git.oblomov.eu Git - git/blob - refs/files-backend.c

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12
  13 struct ref_lock {
  14         char *ref_name;
  15         struct lock_file lk;
  16         struct object_id old_oid;
  17 };
  18
  19 /*
  20  * Future: need to be in "struct repository"
  21  * when doing a full libification.
  22  */
  23 struct files_ref_store {
  24         struct ref_store base;
  25         unsigned int store_flags;
  26
  27         char *gitdir;
  28         char *gitcommondir;
  29
  30         struct ref_cache *loose;
  31
  32         struct ref_store *packed_ref_store;
  33 };
  34
  35 static void clear_loose_ref_cache(struct files_ref_store *refs)
  36 {
  37         if (refs->loose) {
  38                 free_ref_cache(refs->loose);
  39                 refs->loose = NULL;
  40         }
  41 }
  42
  43 /*
  44  * Create a new submodule ref cache and add it to the internal
  45  * set of caches.
  46  */
  47 static struct ref_store *files_ref_store_create(const char *gitdir,
  48                                                 unsigned int flags)
  49 {
  50         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  51         struct ref_store *ref_store = (struct ref_store *)refs;
  52         struct strbuf sb = STRBUF_INIT;
  53
  54         base_ref_store_init(ref_store, &refs_be_files);
  55         refs->store_flags = flags;
  56
  57         refs->gitdir = xstrdup(gitdir);
  58         get_common_dir_noenv(&sb, gitdir);
  59         refs->gitcommondir = strbuf_detach(&sb, NULL);
  60         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
  61         refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
  62         strbuf_release(&sb);
  63
  64         return ref_store;
  65 }
  66
  67 /*
  68  * Die if refs is not the main ref store. caller is used in any
  69  * necessary error messages.
  70  */
  71 static void files_assert_main_repository(struct files_ref_store *refs,
  72                                          const char *caller)
  73 {
  74         if (refs->store_flags & REF_STORE_MAIN)
  75                 return;
  76
  77         die("BUG: operation %s only allowed for main ref store", caller);
  78 }
  79
  80 /*
  81  * Downcast ref_store to files_ref_store. Die if ref_store is not a
  82  * files_ref_store. required_flags is compared with ref_store's
  83  * store_flags to ensure the ref_store has all required capabilities.
  84  * "caller" is used in any necessary error messages.
  85  */
  86 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
  87                                               unsigned int required_flags,
  88                                               const char *caller)
  89 {
  90         struct files_ref_store *refs;
  91
  92         if (ref_store->be != &refs_be_files)
  93                 die("BUG: ref_store is type \"%s\" not \"files\" in %s",
  94                     ref_store->be->name, caller);
  95
  96         refs = (struct files_ref_store *)ref_store;
  97
  98         if ((refs->store_flags & required_flags) != required_flags)
  99                 die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
 100                     caller, required_flags, refs->store_flags);
 101
 102         return refs;
 103 }
 104
 105 static void files_reflog_path(struct files_ref_store *refs,
 106                               struct strbuf *sb,
 107                               const char *refname)
 108 {
 109         switch (ref_type(refname)) {
 110         case REF_TYPE_PER_WORKTREE:
 111         case REF_TYPE_PSEUDOREF:
 112                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 113                 break;
 114         case REF_TYPE_NORMAL:
 115                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 116                 break;
 117         default:
 118                 die("BUG: unknown ref type %d of ref %s",
 119                     ref_type(refname), refname);
 120         }
 121 }
 122
 123 static void files_ref_path(struct files_ref_store *refs,
 124                            struct strbuf *sb,
 125                            const char *refname)
 126 {
 127         switch (ref_type(refname)) {
 128         case REF_TYPE_PER_WORKTREE:
 129         case REF_TYPE_PSEUDOREF:
 130                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 131                 break;
 132         case REF_TYPE_NORMAL:
 133                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 134                 break;
 135         default:
 136                 die("BUG: unknown ref type %d of ref %s",
 137                     ref_type(refname), refname);
 138         }
 139 }
 140
 141 /*
 142  * Read the loose references from the namespace dirname into dir
 143  * (without recursing).  dirname must end with '/'.  dir must be the
 144  * directory entry corresponding to dirname.
 145  */
 146 static void loose_fill_ref_dir(struct ref_store *ref_store,
 147                                struct ref_dir *dir, const char *dirname)
 148 {
 149         struct files_ref_store *refs =
 150                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 151         DIR *d;
 152         struct dirent *de;
 153         int dirnamelen = strlen(dirname);
 154         struct strbuf refname;
 155         struct strbuf path = STRBUF_INIT;
 156         size_t path_baselen;
 157
 158         files_ref_path(refs, &path, dirname);
 159         path_baselen = path.len;
 160
 161         d = opendir(path.buf);
 162         if (!d) {
 163                 strbuf_release(&path);
 164                 return;
 165         }
 166
 167         strbuf_init(&refname, dirnamelen + 257);
 168         strbuf_add(&refname, dirname, dirnamelen);
 169
 170         while ((de = readdir(d)) != NULL) {
 171                 struct object_id oid;
 172                 struct stat st;
 173                 int flag;
 174
 175                 if (de->d_name[0] == '.')
 176                         continue;
 177                 if (ends_with(de->d_name, ".lock"))
 178                         continue;
 179                 strbuf_addstr(&refname, de->d_name);
 180                 strbuf_addstr(&path, de->d_name);
 181                 if (stat(path.buf, &st) < 0) {
 182                         ; /* silently ignore */
 183                 } else if (S_ISDIR(st.st_mode)) {
 184                         strbuf_addch(&refname, '/');
 185                         add_entry_to_dir(dir,
 186                                          create_dir_entry(dir->cache, refname.buf,
 187                                                           refname.len, 1));
 188                 } else {
 189                         if (!refs_resolve_ref_unsafe(&refs->base,
 190                                                      refname.buf,
 191                                                      RESOLVE_REF_READING,
 192                                                      &oid, &flag)) {
 193                                 oidclr(&oid);
 194                                 flag |= REF_ISBROKEN;
 195                         } else if (is_null_oid(&oid)) {
 196                                 /*
 197                                  * It is so astronomically unlikely
 198                                  * that NULL_SHA1 is the SHA-1 of an
 199                                  * actual object that we consider its
 200                                  * appearance in a loose reference
 201                                  * file to be repo corruption
 202                                  * (probably due to a software bug).
 203                                  */
 204                                 flag |= REF_ISBROKEN;
 205                         }
 206
 207                         if (check_refname_format(refname.buf,
 208                                                  REFNAME_ALLOW_ONELEVEL)) {
 209                                 if (!refname_is_safe(refname.buf))
 210                                         die("loose refname is dangerous: %s", refname.buf);
 211                                 oidclr(&oid);
 212                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 213                         }
 214                         add_entry_to_dir(dir,
 215                                          create_ref_entry(refname.buf, &oid, flag));
 216                 }
 217                 strbuf_setlen(&refname, dirnamelen);
 218                 strbuf_setlen(&path, path_baselen);
 219         }
 220         strbuf_release(&refname);
 221         strbuf_release(&path);
 222         closedir(d);
 223
 224         /*
 225          * Manually add refs/bisect, which, being per-worktree, might
 226          * not appear in the directory listing for refs/ in the main
 227          * repo.
 228          */
 229         if (!strcmp(dirname, "refs/")) {
 230                 int pos = search_ref_dir(dir, "refs/bisect/", 12);
 231
 232                 if (pos < 0) {
 233                         struct ref_entry *child_entry = create_dir_entry(
 234                                         dir->cache, "refs/bisect/", 12, 1);
 235                         add_entry_to_dir(dir, child_entry);
 236                 }
 237         }
 238 }
 239
 240 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 241 {
 242         if (!refs->loose) {
 243                 /*
 244                  * Mark the top-level directory complete because we
 245                  * are about to read the only subdirectory that can
 246                  * hold references:
 247                  */
 248                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 249
 250                 /* We're going to fill the top level ourselves: */
 251                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 252
 253                 /*
 254                  * Add an incomplete entry for "refs/" (to be filled
 255                  * lazily):
 256                  */
 257                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 258                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 259         }
 260         return refs->loose;
 261 }
 262
 263 static int files_read_raw_ref(struct ref_store *ref_store,
 264                               const char *refname, struct object_id *oid,
 265                               struct strbuf *referent, unsigned int *type)
 266 {
 267         struct files_ref_store *refs =
 268                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 269         struct strbuf sb_contents = STRBUF_INIT;
 270         struct strbuf sb_path = STRBUF_INIT;
 271         const char *path;
 272         const char *buf;
 273         const char *p;
 274         struct stat st;
 275         int fd;
 276         int ret = -1;
 277         int save_errno;
 278         int remaining_retries = 3;
 279
 280         *type = 0;
 281         strbuf_reset(&sb_path);
 282
 283         files_ref_path(refs, &sb_path, refname);
 284
 285         path = sb_path.buf;
 286
 287 stat_ref:
 288         /*
 289          * We might have to loop back here to avoid a race
 290          * condition: first we lstat() the file, then we try
 291          * to read it as a link or as a file.  But if somebody
 292          * changes the type of the file (file <-> directory
 293          * <-> symlink) between the lstat() and reading, then
 294          * we don't want to report that as an error but rather
 295          * try again starting with the lstat().
 296          *
 297          * We'll keep a count of the retries, though, just to avoid
 298          * any confusing situation sending us into an infinite loop.
 299          */
 300
 301         if (remaining_retries-- <= 0)
 302                 goto out;
 303
 304         if (lstat(path, &st) < 0) {
 305                 if (errno != ENOENT)
 306                         goto out;
 307                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 308                                       oid, referent, type)) {
 309                         errno = ENOENT;
 310                         goto out;
 311                 }
 312                 ret = 0;
 313                 goto out;
 314         }
 315
 316         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 317         if (S_ISLNK(st.st_mode)) {
 318                 strbuf_reset(&sb_contents);
 319                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 320                         if (errno == ENOENT || errno == EINVAL)
 321                                 /* inconsistent with lstat; retry */
 322                                 goto stat_ref;
 323                         else
 324                                 goto out;
 325                 }
 326                 if (starts_with(sb_contents.buf, "refs/") &&
 327                     !check_refname_format(sb_contents.buf, 0)) {
 328                         strbuf_swap(&sb_contents, referent);
 329                         *type |= REF_ISSYMREF;
 330                         ret = 0;
 331                         goto out;
 332                 }
 333                 /*
 334                  * It doesn't look like a refname; fall through to just
 335                  * treating it like a non-symlink, and reading whatever it
 336                  * points to.
 337                  */
 338         }
 339
 340         /* Is it a directory? */
 341         if (S_ISDIR(st.st_mode)) {
 342                 /*
 343                  * Even though there is a directory where the loose
 344                  * ref is supposed to be, there could still be a
 345                  * packed ref:
 346                  */
 347                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 348                                       oid, referent, type)) {
 349                         errno = EISDIR;
 350                         goto out;
 351                 }
 352                 ret = 0;
 353                 goto out;
 354         }
 355
 356         /*
 357          * Anything else, just open it and try to use it as
 358          * a ref
 359          */
 360         fd = open(path, O_RDONLY);
 361         if (fd < 0) {
 362                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 363                         /* inconsistent with lstat; retry */
 364                         goto stat_ref;
 365                 else
 366                         goto out;
 367         }
 368         strbuf_reset(&sb_contents);
 369         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 370                 int save_errno = errno;
 371                 close(fd);
 372                 errno = save_errno;
 373                 goto out;
 374         }
 375         close(fd);
 376         strbuf_rtrim(&sb_contents);
 377         buf = sb_contents.buf;
 378         if (starts_with(buf, "ref:")) {
 379                 buf += 4;
 380                 while (isspace(*buf))
 381                         buf++;
 382
 383                 strbuf_reset(referent);
 384                 strbuf_addstr(referent, buf);
 385                 *type |= REF_ISSYMREF;
 386                 ret = 0;
 387                 goto out;
 388         }
 389
 390         /*
 391          * Please note that FETCH_HEAD has additional
 392          * data after the sha.
