that a delta depends upon must be present within the pack.
31
32       A pack index file (.idx) is generated for fast, random access to the
33       objects in the pack. Placing both the index file (.idx) and the packed
34       archive (.pack) in the pack/ subdirectory of $GIT_OBJECT_DIRECTORY (or
35       any of the directories on $GIT_ALTERNATE_OBJECT_DIRECTORIES) enables
36       Git to read from the pack archive.
37
38       The git unpack-objects command can read the packed archive and expand
39       the objects contained in the pack into "one-file one-object" format;
40       this is typically done by the smart-pull commands when a pack is
41       created on-the-fly for efficient network transport by their peers.
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OPTIONS

44       base-name
45           Write into pairs of files (.pack and .idx), using <base-name> to
46           determine the name of the created file. When this option is used,
47           the two files in a pair are written in
48           <base-name>-<SHA-1>.{pack,idx} files. <SHA-1> is a hash based on
49           the pack content and is written to the standard output of the
50           command.
51
52       --stdout
53           Write the pack contents (what would have been written to .pack
54           file) out to the standard output.
55
56       --revs
57           Read the revision arguments from the standard input, instead of
58           individual object names. The revision arguments are processed the
59           same way as git rev-list with the --objects flag uses its commit
60           arguments to build the list of objects it outputs. The objects on
61           the resulting list are packed. Besides revisions, --not or
62           --shallow <SHA-1> lines are also accepted.
63
64       --unpacked
65           This implies --revs. When processing the list of revision arguments
66           read from the standard input, limit the objects packed to those
67           that are not already packed.
68
69       --all
70           This implies --revs. In addition to the list of revision arguments
71           read from the standard input, pretend as if all refs under refs/
72           are specified to be included.
73
74       --include-tag
75           Include unasked-for annotated tags if the object they reference was
76           included in the resulting packfile. This can be useful to send new
77           tags to native Git clients.
78
79       --window=<n>, --depth=<n>
80           These two options affect how the objects contained in the pack are
81           stored using delta compression. The objects are first internally
82           sorted by type, size and optionally names and compared against the
83           other objects within --window to see if using delta compression
84           saves space. --depth limits the maximum delta depth; making it too
85           deep affects the performance on the unpacker side, because delta
86           data needs to be applied that many times to get to the necessary
87           object.
88
89           The default value for --window is 10 and --depth is 50. The maximum
90           depth is 4095.
91
92       --window-memory=<n>
93           This option provides an additional limit on top of --window; the
94           window size will dynamically scale down so as to not take up more
95           than <n> bytes in memory. This is useful in repositories with a mix
96           of large and small objects to not run out of memory with a large
97           window, but still be able to take advantage of the large window for
98           the smaller objects. The size can be suffixed with "k", "m", or
99           "g".  --window-memory=0 makes memory usage unlimited. The default
100           is taken from the pack.windowMemory configuration variable.
101
102       --max-pack-size=<n>
103           In unusual scenarios, you may not be able to create files larger
104           than a certain size on your filesystem, and this option can be used
105           to tell the command to split the output packfile into multiple
106           independent packfiles, each not larger than the given size. The
107           size can be suffixed with "k", "m", or "g". The minimum size
108           allowed is limited to 1 MiB. This option prevents the creation of a
109           bitmap index. The default is unlimited, unless the config variable
110           pack.packSizeLimit is set.
111
112       --honor-pack-keep
113           This flag causes an object already in a local pack that has a .keep
114           file to be ignored, even if it would have otherwise been packed.
115
116       --keep-pack=<pack-name>
117           This flag causes an object already in the given pack to be ignored,
118           even if it would have otherwise been packed.  <pack-name> is the
119           the pack file name without leading directory (e.g.  pack-123.pack).
120           The option could be specified multiple times to keep multiple
121           packs.
122
123       --incremental
124           This flag causes an object already in a pack to be ignored even if
125           it would have otherwise been packed.
126
127       --local
128           This flag causes an object that is borrowed from an alternate
129           object store to be ignored even if it would have otherwise been
130           packed.
131
132       --non-empty
133           Only create a packed archive if it would contain at least one
134           object.
135
136       --progress
137           Progress status is reported on the standard error stream by default
138           when it is attached to a terminal, unless -q is specified. This
139           flag forces progress status even if the standard error stream is
140           not directed to a terminal.
141
142       --all-progress
143           When --stdout is specified then progress report is displayed during
144           the object count and compression phases but inhibited during the
145           write-out phase. The reason is that in some cases the output stream
146           is directly linked to another command which may wish to display
147           progress status of its own as it processes incoming pack data. This
148           flag is like --progress except that it forces progress report for
149           the write-out phase as well even if --stdout is used.
150
151       --all-progress-implied
152           This is used to imply --all-progress whenever progress display is
153           activated. Unlike --all-progress this flag doesn’t actually force
154           any progress display by itself.
155
156       -q
157           This flag makes the command not to report its progress on the
