git-commit-vandalism/Documentation/git-pack-objects.txt
Dana How 960ccca680 Custom compression levels for objects and packs
Add config variables pack.compression and core.loosecompression ,
and switch --compression=level to pack-objects.

Loose objects will be compressed using core.loosecompression if set,
else core.compression if set, else Z_BEST_SPEED.
Packed objects will be compressed using --compression=level if seen,
else pack.compression if set, else core.compression if set,
else Z_DEFAULT_COMPRESSION.  This is the "pack compression level".

Loose objects added to a pack undeltified will be recompressed
to the pack compression level if it is unequal to the current
loose compression level by the preceding rules,  or if the loose
object was written while core.legacyheaders = true.  Newly
deltified loose objects are always compressed to the current
pack compression level.

Previously packed objects added to a pack are recompressed
to the current pack compression level exactly when their
deltification status changes,  since the previous pack data
cannot be reused.

In either case,  the --no-reuse-object switch from the first
patch below will always force recompression to the current pack
compression level,  instead of assuming the pack compression level
hasn't changed and pack data can be reused when possible.

This applies on top of the following patches from Nicolas Pitre:
[PATCH] allow for undeltified objects not to be reused
[PATCH] make "repack -f" imply "pack-objects --no-reuse-object"

Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
2007-05-10 15:23:09 -07:00

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git-pack-objects(1)
===================
NAME
----
git-pack-objects - Create a packed archive of objects
SYNOPSIS
--------
[verse]
'git-pack-objects' [-q] [--no-reuse-delta] [--delta-base-offset] [--non-empty]
[--local] [--incremental] [--window=N] [--depth=N] [--all-progress]
[--revs [--unpacked | --all]*] [--stdout | base-name] < 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.
A packed archive is an efficient way to transfer set of objects
between two repositories, and also is an archival format which
is efficient to access. The packed archive format (.pack) is
designed to be unpackable without having anything else, but for
random access, accompanied with the pack index file (.idx).
'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.
Placing both in the pack/ subdirectory of $GIT_OBJECT_DIRECTORY (or
any of the directories on $GIT_ALTERNATE_OBJECT_DIRECTORIES)
enables git to read from such an archive.
In a packed archive, an object is either stored as a compressed
whole, or as a difference from some other object. The latter is
often called a delta.
OPTIONS
-------
base-name::
Write into a pair of files (.pack and .idx), using
<base-name> to determine the name of the created file.
When this option is used, the two files are written in
<base-name>-<SHA1>.{pack,idx} files. <SHA1> is a hash
of the sorted object names to make the resulting filename
based on the pack content, and written to the standard
output of the command.
--stdout::
Write the pack contents (what would have been written to
.pack file) out to the standard output.
--revs::
Read the revision arguments from the standard input, instead of
individual object names. The revision arguments are processed
the same way as gitlink:git-rev-list[1] with `--objects` flag
uses its `commit` arguments to build the list of objects it
outputs. The objects on the resulting list are packed.
--unpacked::
This implies `--revs`. When processing the list of
revision arguments read from the standard input, limit
the objects packed to those that are not already packed.
--all::
This implies `--revs`. In addition to the list of
revision arguments read from the standard input, pretend
as if all refs under `$GIT_DIR/refs` are specified to be
included.
--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.
--incremental::
This flag causes an object already in a pack ignored
even if it appears in the standard input.
--local::
This flag is similar to `--incremental`; instead of
ignoring all packed objects, it only ignores objects
that are packed and not in the local object store
(i.e. borrowed from an alternate).
--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 deltification 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.
-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.
Data copied from loose objects will be recompressed
if core.legacyheaders was true when they were created or if
the loose compression level (see core.loosecompression and
core.compression) is now a different value than the pack
compression level. Add --no-reuse-object if you want to force
a uniform compression level on all data no matter the source.
--delta-base-offset::
A packed archive can express base object of a delta as
either 20-byte object name or as an offset in the
stream, but older version of git does not 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.
--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.
Author
------
Written by Linus Torvalds <torvalds@osdl.org>
Documentation
-------------
Documentation by Junio C Hamano
See Also
--------
gitlink:git-rev-list[1]
gitlink:git-repack[1]
gitlink:git-prune-packed[1]
GIT
---
Part of the gitlink:git[7] suite