Be more careful about updating refs

This makes write_ref_sha1() more careful: it actually checks the SHA1 of
the ref it is updating, and refuses to update a ref with an object that it
cannot find.

Perhaps more importantly, it also refuses to update a branch head with a
non-commit object. I don't quite know *how* the stable series maintainers
were able to corrupt their repository to have a HEAD that pointed to a tag
rather than a commit object, but they did. Which results in a totally
broken repository that cannot be cloned or committed on.

So make it harder for people to shoot themselves in the foot like that.

The test t1400-update-ref.sh is fixed at the same time, as it
assumed that the commands involved in the particular test would
not care about corrupted repositories whose refs point at
nonexistant bogus objects.  That assumption does not hold true
anymore.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2 files changed
tree: 68a7def9602e2f847f133081f0b90bd43e622b23
  1. arm/
  2. compat/
  3. contrib/
  4. Documentation/
  5. git-gui/
  6. gitk-git/
  7. gitweb/
  8. mozilla-sha1/
  9. perl/
  10. ppc/
  11. t/
  12. templates/
  13. xdiff/
  14. .gitignore
  15. .mailmap
  16. alloc.c
  17. archive-tar.c
  18. archive-zip.c
  19. archive.h
  20. attr.c
  21. attr.h
  22. base85.c
  23. blob.c
  24. blob.h
  25. builtin-add.c
  26. builtin-annotate.c
  27. builtin-apply.c
  28. builtin-archive.c
  29. builtin-blame.c
  30. builtin-branch.c
  31. builtin-bundle.c
  32. builtin-cat-file.c
  33. builtin-check-attr.c
  34. builtin-check-ref-format.c
  35. builtin-checkout-index.c
  36. builtin-clean.c
  37. builtin-commit-tree.c
  38. builtin-commit.c
  39. builtin-config.c
  40. builtin-count-objects.c
  41. builtin-describe.c
  42. builtin-diff-files.c
  43. builtin-diff-index.c
  44. builtin-diff-tree.c
  45. builtin-diff.c
  46. builtin-fast-export.c
  47. builtin-fetch--tool.c
  48. builtin-fetch-pack.c
  49. builtin-fetch.c
  50. builtin-fmt-merge-msg.c
  51. builtin-for-each-ref.c
  52. builtin-fsck.c
  53. builtin-gc.c
  54. builtin-grep.c
  55. builtin-http-fetch.c
  56. builtin-init-db.c
  57. builtin-log.c
  58. builtin-ls-files.c
  59. builtin-ls-remote.c
  60. builtin-ls-tree.c
  61. builtin-mailinfo.c
  62. builtin-mailsplit.c
  63. builtin-merge-base.c
  64. builtin-merge-file.c
  65. builtin-merge-ours.c
  66. builtin-mv.c
  67. builtin-name-rev.c
  68. builtin-pack-objects.c
  69. builtin-pack-refs.c
  70. builtin-prune-packed.c
  71. builtin-prune.c
  72. builtin-push.c
  73. builtin-read-tree.c
  74. builtin-reflog.c
  75. builtin-rerere.c
  76. builtin-reset.c
  77. builtin-rev-list.c
  78. builtin-rev-parse.c
  79. builtin-revert.c
  80. builtin-rm.c
  81. builtin-send-pack.c
  82. builtin-shortlog.c
  83. builtin-show-branch.c
  84. builtin-show-ref.c
  85. builtin-stripspace.c
  86. builtin-symbolic-ref.c
  87. builtin-tag.c
  88. builtin-tar-tree.c
  89. builtin-unpack-objects.c
  90. builtin-update-index.c
  91. builtin-update-ref.c
  92. builtin-upload-archive.c
  93. builtin-verify-pack.c
  94. builtin-verify-tag.c
  95. builtin-write-tree.c
  96. builtin.h
  97. bundle.c
  98. bundle.h
  99. cache-tree.c
  100. cache-tree.h
  101. cache.h
  102. check-builtins.sh
  103. check-racy.c
  104. color.c
  105. color.h
  106. combine-diff.c
  107. command-list.txt
  108. commit.c
  109. commit.h
  110. config.c
  111. config.mak.in
  112. configure.ac
  113. connect.c
  114. convert.c
  115. copy.c
  116. COPYING
  117. csum-file.c
  118. csum-file.h
  119. ctype.c
  120. daemon.c
