Add structure representing hash algorithm

Since in the future we want to support an additional hash algorithm, add
a structure that represents a hash algorithm and all the data that must
go along with it.  Add a constant to allow easy enumeration of hash
algorithms.  Implement function typedefs to create an abstract API that
can be used by any hash algorithm, and wrappers for the existing SHA1
functions that conform to this API.

Expose a value for hex size as well as binary size.  While one will
always be twice the other, the two values are both used extremely
commonly throughout the codebase and providing both leads to improved
readability.

Don't include an entry in the hash algorithm structure for the null
object ID.  As this value is all zeros, any suitably sized all-zero
object ID can be used, and there's no need to store a given one on a
per-hash basis.

The current hash function transition plan envisions a time when we will
accept input from the user that might be in SHA-1 or in the NewHash
format.  Since we cannot know which the user has provided, add a
constant representing the unknown algorithm to allow us to indicate that
we must look the correct value up.  Provide dummy API functions that die
in this case.

Finally, include git-compat-util.h in hash.h so that the required types
are available.  This aids people using automated tools their editors.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2 files changed
tree: 5880f402a2f3b589dfe56cd336d8433629708491
  1. .github/
  2. block-sha1/
  3. builtin/
  4. ci/
  5. compat/
  6. contrib/
  7. Documentation/
  8. ewah/
  9. git-gui/
  10. gitk-git/
  11. gitweb/
  12. mergetools/
  13. perl/
  14. po/
  15. ppc/
  16. refs/
  17. sha1dc/
  18. t/
  19. templates/
  20. vcs-svn/
  21. xdiff/
  22. .clang-format
  23. .gitattributes
  24. .gitignore
  25. .gitmodules
  26. .mailmap
  27. .travis.yml
  28. .tsan-suppressions
  29. abspath.c
  30. aclocal.m4
  31. advice.c
  32. advice.h
  33. alias.c
  34. alloc.c
  35. apply.c
  36. apply.h
  37. archive-tar.c
  38. archive-zip.c
  39. archive.c
  40. archive.h
  41. argv-array.c
  42. argv-array.h
  43. attr.c
  44. attr.h
  45. base85.c
  46. bisect.c
  47. bisect.h
  48. blame.c
  49. blame.h
  50. blob.c
  51. blob.h
  52. branch.c
  53. branch.h
  54. builtin.h
  55. bulk-checkin.c
  56. bulk-checkin.h
  57. bundle.c
  58. bundle.h
  59. cache-tree.c
  60. cache-tree.h
  61. cache.h
  62. check-builtins.sh
  63. check-racy.c
  64. check_bindir
  65. color.c
  66. color.h
  67. column.c
  68. column.h
  69. combine-diff.c
  70. command-list.txt
  71. commit-slab.h
  72. commit.c
  73. commit.h
  74. common-main.c
  75. config.c
  76. config.h
  77. config.mak.in
  78. config.mak.uname
  79. configure.ac
  80. connect.c
  81. connect.h
  82. connected.c
  83. connected.h
  84. convert.c
  85. convert.h
  86. copy.c
  87. COPYING
  88. credential-cache--daemon.c
  89. credential-cache.c
  90. credential-store.c
  91. credential.c
  92. credential.h
  93. csum-file.c
  94. csum-file.h
  95. ctype.c
  96. daemon.c
  97. date.c
  98. decorate.c
  99. decorate.h
  100. delta.h
  101. diff-delta.c
  102. diff-lib.c
  103. diff-no-index.c
  104. diff.c
  105. diff.h
  106. diffcore-break.c
  107. diffcore-delta.c
  108. diffcore-order.c
  109. diffcore-pickaxe.c
  110. diffcore-rename.c
  111. diffcore.h
  112. dir-iterator.c
  113. dir-iterator.h
  114. dir.c
  115. dir.h
  116. editor.c
  117. entry.c
  118. environment.c
  119. exec_cmd.c
  120. exec_cmd.h
  121. fast-import.c
  122. fetch-pack.c
  123. fetch-pack.h
  124. fmt-merge-msg.h
  125. fsck.c
  126. fsck.h
  127. generate-cmdlist.sh
  128. gettext.c
  129. gettext.h
  130. git-add--interactive.perl
  131. git-archimport.perl
  132. git-bisect.sh
  133. git-compat-util.h
  134. git-cvsexportcommit.perl
  135. git-cvsimport.perl
  136. git-cvsserver.perl
  137. git-difftool--helper.sh
  138. git-filter-branch.sh
  139. git-instaweb.sh
  140. git-merge-octopus.sh
  141. git-merge-one-file.sh
  142. git-merge-resolve.sh
  143. git-mergetool--lib.sh
  144. git-mergetool.sh
  145. git-p4.py
  146. git-parse-remote.sh
  147. git-quiltimport.sh
  148. git-rebase--am.sh
  149. git-rebase--interactive.sh
  150. git-rebase--merge.sh
  151. git-rebase.sh
  152. git-remote-testgit.sh
  153. git-request-pull.sh
  154. git-send-email.perl
  155. git-sh-i18n.sh
  156. git-sh-setup.sh
  157. git-stash.sh
  158. git-submodule.sh
  159. git-svn.perl
  160. GIT-VERSION-GEN
  161. git-web--browse.sh
  162. git.c
  163. git.rc
