reftable: file format documentation

Shawn Pearce explains:

Some repositories contain a lot of references (e.g. android at 866k,
rails at 31k). The reftable format provides:

- Near constant time lookup for any single reference, even when the
  repository is cold and not in process or kernel cache.
- Near constant time verification if a SHA-1 is referred to by at least
  one reference (for allow-tip-sha1-in-want).
- Efficient lookup of an entire namespace, such as `refs/tags/`.
- Support atomic push `O(size_of_update)` operations.
- Combine reflog storage with ref storage.

This file format spec was originally written in July, 2017 by Shawn
Pearce.  Some refinements since then were made by Shawn and by Han-Wen
Nienhuys based on experiences implementing and experimenting with the
format.  (All of this was in the context of our work at Google and
Google is happy to contribute the result to the Git project.)

Imported from JGit[1]'s current version (c217d33ff,
"Documentation/technical/reftable: improve repo layout", 2020-02-04)
of Documentation/technical/reftable.md and converted to asciidoc by
running

  pandoc -t asciidoc -f markdown reftable.md >reftable.txt

using pandoc 2.2.1.  The result required the following additional
minor changes:

- removed the [TOC] directive to add a table of contents, since
  asciidoc does not support it
- replaced git-scm.com/docs links with linkgit: directives that link
  to other pages within Git's documentation

[1] https://eclipse.googlesource.com/jgit/jgit

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2 files changed
tree: 8232984d440a236b01f067332f748215928e10f5
  1. .github/
  2. block-sha1/
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  6. contrib/
  7. Documentation/
  8. ewah/
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  24. xdiff/
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  161. fuzz-pack-headers.c
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  163. generate-cmdlist.sh
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  165. gettext.c
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  167. git-add--interactive.perl
  168. git-archimport.perl
  169. git-bisect.sh
  170. git-compat-util.h
  171. git-cvsexportcommit.perl
  172. git-cvsimport.perl
  173. git-cvsserver.perl
  174. git-difftool--helper.sh
  175. git-filter-branch.sh
  176. git-instaweb.sh
  177. git-merge-octopus.sh
  178. git-merge-one-file.sh
  179. git-merge-resolve.sh
  180. git-mergetool--lib.sh
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  182. git-p4.py
  183. git-parse-remote.sh
  184. git-quiltimport.sh
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  186. git-request-pull.sh
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  190. git-submodule.sh
  191. git-svn.perl
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  216. INSTALL
  217. interdiff.c
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  220. json-writer.c
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  240. list.h
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  245. log-tree.c
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  257. merge-blobs.c
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  276. object.c
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  278. oid-array.c
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  280. oidmap.c
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  284. pack-bitmap-write.c
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  296. pager.c
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  318. prompt.c
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  322. prune-packed.c
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  326. range-diff.c
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  328. reachable.c
  329. reachable.h
  330. read-cache.c
  331. README.md
  332. rebase-interactive.c
  333. rebase-interactive.h
  334. rebase.c
  335. rebase.h
  336. ref-filter.c
  337. ref-filter.h
  338. reflog-walk.c
  339. reflog-walk.h
  340. refs.c
  341. refs.h
  342. refspec.c
  343. refspec.h
  344. remote-curl.c
  345. remote-testsvn.c
  346. remote.c
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  348. replace-object.c
  349. replace-object.h
  350. repo-settings.c
  351. repository.c
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  353. rerere.c
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  355. reset.c
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  359. revision.c
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  361. run-command.c
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  363. send-pack.c
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  365. sequencer.c
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  367. serve.c
  368. serve.h
  369. server-info.c
  370. setup.c
  371. sh-i18n--envsubst.c
  372. sha1-file.c
  373. sha1-lookup.c
  374. sha1-lookup.h
  375. sha1-name.c
  376. sha1dc_git.c
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  378. shallow.c
  379. shell.c
  380. shortlog.h
  381. sideband.c
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  385. split-index.c
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  387. stable-qsort.c
  388. strbuf.c
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  390. streaming.c
  391. streaming.h
  392. string-list.c
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  394. sub-process.c
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  396. submodule-config.c
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  400. symlinks.c
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  404. tempfile.c
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  406. thread-utils.c
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  408. tmp-objdir.c
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  410. trace.c
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  414. trailer.c
  415. trailer.h
  416. transport-helper.c
  417. transport-internal.h
  418. transport.c
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  425. unicode-width.h
  426. unimplemented.sh
  427. unix-socket.c
  428. unix-socket.h
  429. unpack-trees.c
  430. unpack-trees.h
  431. upload-pack.c
  432. upload-pack.h
  433. url.c
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  435. urlmatch.c
  436. urlmatch.h
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  440. utf8.c
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  446. versioncmp.c
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  449. wildmatch.c
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  451. worktree.c
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  453. wrap-for-bin.sh
  454. wrapper.c
  455. write-or-die.c
  456. ws.c
  457. wt-status.c
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  459. xdiff-interface.c
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  461. zlib.c
README.md

Build status

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). To subscribe to the list, send an email with just “subscribe git” in the body to majordomo@vger.kernel.org. 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