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
 993         if (check_refname_format(r->name, 0))
 994                 return;
 995
 996         transaction = ref_store_transaction_begin(&refs->base, &err);
 997         if (!transaction ||
 998             ref_transaction_delete(transaction, r->name, &r->oid,
 999                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
1000             ref_transaction_commit(transaction, &err)) {
1001                 ref_transaction_free(transaction);
1002                 error("%s", err.buf);
1003                 strbuf_release(&err);
1004                 return;
1005         }
1006         ref_transaction_free(transaction);
1007         strbuf_release(&err);
1008 }
1009
1010 /*
1011  * Prune the loose versions of the references in the linked list
1012  * `*refs_to_prune`, freeing the entries in the list as we go.
1013  */
1014 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1015 {
1016         while (*refs_to_prune) {
1017                 struct ref_to_prune *r = *refs_to_prune;
1018                 *refs_to_prune = r->next;
1019                 prune_ref(refs, r);
1020                 free(r);
1021         }
1022 }
1023
1024 /*
1025  * Return true if the specified reference should be packed.
1026  */
1027 static int should_pack_ref(const char *refname,
1028                            const struct object_id *oid, unsigned int ref_flags,
1029                            unsigned int pack_flags)
1030 {
1031         /* Do not pack per-worktree refs: */
1032         if (ref_type(refname) != REF_TYPE_NORMAL)
1033                 return 0;
1034
1035         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1036         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1037                 return 0;
1038
1039         /* Do not pack symbolic refs: */
1040         if (ref_flags & REF_ISSYMREF)
1041                 return 0;
1042
1043         /* Do not pack broken refs: */
1044         if (!ref_resolves_to_object(refname, oid, ref_flags))
1045                 return 0;
1046
1047         return 1;
1048 }
1049
1050 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1051 {
1052         struct files_ref_store *refs =
1053                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1054                                "pack_refs");
1055         struct ref_iterator *iter;
1056         int ok;
1057         struct ref_to_prune *refs_to_prune = NULL;
1058         struct strbuf err = STRBUF_INIT;
1059         struct ref_transaction *transaction;
1060
1061         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1062         if (!transaction)
1063                 return -1;
1064
1065         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1066
1067         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1068         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1069                 /*
1070                  * If the loose reference can be packed, add an entry
1071                  * in the packed ref cache. If the reference should be
1072                  * pruned, also add it to refs_to_prune.
1073                  */
1074                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1075                                      flags))
1076                         continue;
1077
1078                 /*
1079                  * Add a reference creation for this reference to the
1080                  * packed-refs transaction:
1081                  */
1082                 if (ref_transaction_update(transaction, iter->refname,
1083                                            iter->oid, NULL,
1084                                            REF_NODEREF, NULL, &err))
1085                         die("failure preparing to create packed reference %s: %s",
1086                             iter->refname, err.buf);
1087
1088                 /* Schedule the loose reference for pruning if requested. */
1089                 if ((flags & PACK_REFS_PRUNE)) {
1090                         struct ref_to_prune *n;
1091                         FLEX_ALLOC_STR(n, name, iter->refname);
1092                         oidcpy(&n->oid, iter->oid);
1093                         n->next = refs_to_prune;
1094                         refs_to_prune = n;
1095                 }
1096         }
1097         if (ok != ITER_DONE)
1098                 die("error while iterating over references");
1099
1100         if (ref_transaction_commit(transaction, &err))
1101                 die("unable to write new packed-refs: %s", err.buf);
1102
1103         ref_transaction_free(transaction);
1104
1105         packed_refs_unlock(refs->packed_ref_store);
1106
1107         prune_refs(refs, &refs_to_prune);
1108         strbuf_release(&err);
1109         return 0;
1110 }
1111
1112 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1113                              struct string_list *refnames, unsigned int flags)
1114 {
1115         struct files_ref_store *refs =
1116                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1117         struct strbuf err = STRBUF_INIT;
1118         int i, result = 0;
1119
1120         if (!refnames->nr)
1121                 return 0;
1122
1123         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1124                 goto error;
1125
1126         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1127                 packed_refs_unlock(refs->packed_ref_store);
1128                 goto error;
1129         }
1130
1131         packed_refs_unlock(refs->packed_ref_store);
1132
1133         for (i = 0; i < refnames->nr; i++) {
1134                 const char *refname = refnames->items[i].string;
1135
1136                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1137                         result |= error(_("could not remove reference %s"), refname);
1138         }
1139
1140         strbuf_release(&err);
1141         return result;
1142
1143 error:
1144         /*
1145          * If we failed to rewrite the packed-refs file, then it is
1146          * unsafe to try to remove loose refs, because doing so might
1147          * expose an obsolete packed value for a reference that might
1148          * even point at an object that has been garbage collected.
1149          */
1150         if (refnames->nr == 1)
1151                 error(_("could not delete reference %s: %s"),
1152                       refnames->items[0].string, err.buf);
1153         else
1154                 error(_("could not delete references: %s"), err.buf);
1155
1156         strbuf_release(&err);
1157         return -1;
1158 }
1159
1160 /*
1161  * People using contrib's git-new-workdir have .git/logs/refs ->
1162  * /some/other/path/.git/logs/refs, and that may live on another device.
1163  *
1164  * IOW, to avoid cross device rename errors, the temporary renamed log must
1165  * live into logs/refs.
1166  */
1167 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1168
1169 struct rename_cb {
1170         const char *tmp_renamed_log;
1171         int true_errno;
1172 };
1173
1174 static int rename_tmp_log_callback(const char *path, void *cb_data)
1175 {
1176         struct rename_cb *cb = cb_data;
1177
1178         if (rename(cb->tmp_renamed_log, path)) {
1179                 /*
1180                  * rename(a, b) when b is an existing directory ought
1181                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1182                  * Sheesh. Record the true errno for error reporting,
1183                  * but report EISDIR to raceproof_create_file() so
1184                  * that it knows to retry.