  164. gpg-interface.c
  165. gpg-interface.h
  166. graph.c
  167. graph.h
  168. grep.c
  169. grep.h
  170. hash.h
  171. hashmap.c
  172. hashmap.h
  173. help.c
  174. help.h
  175. hex.c
  176. http-backend.c
  177. http-fetch.c
  178. http-push.c
  179. http-walker.c
  180. http.c
  181. http.h
  182. ident.c
  183. imap-send.c
  184. INSTALL
  185. iterator.h
  186. khash.h
  187. kwset.c
  188. kwset.h
  189. levenshtein.c
  190. levenshtein.h
  191. LGPL-2.1
  192. line-log.c
  193. line-log.h
  194. line-range.c
  195. line-range.h
  196. list-objects.c
  197. list-objects.h
  198. list.h
  199. ll-merge.c
  200. ll-merge.h
  201. lockfile.c
  202. lockfile.h
  203. log-tree.c
  204. log-tree.h
  205. mailinfo.c
  206. mailinfo.h
  207. mailmap.c
  208. mailmap.h
  209. Makefile
  210. match-trees.c
  211. merge-blobs.c
  212. merge-blobs.h
  213. merge-recursive.c
  214. merge-recursive.h
  215. merge.c
  216. mergesort.c
  217. mergesort.h
  218. mru.c
  219. mru.h
  220. name-hash.c
  221. notes-cache.c
  222. notes-cache.h
  223. notes-merge.c
  224. notes-merge.h
  225. notes-utils.c
  226. notes-utils.h
  227. notes.c
  228. notes.h
  229. object.c
  230. object.h
  231. oidmap.c
  232. oidmap.h
  233. oidset.c
  234. oidset.h
  235. pack-bitmap-write.c
  236. pack-bitmap.c
  237. pack-bitmap.h
  238. pack-check.c
  239. pack-objects.c
  240. pack-objects.h
  241. pack-revindex.c
  242. pack-revindex.h
  243. pack-write.c
  244. pack.h
  245. packfile.c
  246. packfile.h
  247. pager.c
  248. parse-options-cb.c
  249. parse-options.c
  250. parse-options.h
  251. patch-delta.c
  252. patch-ids.c
  253. patch-ids.h
  254. path.c
  255. path.h
  256. pathspec.c
  257. pathspec.h
  258. pkt-line.c
  259. pkt-line.h
  260. preload-index.c
  261. pretty.c
  262. prio-queue.c
  263. prio-queue.h
  264. progress.c
  265. progress.h
  266. prompt.c
  267. prompt.h
  268. quote.c
  269. quote.h
  270. reachable.c
  271. reachable.h
  272. read-cache.c
  273. README.md
  274. ref-filter.c
  275. ref-filter.h
  276. reflog-walk.c
  277. reflog-walk.h
  278. refs.c
  279. refs.h
  280. remote-curl.c
  281. remote-testsvn.c
  282. remote.c
  283. remote.h
  284. replace_object.c
  285. repository.c
  286. repository.h
  287. rerere.c
  288. rerere.h
  289. resolve-undo.c
  290. resolve-undo.h
  291. revision.c
  292. revision.h
  293. run-command.c
  294. run-command.h
  295. send-pack.c
  296. send-pack.h
  297. sequencer.c
  298. sequencer.h
  299. server-info.c
  300. setup.c
  301. sh-i18n--envsubst.c
  302. sha1-array.c
  303. sha1-array.h
  304. sha1-lookup.c
  305. sha1-lookup.h
  306. sha1_file.c
  307. sha1_name.c
  308. sha1dc_git.c
  309. sha1dc_git.h
  310. shallow.c
  311. shell.c
  312. shortlog.h
  313. show-index.c
  314. sideband.c
  315. sideband.h
  316. sigchain.c
  317. sigchain.h
  318. split-index.c
  319. split-index.h
  320. strbuf.c
  321. strbuf.h
  322. streaming.c
  323. streaming.h
  324. string-list.c
  325. string-list.h
  326. sub-process.c
  327. sub-process.h
  328. submodule-config.c
  329. submodule-config.h
  330. submodule.c
  331. submodule.h
  332. symlinks.c
  333. tag.c
  334. tag.h
  335. tar.h
  336. tempfile.c
  337. tempfile.h
  338. thread-utils.c
  339. thread-utils.h
  340. tmp-objdir.c
  341. tmp-objdir.h
  342. trace.c
  343. trace.h
  344. trailer.c
  345. trailer.h
  346. transport-helper.c
  347. transport.c
  348. transport.h
  349. tree-diff.c
  350. tree-walk.c
  351. tree-walk.h
  352. tree.c
  353. tree.h
  354. unicode_width.h
  355. unimplemented.sh
  356. unix-socket.c
  357. unix-socket.h
  358. unpack-trees.c
  359. unpack-trees.h
  360. upload-pack.c
  361. url.c
  362. url.h
  363. urlmatch.c
  364. urlmatch.h
  365. usage.c
  366. userdiff.c
  367. userdiff.h
  368. utf8.c
  369. utf8.h
  370. varint.c
  371. varint.h
  372. version.c
  373. version.h
  374. versioncmp.c
  375. walker.c
  376. walker.h
  377. wildmatch.c
  378. wildmatch.h
  379. worktree.c
  380. worktree.h
  381. wrap-for-bin.sh
  382. wrapper.c
  383. write_or_die.c
  384. ws.c
  385. wt-status.c
  386. wt-status.h
  387. xdiff-interface.c
  388. xdiff-interface.h
  389. zlib.c
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.txt to get started, then see Documentation/giteveryday.txt for a useful minimum set of commands, and Documentation/git-.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://public-inbox.org/git/, http://marc.info/?l=git and other archival sites.

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