 393          */
 394         if (parse_oid_hex(buf, oid, &p) ||
 395             (*p != '\0' && !isspace(*p))) {
 396                 *type |= REF_ISBROKEN;
 397                 errno = EINVAL;
 398                 goto out;
 399         }
 400
 401         ret = 0;
 402
 403 out:
 404         save_errno = errno;
 405         strbuf_release(&sb_path);
 406         strbuf_release(&sb_contents);
 407         errno = save_errno;
 408         return ret;
 409 }
 410
 411 static void unlock_ref(struct ref_lock *lock)
 412 {
 413         rollback_lock_file(&lock->lk);
 414         free(lock->ref_name);
 415         free(lock);
 416 }
 417
 418 /*
 419  * Lock refname, without following symrefs, and set *lock_p to point
 420  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 421  * and type similarly to read_raw_ref().
 422  *
 423  * The caller must verify that refname is a "safe" reference name (in
 424  * the sense of refname_is_safe()) before calling this function.
 425  *
 426  * If the reference doesn't already exist, verify that refname doesn't
 427  * have a D/F conflict with any existing references. extras and skip
 428  * are passed to refs_verify_refname_available() for this check.
 429  *
 430  * If mustexist is not set and the reference is not found or is
 431  * broken, lock the reference anyway but clear sha1.
 432  *
 433  * Return 0 on success. On failure, write an error message to err and
 434  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 435  *
 436  * Implementation note: This function is basically
 437  *
 438  *     lock reference
 439  *     read_raw_ref()
 440  *
 441  * but it includes a lot more code to
 442  * - Deal with possible races with other processes
 443  * - Avoid calling refs_verify_refname_available() when it can be
 444  *   avoided, namely if we were successfully able to read the ref
 445  * - Generate informative error messages in the case of failure
 446  */
 447 static int lock_raw_ref(struct files_ref_store *refs,
 448                         const char *refname, int mustexist,
 449                         const struct string_list *extras,
 450                         const struct string_list *skip,
 451                         struct ref_lock **lock_p,
 452                         struct strbuf *referent,
 453                         unsigned int *type,
 454                         struct strbuf *err)
 455 {
 456         struct ref_lock *lock;
 457         struct strbuf ref_file = STRBUF_INIT;
 458         int attempts_remaining = 3;
 459         int ret = TRANSACTION_GENERIC_ERROR;
 460
 461         assert(err);
 462         files_assert_main_repository(refs, "lock_raw_ref");
 463
 464         *type = 0;
 465
 466         /* First lock the file so it can't change out from under us. */
 467
 468         *lock_p = lock = xcalloc(1, sizeof(*lock));
 469
 470         lock->ref_name = xstrdup(refname);
 471         files_ref_path(refs, &ref_file, refname);
 472
 473 retry:
 474         switch (safe_create_leading_directories(ref_file.buf)) {
 475         case SCLD_OK:
 476                 break; /* success */
 477         case SCLD_EXISTS:
 478                 /*
 479                  * Suppose refname is "refs/foo/bar". We just failed
 480                  * to create the containing directory, "refs/foo",
 481                  * because there was a non-directory in the way. This
 482                  * indicates a D/F conflict, probably because of
 483                  * another reference such as "refs/foo". There is no
 484                  * reason to expect this error to be transitory.
 485                  */
 486                 if (refs_verify_refname_available(&refs->base, refname,
 487                                                   extras, skip, err)) {
 488                         if (mustexist) {
 489                                 /*
 490                                  * To the user the relevant error is
 491                                  * that the "mustexist" reference is
 492                                  * missing:
 493                                  */
 494                                 strbuf_reset(err);
 495                                 strbuf_addf(err, "unable to resolve reference '%s'",
 496                                             refname);
 497                         } else {
 498                                 /*
 499                                  * The error message set by
 500                                  * refs_verify_refname_available() is
 501                                  * OK.
 502                                  */
 503                                 ret = TRANSACTION_NAME_CONFLICT;
 504                         }
 505                 } else {
 506                         /*
 507                          * The file that is in the way isn't a loose
 508                          * reference. Report it as a low-level
 509                          * failure.
 510                          */
 511                         strbuf_addf(err, "unable to create lock file %s.lock; "
 512                                     "non-directory in the way",
 513                                     ref_file.buf);
 514                 }
 515                 goto error_return;
 516         case SCLD_VANISHED:
 517                 /* Maybe another process was tidying up. Try again. */
 518                 if (--attempts_remaining > 0)
 519                         goto retry;
 520                 /* fall through */
 521         default:
 522                 strbuf_addf(err, "unable to create directory for %s",
 523                             ref_file.buf);
 524                 goto error_return;
 525         }
 526
 527         if (hold_lock_file_for_update_timeout(
 528                             &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 529                             get_files_ref_lock_timeout_ms()) < 0) {
 530                 if (errno == ENOENT && --attempts_remaining > 0) {
 531                         /*
 532                          * Maybe somebody just deleted one of the
 533                          * directories leading to ref_file.  Try
 534                          * again:
 535                          */
 536                         goto retry;
 537                 } else {
 538                         unable_to_lock_message(ref_file.buf, errno, err);
 539                         goto error_return;
 540                 }
 541         }
 542
 543         /*
 544          * Now we hold the lock and can read the reference without
 545          * fear that its value will change.
 546          */
 547
 548         if (files_read_raw_ref(&refs->base, refname,
 549                                &lock->old_oid, referent, type)) {
 550                 if (errno == ENOENT) {
 551                         if (mustexist) {
 552                                 /* Garden variety missing reference. */
 553                                 strbuf_addf(err, "unable to resolve reference '%s'",
 554                                             refname);
 555                                 goto error_return;
 556                         } else {
 557                                 /*
 558                                  * Reference is missing, but that's OK. We
 559                                  * know that there is not a conflict with
 560                                  * another loose reference because
 561                                  * (supposing that we are trying to lock
 562                                  * reference "refs/foo/bar"):
 563                                  *
 564                                  * - We were successfully able to create
 565                                  *   the lockfile refs/foo/bar.lock, so we
 566                                  *   know there cannot be a loose reference
 567                                  *   named "refs/foo".
 568                                  *
 569                                  * - We got ENOENT and not EISDIR, so we
 570                                  *   know that there cannot be a loose
 571                                  *   reference named "refs/foo/bar/baz".
 572                                  */
 573                         }
 574                 } else if (errno == EISDIR) {
 575                         /*
 576                          * There is a directory in the way. It might have
 577                          * contained references that have been deleted. If
 578                          * we don't require that the reference already
 579                          * exists, try to remove the directory so that it
 580                          * doesn't cause trouble when we want to rename the
 581                          * lockfile into place later.
 582                          */
 583                         if (mustexist) {
 584                                 /* Garden variety missing reference. */
 585                                 strbuf_addf(err, "unable to resolve reference '%s'",
 586                                             refname);
 587                                 goto error_return;
 588                         } else if (remove_dir_recursively(&ref_file,
 589                                                           REMOVE_DIR_EMPTY_ONLY)) {
 590                                 if (refs_verify_refname_available(
 591                                                     &refs->base, refname,
 592                                                     extras, skip, err)) {
 593                                         /*
 594                                          * The error message set by
 595                                          * verify_refname_available() is OK.
 596                                          */
 597                                         ret = TRANSACTION_NAME_CONFLICT;
 598                                         goto error_return;
 599                                 } else {
 600                                         /*
 601                                          * We can't delete the directory,
 602                                          * but we also don't know of any
 603                                          * references that it should
 604                                          * contain.
 605                                          */
 606                                         strbuf_addf(err, "there is a non-empty directory '%s' "
 607                                                     "blocking reference '%s'",
 608                                                     ref_file.buf, refname);
 609                                         goto error_return;
 610                                 }
 611                         }
 612                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 613                         strbuf_addf(err, "unable to resolve reference '%s': "
 614                                     "reference broken", refname);
 615                         goto error_return;
 616                 } else {
 617                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 618                                     refname, strerror(errno));
 619                         goto error_return;
 620                 }
 621
 622                 /*
 623                  * If the ref did not exist and we are creating it,
 624                  * make sure there is no existing packed ref that
 625                  * conflicts with refname:
 626                  */
 627                 if (refs_verify_refname_available(
 628                                     refs->packed_ref_store, refname,
 629                                     extras, skip, err))
 630                         goto error_return;
 631         }
 632
 633         ret = 0;
 634         goto out;
 635
 636 error_return:
 637         unlock_ref(lock);
 638         *lock_p = NULL;
 639
 640 out:
 641         strbuf_release(&ref_file);
 642         return ret;
 643 }
 644
 645 struct files_ref_iterator {
 646         struct ref_iterator base;
 647
 648         struct ref_iterator *iter0;
 649         unsigned int flags;
 650 };
 651
 652 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 653 {
 654         struct files_ref_iterator *iter =
 655                 (struct files_ref_iterator *)ref_iterator;
 656         int ok;
 657
 658         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 659                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 660                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 661                         continue;
 662
 663                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 664                     !ref_resolves_to_object(iter->iter0->refname,
 665                                             iter->iter0->oid,
 666                                             iter->iter0->flags))
 667                         continue;
 668
 669                 iter->base.refname = iter->iter0->refname;
 670                 iter->base.oid = iter->iter0->oid;
 671                 iter->base.flags = iter->iter0->flags;
 672                 return ITER_OK;
 673         }
 674
 675         iter->iter0 = NULL;
 676         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 677                 ok = ITER_ERROR;
 678
 679         return ok;
 680 }
 681
 682 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 683                                    struct object_id *peeled)
 684 {
 685         struct files_ref_iterator *iter =
 686                 (struct files_ref_iterator *)ref_iterator;
 687
 688         return ref_iterator_peel(iter->iter0, peeled);
 689 }
 690
 691 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 692 {
 693         struct files_ref_iterator *iter =
 694                 (struct files_ref_iterator *)ref_iterator;
 695         int ok = ITER_DONE;
 696
 697         if (iter->iter0)
 698                 ok = ref_iterator_abort(iter->iter0);
 699
 700         base_ref_iterator_free(ref_iterator);
 701         return ok;
 702 }
 703
 704 static struct ref_iterator_vtable files_ref_iterator_vtable = {
 705         files_ref_iterator_advance,
 706         files_ref_iterator_peel,
 707         files_ref_iterator_abort
 708 };
 709
 710 static struct ref_iterator *files_ref_iterator_begin(
 711                 struct ref_store *ref_store,
 712                 const char *prefix, unsigned int flags)
 713 {
 714         struct files_ref_store *refs;
 715         struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 716         struct files_ref_iterator *iter;
 717         struct ref_iterator *ref_iterator;
 718         unsigned int required_flags = REF_STORE_READ;
 719
 720         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 721                 required_flags |= REF_STORE_ODB;
 722
 723         refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 724
 725         /*
 726          * We must make sure that all loose refs are read before
 727          * accessing the packed-refs file; this avoids a race
 728          * condition if loose refs are migrated to the packed-refs
 729          * file by a simultaneous process, but our in-memory view is
 730          * from before the migration. We ensure this as follows:
 731          * First, we call start the loose refs iteration with its
 732          * `prime_ref` argument set to true. This causes the loose
 733          * references in the subtree to be pre-read into the cache.
 734          * (If they've already been read, that's OK; we only need to
 735          * guarantee that they're read before the packed refs, not
 736          * *how much* before.) After that, we call
 737          * packed_ref_iterator_begin(), which internally checks
 738          * whether the packed-ref cache is up to date with what is on
 739          * disk, and re-reads it if not.
 740          */
 741
 742         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 743                                               prefix, 1);
 744
 745         /*
 746          * The packed-refs file might contain broken references, for
 747          * example an old version of a reference that points at an
 748          * object that has since been garbage-collected. This is OK as
 749          * long as there is a corresponding loose reference that
 750          * overrides it, and we don't want to emit an error message in
 751          * this case. So ask the packed_ref_store for all of its
 752          * references, and (if needed) do our own check for broken
 753          * ones in files_ref_iterator_advance(), after we have merged
 754          * the packed and loose references.
 755          */
 756         packed_iter = refs_ref_iterator_begin(
 757                         refs->packed_ref_store, prefix, 0,
 758                         DO_FOR_EACH_INCLUDE_BROKEN);
 759
 760         overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 761
 762         iter = xcalloc(1, sizeof(*iter));
 763         ref_iterator = &iter->base;
 764         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 765                                overlay_iter->ordered);
 766         iter->iter0 = overlay_iter;
 767         iter->flags = flags;
 768
 769         return ref_iterator;
 770 }
 771
 772 /*
 773  * Verify that the reference locked by lock has the value old_oid
 774  * (unless it is NULL).  Fail if the reference doesn't exist and
 775  * mustexist is set. Return 0 on success. On error, write an error
 776  * message to err, set errno, and return a negative value.
