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When describing a blob, we traverse from HEAD, remembering each commit we saw, and then checking each blob to report the containing commit. But if we haven't seen any commits at all, we'll segfault (we store the "current" commit as an oid initialized to the null oid, causing lookup_commit_reference() to return NULL). This shouldn't be able to happen normally. We always start our traversal at HEAD, which must be a commit (a property which is enforced by the refs code). But you can trigger the segfault like this: blob=$(echo foo | git hash-object -w --stdin) echo $blob >.git/HEAD git describe $blob We can instead catch this case and return an empty result, which hits the usual "we didn't find $blob while traversing HEAD" error. This is a minor lie in that we did "find" the blob. And this even hints at a bigger problem in this code: what if the traversal pointed to the blob as _not_ part of a commit at all, but we had previously filled in the recorded "current commit"? One could imagine this happening due to a tag pointing directly to the blob in question. But that can't happen, because we only traverse from HEAD, never from any other refs. And the intent of the blob-describing code is to find blobs within commits. So I think this matches the original intent as closely as we can (and again, this segfault cannot be triggered without corrupting your repository!). The test here does not use the formula above, which works only for the files backend (and not reftables). Instead we use another loophole to create the bogus state using only Git commands. See the comment in the test for details. Signed-off-by: Jeff King <peff@peff.net> 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>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(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