c08589efdc
Teach index-pack to, when processing the objects in a pack with --promisor specified on the CLI, repack local objects (and the local objects that they refer to, recursively) referenced by these objects into promisor packs. This prevents the situation in which, when fetching from a promisor remote, we end up with promisor objects (newly fetched) referring to non-promisor objects (locally created prior to the fetch). This situation may arise if the client had previously pushed objects to the remote, for example. One issue that arises in this situation is that, if the non-promisor objects become inaccessible except through promisor objects (for example, if the branch pointing to them has moved to point to the promisor object that refers to them), then GC will garbage collect them. There are other ways to solve this, but the simplest seems to be to enforce the invariant that we don't have promisor objects referring to non-promisor objects. This repacking is done from index-pack to minimize the performance impact. During a fetch, the only time most objects are fully inflated in memory is when their object ID is computed, so we also scan the objects (to see which objects they refer to) during this time. Also to minimize the performance impact, an object is calculated to be local if it's a loose object or present in a non-promisor pack. (If it's also in a promisor pack or referred to by an object in a promisor pack, it is technically already a promisor object. But a misidentification of a promisor object as a non-promisor object is relatively benign here - we will thus repack that promisor object into a promisor pack, duplicating it in the object store, but there is no correctness issue, just an issue of inefficiency.) Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
161 lines
6.1 KiB
Plaintext
161 lines
6.1 KiB
Plaintext
git-index-pack(1)
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=================
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NAME
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----
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git-index-pack - Build pack index file for an existing packed archive
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SYNOPSIS
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--------
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[verse]
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'git index-pack' [-v] [-o <index-file>] [--[no-]rev-index] <pack-file>
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'git index-pack' --stdin [--fix-thin] [--keep] [-v] [-o <index-file>]
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[--[no-]rev-index] [<pack-file>]
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DESCRIPTION
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-----------
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Reads a packed archive (.pack) from the specified file,
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builds a pack index file (.idx) for it, and optionally writes a
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reverse-index (.rev) for the specified pack. The packed
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archive, together with the pack index, can then be placed in
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the objects/pack/ directory of a Git repository.
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OPTIONS
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-------
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-v::
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Be verbose about what is going on, including progress status.
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-o <index-file>::
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Write the generated pack index into the specified
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file. Without this option the name of pack index
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file is constructed from the name of packed archive
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file by replacing .pack with .idx (and the program
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fails if the name of packed archive does not end
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with .pack).
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--[no-]rev-index::
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When this flag is provided, generate a reverse index
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(a `.rev` file) corresponding to the given pack. If
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`--verify` is given, ensure that the existing
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reverse index is correct. Takes precedence over
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`pack.writeReverseIndex`.
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--stdin::
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When this flag is provided, the pack is read from stdin
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instead and a copy is then written to <pack-file>. If
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<pack-file> is not specified, the pack is written to
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objects/pack/ directory of the current Git repository with
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a default name determined from the pack content. If
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<pack-file> is not specified consider using --keep to
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prevent a race condition between this process and
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'git repack'.
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--fix-thin::
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Fix a "thin" pack produced by `git pack-objects --thin` (see
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linkgit:git-pack-objects[1] for details) by adding the
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excluded objects the deltified objects are based on to the
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pack. This option only makes sense in conjunction with --stdin.
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--keep::
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Before moving the index into its final destination
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create an empty .keep file for the associated pack file.
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This option is usually necessary with --stdin to prevent a
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simultaneous 'git repack' process from deleting
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the newly constructed pack and index before refs can be
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updated to use objects contained in the pack.
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--keep=<msg>::
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Like --keep, create a .keep file before moving the index into
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its final destination. However, instead of creating an empty file
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place '<msg>' followed by an LF into the .keep file. The '<msg>'
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message can later be searched for within all .keep files to
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locate any which have outlived their usefulness.
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--index-version=<version>[,<offset>]::
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This is intended to be used by the test suite only. It allows
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to force the version for the generated pack index, and to force
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64-bit index entries on objects located above the given offset.
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--strict[=<msg-id>=<severity>...]::
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Die, if the pack contains broken objects or links. An optional
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comma-separated list of `<msg-id>=<severity>` can be passed to change
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the severity of some possible issues, e.g.,
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`--strict="missingEmail=ignore,badTagName=error"`. See the entry for the
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`fsck.<msg-id>` configuration options in linkgit:git-fsck[1] for more
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information on the possible values of `<msg-id>` and `<severity>`.
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--progress-title::
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For internal use only.
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+
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Set the title of the progress bar. The title is "Receiving objects" by
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default and "Indexing objects" when `--stdin` is specified.
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--check-self-contained-and-connected::
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Die if the pack contains broken links. For internal use only.
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--fsck-objects[=<msg-id>=<severity>...]::
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Die if the pack contains broken objects, but unlike `--strict`, don't
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choke on broken links. If the pack contains a tree pointing to a
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.gitmodules blob that does not exist, prints the hash of that blob
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(for the caller to check) after the hash that goes into the name of the
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pack/idx file (see "Notes").
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+
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An optional comma-separated list of `<msg-id>=<severity>` can be passed to
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change the severity of some possible issues, e.g.,
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`--fsck-objects="missingEmail=ignore,badTagName=ignore"`. See the entry for the
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`fsck.<msg-id>` configuration options in linkgit:git-fsck[1] for more
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information on the possible values of `<msg-id>` and `<severity>`.
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--threads=<n>::
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Specifies the number of threads to spawn when resolving
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deltas. This requires that index-pack be compiled with
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pthreads otherwise this option is ignored with a warning.
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This is meant to reduce packing time on multiprocessor
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machines. The required amount of memory for the delta search
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window is however multiplied by the number of threads.
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Specifying 0 will cause Git to auto-detect the number of CPU's
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and use maximum 3 threads.
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--max-input-size=<size>::
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Die, if the pack is larger than <size>.
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--object-format=<hash-algorithm>::
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Specify the given object format (hash algorithm) for the pack. The valid
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values are 'sha1' and (if enabled) 'sha256'. The default is the algorithm for
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the current repository (set by `extensions.objectFormat`), or 'sha1' if no
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value is set or outside a repository.
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+
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This option cannot be used with --stdin.
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+
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include::object-format-disclaimer.txt[]
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--promisor[=<message>]::
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Before committing the pack-index, create a .promisor file for this
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pack. Particularly helpful when writing a promisor pack with --fix-thin
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since the name of the pack is not final until the pack has been fully
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written. If a `<message>` is provided, then that content will be
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written to the .promisor file for future reference. See
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link:technical/partial-clone.html[partial clone] for more information.
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+
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Also, if there are objects in the given pack that references non-promisor
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objects (in the repo), repacks those non-promisor objects into a promisor
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pack. This avoids a situation in which a repo has non-promisor objects that are
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accessible through promisor objects.
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NOTES
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-----
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Once the index has been created, the hash that goes into the name of
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the pack/idx file is printed to stdout. If --stdin was
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also used then this is prefixed by either "pack\t", or "keep\t" if a
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new .keep file was successfully created. This is useful to remove a
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.keep file used as a lock to prevent the race with 'git repack'
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mentioned above.
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GIT
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---
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Part of the linkgit:git[1] suite
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