 777  */
 778 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 779                        const struct object_id *old_oid, int mustexist,
 780                        struct strbuf *err)
 781 {
 782         assert(err);
 783
 784         if (refs_read_ref_full(ref_store, lock->ref_name,
 785                                mustexist ? RESOLVE_REF_READING : 0,
 786                                &lock->old_oid, NULL)) {
 787                 if (old_oid) {
 788                         int save_errno = errno;
 789                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 790                         errno = save_errno;
 791                         return -1;
 792                 } else {
 793                         oidclr(&lock->old_oid);
 794                         return 0;
 795                 }
 796         }
 797         if (old_oid && oidcmp(&lock->old_oid, old_oid)) {
 798                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 799                             lock->ref_name,
 800                             oid_to_hex(&lock->old_oid),
 801                             oid_to_hex(old_oid));
 802                 errno = EBUSY;
 803                 return -1;
 804         }
 805         return 0;
 806 }
 807
 808 static int remove_empty_directories(struct strbuf *path)
 809 {
 810         /*
 811          * we want to create a file but there is a directory there;
 812          * if that is an empty directory (or a directory that contains
 813          * only empty directories), remove them.
 814          */
 815         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 816 }
 817
 818 static int create_reflock(const char *path, void *cb)
 819 {
 820         struct lock_file *lk = cb;
 821
 822         return hold_lock_file_for_update_timeout(
 823                         lk, path, LOCK_NO_DEREF,
 824                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 825 }
 826
 827 /*
 828  * Locks a ref returning the lock on success and NULL on failure.
 829  * On failure errno is set to something meaningful.
 830  */
 831 static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
 832                                            const char *refname,
 833                                            const struct object_id *old_oid,
 834                                            const struct string_list *extras,
 835                                            const struct string_list *skip,
 836                                            unsigned int flags, int *type,
 837                                            struct strbuf *err)
 838 {
 839         struct strbuf ref_file = STRBUF_INIT;
 840         struct ref_lock *lock;
 841         int last_errno = 0;
 842         int mustexist = (old_oid && !is_null_oid(old_oid));
 843         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 844         int resolved;
 845
 846         files_assert_main_repository(refs, "lock_ref_oid_basic");
 847         assert(err);
 848
 849         lock = xcalloc(1, sizeof(struct ref_lock));
 850
 851         if (mustexist)
 852                 resolve_flags |= RESOLVE_REF_READING;
 853         if (flags & REF_DELETING)
 854                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 855
 856         files_ref_path(refs, &ref_file, refname);
 857         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 858                                              refname, resolve_flags,
 859                                              &lock->old_oid, type);
 860         if (!resolved && errno == EISDIR) {
 861                 /*
 862                  * we are trying to lock foo but we used to
 863                  * have foo/bar which now does not exist;
 864                  * it is normal for the empty directory 'foo'
 865                  * to remain.
 866                  */
 867                 if (remove_empty_directories(&ref_file)) {
 868                         last_errno = errno;
 869                         if (!refs_verify_refname_available(
 870                                             &refs->base,
 871                                             refname, extras, skip, err))
 872                                 strbuf_addf(err, "there are still refs under '%s'",
 873                                             refname);
 874                         goto error_return;
 875                 }
 876                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 877                                                      refname, resolve_flags,
 878                                                      &lock->old_oid, type);
 879         }
 880         if (!resolved) {
 881                 last_errno = errno;
 882                 if (last_errno != ENOTDIR ||
 883                     !refs_verify_refname_available(&refs->base, refname,
 884                                                    extras, skip, err))
 885                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 886                                     refname, strerror(last_errno));
 887
 888                 goto error_return;
 889         }
 890
 891         /*
 892          * If the ref did not exist and we are creating it, make sure
 893          * there is no existing packed ref whose name begins with our
 894          * refname, nor a packed ref whose name is a proper prefix of
 895          * our refname.
 896          */
 897         if (is_null_oid(&lock->old_oid) &&
 898             refs_verify_refname_available(refs->packed_ref_store, refname,
 899                                           extras, skip, err)) {
 900                 last_errno = ENOTDIR;
 901                 goto error_return;
 902         }
 903
 904         lock->ref_name = xstrdup(refname);
 905
 906         if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 907                 last_errno = errno;
 908                 unable_to_lock_message(ref_file.buf, errno, err);
 909                 goto error_return;
 910         }
 911
 912         if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
 913                 last_errno = errno;
 914                 goto error_return;
 915         }
 916         goto out;
 917
 918  error_return:
 919         unlock_ref(lock);
 920         lock = NULL;
 921
 922  out:
 923         strbuf_release(&ref_file);
 924         errno = last_errno;
 925         return lock;
 926 }
 927
 928 struct ref_to_prune {
 929         struct ref_to_prune *next;
 930         struct object_id oid;
 931         char name[FLEX_ARRAY];
 932 };
 933
 934 enum {
 935         REMOVE_EMPTY_PARENTS_REF = 0x01,
 936         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 937 };
 938
 939 /*
 940  * Remove empty parent directories associated with the specified
 941  * reference and/or its reflog, but spare [logs/]refs/ and immediate
 942  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 943  * REMOVE_EMPTY_PARENTS_REFLOG.
 944  */
 945 static void try_remove_empty_parents(struct files_ref_store *refs,
 946                                      const char *refname,
 947                                      unsigned int flags)
 948 {
 949         struct strbuf buf = STRBUF_INIT;
 950         struct strbuf sb = STRBUF_INIT;
 951         char *p, *q;
 952         int i;
 953
 954         strbuf_addstr(&buf, refname);
 955         p = buf.buf;
 956         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
 957                 while (*p && *p != '/')
 958                         p++;
 959                 /* tolerate duplicate slashes; see check_refname_format() */
 960                 while (*p == '/')
 961                         p++;
 962         }
 963         q = buf.buf + buf.len;
 964         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
 965                 while (q > p && *q != '/')
 966                         q--;
 967                 while (q > p && *(q-1) == '/')
 968                         q--;
 969                 if (q == p)
 970                         break;
 971                 strbuf_setlen(&buf, q - buf.buf);
 972
 973                 strbuf_reset(&sb);
 974                 files_ref_path(refs, &sb, buf.buf);
 975                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
 976                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
 977
 978                 strbuf_reset(&sb);
 979                 files_reflog_path(refs, &sb, buf.buf);
 980                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
 981                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
 982         }
 983         strbuf_release(&buf);
 984         strbuf_release(&sb);
 985 }
 986
 987 /* make sure nobody touched the ref, and unlink */
 988 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
 989 {
 990         struct ref_transaction *transaction;
 991         struct strbuf err = STRBUF_INIT;
 992         int ret = -1;
 993
 994         if (check_refname_format(r->name, 0))
 995                 return;
 996
 997         transaction = ref_store_transaction_begin(&refs->base, &err);
 998         if (!transaction)
 999                 goto cleanup;
1000         ref_transaction_add_update(
1001                         transaction, r->name,
1002                         REF_NODEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_ISPRUNING,
1003                         &null_oid, &r->oid, NULL);
1004         if (ref_transaction_commit(transaction, &err))
1005                 goto cleanup;
1006
1007         ret = 0;
1008
1009 cleanup:
1010         if (ret)
1011                 error("%s", err.buf);
1012         strbuf_release(&err);
1013         ref_transaction_free(transaction);
1014         return;
1015 }
1016
1017 /*
1018  * Prune the loose versions of the references in the linked list
1019  * `*refs_to_prune`, freeing the entries in the list as we go.
1020  */
1021 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1022 {
1023         while (*refs_to_prune) {
1024                 struct ref_to_prune *r = *refs_to_prune;
1025                 *refs_to_prune = r->next;
1026                 prune_ref(refs, r);
1027                 free(r);
1028         }
1029 }
1030
1031 /*
1032  * Return true if the specified reference should be packed.
1033  */
1034 static int should_pack_ref(const char *refname,
1035                            const struct object_id *oid, unsigned int ref_flags,
1036                            unsigned int pack_flags)
1037 {
1038         /* Do not pack per-worktree refs: */
1039         if (ref_type(refname) != REF_TYPE_NORMAL)
1040                 return 0;
1041
1042         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1043         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1044                 return 0;
1045
1046         /* Do not pack symbolic refs: */
1047         if (ref_flags & REF_ISSYMREF)
1048                 return 0;
1049
1050         /* Do not pack broken refs: */
1051         if (!ref_resolves_to_object(refname, oid, ref_flags))
1052                 return 0;
1053
1054         return 1;
1055 }
1056
1057 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1058 {
1059         struct files_ref_store *refs =
1060                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1061                                "pack_refs");
1062         struct ref_iterator *iter;
1063         int ok;
1064         struct ref_to_prune *refs_to_prune = NULL;
1065         struct strbuf err = STRBUF_INIT;
1066         struct ref_transaction *transaction;
1067
1068         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1069         if (!transaction)
1070                 return -1;
1071
1072         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1073
1074         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1075         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1076                 /*
1077                  * If the loose reference can be packed, add an entry
1078                  * in the packed ref cache. If the reference should be
1079                  * pruned, also add it to refs_to_prune.
1080                  */
1081                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1082                                      flags))
1083                         continue;
1084
1085                 /*
1086                  * Add a reference creation for this reference to the
1087                  * packed-refs transaction:
1088                  */
1089                 if (ref_transaction_update(transaction, iter->refname,
1090                                            iter->oid, NULL,
1091                                            REF_NODEREF, NULL, &err))
1092                         die("failure preparing to create packed reference %s: %s",
1093                             iter->refname, err.buf);
1094
1095                 /* Schedule the loose reference for pruning if requested. */
1096                 if ((flags & PACK_REFS_PRUNE)) {
1097                         struct ref_to_prune *n;
1098                         FLEX_ALLOC_STR(n, name, iter->refname);
1099                         oidcpy(&n->oid, iter->oid);
1100                         n->next = refs_to_prune;
1101                         refs_to_prune = n;
1102                 }
1103         }
1104         if (ok != ITER_DONE)
1105                 die("error while iterating over references");
1106
1107         if (ref_transaction_commit(transaction, &err))
1108                 die("unable to write new packed-refs: %s", err.buf);
1109
1110         ref_transaction_free(transaction);
1111
1112         packed_refs_unlock(refs->packed_ref_store);
1113
1114         prune_refs(refs, &refs_to_prune);
1115         strbuf_release(&err);
1116         return 0;
1117 }
1118
1119 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1120                              struct string_list *refnames, unsigned int flags)
1121 {
1122         struct files_ref_store *refs =
1123                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1124         struct strbuf err = STRBUF_INIT;
1125         int i, result = 0;
1126
1127         if (!refnames->nr)
1128                 return 0;
1129
1130         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1131                 goto error;
1132
1133         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1134                 packed_refs_unlock(refs->packed_ref_store);
1135                 goto error;
1136         }
1137
1138         packed_refs_unlock(refs->packed_ref_store);
1139
1140         for (i = 0; i < refnames->nr; i++) {
1141                 const char *refname = refnames->items[i].string;
1142
1143                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1144                         result |= error(_("could not remove reference %s"), refname);
1145         }
1146
1147         strbuf_release(&err);
1148         return result;
1149
1150 error:
1151         /*
1152          * If we failed to rewrite the packed-refs file, then it is
1153          * unsafe to try to remove loose refs, because doing so might
1154          * expose an obsolete packed value for a reference that might
1155          * even point at an object that has been garbage collected.
1156          */
1157         if (refnames->nr == 1)
1158                 error(_("could not delete reference %s: %s"),
1159                       refnames->items[0].string, err.buf);
1160         else
1161                 error(_("could not delete references: %s"), err.buf);
1162
1163         strbuf_release(&err);
1164         return -1;
1165 }
1166
1167 /*
1168  * People using contrib's git-new-workdir have .git/logs/refs ->
1169  * /some/other/path/.git/logs/refs, and that may live on another device.
1170  *
1171  * IOW, to avoid cross device rename errors, the temporary renamed log must
1172  * live into logs/refs.
1173  */
1174 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1175
1176 struct rename_cb {
1177         const char *tmp_renamed_log;
1178         int true_errno;
1179 };
1180
1181 static int rename_tmp_log_callback(const char *path, void *cb_data)
1182 {
1183         struct rename_cb *cb = cb_data;
1184
1185         if (rename(cb->tmp_renamed_log, path)) {
1186                 /*
1187                  * rename(a, b) when b is an existing directory ought
1188                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1189                  * Sheesh. Record the true errno for error reporting,
1190                  * but report EISDIR to raceproof_create_file() so
1191                  * that it knows to retry.