1185                  */
1186                 cb->true_errno = errno;
1187                 if (errno == ENOTDIR)
1188                         errno = EISDIR;
1189                 return -1;
1190         } else {
1191                 return 0;
1192         }
1193 }
1194
1195 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1196 {
1197         struct strbuf path = STRBUF_INIT;
1198         struct strbuf tmp = STRBUF_INIT;
1199         struct rename_cb cb;
1200         int ret;
1201
1202         files_reflog_path(refs, &path, newrefname);
1203         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1204         cb.tmp_renamed_log = tmp.buf;
1205         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1206         if (ret) {
1207                 if (errno == EISDIR)
1208                         error("directory not empty: %s", path.buf);
1209                 else
1210                         error("unable to move logfile %s to %s: %s",
1211                               tmp.buf, path.buf,
1212                               strerror(cb.true_errno));
1213         }
1214
1215         strbuf_release(&path);
1216         strbuf_release(&tmp);
1217         return ret;
1218 }
1219
1220 static int write_ref_to_lockfile(struct ref_lock *lock,
1221                                  const struct object_id *oid, struct strbuf *err);
1222 static int commit_ref_update(struct files_ref_store *refs,
1223                              struct ref_lock *lock,
1224                              const struct object_id *oid, const char *logmsg,
1225                              struct strbuf *err);
1226
1227 static int files_copy_or_rename_ref(struct ref_store *ref_store,
1228                             const char *oldrefname, const char *newrefname,
1229                             const char *logmsg, int copy)
1230 {
1231         struct files_ref_store *refs =
1232                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1233         struct object_id oid, orig_oid;
1234         int flag = 0, logmoved = 0;
1235         struct ref_lock *lock;
1236         struct stat loginfo;
1237         struct strbuf sb_oldref = STRBUF_INIT;
1238         struct strbuf sb_newref = STRBUF_INIT;
1239         struct strbuf tmp_renamed_log = STRBUF_INIT;
1240         int log, ret;
1241         struct strbuf err = STRBUF_INIT;
1242
1243         files_reflog_path(refs, &sb_oldref, oldrefname);
1244         files_reflog_path(refs, &sb_newref, newrefname);
1245         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1246
1247         log = !lstat(sb_oldref.buf, &loginfo);
1248         if (log && S_ISLNK(loginfo.st_mode)) {
1249                 ret = error("reflog for %s is a symlink", oldrefname);
1250                 goto out;
1251         }
1252
1253         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1254                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1255                                 &orig_oid, &flag)) {
1256                 ret = error("refname %s not found", oldrefname);
1257                 goto out;
1258         }
1259
1260         if (flag & REF_ISSYMREF) {
1261                 if (copy)
1262                         ret = error("refname %s is a symbolic ref, copying it is not supported",
1263                                     oldrefname);
1264                 else
1265                         ret = error("refname %s is a symbolic ref, renaming it is not supported",
1266                                     oldrefname);
1267                 goto out;
1268         }
1269         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1270                 ret = 1;
1271                 goto out;
1272         }
1273
1274         if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1275                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1276                             oldrefname, strerror(errno));
1277                 goto out;
1278         }
1279
1280         if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1281                 ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1282                             oldrefname, strerror(errno));
1283                 goto out;
1284         }
1285
1286         if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1287                             &orig_oid, REF_NODEREF)) {
1288                 error("unable to delete old %s", oldrefname);
1289                 goto rollback;
1290         }
1291
1292         /*
1293          * Since we are doing a shallow lookup, oid is not the
1294          * correct value to pass to delete_ref as old_oid. But that
1295          * doesn't matter, because an old_oid check wouldn't add to
1296          * the safety anyway; we want to delete the reference whatever
1297          * its current value.
1298          */
1299         if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1300                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1301                                 &oid, NULL) &&
1302             refs_delete_ref(&refs->base, NULL, newrefname,
1303                             NULL, REF_NODEREF)) {
1304                 if (errno == EISDIR) {
1305                         struct strbuf path = STRBUF_INIT;
1306                         int result;
1307
1308                         files_ref_path(refs, &path, newrefname);
1309                         result = remove_empty_directories(&path);
1310                         strbuf_release(&path);
1311
1312                         if (result) {
1313                                 error("Directory not empty: %s", newrefname);
1314                                 goto rollback;
1315                         }
1316                 } else {
1317                         error("unable to delete existing %s", newrefname);
1318                         goto rollback;
1319                 }
1320         }
1321
1322         if (log && rename_tmp_log(refs, newrefname))
1323                 goto rollback;
1324
1325         logmoved = log;
1326
1327         lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1328                                   REF_NODEREF, NULL, &err);
1329         if (!lock) {
1330                 if (copy)
1331                         error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1332                 else
1333                         error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1334                 strbuf_release(&err);
1335                 goto rollback;
1336         }
1337         oidcpy(&lock->old_oid, &orig_oid);
1338
1339         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1340             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1341                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1342                 strbuf_release(&err);
1343                 goto rollback;
1344         }
1345
1346         ret = 0;
1347         goto out;
1348
1349  rollback:
1350         lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1351                                   REF_NODEREF, NULL, &err);
1352         if (!lock) {
1353                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1354                 strbuf_release(&err);
1355                 goto rollbacklog;
1356         }
1357
1358         flag = log_all_ref_updates;
1359         log_all_ref_updates = LOG_REFS_NONE;
1360         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1361             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1362                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1363                 strbuf_release(&err);
1364         }
1365         log_all_ref_updates = flag;
1366
1367  rollbacklog:
1368         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1369                 error("unable to restore logfile %s from %s: %s",
1370                         oldrefname, newrefname, strerror(errno));
1371         if (!logmoved && log &&
1372             rename(tmp_renamed_log.buf, sb_oldref.buf))
1373                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1374                         oldrefname, strerror(errno));
1375         ret = 1;
1376  out:
1377         strbuf_release(&sb_newref);
1378         strbuf_release(&sb_oldref);
1379         strbuf_release(&tmp_renamed_log);
1380
1381         return ret;
1382 }
1383
1384 static int files_rename_ref(struct ref_store *ref_store,
1385                             const char *oldrefname, const char *newrefname,
1386                             const char *logmsg)
1387 {
1388         return files_copy_or_rename_ref(ref_store, oldrefname,
1389                                  newrefname, logmsg, 0);
1390 }
1391
1392 static int files_copy_ref(struct ref_store *ref_store,
1393                             const char *oldrefname, const char *newrefname,
1394                             const char *logmsg)
1395 {
1396         return files_copy_or_rename_ref(ref_store, oldrefname,
1397                                  newrefname, logmsg, 1);
1398 }
1399
1400 static int close_ref_gently(struct ref_lock *lock)
1401 {
1402         if (close_lock_file_gently(&lock->lk))
1403                 return -1;
1404         return 0;
1405 }
1406
1407 static int commit_ref(struct ref_lock *lock)
1408 {
1409         char *path = get_locked_file_path(&lock->lk);
1410         struct stat st;
1411
1412         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1413                 /*
1414                  * There is a directory at the path we want to rename
1415                  * the lockfile to. Hopefully it is empty; try to
1416                  * delete it.
