ddac965965
Each reftable may contain multiple types of blocks for refs, objects and
reflog records, where each of these may have an index that makes it more
efficient to find the records. It was observed that the index for log
records can become corrupted under certain circumstances, where the
first entry of the index points into the object index instead of to the
log records.
As it turns out, this corruption can occur whenever we write a log index
as well as at least one additional index. Writing records and their index
is basically a two-step process:
1. We write all blocks for the corresponding record. Each block that
gets written is added to a list of blocks to index.
2. Once all blocks were written we finish the section. If at least two
blocks have been added to the list of blocks to index then we will
now write the index for those blocks and flush it, as well.
When we have a very large number of blocks then we may decide to write a
multi-level index, which is why we also keep track of the list of the
index blocks in the same way as we previously kept track of the blocks
to index.
Now when we have finished writing all index blocks we clear the index
and flush the last block to disk. This is done in the wrong order though
because flushing the block to disk will re-add it to the list of blocks
to be indexed. The result is that the next section we are about to write
will have an entry in the list of blocks to index that points to the
last block of the preceding section's index, which will corrupt the log
index.
Fix this corruption by clearing the index after having written the last
block.
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).
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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