1192                  */
1193                 cb->true_errno = errno;
1194                 if (errno == ENOTDIR)
1195                         errno = EISDIR;
1196                 return -1;
1197         } else {
1198                 return 0;
1199         }
1200 }
1201
1202 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1203 {
1204         struct strbuf path = STRBUF_INIT;
1205         struct strbuf tmp = STRBUF_INIT;
1206         struct rename_cb cb;
1207         int ret;
1208
1209         files_reflog_path(refs, &path, newrefname);
1210         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1211         cb.tmp_renamed_log = tmp.buf;
1212         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1213         if (ret) {
1214                 if (errno == EISDIR)
1215                         error("directory not empty: %s", path.buf);
1216                 else
1217                         error("unable to move logfile %s to %s: %s",
1218                               tmp.buf, path.buf,
1219                               strerror(cb.true_errno));
1220         }
1221
1222         strbuf_release(&path);
1223         strbuf_release(&tmp);
1224         return ret;
1225 }
1226
1227 static int write_ref_to_lockfile(struct ref_lock *lock,
1228                                  const struct object_id *oid, struct strbuf *err);
1229 static int commit_ref_update(struct files_ref_store *refs,
1230                              struct ref_lock *lock,
1231                              const struct object_id *oid, const char *logmsg,
1232                              struct strbuf *err);
1233
1234 static int files_copy_or_rename_ref(struct ref_store *ref_store,
1235                             const char *oldrefname, const char *newrefname,
1236                             const char *logmsg, int copy)
1237 {
1238         struct files_ref_store *refs =
1239                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1240         struct object_id oid, orig_oid;
1241         int flag = 0, logmoved = 0;
1242         struct ref_lock *lock;
1243         struct stat loginfo;
1244         struct strbuf sb_oldref = STRBUF_INIT;
1245         struct strbuf sb_newref = STRBUF_INIT;
1246         struct strbuf tmp_renamed_log = STRBUF_INIT;
1247         int log, ret;
1248         struct strbuf err = STRBUF_INIT;
1249
1250         files_reflog_path(refs, &sb_oldref, oldrefname);
1251         files_reflog_path(refs, &sb_newref, newrefname);
1252         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1253
1254         log = !lstat(sb_oldref.buf, &loginfo);
1255         if (log && S_ISLNK(loginfo.st_mode)) {
1256                 ret = error("reflog for %s is a symlink", oldrefname);
1257                 goto out;
1258         }
1259
1260         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1261                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1262                                 &orig_oid, &flag)) {
1263                 ret = error("refname %s not found", oldrefname);
1264                 goto out;
1265         }
1266
1267         if (flag & REF_ISSYMREF) {
1268                 if (copy)
1269                         ret = error("refname %s is a symbolic ref, copying it is not supported",
1270                                     oldrefname);
1271                 else
1272                         ret = error("refname %s is a symbolic ref, renaming it is not supported",
1273                                     oldrefname);
1274                 goto out;
1275         }
1276         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1277                 ret = 1;
1278                 goto out;
1279         }
1280
1281         if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1282                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1283                             oldrefname, strerror(errno));
1284                 goto out;
1285         }
1286
1287         if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1288                 ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1289                             oldrefname, strerror(errno));
1290                 goto out;
1291         }
1292
1293         if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1294                             &orig_oid, REF_NODEREF)) {
1295                 error("unable to delete old %s", oldrefname);
1296                 goto rollback;
1297         }
1298
1299         /*
1300          * Since we are doing a shallow lookup, oid is not the
1301          * correct value to pass to delete_ref as old_oid. But that
1302          * doesn't matter, because an old_oid check wouldn't add to
1303          * the safety anyway; we want to delete the reference whatever
1304          * its current value.
1305          */
1306         if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1307                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1308                                 &oid, NULL) &&
1309             refs_delete_ref(&refs->base, NULL, newrefname,
1310                             NULL, REF_NODEREF)) {
1311                 if (errno == EISDIR) {
1312                         struct strbuf path = STRBUF_INIT;
1313                         int result;
1314
1315                         files_ref_path(refs, &path, newrefname);
1316                         result = remove_empty_directories(&path);
1317                         strbuf_release(&path);
1318
1319                         if (result) {
1320                                 error("Directory not empty: %s", newrefname);
1321                                 goto rollback;
1322                         }
1323                 } else {
1324                         error("unable to delete existing %s", newrefname);
1325                         goto rollback;
1326                 }
1327         }
1328
1329         if (log && rename_tmp_log(refs, newrefname))
1330                 goto rollback;
1331
1332         logmoved = log;
1333
1334         lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1335                                   REF_NODEREF, NULL, &err);
1336         if (!lock) {
1337                 if (copy)
1338                         error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1339                 else
1340                         error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1341                 strbuf_release(&err);
1342                 goto rollback;
1343         }
1344         oidcpy(&lock->old_oid, &orig_oid);
1345
1346         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1347             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1348                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1349                 strbuf_release(&err);
1350                 goto rollback;
1351         }
1352
1353         ret = 0;
1354         goto out;
1355
1356  rollback:
1357         lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1358                                   REF_NODEREF, NULL, &err);
1359         if (!lock) {
1360                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1361                 strbuf_release(&err);
1362                 goto rollbacklog;
1363         }
1364
1365         flag = log_all_ref_updates;
1366         log_all_ref_updates = LOG_REFS_NONE;
1367         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1368             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1369                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1370                 strbuf_release(&err);
1371         }
1372         log_all_ref_updates = flag;
1373
1374  rollbacklog:
1375         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1376                 error("unable to restore logfile %s from %s: %s",
1377                         oldrefname, newrefname, strerror(errno));
1378         if (!logmoved && log &&
1379             rename(tmp_renamed_log.buf, sb_oldref.buf))
1380                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1381                         oldrefname, strerror(errno));
1382         ret = 1;
1383  out:
1384         strbuf_release(&sb_newref);
1385         strbuf_release(&sb_oldref);
1386         strbuf_release(&tmp_renamed_log);
1387
1388         return ret;
1389 }
1390
1391 static int files_rename_ref(struct ref_store *ref_store,
1392                             const char *oldrefname, const char *newrefname,
1393                             const char *logmsg)
1394 {
1395         return files_copy_or_rename_ref(ref_store, oldrefname,
1396                                  newrefname, logmsg, 0);
1397 }
1398
1399 static int files_copy_ref(struct ref_store *ref_store,
1400                             const char *oldrefname, const char *newrefname,
1401                             const char *logmsg)
1402 {
1403         return files_copy_or_rename_ref(ref_store, oldrefname,
1404                                  newrefname, logmsg, 1);
1405 }
1406
1407 static int close_ref_gently(struct ref_lock *lock)
1408 {
1409         if (close_lock_file_gently(&lock->lk))
1410                 return -1;
1411         return 0;
1412 }
1413
1414 static int commit_ref(struct ref_lock *lock)
1415 {
1416         char *path = get_locked_file_path(&lock->lk);
1417         struct stat st;
1418
1419         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1420                 /*
1421                  * There is a directory at the path we want to rename
1422                  * the lockfile to. Hopefully it is empty; try to
1423                  * delete it.
1424                  */
1425                 size_t len = strlen(path);
1426                 struct strbuf sb_path = STRBUF_INIT;
1427
1428                 strbuf_attach(&sb_path, path, len, len);
1429
1430                 /*
1431                  * If this fails, commit_lock_file() will also fail
1432                  * and will report the problem.
1433                  */
1434                 remove_empty_directories(&sb_path);
1435                 strbuf_release(&sb_path);
1436         } else {
1437                 free(path);
1438         }
1439
1440         if (commit_lock_file(&lock->lk))
1441                 return -1;
1442         return 0;
1443 }
1444
1445 static int open_or_create_logfile(const char *path, void *cb)
1446 {
1447         int *fd = cb;
1448
1449         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1450         return (*fd < 0) ? -1 : 0;
1451 }
1452
1453 /*
1454  * Create a reflog for a ref. If force_create = 0, only create the
1455  * reflog for certain refs (those for which should_autocreate_reflog
1456  * returns non-zero). Otherwise, create it regardless of the reference
1457  * name. If the logfile already existed or was created, return 0 and
1458  * set *logfd to the file descriptor opened for appending to the file.
1459  * If no logfile exists and we decided not to create one, return 0 and
1460  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1461  * return -1.
1462  */
1463 static int log_ref_setup(struct files_ref_store *refs,
1464                          const char *refname, int force_create,
1465                          int *logfd, struct strbuf *err)
1466 {
1467         struct strbuf logfile_sb = STRBUF_INIT;
1468         char *logfile;
1469
1470         files_reflog_path(refs, &logfile_sb, refname);
1471         logfile = strbuf_detach(&logfile_sb, NULL);
1472
1473         if (force_create || should_autocreate_reflog(refname)) {
1474                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1475                         if (errno == ENOENT)
1476                                 strbuf_addf(err, "unable to create directory for '%s': "
1477                                             "%s", logfile, strerror(errno));
1478                         else if (errno == EISDIR)
1479                                 strbuf_addf(err, "there are still logs under '%s'",
1480                                             logfile);
1481                         else
1482                                 strbuf_addf(err, "unable to append to '%s': %s",
1483                                             logfile, strerror(errno));
1484
1485                         goto error;
1486                 }
1487         } else {
1488                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1489                 if (*logfd < 0) {
1490                         if (errno == ENOENT || errno == EISDIR) {
1491                                 /*
1492                                  * The logfile doesn't already exist,
1493                                  * but that is not an error; it only
1494                                  * means that we won't write log
1495                                  * entries to it.
1496                                  */
1497                                 ;
1498                         } else {
1499                                 strbuf_addf(err, "unable to append to '%s': %s",
1500                                             logfile, strerror(errno));
1501                                 goto error;
1502                         }
1503                 }
1504         }
1505
1506         if (*logfd >= 0)
1507                 adjust_shared_perm(logfile);
1508
1509         free(logfile);
1510         return 0;
1511
1512 error:
1513         free(logfile);
1514         return -1;
1515 }
1516
1517 static int files_create_reflog(struct ref_store *ref_store,
1518                                const char *refname, int force_create,
1519                                struct strbuf *err)
1520 {
1521         struct files_ref_store *refs =
1522                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1523         int fd;
1524
1525         if (log_ref_setup(refs, refname, force_create, &fd, err))
1526                 return -1;
1527
1528         if (fd >= 0)
1529                 close(fd);
1530
1531         return 0;
1532 }
1533
1534 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1535                             const struct object_id *new_oid,
1536                             const char *committer, const char *msg)
1537 {
1538         int msglen, written;
1539         unsigned maxlen, len;
1540         char *logrec;
1541
1542         msglen = msg ? strlen(msg) : 0;
1543         maxlen = strlen(committer) + msglen + 100;
1544         logrec = xmalloc(maxlen);
1545         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1546                         oid_to_hex(old_oid),
1547                         oid_to_hex(new_oid),
1548                         committer);
1549         if (msglen)
1550                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1551
1552         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1553         free(logrec);
1554         if (written < 0)
1555                 return -1;
1556
1557         return 0;
1558 }
1559
1560 static int files_log_ref_write(struct files_ref_store *refs,
1561                                const char *refname, const struct object_id *old_oid,
1562                                const struct object_id *new_oid, const char *msg,
1563                                int flags, struct strbuf *err)
1564 {
1565         int logfd, result;
1566
1567         if (log_all_ref_updates == LOG_REFS_UNSET)
1568                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1569
1570         result = log_ref_setup(refs, refname,
1571                                flags & REF_FORCE_CREATE_REFLOG,
1572                                &logfd, err);
1573
1574         if (result)
1575                 return result;
1576
1577         if (logfd < 0)
1578                 return 0;
1579         result = log_ref_write_fd(logfd, old_oid, new_oid,
1580                                   git_committer_info(0), msg);
1581         if (result) {
1582                 struct strbuf sb = STRBUF_INIT;
1583                 int save_errno = errno;
1584
1585                 files_reflog_path(refs, &sb, refname);
1586                 strbuf_addf(err, "unable to append to '%s': %s",
1587                             sb.buf, strerror(save_errno));
1588                 strbuf_release(&sb);
1589                 close(logfd);
1590                 return -1;
1591         }
1592         if (close(logfd)) {
1593                 struct strbuf sb = STRBUF_INIT;
1594                 int save_errno = errno;
1595
1596                 files_reflog_path(refs, &sb, refname);
1597                 strbuf_addf(err, "unable to append to '%s': %s",
1598                             sb.buf, strerror(save_errno));
1599                 strbuf_release(&sb);
1600                 return -1;
1601         }
1602         return 0;
1603 }
1604
1605 /*
1606  * Write sha1 into the open lockfile, then close the lockfile. On
1607  * errors, rollback the lockfile, fill in *err and
1608  * return -1.