1417                  */
1418                 size_t len = strlen(path);
1419                 struct strbuf sb_path = STRBUF_INIT;
1420
1421                 strbuf_attach(&sb_path, path, len, len);
1422
1423                 /*
1424                  * If this fails, commit_lock_file() will also fail
1425                  * and will report the problem.
1426                  */
1427                 remove_empty_directories(&sb_path);
1428                 strbuf_release(&sb_path);
1429         } else {
1430                 free(path);
1431         }
1432
1433         if (commit_lock_file(&lock->lk))
1434                 return -1;
1435         return 0;
1436 }
1437
1438 static int open_or_create_logfile(const char *path, void *cb)
1439 {
1440         int *fd = cb;
1441
1442         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1443         return (*fd < 0) ? -1 : 0;
1444 }
1445
1446 /*
1447  * Create a reflog for a ref. If force_create = 0, only create the
1448  * reflog for certain refs (those for which should_autocreate_reflog
1449  * returns non-zero). Otherwise, create it regardless of the reference
1450  * name. If the logfile already existed or was created, return 0 and
1451  * set *logfd to the file descriptor opened for appending to the file.
1452  * If no logfile exists and we decided not to create one, return 0 and
1453  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1454  * return -1.
1455  */
1456 static int log_ref_setup(struct files_ref_store *refs,
1457                          const char *refname, int force_create,
1458                          int *logfd, struct strbuf *err)
1459 {
1460         struct strbuf logfile_sb = STRBUF_INIT;
1461         char *logfile;
1462
1463         files_reflog_path(refs, &logfile_sb, refname);
1464         logfile = strbuf_detach(&logfile_sb, NULL);
1465
1466         if (force_create || should_autocreate_reflog(refname)) {
1467                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1468                         if (errno == ENOENT)
1469                                 strbuf_addf(err, "unable to create directory for '%s': "
1470                                             "%s", logfile, strerror(errno));
1471                         else if (errno == EISDIR)
1472                                 strbuf_addf(err, "there are still logs under '%s'",
1473                                             logfile);
1474                         else
1475                                 strbuf_addf(err, "unable to append to '%s': %s",
1476                                             logfile, strerror(errno));
1477
1478                         goto error;
1479                 }
1480         } else {
1481                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1482                 if (*logfd < 0) {
1483                         if (errno == ENOENT || errno == EISDIR) {
1484                                 /*
1485                                  * The logfile doesn't already exist,
1486                                  * but that is not an error; it only
1487                                  * means that we won't write log
1488                                  * entries to it.
1489                                  */
1490                                 ;
1491                         } else {
1492                                 strbuf_addf(err, "unable to append to '%s': %s",
1493                                             logfile, strerror(errno));
1494                                 goto error;
1495                         }
1496                 }
1497         }
1498
1499         if (*logfd >= 0)
1500                 adjust_shared_perm(logfile);
1501
1502         free(logfile);
1503         return 0;
1504
1505 error:
1506         free(logfile);
1507         return -1;
1508 }
1509
1510 static int files_create_reflog(struct ref_store *ref_store,
1511                                const char *refname, int force_create,
1512                                struct strbuf *err)
1513 {
1514         struct files_ref_store *refs =
1515                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1516         int fd;
1517
1518         if (log_ref_setup(refs, refname, force_create, &fd, err))
1519                 return -1;
1520
1521         if (fd >= 0)
1522                 close(fd);
1523
1524         return 0;
1525 }
1526
1527 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1528                             const struct object_id *new_oid,
1529                             const char *committer, const char *msg)
1530 {
1531         int msglen, written;
1532         unsigned maxlen, len;
1533         char *logrec;
1534
1535         msglen = msg ? strlen(msg) : 0;
1536         maxlen = strlen(committer) + msglen + 100;
1537         logrec = xmalloc(maxlen);
1538         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1539                         oid_to_hex(old_oid),
1540                         oid_to_hex(new_oid),
1541                         committer);
1542         if (msglen)
1543                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1544
1545         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1546         free(logrec);
1547         if (written < 0)
1548                 return -1;
1549
1550         return 0;
1551 }
1552
1553 static int files_log_ref_write(struct files_ref_store *refs,
1554                                const char *refname, const struct object_id *old_oid,
1555                                const struct object_id *new_oid, const char *msg,
1556                                int flags, struct strbuf *err)
1557 {
1558         int logfd, result;
1559
1560         if (log_all_ref_updates == LOG_REFS_UNSET)
1561                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1562
1563         result = log_ref_setup(refs, refname,
1564                                flags & REF_FORCE_CREATE_REFLOG,
1565                                &logfd, err);
1566
1567         if (result)
1568                 return result;
1569
1570         if (logfd < 0)
1571                 return 0;
1572         result = log_ref_write_fd(logfd, old_oid, new_oid,
1573                                   git_committer_info(0), msg);
1574         if (result) {
1575                 struct strbuf sb = STRBUF_INIT;
1576                 int save_errno = errno;
1577
1578                 files_reflog_path(refs, &sb, refname);
1579                 strbuf_addf(err, "unable to append to '%s': %s",
1580                             sb.buf, strerror(save_errno));
1581                 strbuf_release(&sb);
1582                 close(logfd);
1583                 return -1;
1584         }
1585         if (close(logfd)) {
1586                 struct strbuf sb = STRBUF_INIT;
1587                 int save_errno = errno;
1588
1589                 files_reflog_path(refs, &sb, refname);
1590                 strbuf_addf(err, "unable to append to '%s': %s",
1591                             sb.buf, strerror(save_errno));
1592                 strbuf_release(&sb);
1593                 return -1;
1594         }
1595         return 0;
1596 }
1597
1598 /*
1599  * Write sha1 into the open lockfile, then close the lockfile. On
1600  * errors, rollback the lockfile, fill in *err and
1601  * return -1.
