When invoked with '--stdin-packs', pack-objects will generate a pack
which contains the objects found in the "included" packs, less any
objects from "excluded" packs.
Packs that exist in the repository but weren't specified as either
included or excluded are in practice treated like the latter, at least
in the sense that pack-objects won't include objects from those packs.
This behavior forces us to include any cruft pack(s) in a repository's
multi-pack index for the reasons described in ddee3703b3
(builtin/repack.c: add cruft packs to MIDX during geometric repack,
2022-05-20).
The full details are in ddee3703b3, but the gist is if you
have a once-unreachable object in a cruft pack which later becomes
reachable via one or more commits in a pack generated with
'--stdin-packs', you *have* to include that object in the MIDX via the
copy in the cruft pack, otherwise we cannot generate reachability
bitmaps for any commits which reach that object.
Note that the traversal here is best-effort, similar to the existing
traversal which provides name-hash hints. This means that the object
traversal may hand us back a blob that does not actually exist. We
*won't* see missing trees/commits with 'ignore_missing_links' because:
- missing commit parents are discarded at the commit traversal stage by
revision.c::process_parents()
- missing tag objects are discarded by revision.c::handle_commit()
- missing tree objects are discarded by the list-objects code in
list-objects.c::process_tree()
But we have to handle potentially-missing blobs specially by making a
separate check to ensure they exist in the repository. Failing to do so
would mean that we'd add an object to the packing list which doesn't
actually exist, rendering us unable to write out the pack.
This prepares us for new repacking behavior which will "resurrect"
objects found in cruft or otherwise unspecified packs when generating
new packs. In the context of geometric repacking, this may be used to
maintain a sequence of geometrically-repacked packs, the union of which
is closed under reachability, even in the case described earlier.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public
License version 2 (some parts of it are under different licenses,
compatible with the GPLv2). It was originally written by Linus
Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/
including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
Issues which are security relevant should be disclosed privately to
the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that
list the current status of various development topics to the mailing
list. The discussion following them give a good reference for
project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very
first version. He described the tool as "the stupid content tracker"
and the name as (depending on your mood):
random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
"global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
"goddamn idiotic truckload of sh*t": when it breaks