1609  */
1610 static int write_ref_to_lockfile(struct ref_lock *lock,
1611                                  const struct object_id *oid, struct strbuf *err)
1612 {
1613         static char term = '\n';
1614         struct object *o;
1615         int fd;
1616
1617         o = parse_object(oid);
1618         if (!o) {
1619                 strbuf_addf(err,
1620                             "trying to write ref '%s' with nonexistent object %s",
1621                             lock->ref_name, oid_to_hex(oid));
1622                 unlock_ref(lock);
1623                 return -1;
1624         }
1625         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1626                 strbuf_addf(err,
1627                             "trying to write non-commit object %s to branch '%s'",
1628                             oid_to_hex(oid), lock->ref_name);
1629                 unlock_ref(lock);
1630                 return -1;
1631         }
1632         fd = get_lock_file_fd(&lock->lk);
1633         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1634             write_in_full(fd, &term, 1) < 0 ||
1635             close_ref_gently(lock) < 0) {
1636                 strbuf_addf(err,
1637                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1638                 unlock_ref(lock);
1639                 return -1;
1640         }
1641         return 0;
1642 }
1643
1644 /*
1645  * Commit a change to a loose reference that has already been written
1646  * to the loose reference lockfile. Also update the reflogs if
1647  * necessary, using the specified lockmsg (which can be NULL).
1648  */
1649 static int commit_ref_update(struct files_ref_store *refs,
1650                              struct ref_lock *lock,
1651                              const struct object_id *oid, const char *logmsg,
1652                              struct strbuf *err)
1653 {
1654         files_assert_main_repository(refs, "commit_ref_update");
1655
1656         clear_loose_ref_cache(refs);
1657         if (files_log_ref_write(refs, lock->ref_name,
1658                                 &lock->old_oid, oid,
1659                                 logmsg, 0, err)) {
1660                 char *old_msg = strbuf_detach(err, NULL);
1661                 strbuf_addf(err, "cannot update the ref '%s': %s",
1662                             lock->ref_name, old_msg);
1663                 free(old_msg);
1664                 unlock_ref(lock);
1665                 return -1;
1666         }
1667
1668         if (strcmp(lock->ref_name, "HEAD") != 0) {
1669                 /*
1670                  * Special hack: If a branch is updated directly and HEAD
1671                  * points to it (may happen on the remote side of a push
1672                  * for example) then logically the HEAD reflog should be
1673                  * updated too.
1674                  * A generic solution implies reverse symref information,
1675                  * but finding all symrefs pointing to the given branch
1676                  * would be rather costly for this rare event (the direct
1677                  * update of a branch) to be worth it.  So let's cheat and
1678                  * check with HEAD only which should cover 99% of all usage
1679                  * scenarios (even 100% of the default ones).
1680                  */
1681                 int head_flag;
1682                 const char *head_ref;
1683
1684                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1685                                                    RESOLVE_REF_READING,
1686                                                    NULL, &head_flag);
1687                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1688                     !strcmp(head_ref, lock->ref_name)) {
1689                         struct strbuf log_err = STRBUF_INIT;
1690                         if (files_log_ref_write(refs, "HEAD",
1691                                                 &lock->old_oid, oid,
1692                                                 logmsg, 0, &log_err)) {
1693                                 error("%s", log_err.buf);
1694                                 strbuf_release(&log_err);
1695                         }
1696                 }
1697         }
1698
1699         if (commit_ref(lock)) {
1700                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1701                 unlock_ref(lock);
1702                 return -1;
1703         }
1704
1705         unlock_ref(lock);
1706         return 0;
1707 }
1708
1709 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1710 {
1711         int ret = -1;
1712 #ifndef NO_SYMLINK_HEAD
1713         char *ref_path = get_locked_file_path(&lock->lk);
1714         unlink(ref_path);
1715         ret = symlink(target, ref_path);
1716         free(ref_path);
1717
1718         if (ret)
1719                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1720 #endif
1721         return ret;
1722 }
1723
1724 static void update_symref_reflog(struct files_ref_store *refs,
1725                                  struct ref_lock *lock, const char *refname,
1726                                  const char *target, const char *logmsg)
1727 {
1728         struct strbuf err = STRBUF_INIT;
1729         struct object_id new_oid;
1730         if (logmsg &&
1731             !refs_read_ref_full(&refs->base, target,
1732                                 RESOLVE_REF_READING, &new_oid, NULL) &&
1733             files_log_ref_write(refs, refname, &lock->old_oid,
1734                                 &new_oid, logmsg, 0, &err)) {
1735                 error("%s", err.buf);
1736                 strbuf_release(&err);
1737         }
1738 }
1739
1740 static int create_symref_locked(struct files_ref_store *refs,
1741                                 struct ref_lock *lock, const char *refname,
1742                                 const char *target, const char *logmsg)
1743 {
1744         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1745                 update_symref_reflog(refs, lock, refname, target, logmsg);
1746                 return 0;
1747         }
1748
1749         if (!fdopen_lock_file(&lock->lk, "w"))
1750                 return error("unable to fdopen %s: %s",
1751                              lock->lk.tempfile->filename.buf, strerror(errno));
1752
1753         update_symref_reflog(refs, lock, refname, target, logmsg);
1754
1755         /* no error check; commit_ref will check ferror */
1756         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1757         if (commit_ref(lock) < 0)
1758                 return error("unable to write symref for %s: %s", refname,
1759                              strerror(errno));
1760         return 0;
1761 }
1762
1763 static int files_create_symref(struct ref_store *ref_store,
1764                                const char *refname, const char *target,
1765                                const char *logmsg)
1766 {
1767         struct files_ref_store *refs =
1768                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1769         struct strbuf err = STRBUF_INIT;
1770         struct ref_lock *lock;
1771         int ret;
1772
1773         lock = lock_ref_oid_basic(refs, refname, NULL,
1774                                   NULL, NULL, REF_NODEREF, NULL,
1775                                   &err);
1776         if (!lock) {
1777                 error("%s", err.buf);
1778                 strbuf_release(&err);
1779                 return -1;
1780         }
1781
1782         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1783         unlock_ref(lock);
1784         return ret;
1785 }
1786
1787 static int files_reflog_exists(struct ref_store *ref_store,
1788                                const char *refname)
1789 {
1790         struct files_ref_store *refs =
1791                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1792         struct strbuf sb = STRBUF_INIT;
1793         struct stat st;
1794         int ret;
1795
1796         files_reflog_path(refs, &sb, refname);
1797         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1798         strbuf_release(&sb);
1799         return ret;
1800 }
1801
1802 static int files_delete_reflog(struct ref_store *ref_store,
1803                                const char *refname)
1804 {
1805         struct files_ref_store *refs =
1806                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1807         struct strbuf sb = STRBUF_INIT;
1808         int ret;
1809
1810         files_reflog_path(refs, &sb, refname);
1811         ret = remove_path(sb.buf);
1812         strbuf_release(&sb);
1813         return ret;
1814 }
1815
1816 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1817 {
1818         struct object_id ooid, noid;
1819         char *email_end, *message;
1820         timestamp_t timestamp;
1821         int tz;
1822         const char *p = sb->buf;
1823
1824         /* old SP new SP name <email> SP time TAB msg LF */
1825         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1826             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1827             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1828             !(email_end = strchr(p, '>')) ||
1829             email_end[1] != ' ' ||
1830             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1831             !message || message[0] != ' ' ||
1832             (message[1] != '+' && message[1] != '-') ||
1833             !isdigit(message[2]) || !isdigit(message[3]) ||
1834             !isdigit(message[4]) || !isdigit(message[5]))
1835                 return 0; /* corrupt? */
1836         email_end[1] = '\0';
1837         tz = strtol(message + 1, NULL, 10);
1838         if (message[6] != '\t')
1839                 message += 6;
1840         else
1841                 message += 7;
1842         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1843 }
1844
1845 static char *find_beginning_of_line(char *bob, char *scan)
1846 {
1847         while (bob < scan && *(--scan) != '\n')
1848                 ; /* keep scanning backwards */
1849         /*
1850          * Return either beginning of the buffer, or LF at the end of
1851          * the previous line.
1852          */
1853         return scan;
1854 }
1855
1856 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1857                                              const char *refname,
1858                                              each_reflog_ent_fn fn,
1859                                              void *cb_data)
1860 {
1861         struct files_ref_store *refs =
1862                 files_downcast(ref_store, REF_STORE_READ,
1863                                "for_each_reflog_ent_reverse");
1864         struct strbuf sb = STRBUF_INIT;
1865         FILE *logfp;
1866         long pos;
1867         int ret = 0, at_tail = 1;
1868
1869         files_reflog_path(refs, &sb, refname);
1870         logfp = fopen(sb.buf, "r");
1871         strbuf_release(&sb);
1872         if (!logfp)
1873                 return -1;
1874
1875         /* Jump to the end */
1876         if (fseek(logfp, 0, SEEK_END) < 0)
1877                 ret = error("cannot seek back reflog for %s: %s",
1878                             refname, strerror(errno));
1879         pos = ftell(logfp);
1880         while (!ret && 0 < pos) {
1881                 int cnt;
1882                 size_t nread;
1883                 char buf[BUFSIZ];
1884                 char *endp, *scanp;
1885
1886                 /* Fill next block from the end */
1887                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1888                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1889                         ret = error("cannot seek back reflog for %s: %s",
1890                                     refname, strerror(errno));
1891                         break;
1892                 }
1893                 nread = fread(buf, cnt, 1, logfp);
1894                 if (nread != 1) {
1895                         ret = error("cannot read %d bytes from reflog for %s: %s",
1896                                     cnt, refname, strerror(errno));
1897                         break;
1898                 }
1899                 pos -= cnt;
1900
1901                 scanp = endp = buf + cnt;
1902                 if (at_tail && scanp[-1] == '\n')
1903                         /* Looking at the final LF at the end of the file */
1904                         scanp--;
1905                 at_tail = 0;
1906
1907                 while (buf < scanp) {
1908                         /*
1909                          * terminating LF of the previous line, or the beginning
1910                          * of the buffer.
1911                          */
1912                         char *bp;
1913
1914                         bp = find_beginning_of_line(buf, scanp);
1915
1916                         if (*bp == '\n') {
1917                                 /*
1918                                  * The newline is the end of the previous line,
1919                                  * so we know we have complete line starting
1920                                  * at (bp + 1). Prefix it onto any prior data
1921                                  * we collected for the line and process it.
1922                                  */
1923                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1924                                 scanp = bp;
1925                                 endp = bp + 1;
1926                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1927                                 strbuf_reset(&sb);
1928                                 if (ret)
1929                                         break;
1930                         } else if (!pos) {
1931                                 /*
1932                                  * We are at the start of the buffer, and the
1933                                  * start of the file; there is no previous
1934                                  * line, and we have everything for this one.
1935                                  * Process it, and we can end the loop.
1936                                  */
1937                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1938                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1939                                 strbuf_reset(&sb);
1940                                 break;
1941                         }
1942
1943                         if (bp == buf) {
1944                                 /*
1945                                  * We are at the start of the buffer, and there
1946                                  * is more file to read backwards. Which means
1947                                  * we are in the middle of a line. Note that we
1948                                  * may get here even if *bp was a newline; that
1949                                  * just means we are at the exact end of the
1950                                  * previous line, rather than some spot in the
1951                                  * middle.
1952                                  *
1953                                  * Save away what we have to be combined with
1954                                  * the data from the next read.
