checkout: restrict @-expansions when finding branch

When we parse "git checkout $NAME", we try to interpret
$NAME as a local branch-name. If it is, then we point HEAD
to that branch. Otherwise, we detach the HEAD at whatever
commit $NAME points to.

We do the interpretation by calling strbuf_branchname(), and
then blindly sticking "refs/heads/" on the front. This leads
to nonsense results when expansions like "@{upstream}" or
"@" point to something besides a local branch. We end up
with a local branch name like "refs/heads/origin/master" or
"refs/heads/HEAD".

Normally this has no user-visible effect because those
branches don't exist, and so we fallback to feeding the
result to get_sha1(), which resolves them correctly.

But as the new test in t3204 shows, there are corner cases
where the effect is observable, and we check out the wrong
local branch rather than detaching to the correct one.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2 files changed
tree: 22b7d5f9415dd2a1d74f885d95af2e29608f9a88
  1. block-sha1/
  2. builtin/
  3. ci/
  4. compat/
  5. contrib/
  6. Documentation/
  7. ewah/
  8. git-gui/
  9. gitk-git/
  10. gitweb/
  11. mergetools/
  12. perl/
  13. po/
  14. ppc/
  15. refs/
  16. t/
  17. templates/
  18. vcs-svn/
  19. xdiff/
  20. .gitattributes
  21. .gitignore
  22. .mailmap
  23. .travis.yml
  24. abspath.c
  25. aclocal.m4
  26. advice.c
  27. advice.h
  28. alias.c
  29. alloc.c
  30. apply.c
  31. apply.h
  32. archive-tar.c
  33. archive-zip.c
  34. archive.c
  35. archive.h
  36. argv-array.c
  37. argv-array.h
  38. attr.c
  39. attr.h
  40. base85.c
  41. bisect.c
  42. bisect.h
  43. blob.c
  44. blob.h
  45. branch.c
  46. branch.h
  47. builtin.h
  48. bulk-checkin.c
  49. bulk-checkin.h
  50. bundle.c
  51. bundle.h
  52. cache-tree.c
  53. cache-tree.h
  54. cache.h
  55. check-builtins.sh
  56. check-racy.c
  57. check_bindir
  58. color.c
  59. color.h
  60. column.c
  61. column.h
  62. combine-diff.c
  63. command-list.txt
  64. commit-slab.h
  65. commit.c
  66. commit.h
  67. common-main.c
  68. config.c
  69. config.mak.in
  70. config.mak.uname
  71. configure.ac
  72. connect.c
  73. connect.h
  74. connected.c
  75. connected.h
  76. convert.c
  77. convert.h
  78. copy.c
  79. COPYING
  80. credential-cache--daemon.c
  81. credential-cache.c
  82. credential-store.c
  83. credential.c
  84. credential.h
  85. csum-file.c
  86. csum-file.h
  87. ctype.c
  88. daemon.c
  89. date.c
  90. decorate.c
  91. decorate.h
  92. delta.h
  93. diff-delta.c
  94. diff-lib.c
  95. diff-no-index.c
  96. diff.c
  97. diff.h
  98. diffcore-break.c
  99. diffcore-delta.c
  100. diffcore-order.c
  101. diffcore-pickaxe.c
  102. diffcore-rename.c
  103. diffcore.h
  104. dir-iterator.c
  105. dir-iterator.h
  106. dir.c
  107. dir.h
  108. editor.c
  109. entry.c
  110. environment.c
  111. exec_cmd.c
  112. exec_cmd.h
  113. fast-import.c
  114. fetch-pack.c
  115. fetch-pack.h
  116. fmt-merge-msg.h
  117. fsck.c
  118. fsck.h
  119. generate-cmdlist.sh
  120. gettext.c
  121. gettext.h
  122. git-add--interactive.perl
  123. git-archimport.perl
  124. git-bisect.sh
  125. git-compat-util.h
  126. git-cvsexportcommit.perl
  127. git-cvsimport.perl
  128. git-cvsserver.perl
  129. git-difftool--helper.sh
  130. git-difftool.perl
  131. git-filter-branch.sh
  132. git-instaweb.sh
  133. git-merge-octopus.sh
  134. git-merge-one-file.sh
  135. git-merge-resolve.sh
  136. git-mergetool--lib.sh
  137. git-mergetool.sh
  138. git-p4.py
  139. git-parse-remote.sh
  140. git-quiltimport.sh
  141. git-rebase--am.sh
  142. git-rebase--interactive.sh
  143. git-rebase--merge.sh
  144. git-rebase.sh
  145. git-relink.perl
  146. git-remote-testgit.sh
  147. git-request-pull.sh
  148. git-send-email.perl
  149. git-sh-i18n.sh
  150. git-sh-setup.sh
  151. git-stash.sh
  152. git-submodule.sh
  153. git-svn.perl
  154. GIT-VERSION-GEN
  155. git-web--browse.sh
  156. git.c
  157. git.rc
  158. gpg-interface.c
