aab7bea14f
When doing a `--geometric=<d>` repack, `git repack` determines a
splitting point among packs ordered by their object count such that:
- each pack above the split has at least `<d>` times as many objects
as the next-largest pack by object count, and
- the first pack above the split has at least `<d>` times as many
object as the sum of all packs below the split line combined
`git repack` then creates a pack containing all of the objects contained
in packs below the split line by running `git pack-objects
--stdin-packs` underneath. Once packs are moved into place, then any
packs below the split line are removed, since their objects were just
combined into a new pack.
But `git repack` tries to be careful to avoid removing a pack that it
just wrote, by checking:
struct packed_git *p = geometry->pack[i];
if (string_list_has_string(&names, hash_to_hex(p->hash)))
continue;
in the `delete_redundant` and `geometric` conditional towards the end of
`cmd_repack`.
But it's possible to trick `git repack` into not recognizing a pack that
it just wrote when `names` is out-of-order (which violates
`string_list_has_string()`'s assumption that the list is sorted and thus
binary search-able).
When this happens in just the right circumstances, it is possible to
remove a pack that we just wrote, leading to object corruption.
Luckily, this is quite difficult to provoke in practice (for a couple of
reasons):
- we ordinarily write just one pack, so `names` usually contains just
one entry, and is thus sorted
- when we do write more than one pack (e.g., due to `--max-pack-size`)
we have to: (a) write a pack identical to one that already
exists, (b) have that pack be below the split line, and (c) have
the set of packs written by `pack-objects` occur in an order which
tricks `string_list_has_string()`.
Demonstrate the above scenario in a failing test, which causes `git
repack --geometric` to write a pack which occurs below the split line,
_and_ fail to recognize that it wrote that pack.
The following patch will fix this bug.
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.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt 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>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
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).
To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org (not the Git list). The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
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