1955                                  */
1956                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1957                                 break;
1958                         }
1959                 }
1960
1961         }
1962         if (!ret && sb.len)
1963                 die("BUG: reverse reflog parser had leftover data");
1964
1965         fclose(logfp);
1966         strbuf_release(&sb);
1967         return ret;
1968 }
1969
1970 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1971                                      const char *refname,
1972                                      each_reflog_ent_fn fn, void *cb_data)
1973 {
1974         struct files_ref_store *refs =
1975                 files_downcast(ref_store, REF_STORE_READ,
1976                                "for_each_reflog_ent");
1977         FILE *logfp;
1978         struct strbuf sb = STRBUF_INIT;
1979         int ret = 0;
1980
1981         files_reflog_path(refs, &sb, refname);
1982         logfp = fopen(sb.buf, "r");
1983         strbuf_release(&sb);
1984         if (!logfp)
1985                 return -1;
1986
1987         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
1988                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1989         fclose(logfp);
1990         strbuf_release(&sb);
1991         return ret;
1992 }
1993
1994 struct files_reflog_iterator {
1995         struct ref_iterator base;
1996
1997         struct ref_store *ref_store;
1998         struct dir_iterator *dir_iterator;
1999         struct object_id oid;
2000 };
2001
2002 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2003 {
2004         struct files_reflog_iterator *iter =
2005                 (struct files_reflog_iterator *)ref_iterator;
2006         struct dir_iterator *diter = iter->dir_iterator;
2007         int ok;
2008
2009         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2010                 int flags;
2011
2012                 if (!S_ISREG(diter->st.st_mode))
2013                         continue;
2014                 if (diter->basename[0] == '.')
2015                         continue;
2016                 if (ends_with(diter->basename, ".lock"))
2017                         continue;
2018
2019                 if (refs_read_ref_full(iter->ref_store,
2020                                        diter->relative_path, 0,
2021                                        &iter->oid, &flags)) {
2022                         error("bad ref for %s", diter->path.buf);
2023                         continue;
2024                 }
2025
2026                 iter->base.refname = diter->relative_path;
2027                 iter->base.oid = &iter->oid;
2028                 iter->base.flags = flags;
2029                 return ITER_OK;
2030         }
2031
2032         iter->dir_iterator = NULL;
2033         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2034                 ok = ITER_ERROR;
2035         return ok;
2036 }
2037
2038 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2039                                    struct object_id *peeled)
2040 {
2041         die("BUG: ref_iterator_peel() called for reflog_iterator");
2042 }
2043
2044 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2045 {
2046         struct files_reflog_iterator *iter =
2047                 (struct files_reflog_iterator *)ref_iterator;
2048         int ok = ITER_DONE;
2049
2050         if (iter->dir_iterator)
2051                 ok = dir_iterator_abort(iter->dir_iterator);
2052
2053         base_ref_iterator_free(ref_iterator);
2054         return ok;
2055 }
2056
2057 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2058         files_reflog_iterator_advance,
2059         files_reflog_iterator_peel,
2060         files_reflog_iterator_abort
2061 };
2062
2063 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2064                                                   const char *gitdir)
2065 {
2066         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2067         struct ref_iterator *ref_iterator = &iter->base;
2068         struct strbuf sb = STRBUF_INIT;
2069
2070         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2071         strbuf_addf(&sb, "%s/logs", gitdir);
2072         iter->dir_iterator = dir_iterator_begin(sb.buf);
2073         iter->ref_store = ref_store;
2074         strbuf_release(&sb);
2075
2076         return ref_iterator;
2077 }
2078
2079 static enum iterator_selection reflog_iterator_select(
2080         struct ref_iterator *iter_worktree,
2081         struct ref_iterator *iter_common,
2082         void *cb_data)
2083 {
2084         if (iter_worktree) {
2085                 /*
2086                  * We're a bit loose here. We probably should ignore
2087                  * common refs if they are accidentally added as
2088                  * per-worktree refs.
2089                  */
2090                 return ITER_SELECT_0;
2091         } else if (iter_common) {
2092                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2093                         return ITER_SELECT_1;
2094
2095                 /*
2096                  * The main ref store may contain main worktree's
2097                  * per-worktree refs, which should be ignored
2098                  */
2099                 return ITER_SKIP_1;
2100         } else
2101                 return ITER_DONE;
2102 }
2103
2104 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2105 {
2106         struct files_ref_store *refs =
2107                 files_downcast(ref_store, REF_STORE_READ,
2108                                "reflog_iterator_begin");
2109
2110         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2111                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2112         } else {
2113                 return merge_ref_iterator_begin(
2114                         0,
2115                         reflog_iterator_begin(ref_store, refs->gitdir),
2116                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2117                         reflog_iterator_select, refs);
2118         }
2119 }
2120
2121 /*
2122  * If update is a direct update of head_ref (the reference pointed to
2123  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2124  */
2125 static int split_head_update(struct ref_update *update,
2126                              struct ref_transaction *transaction,
2127                              const char *head_ref,
2128                              struct string_list *affected_refnames,
2129                              struct strbuf *err)
2130 {
2131         struct string_list_item *item;
2132         struct ref_update *new_update;
2133
2134         if ((update->flags & REF_LOG_ONLY) ||
2135             (update->flags & REF_ISPRUNING) ||
2136             (update->flags & REF_UPDATE_VIA_HEAD))
2137                 return 0;
2138
2139         if (strcmp(update->refname, head_ref))
2140                 return 0;
2141
2142         /*
2143          * First make sure that HEAD is not already in the
2144          * transaction. This check is O(lg N) in the transaction
2145          * size, but it happens at most once per transaction.
2146          */
2147         if (string_list_has_string(affected_refnames, "HEAD")) {
2148                 /* An entry already existed */
2149                 strbuf_addf(err,
2150                             "multiple updates for 'HEAD' (including one "
2151                             "via its referent '%s') are not allowed",
2152                             update->refname);
2153                 return TRANSACTION_NAME_CONFLICT;
2154         }
2155
2156         new_update = ref_transaction_add_update(
2157                         transaction, "HEAD",
2158                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2159                         &update->new_oid, &update->old_oid,
2160                         update->msg);
2161
2162         /*
2163          * Add "HEAD". This insertion is O(N) in the transaction
2164          * size, but it happens at most once per transaction.
2165          * Add new_update->refname instead of a literal "HEAD".
2166          */
2167         if (strcmp(new_update->refname, "HEAD"))
2168                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2169         item = string_list_insert(affected_refnames, new_update->refname);
2170         item->util = new_update;
2171
2172         return 0;
2173 }
2174
2175 /*
2176  * update is for a symref that points at referent and doesn't have
2177  * REF_NODEREF set. Split it into two updates:
2178  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2179  * - A new, separate update for the referent reference
2180  * Note that the new update will itself be subject to splitting when
2181  * the iteration gets to it.
2182  */
2183 static int split_symref_update(struct files_ref_store *refs,
2184                                struct ref_update *update,
2185                                const char *referent,
2186                                struct ref_transaction *transaction,
2187                                struct string_list *affected_refnames,
2188                                struct strbuf *err)
2189 {
2190         struct string_list_item *item;
2191         struct ref_update *new_update;
2192         unsigned int new_flags;
2193
2194         /*
2195          * First make sure that referent is not already in the
2196          * transaction. This check is O(lg N) in the transaction
2197          * size, but it happens at most once per symref in a
2198          * transaction.
2199          */
2200         if (string_list_has_string(affected_refnames, referent)) {
2201                 /* An entry already exists */
2202                 strbuf_addf(err,
2203                             "multiple updates for '%s' (including one "
2204                             "via symref '%s') are not allowed",
2205                             referent, update->refname);
2206                 return TRANSACTION_NAME_CONFLICT;
2207         }
2208
2209         new_flags = update->flags;
2210         if (!strcmp(update->refname, "HEAD")) {
2211                 /*
2212                  * Record that the new update came via HEAD, so that
2213                  * when we process it, split_head_update() doesn't try
2214                  * to add another reflog update for HEAD. Note that
2215                  * this bit will be propagated if the new_update
2216                  * itself needs to be split.
2217                  */
2218                 new_flags |= REF_UPDATE_VIA_HEAD;
2219         }
2220
2221         new_update = ref_transaction_add_update(
2222                         transaction, referent, new_flags,
2223                         &update->new_oid, &update->old_oid,
2224                         update->msg);
2225
2226         new_update->parent_update = update;
2227
2228         /*
2229          * Change the symbolic ref update to log only. Also, it
2230          * doesn't need to check its old SHA-1 value, as that will be
2231          * done when new_update is processed.
2232          */
2233         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2234         update->flags &= ~REF_HAVE_OLD;
2235
2236         /*
2237          * Add the referent. This insertion is O(N) in the transaction
2238          * size, but it happens at most once per symref in a
2239          * transaction. Make sure to add new_update->refname, which will
2240          * be valid as long as affected_refnames is in use, and NOT
2241          * referent, which might soon be freed by our caller.
2242          */
2243         item = string_list_insert(affected_refnames, new_update->refname);
2244         if (item->util)
2245                 BUG("%s unexpectedly found in affected_refnames",
2246                     new_update->refname);
2247         item->util = new_update;
2248
2249         return 0;
2250 }
2251
2252 /*
2253  * Return the refname under which update was originally requested.
2254  */
2255 static const char *original_update_refname(struct ref_update *update)
2256 {
2257         while (update->parent_update)
2258                 update = update->parent_update;
2259
2260         return update->refname;
2261 }
2262
2263 /*
2264  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2265  * are consistent with oid, which is the reference's current value. If
2266  * everything is OK, return 0; otherwise, write an error message to
2267  * err and return -1.
2268  */
2269 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2270                          struct strbuf *err)
2271 {
2272         if (!(update->flags & REF_HAVE_OLD) ||
2273                    !oidcmp(oid, &update->old_oid))
2274                 return 0;
2275
2276         if (is_null_oid(&update->old_oid))
2277                 strbuf_addf(err, "cannot lock ref '%s': "
2278                             "reference already exists",
2279                             original_update_refname(update));
2280         else if (is_null_oid(oid))
2281                 strbuf_addf(err, "cannot lock ref '%s': "
2282                             "reference is missing but expected %s",
2283                             original_update_refname(update),
2284                             oid_to_hex(&update->old_oid));
2285         else
2286                 strbuf_addf(err, "cannot lock ref '%s': "
2287                             "is at %s but expected %s",
2288                             original_update_refname(update),
2289                             oid_to_hex(oid),
2290                             oid_to_hex(&update->old_oid));
2291
2292         return -1;
2293 }
2294
2295 /*
2296  * Prepare for carrying out update:
2297  * - Lock the reference referred to by update.
2298  * - Read the reference under lock.
2299  * - Check that its old SHA-1 value (if specified) is correct, and in
2300  *   any case record it in update->lock->old_oid for later use when
2301  *   writing the reflog.
2302  * - If it is a symref update without REF_NODEREF, split it up into a
2303  *   REF_LOG_ONLY update of the symref and add a separate update for
2304  *   the referent to transaction.
2305  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2306  *   update of HEAD.
2307  */
2308 static int lock_ref_for_update(struct files_ref_store *refs,
2309                                struct ref_update *update,
2310                                struct ref_transaction *transaction,
2311                                const char *head_ref,
2312                                struct string_list *affected_refnames,
2313                                struct strbuf *err)
2314 {
2315         struct strbuf referent = STRBUF_INIT;
2316         int mustexist = (update->flags & REF_HAVE_OLD) &&
2317                 !is_null_oid(&update->old_oid);
2318         int ret = 0;
2319         struct ref_lock *lock;
2320
2321         files_assert_main_repository(refs, "lock_ref_for_update");
2322
2323         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2324                 update->flags |= REF_DELETING;
2325
2326         if (head_ref) {
2327                 ret = split_head_update(update, transaction, head_ref,
2328                                         affected_refnames, err);
2329                 if (ret)
2330                         goto out;
2331         }
2332
2333         ret = lock_raw_ref(refs, update->refname, mustexist,
2334                            affected_refnames, NULL,
2335                            &lock, &referent,
2336                            &update->type, err);
2337         if (ret) {
2338                 char *reason;
2339
2340                 reason = strbuf_detach(err, NULL);
2341                 strbuf_addf(err, "cannot lock ref '%s': %s",
2342                             original_update_refname(update), reason);
2343                 free(reason);
2344                 goto out;
2345         }
2346
2347         update->backend_data = lock;
2348
2349         if (update->type & REF_ISSYMREF) {
2350                 if (update->flags & REF_NODEREF) {
2351                         /*
2352                          * We won't be reading the referent as part of
2353                          * the transaction, so we have to read it here
2354                          * to record and possibly check old_sha1:
2355                          */
2356                         if (refs_read_ref_full(&refs->base,
2357                                                referent.buf, 0,
2358                                                &lock->old_oid, NULL)) {
2359                                 if (update->flags & REF_HAVE_OLD) {
2360                                         strbuf_addf(err, "cannot lock ref '%s': "
2361                                                     "error reading reference",
2362                                                     original_update_refname(update));
2363                                         ret = TRANSACTION_GENERIC_ERROR;
2364                                         goto out;
2365                                 }
2366                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2367                                 ret = TRANSACTION_GENERIC_ERROR;
2368                                 goto out;
2369                         }
2370                 } else {
2371                         /*
2372                          * Create a new update for the reference this
2373                          * symref is pointing at. Also, we will record
2374                          * and verify old_sha1 for this update as part
2375                          * of processing the split-off update, so we
2376                          * don't have to do it here.