1602  */
1603 static int write_ref_to_lockfile(struct ref_lock *lock,
1604                                  const struct object_id *oid, struct strbuf *err)
1605 {
1606         static char term = '\n';
1607         struct object *o;
1608         int fd;
1609
1610         o = parse_object(oid);
1611         if (!o) {
1612                 strbuf_addf(err,
1613                             "trying to write ref '%s' with nonexistent object %s",
1614                             lock->ref_name, oid_to_hex(oid));
1615                 unlock_ref(lock);
1616                 return -1;
1617         }
1618         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1619                 strbuf_addf(err,
1620                             "trying to write non-commit object %s to branch '%s'",
1621                             oid_to_hex(oid), lock->ref_name);
1622                 unlock_ref(lock);
1623                 return -1;
1624         }
1625         fd = get_lock_file_fd(&lock->lk);
1626         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1627             write_in_full(fd, &term, 1) < 0 ||
1628             close_ref_gently(lock) < 0) {
1629                 strbuf_addf(err,
1630                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1631                 unlock_ref(lock);
1632                 return -1;
1633         }
1634         return 0;
1635 }
1636
1637 /*
1638  * Commit a change to a loose reference that has already been written
1639  * to the loose reference lockfile. Also update the reflogs if
1640  * necessary, using the specified lockmsg (which can be NULL).
1641  */
1642 static int commit_ref_update(struct files_ref_store *refs,
1643                              struct ref_lock *lock,
1644                              const struct object_id *oid, const char *logmsg,
1645                              struct strbuf *err)
1646 {
1647         files_assert_main_repository(refs, "commit_ref_update");
1648
1649         clear_loose_ref_cache(refs);
1650         if (files_log_ref_write(refs, lock->ref_name,
1651                                 &lock->old_oid, oid,
1652                                 logmsg, 0, err)) {
1653                 char *old_msg = strbuf_detach(err, NULL);
1654                 strbuf_addf(err, "cannot update the ref '%s': %s",
1655                             lock->ref_name, old_msg);
1656                 free(old_msg);
1657                 unlock_ref(lock);
1658                 return -1;
1659         }
1660
1661         if (strcmp(lock->ref_name, "HEAD") != 0) {
1662                 /*
1663                  * Special hack: If a branch is updated directly and HEAD
1664                  * points to it (may happen on the remote side of a push
1665                  * for example) then logically the HEAD reflog should be
1666                  * updated too.
1667                  * A generic solution implies reverse symref information,
1668                  * but finding all symrefs pointing to the given branch
1669                  * would be rather costly for this rare event (the direct
1670                  * update of a branch) to be worth it.  So let's cheat and
1671                  * check with HEAD only which should cover 99% of all usage
1672                  * scenarios (even 100% of the default ones).
1673                  */
1674                 int head_flag;
1675                 const char *head_ref;
1676
1677                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1678                                                    RESOLVE_REF_READING,
1679                                                    NULL, &head_flag);
1680                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1681                     !strcmp(head_ref, lock->ref_name)) {
1682                         struct strbuf log_err = STRBUF_INIT;
1683                         if (files_log_ref_write(refs, "HEAD",
1684                                                 &lock->old_oid, oid,
1685                                                 logmsg, 0, &log_err)) {
1686                                 error("%s", log_err.buf);
1687                                 strbuf_release(&log_err);
1688                         }
1689                 }
1690         }
1691
1692         if (commit_ref(lock)) {
1693                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1694                 unlock_ref(lock);
1695                 return -1;
1696         }
1697
1698         unlock_ref(lock);
1699         return 0;
1700 }
1701
1702 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1703 {
1704         int ret = -1;
1705 #ifndef NO_SYMLINK_HEAD
1706         char *ref_path = get_locked_file_path(&lock->lk);
1707         unlink(ref_path);
1708         ret = symlink(target, ref_path);
1709         free(ref_path);
1710
1711         if (ret)
1712                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1713 #endif
1714         return ret;
1715 }
1716
1717 static void update_symref_reflog(struct files_ref_store *refs,
1718                                  struct ref_lock *lock, const char *refname,
1719                                  const char *target, const char *logmsg)
1720 {
1721         struct strbuf err = STRBUF_INIT;
1722         struct object_id new_oid;
1723         if (logmsg &&
1724             !refs_read_ref_full(&refs->base, target,
1725                                 RESOLVE_REF_READING, &new_oid, NULL) &&
1726             files_log_ref_write(refs, refname, &lock->old_oid,
1727                                 &new_oid, logmsg, 0, &err)) {
1728                 error("%s", err.buf);
1729                 strbuf_release(&err);
1730         }
1731 }
1732
1733 static int create_symref_locked(struct files_ref_store *refs,
1734                                 struct ref_lock *lock, const char *refname,
1735                                 const char *target, const char *logmsg)
1736 {
1737         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1738                 update_symref_reflog(refs, lock, refname, target, logmsg);
1739                 return 0;
1740         }
1741
1742         if (!fdopen_lock_file(&lock->lk, "w"))
1743                 return error("unable to fdopen %s: %s",
1744                              lock->lk.tempfile->filename.buf, strerror(errno));
1745
1746         update_symref_reflog(refs, lock, refname, target, logmsg);
1747
1748         /* no error check; commit_ref will check ferror */
1749         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1750         if (commit_ref(lock) < 0)
1751                 return error("unable to write symref for %s: %s", refname,
1752                              strerror(errno));
1753         return 0;
1754 }
1755
1756 static int files_create_symref(struct ref_store *ref_store,
1757                                const char *refname, const char *target,
1758                                const char *logmsg)
1759 {
1760         struct files_ref_store *refs =
1761                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1762         struct strbuf err = STRBUF_INIT;
1763         struct ref_lock *lock;
1764         int ret;
1765
1766         lock = lock_ref_oid_basic(refs, refname, NULL,
1767                                   NULL, NULL, REF_NODEREF, NULL,
1768                                   &err);
1769         if (!lock) {
1770                 error("%s", err.buf);
1771                 strbuf_release(&err);
1772                 return -1;
1773         }
1774
1775         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1776         unlock_ref(lock);
1777         return ret;
1778 }
1779
1780 static int files_reflog_exists(struct ref_store *ref_store,
1781                                const char *refname)
1782 {
1783         struct files_ref_store *refs =
1784                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1785         struct strbuf sb = STRBUF_INIT;
1786         struct stat st;
1787         int ret;
1788
1789         files_reflog_path(refs, &sb, refname);
1790         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1791         strbuf_release(&sb);
1792         return ret;
1793 }
1794
1795 static int files_delete_reflog(struct ref_store *ref_store,
1796                                const char *refname)
1797 {
1798         struct files_ref_store *refs =
1799                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1800         struct strbuf sb = STRBUF_INIT;
1801         int ret;
1802
1803         files_reflog_path(refs, &sb, refname);
1804         ret = remove_path(sb.buf);
1805         strbuf_release(&sb);
1806         return ret;
1807 }
1808
