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ff233d8dda
After eff45daab8 ("repository: enable SHA-256 support by default",
2020-07-29), vanilla builds of Git enable the user to run, e.g.,
git init --object-format=sha256
and hack away. This can be a good way to gain experience with the
SHA-256 world, e.g., to find bugs that
GIT_TEST_DEFAULT_HASH=sha256 make test
doesn't spot.
But it really is a separate world: Such SHA-256 repos will live entirely
separate from the (by now fairly large) set of SHA-1 repos. Interacting
across the border is possible in principle, e.g., through "diff + apply"
(or "format-patch + am"), but even that has its limitations: Applying a
SHA-256 diff in a SHA-1 repo works in the simple case, but if you need
to resort to `-3`, you're out of luck.
Similarly, "push + pull" should work, but you really will be operating
mostly offset from the rest of the world. That might be ok by the time
you initialize your repository, and it might be ok for several months
after that, but there might come a day when you're starting to regret
your use of `git init --object-format=sha256` and have dug yourself into
a fairly deep hole.
There are currently topics in flight to document our data formats and
protocols regarding SHA-256 and in some cases (midx and commit-graph),
we're considering adjusting how the file formats indicate which object
format to use.
Wherever `--object-format` is mentioned in our documentation, let's make
it clear that using it with "sha256" is experimental. If we later need
to explain why we can't handle data we generated back in 2020, we can
always point to this paragraph we're adding here.
By "include::"-ing a small blurb, we should be able to be consistent
throughout the documentation and can eventually gradually tone down the
severity of this text. One day, we might even use it to start phasing
out `--object-format=sha1`, but let's not get ahead of ourselves...
There's also `extensions.objectFormat`, but it's only mentioned three
times. Twice where we're adding this new disclaimer and in the third
spot we already have a "do not edit" warning. From there, interested
readers should eventually find this new one that we're adding here.
Because `GIT_DEFAULT_HASH` provides another entry point to this
functionality, document the experimental nature of it too.
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
118 lines
3.9 KiB
Text
118 lines
3.9 KiB
Text
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>] <pack-file>
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'git index-pack' --stdin [--fix-thin] [--keep] [-v] [-o <index-file>]
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[<pack-file>]
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DESCRIPTION
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-----------
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Reads a packed archive (.pack) from the specified file, and
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builds a pack index file (.idx) for it. The packed archive
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together with the pack index can then be placed in the
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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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--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, but rather than 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::
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Die, if the pack contains broken objects or links.
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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::
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Die if the pack contains broken objects. For internal use only.
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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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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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