2377                          */
2378                         ret = split_symref_update(refs, update,
2379                                                   referent.buf, transaction,
2380                                                   affected_refnames, err);
2381                         if (ret)
2382                                 goto out;
2383                 }
2384         } else {
2385                 struct ref_update *parent_update;
2386
2387                 if (check_old_oid(update, &lock->old_oid, err)) {
2388                         ret = TRANSACTION_GENERIC_ERROR;
2389                         goto out;
2390                 }
2391
2392                 /*
2393                  * If this update is happening indirectly because of a
2394                  * symref update, record the old SHA-1 in the parent
2395                  * update:
2396                  */
2397                 for (parent_update = update->parent_update;
2398                      parent_update;
2399                      parent_update = parent_update->parent_update) {
2400                         struct ref_lock *parent_lock = parent_update->backend_data;
2401                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2402                 }
2403         }
2404
2405         if ((update->flags & REF_HAVE_NEW) &&
2406             !(update->flags & REF_DELETING) &&
2407             !(update->flags & REF_LOG_ONLY)) {
2408                 if (!(update->type & REF_ISSYMREF) &&
2409                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2410                         /*
2411                          * The reference already has the desired
2412                          * value, so we don't need to write it.
2413                          */
2414                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2415                                                  err)) {
2416                         char *write_err = strbuf_detach(err, NULL);
2417
2418                         /*
2419                          * The lock was freed upon failure of
2420                          * write_ref_to_lockfile():
2421                          */
2422                         update->backend_data = NULL;
2423                         strbuf_addf(err,
2424                                     "cannot update ref '%s': %s",
2425                                     update->refname, write_err);
2426                         free(write_err);
2427                         ret = TRANSACTION_GENERIC_ERROR;
2428                         goto out;
2429                 } else {
2430                         update->flags |= REF_NEEDS_COMMIT;
2431                 }
2432         }
2433         if (!(update->flags & REF_NEEDS_COMMIT)) {
2434                 /*
2435                  * We didn't call write_ref_to_lockfile(), so
2436                  * the lockfile is still open. Close it to
2437                  * free up the file descriptor:
2438                  */
2439                 if (close_ref_gently(lock)) {
2440                         strbuf_addf(err, "couldn't close '%s.lock'",
2441                                     update->refname);
2442                         ret = TRANSACTION_GENERIC_ERROR;
2443                         goto out;
2444                 }
2445         }
2446
2447 out:
2448         strbuf_release(&referent);
2449         return ret;
2450 }
2451
2452 struct files_transaction_backend_data {
2453         struct ref_transaction *packed_transaction;
2454         int packed_refs_locked;
2455 };
2456
2457 /*
2458  * Unlock any references in `transaction` that are still locked, and
2459  * mark the transaction closed.
2460  */
2461 static void files_transaction_cleanup(struct files_ref_store *refs,
2462                                       struct ref_transaction *transaction)
2463 {
2464         size_t i;
2465         struct files_transaction_backend_data *backend_data =
2466                 transaction->backend_data;
2467         struct strbuf err = STRBUF_INIT;
2468
2469         for (i = 0; i < transaction->nr; i++) {
2470                 struct ref_update *update = transaction->updates[i];
2471                 struct ref_lock *lock = update->backend_data;
2472
2473                 if (lock) {
2474                         unlock_ref(lock);
2475                         update->backend_data = NULL;
2476                 }
2477         }
2478
2479         if (backend_data->packed_transaction &&
2480             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2481                 error("error aborting transaction: %s", err.buf);
2482                 strbuf_release(&err);
2483         }
2484
2485         if (backend_data->packed_refs_locked)
2486                 packed_refs_unlock(refs->packed_ref_store);
2487
2488         free(backend_data);
2489
2490         transaction->state = REF_TRANSACTION_CLOSED;
2491 }
2492
2493 static int files_transaction_prepare(struct ref_store *ref_store,
2494                                      struct ref_transaction *transaction,
2495                                      struct strbuf *err)
2496 {
2497         struct files_ref_store *refs =
2498                 files_downcast(ref_store, REF_STORE_WRITE,
2499                                "ref_transaction_prepare");
2500         size_t i;
2501         int ret = 0;
2502         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2503         char *head_ref = NULL;
2504         int head_type;
2505         struct files_transaction_backend_data *backend_data;
2506         struct ref_transaction *packed_transaction = NULL;
2507
2508         assert(err);
2509
2510         if (!transaction->nr)
2511                 goto cleanup;
2512
2513         backend_data = xcalloc(1, sizeof(*backend_data));
2514         transaction->backend_data = backend_data;
2515
2516         /*
2517          * Fail if a refname appears more than once in the
2518          * transaction. (If we end up splitting up any updates using
2519          * split_symref_update() or split_head_update(), those
2520          * functions will check that the new updates don't have the
2521          * same refname as any existing ones.)
2522          */
2523         for (i = 0; i < transaction->nr; i++) {
2524                 struct ref_update *update = transaction->updates[i];
2525                 struct string_list_item *item =
2526                         string_list_append(&affected_refnames, update->refname);
2527
2528                 /*
2529                  * We store a pointer to update in item->util, but at
2530                  * the moment we never use the value of this field
2531                  * except to check whether it is non-NULL.
2532                  */
2533                 item->util = update;
2534         }
2535         string_list_sort(&affected_refnames);
2536         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2537                 ret = TRANSACTION_GENERIC_ERROR;
2538                 goto cleanup;
2539         }
2540
2541         /*
2542          * Special hack: If a branch is updated directly and HEAD
2543          * points to it (may happen on the remote side of a push
2544          * for example) then logically the HEAD reflog should be
2545          * updated too.
2546          *
2547          * A generic solution would require reverse symref lookups,
2548          * but finding all symrefs pointing to a given branch would be
2549          * rather costly for this rare event (the direct update of a
2550          * branch) to be worth it. So let's cheat and check with HEAD
2551          * only, which should cover 99% of all usage scenarios (even
2552          * 100% of the default ones).
2553          *
2554          * So if HEAD is a symbolic reference, then record the name of
2555          * the reference that it points to. If we see an update of
2556          * head_ref within the transaction, then split_head_update()
2557          * arranges for the reflog of HEAD to be updated, too.
2558          */
2559         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2560                                        RESOLVE_REF_NO_RECURSE,
2561                                        NULL, &head_type);
2562
2563         if (head_ref && !(head_type & REF_ISSYMREF)) {
2564                 FREE_AND_NULL(head_ref);
2565         }
2566
2567         /*
2568          * Acquire all locks, verify old values if provided, check
2569          * that new values are valid, and write new values to the
2570          * lockfiles, ready to be activated. Only keep one lockfile
2571          * open at a time to avoid running out of file descriptors.
2572          * Note that lock_ref_for_update() might append more updates
2573          * to the transaction.
2574          */
2575         for (i = 0; i < transaction->nr; i++) {
2576                 struct ref_update *update = transaction->updates[i];
2577
2578                 ret = lock_ref_for_update(refs, update, transaction,
2579                                           head_ref, &affected_refnames, err);
2580                 if (ret)
2581                         goto cleanup;
2582
2583                 if (update->flags & REF_DELETING &&
2584                     !(update->flags & REF_LOG_ONLY) &&
2585                     !(update->flags & REF_ISPRUNING)) {
2586                         /*
2587                          * This reference has to be deleted from
2588                          * packed-refs if it exists there.
2589                          */
2590                         if (!packed_transaction) {
2591                                 packed_transaction = ref_store_transaction_begin(
2592                                                 refs->packed_ref_store, err);
2593                                 if (!packed_transaction) {
2594                                         ret = TRANSACTION_GENERIC_ERROR;
2595                                         goto cleanup;
2596                                 }
2597
2598                                 backend_data->packed_transaction =
2599                                         packed_transaction;
2600                         }
2601
2602                         ref_transaction_add_update(
2603                                         packed_transaction, update->refname,
2604                                         REF_HAVE_NEW | REF_NODEREF,
2605                                         &update->new_oid, NULL,
2606                                         NULL);
2607                 }
2608         }
2609
2610         if (packed_transaction) {
2611                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2612                         ret = TRANSACTION_GENERIC_ERROR;
2613                         goto cleanup;
2614                 }
2615                 backend_data->packed_refs_locked = 1;
2616                 ret = ref_transaction_prepare(packed_transaction, err);
2617         }
2618
2619 cleanup:
2620         free(head_ref);
2621         string_list_clear(&affected_refnames, 0);
2622
2623         if (ret)
2624                 files_transaction_cleanup(refs, transaction);
2625         else
2626                 transaction->state = REF_TRANSACTION_PREPARED;
2627
2628         return ret;
2629 }
2630
2631 static int files_transaction_finish(struct ref_store *ref_store,
2632                                     struct ref_transaction *transaction,
2633                                     struct strbuf *err)
2634 {
2635         struct files_ref_store *refs =
2636                 files_downcast(ref_store, 0, "ref_transaction_finish");
2637         size_t i;
2638         int ret = 0;
2639         struct strbuf sb = STRBUF_INIT;
2640         struct files_transaction_backend_data *backend_data;
2641         struct ref_transaction *packed_transaction;
2642
2643
2644         assert(err);
2645
2646         if (!transaction->nr) {
2647                 transaction->state = REF_TRANSACTION_CLOSED;
2648                 return 0;
2649         }
2650
2651         backend_data = transaction->backend_data;
2652         packed_transaction = backend_data->packed_transaction;
2653
2654         /* Perform updates first so live commits remain referenced */
2655         for (i = 0; i < transaction->nr; i++) {
2656                 struct ref_update *update = transaction->updates[i];
2657                 struct ref_lock *lock = update->backend_data;
2658
2659                 if (update->flags & REF_NEEDS_COMMIT ||
2660                     update->flags & REF_LOG_ONLY) {
2661                         if (files_log_ref_write(refs,
2662                                                 lock->ref_name,
2663                                                 &lock->old_oid,
2664                                                 &update->new_oid,
2665                                                 update->msg, update->flags,
2666                                                 err)) {
2667                                 char *old_msg = strbuf_detach(err, NULL);
2668
2669                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2670                                             lock->ref_name, old_msg);
2671                                 free(old_msg);
2672                                 unlock_ref(lock);
2673                                 update->backend_data = NULL;
2674                                 ret = TRANSACTION_GENERIC_ERROR;
2675                                 goto cleanup;
2676                         }
2677                 }
2678                 if (update->flags & REF_NEEDS_COMMIT) {
2679                         clear_loose_ref_cache(refs);
2680                         if (commit_ref(lock)) {
2681                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2682                                 unlock_ref(lock);
2683                                 update->backend_data = NULL;
2684                                 ret = TRANSACTION_GENERIC_ERROR;
2685                                 goto cleanup;
2686                         }
2687                 }
2688         }
2689
2690         /*
2691          * Now that updates are safely completed, we can perform
2692          * deletes. First delete the reflogs of any references that
2693          * will be deleted, since (in the unexpected event of an
2694          * error) leaving a reference without a reflog is less bad
2695          * than leaving a reflog without a reference (the latter is a
2696          * mildly invalid repository state):
2697          */
2698         for (i = 0; i < transaction->nr; i++) {
2699                 struct ref_update *update = transaction->updates[i];
2700                 if (update->flags & REF_DELETING &&
2701                     !(update->flags & REF_LOG_ONLY) &&
2702                     !(update->flags & REF_ISPRUNING)) {
2703                         strbuf_reset(&sb);
2704                         files_reflog_path(refs, &sb, update->refname);
2705                         if (!unlink_or_warn(sb.buf))
2706                                 try_remove_empty_parents(refs, update->refname,
2707                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2708                 }
2709         }
2710
2711         /*
2712          * Perform deletes now that updates are safely completed.