  121. date.c
  122. decorate.c
  123. decorate.h
  124. delta.h
  125. diff-delta.c
  126. diff-lib.c
  127. diff.c
  128. diff.h
  129. diffcore-break.c
  130. diffcore-delta.c
  131. diffcore-order.c
  132. diffcore-pickaxe.c
  133. diffcore-rename.c
  134. diffcore.h
  135. dir.c
  136. dir.h
  137. dump-cache-tree.c
  138. entry.c
  139. environment.c
  140. exec_cmd.c
  141. exec_cmd.h
  142. fast-import.c
  143. fetch-pack.h
  144. fixup-builtins
  145. generate-cmdlist.sh
  146. git-add--interactive.perl
  147. git-am.sh
  148. git-archimport.perl
  149. git-bisect.sh
  150. git-checkout.sh
  151. git-clone.sh
  152. git-compat-util.h
  153. git-cvsexportcommit.perl
  154. git-cvsimport.perl
  155. git-cvsserver.perl
  156. git-filter-branch.sh
  157. git-help--browse.sh
  158. git-instaweb.sh
  159. git-lost-found.sh
  160. git-merge-octopus.sh
  161. git-merge-one-file.sh
  162. git-merge-resolve.sh
  163. git-merge-stupid.sh
  164. git-merge.sh
  165. git-mergetool.sh
  166. git-parse-remote.sh
  167. git-pull.sh
  168. git-quiltimport.sh
  169. git-rebase--interactive.sh
  170. git-rebase.sh
  171. git-relink.perl
  172. git-remote.perl
  173. git-repack.sh
  174. git-request-pull.sh
  175. git-send-email.perl
  176. git-sh-setup.sh
  177. git-stash.sh
  178. git-submodule.sh
  179. git-svn.perl
  180. GIT-VERSION-GEN
  181. git.c
  182. git.spec.in
  183. grep.c
  184. grep.h
  185. hash-object.c
  186. hash.c
  187. hash.h
  188. help.c
  189. http-push.c
  190. http-walker.c
  191. http.c
  192. http.h
  193. ident.c
  194. imap-send.c
  195. index-pack.c
  196. INSTALL
  197. interpolate.c
  198. interpolate.h
  199. list-objects.c
  200. list-objects.h
  201. lockfile.c
  202. log-tree.c
  203. log-tree.h
  204. mailmap.c
  205. mailmap.h
  206. Makefile
  207. match-trees.c
  208. merge-file.c
  209. merge-index.c
  210. merge-recursive.c
  211. merge-tree.c
  212. mktag.c
  213. mktree.c
  214. object-refs.c
  215. object.c
  216. object.h
  217. pack-check.c
  218. pack-redundant.c
  219. pack-write.c
  220. pack.h
  221. pager.c
  222. parse-options.c
  223. parse-options.h
  224. patch-delta.c
  225. patch-id.c
  226. patch-ids.c
  227. patch-ids.h
  228. path-list.c
  229. path-list.h
  230. path.c
  231. pkt-line.c
  232. pkt-line.h
  233. pretty.c
  234. progress.c
  235. progress.h
  236. quote.c
  237. quote.h
  238. reachable.c
  239. reachable.h
  240. read-cache.c
  241. README
  242. receive-pack.c
  243. reflog-walk.c
  244. reflog-walk.h
  245. refs.c
  246. refs.h
  247. remote.c
  248. remote.h
  249. revision.c
  250. revision.h
  251. run-command.c
  252. run-command.h
  253. send-pack.h
  254. server-info.c
  255. setup.c
  256. sha1_file.c
  257. sha1_name.c
  258. shallow.c
  259. shell.c
  260. show-index.c
  261. sideband.c
  262. sideband.h
  263. strbuf.c
  264. strbuf.h
  265. symlinks.c
  266. tag.c
  267. tag.h
  268. tar.h
  269. test-absolute-path.c
  270. test-chmtime.c
  271. test-date.c
  272. test-delta.c
  273. test-genrandom.c
  274. test-match-trees.c
  275. test-parse-options.c
  276. test-sha1.c
  277. test-sha1.sh
  278. trace.c
  279. transport.c
  280. transport.h
  281. tree-diff.c
  282. tree-walk.c
  283. tree-walk.h
  284. tree.c
  285. tree.h
  286. unpack-file.c
  287. unpack-trees.c
  288. unpack-trees.h
  289. update-server-info.c
  290. upload-pack.c
  291. usage.c
  292. utf8.c
  293. utf8.h
  294. var.c
  295. walker.c
  296. walker.h
  297. write_or_die.c
  298. ws.c
  299. wt-status.c
  300. wt-status.h
  301. xdiff-interface.c
  302. xdiff-interface.h