98f8854c94
As detailed in the previous changes to t5309-pack-delta-cycles.sh, the logic within 'git index-pack' to analyze an incoming thin packfile with REF_DELTAs is suspect. The algorithm is overly cautious around delta cycles, and that leads in fact to failing even when there is no cycle. This change adjusts the algorithm to no longer fail in these cases. In fact, these cycle cases will no longer fail but more importantly the valid cases will no longer fail, either. The resulting packfile from the --fix-thin operation will not have cycles either since REF_DELTAs are forbidden from the on-disk format and OFS_DELTAs are impossible to write as a cycle. The crux of the matter is how the algorithm works when the REF_DELTAs point to base objects that exist in the local repository. When reading the thin packfile, the object IDs for the delta objects are unknown so we do not have the delta chain structure automatically. Instead, we need to start somewhere by selecting a delta whose base is inside our current object database. Consider the case where the packfile has two REF_DELTA objects, A and B, and the delta chain looks like "A depends on B" and "B depends on C" for some third object C, where C is already in the current repository. The algorithm _should_ start with all objects that depend on C, finding B, and then moving on to all objects depending on B, finding A. However, if the repository also already has object B, then the delta chain can be analyzed in a different order. The deltas with base B can be analyzed first, finding A, and then the deltas with base C are analyzed, finding B. The algorithm currently continues to look for objects that depend on B, finding A again. This fails due to A's 'real_type' member already being overwritten from OBJ_REF_DELTA to the correct object type. This scenario is possible in a typical 'git fetch' where the client does not advertise B as a 'have' but requests A as a 'want' (and C is noticed as a common object based on other 'have's). The reason this isn't typically seen is that most Git servers use OFS_DELTAs to represent deltas within a packfile. However, if a server uses only REF_DELTAs, then this kind of issue can occur. There is nothing in the explicit packfile format that states this use of inter-pack REF_DELTA is incorrect, only that REF_DELTAs should not be used in the on-disk representation to avoid cycles. This die() was introduced in |
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| builtin | ||
| ci | ||
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| ewah | ||
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| reftable | ||
| sha1 | ||
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| CODE_OF_CONDUCT.md | ||
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| INSTALL | ||
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| Makefile | ||
| README.md | ||
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| SECURITY.md | ||
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README.md
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