1809 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1810 {
1811         struct object_id ooid, noid;
1812         char *email_end, *message;
1813         timestamp_t timestamp;
1814         int tz;
1815         const char *p = sb->buf;
1816
1817         /* old SP new SP name <email> SP time TAB msg LF */
1818         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1819             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1820             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1821             !(email_end = strchr(p, '>')) ||
1822             email_end[1] != ' ' ||
1823             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1824             !message || message[0] != ' ' ||
1825             (message[1] != '+' && message[1] != '-') ||
1826             !isdigit(message[2]) || !isdigit(message[3]) ||
1827             !isdigit(message[4]) || !isdigit(message[5]))
1828                 return 0; /* corrupt? */
1829         email_end[1] = '\0';
1830         tz = strtol(message + 1, NULL, 10);
1831         if (message[6] != '\t')
1832                 message += 6;
1833         else
1834                 message += 7;
1835         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1836 }
1837
1838 static char *find_beginning_of_line(char *bob, char *scan)
1839 {
1840         while (bob < scan && *(--scan) != '\n')
1841                 ; /* keep scanning backwards */
1842         /*
1843          * Return either beginning of the buffer, or LF at the end of
1844          * the previous line.
1845          */
1846         return scan;
1847 }
1848
1849 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1850                                              const char *refname,
1851                                              each_reflog_ent_fn fn,
1852                                              void *cb_data)
1853 {
1854         struct files_ref_store *refs =
1855                 files_downcast(ref_store, REF_STORE_READ,
1856                                "for_each_reflog_ent_reverse");
1857         struct strbuf sb = STRBUF_INIT;
1858         FILE *logfp;
1859         long pos;
1860         int ret = 0, at_tail = 1;
1861
1862         files_reflog_path(refs, &sb, refname);
1863         logfp = fopen(sb.buf, "r");
1864         strbuf_release(&sb);
1865         if (!logfp)
1866                 return -1;
1867
1868         /* Jump to the end */
1869         if (fseek(logfp, 0, SEEK_END) < 0)
1870                 ret = error("cannot seek back reflog for %s: %s",
1871                             refname, strerror(errno));
1872         pos = ftell(logfp);
1873         while (!ret && 0 < pos) {
1874                 int cnt;
1875                 size_t nread;
1876                 char buf[BUFSIZ];
1877                 char *endp, *scanp;
1878
1879                 /* Fill next block from the end */
1880                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1881                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1882                         ret = error("cannot seek back reflog for %s: %s",
1883                                     refname, strerror(errno));
1884                         break;
1885                 }
1886                 nread = fread(buf, cnt, 1, logfp);
1887                 if (nread != 1) {
1888                         ret = error("cannot read %d bytes from reflog for %s: %s",
1889                                     cnt, refname, strerror(errno));
1890                         break;
1891                 }
1892                 pos -= cnt;
1893
1894                 scanp = endp = buf + cnt;
1895                 if (at_tail && scanp[-1] == '\n')
1896                         /* Looking at the final LF at the end of the file */
1897                         scanp--;
1898                 at_tail = 0;
1899
1900                 while (buf < scanp) {
1901                         /*
1902                          * terminating LF of the previous line, or the beginning
1903                          * of the buffer.
1904                          */
1905                         char *bp;
1906
1907                         bp = find_beginning_of_line(buf, scanp);
1908
1909                         if (*bp == '\n') {
1910                                 /*
1911                                  * The newline is the end of the previous line,
1912                                  * so we know we have complete line starting
1913                                  * at (bp + 1). Prefix it onto any prior data
1914                                  * we collected for the line and process it.
1915                                  */
1916                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1917                                 scanp = bp;
1918                                 endp = bp + 1;
1919                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1920                                 strbuf_reset(&sb);
1921                                 if (ret)
1922                                         break;
1923                         } else if (!pos) {
1924                                 /*
1925                                  * We are at the start of the buffer, and the
1926                                  * start of the file; there is no previous
1927                                  * line, and we have everything for this one.
1928                                  * Process it, and we can end the loop.
1929                                  */
1930                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1931                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1932                                 strbuf_reset(&sb);
1933                                 break;
1934                         }
1935
1936                         if (bp == buf) {
1937                                 /*
1938                                  * We are at the start of the buffer, and there
1939                                  * is more file to read backwards. Which means
1940                                  * we are in the middle of a line. Note that we
1941                                  * may get here even if *bp was a newline; that
1942                                  * just means we are at the exact end of the
1943                                  * previous line, rather than some spot in the
1944                                  * middle.
1945                                  *
1946                                  * Save away what we have to be combined with
1947                                  * the data from the next read.
1948                                  */
1949                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1950                                 break;
1951                         }
1952                 }
1953
1954         }
1955         if (!ret && sb.len)
1956                 die("BUG: reverse reflog parser had leftover data");
1957
1958         fclose(logfp);
1959         strbuf_release(&sb);
1960         return ret;
1961 }
1962
1963 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1964                                      const char *refname,
1965                                      each_reflog_ent_fn fn, void *cb_data)
1966 {
1967         struct files_ref_store *refs =
1968                 files_downcast(ref_store, REF_STORE_READ,
1969                                "for_each_reflog_ent");
1970         FILE *logfp;
1971         struct strbuf sb = STRBUF_INIT;
1972         int ret = 0;
1973
1974         files_reflog_path(refs, &sb, refname);
1975         logfp = fopen(sb.buf, "r");
1976         strbuf_release(&sb);
1977         if (!logfp)
1978                 return -1;
1979
1980         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
1981                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1982         fclose(logfp);
1983         strbuf_release(&sb);
1984         return ret;
1985 }
1986
1987 struct files_reflog_iterator {
1988         struct ref_iterator base;
1989
1990         struct ref_store *ref_store;
1991         struct dir_iterator *dir_iterator;
1992         struct object_id oid;
1993 };
1994
1995 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
1996 {
1997         struct files_reflog_iterator *iter =
1998                 (struct files_reflog_iterator *)ref_iterator;
1999         struct dir_iterator *diter = iter->dir_iterator;
2000         int ok;
2001
2002         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2003                 int flags;
2004
2005                 if (!S_ISREG(diter->st.st_mode))
2006                         continue;
2007                 if (diter->basename[0] == '.')