  159. gpg-interface.h
  160. graph.c
  161. graph.h
  162. grep.c
  163. grep.h
  164. hashmap.c
  165. hashmap.h
  166. help.c
  167. help.h
  168. hex.c
  169. http-backend.c
  170. http-fetch.c
  171. http-push.c
  172. http-walker.c
  173. http.c
  174. http.h
  175. ident.c
  176. imap-send.c
  177. INSTALL
  178. iterator.h
  179. khash.h
  180. kwset.c
  181. kwset.h
  182. levenshtein.c
  183. levenshtein.h
  184. LGPL-2.1
  185. line-log.c
  186. line-log.h
  187. line-range.c
  188. line-range.h
  189. list-objects.c
  190. list-objects.h
  191. list.h
  192. ll-merge.c
  193. ll-merge.h
  194. lockfile.c
  195. lockfile.h
  196. log-tree.c
  197. log-tree.h
  198. mailinfo.c
  199. mailinfo.h
  200. mailmap.c
  201. mailmap.h
  202. Makefile
  203. match-trees.c
  204. merge-blobs.c
  205. merge-blobs.h
  206. merge-recursive.c
  207. merge-recursive.h
  208. merge.c
  209. mergesort.c
  210. mergesort.h
  211. mru.c
  212. mru.h
  213. name-hash.c
  214. notes-cache.c
  215. notes-cache.h
  216. notes-merge.c
  217. notes-merge.h
  218. notes-utils.c
  219. notes-utils.h
  220. notes.c
  221. notes.h
  222. object.c
  223. object.h
  224. pack-bitmap-write.c
  225. pack-bitmap.c
  226. pack-bitmap.h
  227. pack-check.c
  228. pack-objects.c
  229. pack-objects.h
  230. pack-revindex.c
  231. pack-revindex.h
  232. pack-write.c
  233. pack.h
  234. pager.c
  235. parse-options-cb.c
  236. parse-options.c
  237. parse-options.h
  238. patch-delta.c
  239. patch-ids.c
  240. patch-ids.h
  241. path.c
  242. pathspec.c
  243. pathspec.h
  244. pkt-line.c
  245. pkt-line.h
  246. preload-index.c
  247. pretty.c
  248. prio-queue.c
  249. prio-queue.h
  250. progress.c
  251. progress.h
  252. prompt.c
  253. prompt.h
  254. quote.c
  255. quote.h
  256. reachable.c
  257. reachable.h
  258. read-cache.c
  259. README.md
  260. ref-filter.c
  261. ref-filter.h
  262. reflog-walk.c
  263. reflog-walk.h
  264. refs.c
  265. refs.h
  266. remote-curl.c
  267. remote-testsvn.c
  268. remote.c
  269. remote.h
  270. replace_object.c
  271. rerere.c
  272. rerere.h
  273. resolve-undo.c
  274. resolve-undo.h
  275. revision.c
  276. revision.h
  277. run-command.c
  278. run-command.h
  279. send-pack.c
  280. send-pack.h
  281. sequencer.c
  282. sequencer.h
  283. server-info.c
  284. setup.c
  285. sh-i18n--envsubst.c
  286. sha1-array.c
  287. sha1-array.h
  288. sha1-lookup.c
  289. sha1-lookup.h
  290. sha1_file.c
  291. sha1_name.c
  292. shallow.c
  293. shell.c
  294. shortlog.h
  295. show-index.c
  296. sideband.c
  297. sideband.h
  298. sigchain.c
  299. sigchain.h
  300. split-index.c
  301. split-index.h
  302. strbuf.c
  303. strbuf.h
  304. streaming.c
  305. streaming.h
  306. string-list.c
  307. string-list.h
  308. submodule-config.c
  309. submodule-config.h
  310. submodule.c
  311. submodule.h
  312. symlinks.c
  313. tag.c
  314. tag.h
  315. tar.h
  316. tempfile.c
  317. tempfile.h
  318. thread-utils.c
  319. thread-utils.h
  320. tmp-objdir.c
  321. tmp-objdir.h
  322. trace.c
  323. trace.h
  324. trailer.c
  325. trailer.h
  326. transport-helper.c
  327. transport.c
  328. transport.h
  329. tree-diff.c
  330. tree-walk.c
  331. tree-walk.h
  332. tree.c
  333. tree.h
  334. unicode_width.h
  335. unimplemented.sh
  336. unix-socket.c
  337. unix-socket.h
  338. unpack-trees.c
  339. unpack-trees.h
  340. upload-pack.c
  341. url.c
  342. url.h
  343. urlmatch.c
  344. urlmatch.h
  345. usage.c
  346. userdiff.c
  347. userdiff.h
  348. utf8.c
  349. utf8.h
  350. varint.c
  351. varint.h
  352. version.c
  353. version.h
  354. versioncmp.c
  355. walker.c
  356. walker.h
  357. wildmatch.c
  358. wildmatch.h
  359. worktree.c
  360. worktree.h
  361. wrap-for-bin.sh
  362. wrapper.c
  363. write_or_die.c
  364. ws.c
  365. wt-status.c
  366. wt-status.h
  367. xdiff-interface.c
  368. xdiff-interface.h
  369. 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 http://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