git-commit-vandalism/Documentation/git-repack.txt
Jeff King e26a8c4721 repack: extend --keep-unreachable to loose objects
If you use "repack -adk" currently, we will pack all objects
that are already packed into the new pack, and then drop the
old packs. However, loose unreachable objects will be left
as-is. In theory these are meant to expire eventually with
"git prune". But if you are using "repack -k", you probably
want to keep things forever and therefore do not run "git
prune" at all. Meaning those loose objects may build up over
time and end up fooling any object-count heuristics (such as
the one done by "gc --auto", though since git-gc does not
support "repack -k", this really applies to whatever custom
scripts people might have driving "repack -k").

With this patch, we instead stuff any loose unreachable
objects into the pack along with the already-packed
unreachable objects. This may seem wasteful, but it is
really no more so than using "repack -k" in the first place.
We are at a slight disadvantage, in that we have no useful
ordering for the result, or names to hand to the delta code.
However, this is again no worse than what "repack -k" is
already doing for the packed objects. The packing of these
objects doesn't matter much because they should not be
accessed frequently (unless they actually _do_ become
referenced, but then they would get moved to a different
part of the packfile during the next repack).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-06-14 13:57:45 -07:00

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git-repack(1)
=============
NAME
----
git-repack - Pack unpacked objects in a repository
SYNOPSIS
--------
[verse]
'git repack' [-a] [-A] [-d] [-f] [-F] [-l] [-n] [-q] [-b] [--window=<n>] [--depth=<n>]
DESCRIPTION
-----------
This command is used to combine all objects that do not currently
reside in a "pack", into a pack. It can also be used to re-organize
existing packs into a single, more efficient pack.
A pack is a collection of objects, individually compressed, with
delta compression applied, stored in a single file, with an
associated index file.
Packs are used to reduce the load on mirror systems, backup
engines, disk storage, etc.
OPTIONS
-------
-a::
Instead of incrementally packing the unpacked objects,
pack everything referenced into a single pack.
Especially useful when packing a repository that is used
for private development. Use
with '-d'. This will clean up the objects that `git prune`
leaves behind, but `git fsck --full --dangling` shows as
dangling.
+
Note that users fetching over dumb protocols will have to fetch the
whole new pack in order to get any contained object, no matter how many
other objects in that pack they already have locally.
-A::
Same as `-a`, unless '-d' is used. Then any unreachable
objects in a previous pack become loose, unpacked objects,
instead of being left in the old pack. Unreachable objects
are never intentionally added to a pack, even when repacking.
This option prevents unreachable objects from being immediately
deleted by way of being left in the old pack and then
removed. Instead, the loose unreachable objects
will be pruned according to normal expiry rules
with the next 'git gc' invocation. See linkgit:git-gc[1].
-d::
After packing, if the newly created packs make some
existing packs redundant, remove the redundant packs.
Also run 'git prune-packed' to remove redundant
loose object files.
-l::
Pass the `--local` option to 'git pack-objects'. See
linkgit:git-pack-objects[1].
-f::
Pass the `--no-reuse-delta` option to `git-pack-objects`, see
linkgit:git-pack-objects[1].
-F::
Pass the `--no-reuse-object` option to `git-pack-objects`, see
linkgit:git-pack-objects[1].
-q::
Pass the `-q` option to 'git pack-objects'. See
linkgit:git-pack-objects[1].
-n::
Do not update the server information with
'git update-server-info'. This option skips
updating local catalog files needed to publish
this repository (or a direct copy of it)
over HTTP or FTP. See linkgit:git-update-server-info[1].
--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.
--window-memory=<n>::
This option provides an additional limit on top of `--window`;
the window size will dynamically scale down so as to not take
up more than '<n>' bytes in memory. This is useful in
repositories with a mix of large and small objects to not run
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.
--max-pack-size=<n>::
Maximum size of each output pack file. 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
prevents the creation of a bitmap index.
The default is unlimited, unless the config variable
`pack.packSizeLimit` is set.
-b::
--write-bitmap-index::
Write a reachability bitmap index as part of the repack. This
only makes sense when used with `-a` or `-A`, as the bitmaps
must be able to refer to all reachable objects. This option
overrides the setting of `repack.writeBitmaps`. This option
has no effect if multiple packfiles are created.
--pack-kept-objects::
Include objects in `.keep` files when repacking. Note that we
still do not delete `.keep` packs after `pack-objects` finishes.
This means that we may duplicate objects, but this makes the
option safe to use when there are concurrent pushes or fetches.
This option is generally only useful if you are writing bitmaps
with `-b` or `repack.writeBitmaps`, as it ensures that the
bitmapped packfile has the necessary objects.
--unpack-unreachable=<when>::
When loosening unreachable objects, do not bother loosening any
objects older than `<when>`. This can be used to optimize out
the write of any objects that would be immediately pruned by
a follow-up `git prune`.
-k::
--keep-unreachable::
When used with `-ad`, any unreachable objects from existing
packs will be appended to the end of the packfile instead of
being removed. In addition, any unreachable loose objects will
be packed (and their loose counterparts removed).
Configuration
-------------
By default, the command passes `--delta-base-offset` option to
'git pack-objects'; this typically results in slightly smaller packs,
but the generated packs are incompatible with versions of Git older than
version 1.4.4. If you need to share your repository with such ancient Git
versions, either directly or via the dumb http protocol, then you
need to set the configuration variable `repack.UseDeltaBaseOffset` to
"false" and repack. Access from old Git versions over the native protocol
is unaffected by this option as the conversion is performed on the fly
as needed in that case.
SEE ALSO
--------
linkgit:git-pack-objects[1]
linkgit:git-prune-packed[1]
GIT
---
Part of the linkgit:git[1] suite