2008                         continue;
2009                 if (ends_with(diter->basename, ".lock"))
2010                         continue;
2011
2012                 if (refs_read_ref_full(iter->ref_store,
2013                                        diter->relative_path, 0,
2014                                        &iter->oid, &flags)) {
2015                         error("bad ref for %s", diter->path.buf);
2016                         continue;
2017                 }
2018
2019                 iter->base.refname = diter->relative_path;
2020                 iter->base.oid = &iter->oid;
2021                 iter->base.flags = flags;
2022                 return ITER_OK;
2023         }
2024
2025         iter->dir_iterator = NULL;
2026         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2027                 ok = ITER_ERROR;
2028         return ok;
2029 }
2030
2031 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2032                                    struct object_id *peeled)
2033 {
2034         die("BUG: ref_iterator_peel() called for reflog_iterator");
2035 }
2036
2037 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2038 {
2039         struct files_reflog_iterator *iter =
2040                 (struct files_reflog_iterator *)ref_iterator;
2041         int ok = ITER_DONE;
2042
2043         if (iter->dir_iterator)
2044                 ok = dir_iterator_abort(iter->dir_iterator);
2045
2046         base_ref_iterator_free(ref_iterator);
2047         return ok;
2048 }
2049
2050 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2051         files_reflog_iterator_advance,
2052         files_reflog_iterator_peel,
2053         files_reflog_iterator_abort
2054 };
2055
2056 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2057                                                   const char *gitdir)
2058 {
2059         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2060         struct ref_iterator *ref_iterator = &iter->base;
2061         struct strbuf sb = STRBUF_INIT;
2062
2063         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2064         strbuf_addf(&sb, "%s/logs", gitdir);
2065         iter->dir_iterator = dir_iterator_begin(sb.buf);
2066         iter->ref_store = ref_store;
2067         strbuf_release(&sb);
2068
2069         return ref_iterator;
2070 }
2071
2072 static enum iterator_selection reflog_iterator_select(
2073         struct ref_iterator *iter_worktree,
2074         struct ref_iterator *iter_common,
2075         void *cb_data)
2076 {
2077         if (iter_worktree) {
2078                 /*
2079                  * We're a bit loose here. We probably should ignore
2080                  * common refs if they are accidentally added as
2081                  * per-worktree refs.
2082                  */
2083                 return ITER_SELECT_0;
2084         } else if (iter_common) {
2085                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2086                         return ITER_SELECT_1;
2087
2088                 /*
2089                  * The main ref store may contain main worktree's
2090                  * per-worktree refs, which should be ignored
2091                  */
2092                 return ITER_SKIP_1;
2093         } else
2094                 return ITER_DONE;
2095 }
2096
2097 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2098 {
2099         struct files_ref_store *refs =
2100                 files_downcast(ref_store, REF_STORE_READ,
2101                                "reflog_iterator_begin");
2102
2103         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2104                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2105         } else {
2106                 return merge_ref_iterator_begin(
2107                         0,
2108                         reflog_iterator_begin(ref_store, refs->gitdir),
2109                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2110                         reflog_iterator_select, refs);
2111         }
2112 }
2113
2114 /*
2115  * If update is a direct update of head_ref (the reference pointed to
2116  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2117  */
2118 static int split_head_update(struct ref_update *update,
2119                              struct ref_transaction *transaction,
2120                              const char *head_ref,
2121                              struct string_list *affected_refnames,
2122                              struct strbuf *err)
2123 {
2124         struct string_list_item *item;
2125         struct ref_update *new_update;
2126
2127         if ((update->flags & REF_LOG_ONLY) ||
2128             (update->flags & REF_ISPRUNING) ||
2129             (update->flags & REF_UPDATE_VIA_HEAD))
2130                 return 0;
2131
2132         if (strcmp(update->refname, head_ref))
2133                 return 0;
2134
2135         /*
2136          * First make sure that HEAD is not already in the
2137          * transaction. This check is O(lg N) in the transaction
2138          * size, but it happens at most once per transaction.
2139          */
2140         if (string_list_has_string(affected_refnames, "HEAD")) {
2141                 /* An entry already existed */
2142                 strbuf_addf(err,
2143                             "multiple updates for 'HEAD' (including one "
2144                             "via its referent '%s') are not allowed",
2145                             update->refname);
2146                 return TRANSACTION_NAME_CONFLICT;
2147         }
2148
2149         new_update = ref_transaction_add_update(
2150                         transaction, "HEAD",
2151                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2152                         &update->new_oid, &update->old_oid,
2153                         update->msg);
2154
2155         /*
2156          * Add "HEAD". This insertion is O(N) in the transaction
2157          * size, but it happens at most once per transaction.
2158          * Add new_update->refname instead of a literal "HEAD".
2159          */
2160         if (strcmp(new_update->refname, "HEAD"))
2161                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2162         item = string_list_insert(affected_refnames, new_update->refname);
2163         item->util = new_update;
2164
2165         return 0;
2166 }
2167
2168 /*
2169  * update is for a symref that points at referent and doesn't have
2170  * REF_NODEREF set. Split it into two updates:
2171  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2172  * - A new, separate update for the referent reference
2173  * Note that the new update will itself be subject to splitting when
2174  * the iteration gets to it.
