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Diffstat (limited to 'Documentation/git-pack-objects.txt')
| -rw-r--r-- | Documentation/git-pack-objects.txt | 175 |
1 files changed, 165 insertions, 10 deletions
diff --git a/Documentation/git-pack-objects.txt b/Documentation/git-pack-objects.txt index 19cdcd0..40c825c 100644 --- a/Documentation/git-pack-objects.txt +++ b/Documentation/git-pack-objects.txt @@ -12,14 +12,16 @@ SYNOPSIS '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]] [--stdout | base-name] + [--revs [--unpacked | --all]] [--keep-pack=<pack-name>] + [--stdout [--filter=<filter-spec>] | base-name] [--shallow] [--keep-true-parents] < object-list DESCRIPTION ----------- -Reads list of objects from the standard input, and writes a packed -archive with specified base-name, or to the standard output. +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 @@ -47,9 +49,9 @@ transport by their peers. OPTIONS ------- base-name:: - Write into a pair of files (.pack and .idx), using + 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 are written in + 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. @@ -94,7 +96,9 @@ base-name:: 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 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`; @@ -104,13 +108,17 @@ base-name:: 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, which is the - default. + `--window-memory=0` makes memory usage unlimited. The default + is taken from the `pack.windowMemory` configuration variable. --max-pack-size=<n>:: - Maximum size of each output pack file. The size can be suffixed with + 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. - If specified, multiple packfiles may be created, which also + This option prevents the creation of a bitmap index. The default is unlimited, unless the config variable `pack.packSizeLimit` is set. @@ -120,6 +128,13 @@ base-name:: 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 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. @@ -231,6 +246,146 @@ So does `git bundle` (see linkgit:git-bundle[1]) when it creates a bundle. 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] |