158           standard error stream.
159
160       --no-reuse-delta
161           When creating a packed archive in a repository that has existing
162           packs, the command reuses existing deltas. This sometimes results
163           in a slightly suboptimal pack. This flag tells the command not to
164           reuse existing deltas but compute them from scratch.
165
166       --no-reuse-object
167           This flag tells the command not to reuse existing object data at
168           all, including non deltified object, forcing recompression of
169           everything. This implies --no-reuse-delta. Useful only in the
170           obscure case where wholesale enforcement of a different compression
171           level on the packed data is desired.
172
173       --compression=<n>
174           Specifies compression level for newly-compressed data in the
175           generated pack. If not specified, pack compression level is
176           determined first by pack.compression, then by core.compression, and
177           defaults to -1, the zlib default, if neither is set. Add
178           --no-reuse-object if you want to force a uniform compression level
179           on all data no matter the source.
180
181       --sparse
182           Use the "sparse" algorithm to determine which objects to include in
183           the pack, when combined with the "--revs" option. This algorithm
184           only walks trees that appear in paths that introduce new objects.
185           This can have significant performance benefits when computing a
186           pack to send a small change. However, it is possible that extra
187           objects are added to the pack-file if the included commits contain
188           certain types of direct renames.
189
190       --thin
191           Create a "thin" pack by omitting the common objects between a
192           sender and a receiver in order to reduce network transfer. This
193           option only makes sense in conjunction with --stdout.
194
195           Note: A thin pack violates the packed archive format by omitting
196           required objects and is thus unusable by Git without making it
197           self-contained. Use git index-pack --fix-thin (see git-index-
198           pack(1)) to restore the self-contained property.
199
200       --shallow
201           Optimize a pack that will be provided to a client with a shallow
202           repository. This option, combined with --thin, can result in a
203           smaller pack at the cost of speed.
204
205       --delta-base-offset
206           A packed archive can express the base object of a delta as either a
207           20-byte object name or as an offset in the stream, but ancient
208           versions of Git don’t understand the latter. By default, git
209           pack-objects only uses the former format for better compatibility.
210           This option allows the command to use the latter format for
211           compactness. Depending on the average delta chain length, this
212           option typically shrinks the resulting packfile by 3-5 per-cent.
213
214           Note: Porcelain commands such as git gc (see git-gc(1)), git repack
215           (see git-repack(1)) pass this option by default in modern Git when
216           they put objects in your repository into pack files. So does git
217           bundle (see git-bundle(1)) when it creates a bundle.
218
219       --threads=<n>
220           Specifies the number of threads to spawn when searching for best
221           delta matches. This requires that pack-objects be compiled with
222           pthreads otherwise this option is ignored with a warning. This is
223           meant to reduce packing time on multiprocessor machines. The
224           required amount of memory for the delta search window is however
225           multiplied by the number of threads. Specifying 0 will cause Git to
226           auto-detect the number of CPU’s and set the number of threads
227           accordingly.
228
229       --index-version=<version>[,<offset>]
230           This is intended to be used by the test suite only. It allows to
231           force the version for the generated pack index, and to force 64-bit
232           index entries on objects located above the given offset.
233
234       --keep-true-parents
235           With this option, parents that are hidden by grafts are packed
236           nevertheless.
237
238       --filter=<filter-spec>
239           Requires --stdout. Omits certain objects (usually blobs) from the
240           resulting packfile. See git-rev-list(1) for valid <filter-spec>
241           forms.
242
243       --no-filter
244           Turns off any previous --filter= argument.
245
246       --missing=<missing-action>
247           A debug option to help with future "partial clone" development.
248           This option specifies how missing objects are handled.
249
250           The form --missing=error requests that pack-objects stop with an
251           error if a missing object is encountered. This is the default
252           action.
253
254           The form --missing=allow-any will allow object traversal to
255           continue if a missing object is encountered. Missing objects will
256           silently be omitted from the results.
257
258           The form --missing=allow-promisor is like allow-any, but will only
259           allow object traversal to continue for EXPECTED promisor missing
260           objects. Unexpected missing object will raise an error.
261
262       --exclude-promisor-objects
263           Omit objects that are known to be in the promisor remote. (This
264           option has the purpose of operating only on locally created
265           objects, so that when we repack, we still maintain a distinction
266           between locally created objects [without .promisor] and objects
267           from the promisor remote [with .promisor].) This is used with
268           partial clone.
269
270       --keep-unreachable
271           Objects unreachable from the refs in packs named with --unpacked=
272           option are added to the resulting pack, in addition to the
273           reachable objects that are not in packs marked with *.keep files.
274           This implies --revs.
275
276       --pack-loose-unreachable
277           Pack unreachable loose objects (and their loose counterparts
278           removed). This implies --revs.
279
280       --unpack-unreachable
281           Keep unreachable objects in loose form. This implies --revs.
282
283       --delta-islands
284           Restrict delta matches based on "islands". See DELTA ISLANDS below.
285