2175  */
2176 static int split_symref_update(struct files_ref_store *refs,
2177                                struct ref_update *update,
2178                                const char *referent,
2179                                struct ref_transaction *transaction,
2180                                struct string_list *affected_refnames,
2181                                struct strbuf *err)
2182 {
2183         struct string_list_item *item;
2184         struct ref_update *new_update;
2185         unsigned int new_flags;
2186
2187         /*
2188          * First make sure that referent is not already in the
2189          * transaction. This check is O(lg N) in the transaction
2190          * size, but it happens at most once per symref in a
2191          * transaction.
2192          */
2193         if (string_list_has_string(affected_refnames, referent)) {
2194                 /* An entry already exists */
2195                 strbuf_addf(err,
2196                             "multiple updates for '%s' (including one "
2197                             "via symref '%s') are not allowed",
2198                             referent, update->refname);
2199                 return TRANSACTION_NAME_CONFLICT;
2200         }
2201
2202         new_flags = update->flags;
2203         if (!strcmp(update->refname, "HEAD")) {
2204                 /*
2205                  * Record that the new update came via HEAD, so that
2206                  * when we process it, split_head_update() doesn't try
2207                  * to add another reflog update for HEAD. Note that
2208                  * this bit will be propagated if the new_update
2209                  * itself needs to be split.
2210                  */
2211                 new_flags |= REF_UPDATE_VIA_HEAD;
2212         }
2213
2214         new_update = ref_transaction_add_update(
2215                         transaction, referent, new_flags,
2216                         &update->new_oid, &update->old_oid,
2217                         update->msg);
2218
2219         new_update->parent_update = update;
2220
2221         /*
2222          * Change the symbolic ref update to log only. Also, it
2223          * doesn't need to check its old SHA-1 value, as that will be
2224          * done when new_update is processed.
2225          */
2226         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2227         update->flags &= ~REF_HAVE_OLD;
2228
2229         /*
2230          * Add the referent. This insertion is O(N) in the transaction
2231          * size, but it happens at most once per symref in a
2232          * transaction. Make sure to add new_update->refname, which will
2233          * be valid as long as affected_refnames is in use, and NOT
2234          * referent, which might soon be freed by our caller.
2235          */
2236         item = string_list_insert(affected_refnames, new_update->refname);
2237         if (item->util)
2238                 BUG("%s unexpectedly found in affected_refnames",
2239                     new_update->refname);
2240         item->util = new_update;
2241
2242         return 0;
2243 }
2244
2245 /*
2246  * Return the refname under which update was originally requested.
2247  */
2248 static const char *original_update_refname(struct ref_update *update)
2249 {
2250         while (update->parent_update)
2251                 update = update->parent_update;
2252
2253         return update->refname;
2254 }
2255
2256 /*
2257  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2258  * are consistent with oid, which is the reference's current value. If
2259  * everything is OK, return 0; otherwise, write an error message to
2260  * err and return -1.
2261  */
2262 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2263                          struct strbuf *err)
2264 {
2265         if (!(update->flags & REF_HAVE_OLD) ||
2266                    !oidcmp(oid, &update->old_oid))
2267                 return 0;
2268
2269         if (is_null_oid(&update->old_oid))
2270                 strbuf_addf(err, "cannot lock ref '%s': "
2271                             "reference already exists",
2272                             original_update_refname(update));
2273         else if (is_null_oid(oid))
2274                 strbuf_addf(err, "cannot lock ref '%s': "
2275                             "reference is missing but expected %s",
2276                             original_update_refname(update),
2277                             oid_to_hex(&update->old_oid));
2278         else
2279                 strbuf_addf(err, "cannot lock ref '%s': "
2280                             "is at %s but expected %s",
2281                             original_update_refname(update),
2282                             oid_to_hex(oid),
2283                             oid_to_hex(&update->old_oid));
2284
2285         return -1;
2286 }
2287
2288 /*
2289  * Prepare for carrying out update:
2290  * - Lock the reference referred to by update.
2291  * - Read the reference under lock.
2292  * - Check that its old SHA-1 value (if specified) is correct, and in
2293  *   any case record it in update->lock->old_oid for later use when
2294  *   writing the reflog.
2295  * - If it is a symref update without REF_NODEREF, split it up into a
2296  *   REF_LOG_ONLY update of the symref and add a separate update for
2297  *   the referent to transaction.
2298  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2299  *   update of HEAD.
2300  */
2301 static int lock_ref_for_update(struct files_ref_store *refs,
2302                                struct ref_update *update,
2303                                struct ref_transaction *transaction,
2304                                const char *head_ref,
2305                                struct string_list *affected_refnames,
2306                                struct strbuf *err)
2307 {
2308         struct strbuf referent = STRBUF_INIT;
2309         int mustexist = (update->flags & REF_HAVE_OLD) &&
2310                 !is_null_oid(&update->old_oid);
2311         int ret = 0;
2312         struct ref_lock *lock;
2313
2314         files_assert_main_repository(refs, "lock_ref_for_update");
2315
2316         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2317                 update->flags |= REF_DELETING;
2318
2319         if (head_ref) {
2320                 ret = split_head_update(update, transaction, head_ref,
2321                                         affected_refnames, err);
2322                 if (ret)
2323                         goto out;
2324         }
2325
2326         ret = lock_raw_ref(refs, update->refname, mustexist,
2327                            affected_refnames, NULL,
2328                            &lock, &referent,
2329                            &update->type, err);
2330         if (ret) {
2331                 char *reason;
2332
2333                 reason = strbuf_detach(err, NULL);
2334                 strbuf_addf(err, "cannot lock ref '%s': %s",
2335                             original_update_refname(update), reason);
2336                 free(reason);
2337                 goto out;
2338         }
2339
2340         update->backend_data = lock;
2341
2342         if (update->type & REF_ISSYMREF) {
2343                 if (update->flags & REF_NODEREF) {
2344                         /*
2345                          * We won't be reading the referent as part of
2346                          * the transaction, so we have to read it here
2347                          * to record and possibly check old_sha1:
2348                          */
2349                         if (refs_read_ref_full(&refs->base,
2350                                                referent.buf, 0,
2351                                                &lock->old_oid, NULL)) {
2352                                 if (update->flags & REF_HAVE_OLD) {
2353                                         strbuf_addf(err, "cannot lock ref '%s': "
2354                                                     "error reading reference",
2355                                                     original_update_refname(update));
2356                                         ret = TRANSACTION_GENERIC_ERROR;
2357                                         goto out;
2358                                 }
2359                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2360                                 ret = TRANSACTION_GENERIC_ERROR;
2361                                 goto out;
2362                         }
2363                 } else {
2364                         /*
2365                          * Create a new update for the reference this
2366                          * symref is pointing at. Also, we will record
2367                          * and verify old_sha1 for this update as part
2368                          * of processing the split-off update, so we
2369                          * don't have to do it here.