2713          *
2714          * First delete any packed versions of the references, while
2715          * retaining the packed-refs lock:
2716          */
2717         if (packed_transaction) {
2718                 ret = ref_transaction_commit(packed_transaction, err);
2719                 ref_transaction_free(packed_transaction);
2720                 packed_transaction = NULL;
2721                 backend_data->packed_transaction = NULL;
2722                 if (ret)
2723                         goto cleanup;
2724         }
2725
2726         /* Now delete the loose versions of the references: */
2727         for (i = 0; i < transaction->nr; i++) {
2728                 struct ref_update *update = transaction->updates[i];
2729                 struct ref_lock *lock = update->backend_data;
2730
2731                 if (update->flags & REF_DELETING &&
2732                     !(update->flags & REF_LOG_ONLY)) {
2733                         if (!(update->type & REF_ISPACKED) ||
2734                             update->type & REF_ISSYMREF) {
2735                                 /* It is a loose reference. */
2736                                 strbuf_reset(&sb);
2737                                 files_ref_path(refs, &sb, lock->ref_name);
2738                                 if (unlink_or_msg(sb.buf, err)) {
2739                                         ret = TRANSACTION_GENERIC_ERROR;
2740                                         goto cleanup;
2741                                 }
2742                                 update->flags |= REF_DELETED_LOOSE;
2743                         }
2744                 }
2745         }
2746
2747         clear_loose_ref_cache(refs);
2748
2749 cleanup:
2750         files_transaction_cleanup(refs, transaction);
2751
2752         for (i = 0; i < transaction->nr; i++) {
2753                 struct ref_update *update = transaction->updates[i];
2754
2755                 if (update->flags & REF_DELETED_LOOSE) {
2756                         /*
2757                          * The loose reference was deleted. Delete any
2758                          * empty parent directories. (Note that this
2759                          * can only work because we have already
2760                          * removed the lockfile.)
2761                          */
2762                         try_remove_empty_parents(refs, update->refname,
2763                                                  REMOVE_EMPTY_PARENTS_REF);
2764                 }
2765         }
2766
2767         strbuf_release(&sb);
2768         return ret;
2769 }
2770
2771 static int files_transaction_abort(struct ref_store *ref_store,
2772                                    struct ref_transaction *transaction,
2773                                    struct strbuf *err)
2774 {
2775         struct files_ref_store *refs =
2776                 files_downcast(ref_store, 0, "ref_transaction_abort");
2777
2778         files_transaction_cleanup(refs, transaction);
2779         return 0;
2780 }
2781
2782 static int ref_present(const char *refname,
2783                        const struct object_id *oid, int flags, void *cb_data)
2784 {
2785         struct string_list *affected_refnames = cb_data;
2786
2787         return string_list_has_string(affected_refnames, refname);
2788 }
2789
2790 static int files_initial_transaction_commit(struct ref_store *ref_store,
2791                                             struct ref_transaction *transaction,
2792                                             struct strbuf *err)
2793 {
2794         struct files_ref_store *refs =
2795                 files_downcast(ref_store, REF_STORE_WRITE,
2796                                "initial_ref_transaction_commit");
2797         size_t i;
2798         int ret = 0;
2799         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2800         struct ref_transaction *packed_transaction = NULL;
2801
2802         assert(err);
2803
2804         if (transaction->state != REF_TRANSACTION_OPEN)
2805                 die("BUG: commit called for transaction that is not open");
2806
2807         /* Fail if a refname appears more than once in the transaction: */
2808         for (i = 0; i < transaction->nr; i++)
2809                 string_list_append(&affected_refnames,
2810                                    transaction->updates[i]->refname);
2811         string_list_sort(&affected_refnames);
2812         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2813                 ret = TRANSACTION_GENERIC_ERROR;
2814                 goto cleanup;
2815         }
2816
2817         /*
2818          * It's really undefined to call this function in an active
2819          * repository or when there are existing references: we are
2820          * only locking and changing packed-refs, so (1) any
2821          * simultaneous processes might try to change a reference at
2822          * the same time we do, and (2) any existing loose versions of
2823          * the references that we are setting would have precedence
2824          * over our values. But some remote helpers create the remote
2825          * "HEAD" and "master" branches before calling this function,
2826          * so here we really only check that none of the references
2827          * that we are creating already exists.
2828          */
2829         if (refs_for_each_rawref(&refs->base, ref_present,
2830                                  &affected_refnames))
2831                 die("BUG: initial ref transaction called with existing refs");
2832
2833         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2834         if (!packed_transaction) {
2835                 ret = TRANSACTION_GENERIC_ERROR;
2836                 goto cleanup;
2837         }
2838
2839         for (i = 0; i < transaction->nr; i++) {
2840                 struct ref_update *update = transaction->updates[i];
2841
2842                 if ((update->flags & REF_HAVE_OLD) &&
2843                     !is_null_oid(&update->old_oid))
2844                         die("BUG: initial ref transaction with old_sha1 set");
2845                 if (refs_verify_refname_available(&refs->base, update->refname,
2846                                                   &affected_refnames, NULL,
2847                                                   err)) {
2848                         ret = TRANSACTION_NAME_CONFLICT;
2849                         goto cleanup;
2850                 }
2851
2852                 /*
2853                  * Add a reference creation for this reference to the
2854                  * packed-refs transaction:
2855                  */
2856                 ref_transaction_add_update(packed_transaction, update->refname,
2857                                            update->flags & ~REF_HAVE_OLD,
2858                                            &update->new_oid, &update->old_oid,
2859                                            NULL);
2860         }
2861
2862         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2863                 ret = TRANSACTION_GENERIC_ERROR;
2864                 goto cleanup;
2865         }
2866
2867         if (initial_ref_transaction_commit(packed_transaction, err)) {
2868                 ret = TRANSACTION_GENERIC_ERROR;
2869                 goto cleanup;
2870         }
2871
2872 cleanup:
2873         if (packed_transaction)
2874                 ref_transaction_free(packed_transaction);
2875         packed_refs_unlock(refs->packed_ref_store);
2876         transaction->state = REF_TRANSACTION_CLOSED;
2877         string_list_clear(&affected_refnames, 0);
2878         return ret;
2879 }
2880
2881 struct expire_reflog_cb {
2882         unsigned int flags;
2883         reflog_expiry_should_prune_fn *should_prune_fn;
2884         void *policy_cb;
2885         FILE *newlog;
2886         struct object_id last_kept_oid;
2887 };
2888
2889 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2890                              const char *email, timestamp_t timestamp, int tz,
2891                              const char *message, void *cb_data)
2892 {
2893         struct expire_reflog_cb *cb = cb_data;
2894         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2895
2896         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2897                 ooid = &cb->last_kept_oid;
2898
2899         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2900                                    message, policy_cb)) {
2901                 if (!cb->newlog)
2902                         printf("would prune %s", message);
2903                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2904                         printf("prune %s", message);
2905         } else {
2906                 if (cb->newlog) {
2907                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2908                                 oid_to_hex(ooid), oid_to_hex(noid),
2909                                 email, timestamp, tz, message);
2910                         oidcpy(&cb->last_kept_oid, noid);
2911                 }
2912                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2913                         printf("keep %s", message);
2914         }
2915         return 0;
2916 }
2917
2918 static int files_reflog_expire(struct ref_store *ref_store,
2919                                const char *refname, const struct object_id *oid,
2920                                unsigned int flags,
2921                                reflog_expiry_prepare_fn prepare_fn,
2922                                reflog_expiry_should_prune_fn should_prune_fn,
2923                                reflog_expiry_cleanup_fn cleanup_fn,
2924                                void *policy_cb_data)
2925 {
2926         struct files_ref_store *refs =
2927                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2928         static struct lock_file reflog_lock;
2929         struct expire_reflog_cb cb;
2930         struct ref_lock *lock;
2931         struct strbuf log_file_sb = STRBUF_INIT;
2932         char *log_file;
2933         int status = 0;
2934         int type;
2935         struct strbuf err = STRBUF_INIT;
2936
2937         memset(&cb, 0, sizeof(cb));
2938         cb.flags = flags;
2939         cb.policy_cb = policy_cb_data;
2940         cb.should_prune_fn = should_prune_fn;
2941
2942         /*
2943          * The reflog file is locked by holding the lock on the
2944          * reference itself, plus we might need to update the
2945          * reference if --updateref was specified:
2946          */
2947         lock = lock_ref_oid_basic(refs, refname, oid,
2948                                   NULL, NULL, REF_NODEREF,
2949                                   &type, &err);
2950         if (!lock) {
2951                 error("cannot lock ref '%s': %s", refname, err.buf);
2952                 strbuf_release(&err);
2953                 return -1;
2954         }
2955         if (!refs_reflog_exists(ref_store, refname)) {
2956                 unlock_ref(lock);
2957                 return 0;
2958         }
2959
2960         files_reflog_path(refs, &log_file_sb, refname);
2961         log_file = strbuf_detach(&log_file_sb, NULL);
2962         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2963                 /*
2964                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2965                  * no locking implications, we use the lock_file
2966                  * machinery here anyway because it does a lot of the
2967                  * work we need, including cleaning up if the program
2968                  * exits unexpectedly.
2969                  */
2970                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2971                         struct strbuf err = STRBUF_INIT;
2972                         unable_to_lock_message(log_file, errno, &err);
2973                         error("%s", err.buf);
2974                         strbuf_release(&err);
2975                         goto failure;
2976                 }
2977                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
2978                 if (!cb.newlog) {
2979                         error("cannot fdopen %s (%s)",
2980                               get_lock_file_path(&reflog_lock), strerror(errno));
2981                         goto failure;
2982                 }
2983         }
2984
2985         (*prepare_fn)(refname, oid, cb.policy_cb);
2986         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
2987         (*cleanup_fn)(cb.policy_cb);
2988
2989         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2990                 /*
2991                  * It doesn't make sense to adjust a reference pointed
2992                  * to by a symbolic ref based on expiring entries in
2993                  * the symbolic reference's reflog. Nor can we update
2994                  * a reference if there are no remaining reflog
2995                  * entries.
2996                  */
2997                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
2998                         !(type & REF_ISSYMREF) &&
2999                         !is_null_oid(&cb.last_kept_oid);
3000
3001                 if (close_lock_file_gently(&reflog_lock)) {
3002                         status |= error("couldn't write %s: %s", log_file,
3003                                         strerror(errno));
3004                         rollback_lock_file(&reflog_lock);
3005                 } else if (update &&
3006                            (write_in_full(get_lock_file_fd(&lock->lk),
3007                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3008                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3009                             close_ref_gently(lock) < 0)) {
3010                         status |= error("couldn't write %s",
3011                                         get_lock_file_path(&lock->lk));
3012                         rollback_lock_file(&reflog_lock);
3013                 } else if (commit_lock_file(&reflog_lock)) {
3014                         status |= error("unable to write reflog '%s' (%s)",
3015                                         log_file, strerror(errno));
3016                 } else if (update && commit_ref(lock)) {
3017                         status |= error("couldn't set %s", lock->ref_name);
3018                 }
3019         }
3020         free(log_file);
3021         unlock_ref(lock);
3022         return status;
3023
3024  failure:
3025         rollback_lock_file(&reflog_lock);
3026         free(log_file);
3027         unlock_ref(lock);
3028         return -1;
3029 }
3030
3031 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3032 {
3033         struct files_ref_store *refs =
3034                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3035         struct strbuf sb = STRBUF_INIT;
3036
3037         /*
3038          * Create .git/refs/{heads,tags}
3039          */
3040         files_ref_path(refs, &sb, "refs/heads");
3041         safe_create_dir(sb.buf, 1);
3042
3043         strbuf_reset(&sb);
3044         files_ref_path(refs, &sb, "refs/tags");
3045         safe_create_dir(sb.buf, 1);
3046
3047         strbuf_release(&sb);
3048         return 0;
3049 }
3050
3051 struct ref_storage_be refs_be_files = {
3052         NULL,
3053         "files",
3054         files_ref_store_create,
3055         files_init_db,
3056         files_transaction_prepare,
3057         files_transaction_finish,
3058         files_transaction_abort,
3059         files_initial_transaction_commit,
3060
3061         files_pack_refs,
3062         files_create_symref,
3063         files_delete_refs,
3064         files_rename_ref,
3065         files_copy_ref,
3066
3067         files_ref_iterator_begin,
3068         files_read_raw_ref,
3069
3070         files_reflog_iterator_begin,
3071         files_for_each_reflog_ent,
3072         files_for_each_reflog_ent_reverse,
3073         files_reflog_exists,
3074         files_create_reflog,
3075         files_delete_reflog,
3076         files_reflog_expire
3077 };