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b2755c15e2
The hash context is supposed to be updated via the `git_hash_algo` structure, which contains a list of function pointers to update, clone or finalize a hashing context. This requires the callers to track which algorithm was used to initialize the context and continue to use the exact same algorithm. If they fail to do that correctly, it can happen that we start to access context state of one hash algorithm with functions of a different hash algorithm. The result would typically be a segfault, as could be seen e.g. in the patches part of98422943f0(Merge branch 'ps/weak-sha1-for-tail-sum-fix', 2025-01-01). The situation was significantly improved starting with04292c3796(hash.h: drop unsafe_ function variants, 2025-01-23) and its parent commits. These refactorings ensure that it is not possible to mix up safe and unsafe variants of the same hash algorithm anymore. But in theory, it is still possible to mix up different hash algorithms with each other, even though this is a lot less likely to happen. But still, we can do better: instead of asking the caller to remember the hash algorithm used to initialize a context, we can instead make the context itself remember which algorithm it has been initialized with. If we do so, callers can use a set of generic helpers to update the context and don't need to be aware of the hash algorithm at all anymore. Adapt the context initialization functions to store the hash algorithm in the hashing context and introduce these generic helpers. Callers will be adapted in the subsequent commit. Signed-off-by: Patrick Steinhardt <ps@pks.im> 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 to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://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