DELTA ISLANDS

287       When possible, pack-objects tries to reuse existing on-disk deltas to
288       avoid having to search for new ones on the fly. This is an important
289       optimization for serving fetches, because it means the server can avoid
290       inflating most objects at all and just send the bytes directly from
291       disk. This optimization can’t work when an object is stored as a delta
292       against a base which the receiver does not have (and which we are not
293       already sending). In that case the server "breaks" the delta and has to
294       find a new one, which has a high CPU cost. Therefore it’s important for
295       performance that the set of objects in on-disk delta relationships
296       match what a client would fetch.
297
298       In a normal repository, this tends to work automatically. The objects
299       are mostly reachable from the branches and tags, and that’s what
300       clients fetch. Any deltas we find on the server are likely to be
301       between objects the client has or will have.
302
303       But in some repository setups, you may have several related but
304       separate groups of ref tips, with clients tending to fetch those groups
305       independently. For example, imagine that you are hosting several
306       "forks" of a repository in a single shared object store, and letting
307       clients view them as separate repositories through GIT_NAMESPACE or
308       separate repos using the alternates mechanism. A naive repack may find
309       that the optimal delta for an object is against a base that is only
310       found in another fork. But when a client fetches, they will not have
311       the base object, and we’ll have to find a new delta on the fly.
312
313       A similar situation may exist if you have many refs outside of
314       refs/heads/ and refs/tags/ that point to related objects (e.g.,
315       refs/pull or refs/changes used by some hosting providers). By default,
316       clients fetch only heads and tags, and deltas against objects found
317       only in those other groups cannot be sent as-is.
318
319       Delta islands solve this problem by allowing you to group your refs
320       into distinct "islands". Pack-objects computes which objects are
321       reachable from which islands, and refuses to make a delta from an
322       object A against a base which is not present in all of A's islands.
323       This results in slightly larger packs (because we miss some delta
324       opportunities), but guarantees that a fetch of one island will not have
325       to recompute deltas on the fly due to crossing island boundaries.
326
327       When repacking with delta islands the delta window tends to get clogged
328       with candidates that are forbidden by the config. Repacking with a big
329       --window helps (and doesn’t take as long as it otherwise might because
330       we can reject some object pairs based on islands before doing any
331       computation on the content).
332
333       Islands are configured via the pack.island option, which can be
334       specified multiple times. Each value is a left-anchored regular
335       expressions matching refnames. For example:
336
337           [pack]
338           island = refs/heads/
339           island = refs/tags/
340
341
342       puts heads and tags into an island (whose name is the empty string; see
343       below for more on naming). Any refs which do not match those regular
344       expressions (e.g., refs/pull/123) is not in any island. Any object
345       which is reachable only from refs/pull/ (but not heads or tags) is
346       therefore not a candidate to be used as a base for refs/heads/.
347
348       Refs are grouped into islands based on their "names", and two regexes
349       that produce the same name are considered to be in the same island. The
350       names are computed from the regexes by concatenating any capture groups
351       from the regex, with a - dash in between. (And if there are no capture
352       groups, then the name is the empty string, as in the above example.)
353       This allows you to create arbitrary numbers of islands. Only up to 14
354       such capture groups are supported though.
355
356       For example, imagine you store the refs for each fork in
357       refs/virtual/ID, where ID is a numeric identifier. You might then
358       configure:
359
360           [pack]
361           island = refs/virtual/([0-9]+)/heads/
362           island = refs/virtual/([0-9]+)/tags/
363           island = refs/virtual/([0-9]+)/(pull)/
364
365
366       That puts the heads and tags for each fork in their own island (named
367       "1234" or similar), and the pull refs for each go into their own
368       "1234-pull".
369
370       Note that we pick a single island for each regex to go into, using
371       "last one wins" ordering (which allows repo-specific config to take
372       precedence over user-wide config, and so forth).
373

SEE ALSO

375       git-rev-list(1) git-repack(1) git-prune-packed(1)
376

GIT

378       Part of the git(1) suite
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382Git 2.21.0                        02/24/2019               GIT-PACK-OBJECTS(1)
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