2370                          */
2371                         ret = split_symref_update(refs, update,
2372                                                   referent.buf, transaction,
2373                                                   affected_refnames, err);
2374                         if (ret)
2375                                 goto out;
2376                 }
2377         } else {
2378                 struct ref_update *parent_update;
2379
2380                 if (check_old_oid(update, &lock->old_oid, err)) {
2381                         ret = TRANSACTION_GENERIC_ERROR;
2382                         goto out;
2383                 }
2384
2385                 /*
2386                  * If this update is happening indirectly because of a
2387                  * symref update, record the old SHA-1 in the parent
2388                  * update:
2389                  */
2390                 for (parent_update = update->parent_update;
2391                      parent_update;
2392                      parent_update = parent_update->parent_update) {
2393                         struct ref_lock *parent_lock = parent_update->backend_data;
2394                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2395                 }
2396         }
2397
2398         if ((update->flags & REF_HAVE_NEW) &&
2399             !(update->flags & REF_DELETING) &&
2400             !(update->flags & REF_LOG_ONLY)) {
2401                 if (!(update->type & REF_ISSYMREF) &&
2402                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2403                         /*
2404                          * The reference already has the desired
2405                          * value, so we don't need to write it.
2406                          */
2407                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2408                                                  err)) {
2409                         char *write_err = strbuf_detach(err, NULL);
2410
2411                         /*
2412                          * The lock was freed upon failure of
2413                          * write_ref_to_lockfile():
2414                          */
2415                         update->backend_data = NULL;
2416                         strbuf_addf(err,
2417                                     "cannot update ref '%s': %s",
2418                                     update->refname, write_err);
2419                         free(write_err);
2420                         ret = TRANSACTION_GENERIC_ERROR;
2421                         goto out;
2422                 } else {
2423                         update->flags |= REF_NEEDS_COMMIT;
2424                 }
2425         }
2426         if (!(update->flags & REF_NEEDS_COMMIT)) {
2427                 /*
2428                  * We didn't call write_ref_to_lockfile(), so
2429                  * the lockfile is still open. Close it to
2430                  * free up the file descriptor:
2431                  */
2432                 if (close_ref_gently(lock)) {
2433                         strbuf_addf(err, "couldn't close '%s.lock'",
2434                                     update->refname);
2435                         ret = TRANSACTION_GENERIC_ERROR;
2436                         goto out;
2437                 }
2438         }
2439
2440 out:
2441         strbuf_release(&referent);
2442         return ret;
2443 }
2444
2445 struct files_transaction_backend_data {
2446         struct ref_transaction *packed_transaction;
2447         int packed_refs_locked;
2448 };
2449
2450 /*
2451  * Unlock any references in `transaction` that are still locked, and
2452  * mark the transaction closed.
2453  */
2454 static void files_transaction_cleanup(struct files_ref_store *refs,
2455                                       struct ref_transaction *transaction)
2456 {
2457         size_t i;
2458         struct files_transaction_backend_data *backend_data =
2459                 transaction->backend_data;
2460         struct strbuf err = STRBUF_INIT;
2461
2462         for (i = 0; i < transaction->nr; i++) {
2463                 struct ref_update *update = transaction->updates[i];
2464                 struct ref_lock *lock = update->backend_data;
2465
2466                 if (lock) {
2467                         unlock_ref(lock);
2468                         update->backend_data = NULL;
2469                 }
2470         }
2471
2472         if (backend_data->packed_transaction &&
2473             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2474                 error("error aborting transaction: %s", err.buf);
2475                 strbuf_release(&err);
2476         }
2477
2478         if (backend_data->packed_refs_locked)
2479                 packed_refs_unlock(refs->packed_ref_store);
2480
2481         free(backend_data);
2482
2483         transaction->state = REF_TRANSACTION_CLOSED;
2484 }
2485
2486 static int files_transaction_prepare(struct ref_store *ref_store,
2487                                      struct ref_transaction *transaction,
2488                                      struct strbuf *err)
2489 {
2490         struct files_ref_store *refs =
2491                 files_downcast(ref_store, REF_STORE_WRITE,
2492                                "ref_transaction_prepare");
2493         size_t i;
2494         int ret = 0;
2495         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2496         char *head_ref = NULL;
2497         int head_type;
2498         struct files_transaction_backend_data *backend_data;
2499         struct ref_transaction *packed_transaction = NULL;
2500
2501         assert(err);
2502
2503         if (!transaction->nr)
2504                 goto cleanup;
2505
2506         backend_data = xcalloc(1, sizeof(*backend_data));
2507         transaction->backend_data = backend_data;
2508
2509         /*
2510          * Fail if a refname appears more than once in the
2511          * transaction. (If we end up splitting up any updates using
2512          * split_symref_update() or split_head_update(), those
2513          * functions will check that the new updates don't have the
2514          * same refname as any existing ones.)
2515          */
2516         for (i = 0; i < transaction->nr; i++) {
2517                 struct ref_update *update = transaction->updates[i];
2518                 struct string_list_item *item =
2519                         string_list_append(&affected_refnames, update->refname);
2520
2521                 /*
2522                  * We store a pointer to update in item->util, but at
2523                  * the moment we never use the value of this field
2524                  * except to check whether it is non-NULL.
2525                  */
2526                 item->util = update;
2527         }
2528         string_list_sort(&affected_refnames);
2529         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2530                 ret = TRANSACTION_GENERIC_ERROR;
2531                 goto cleanup;
2532         }
2533
2534         /*
2535          * Special hack: If a branch is updated directly and HEAD
2536          * points to it (may happen on the remote side of a push
2537          * for example) then logically the HEAD reflog should be
2538          * updated too.
2539          *
2540          * A generic solution would require reverse symref lookups,
2541          * but finding all symrefs pointing to a given branch would be
2542          * rather costly for this rare event (the direct update of a
2543          * branch) to be worth it. So let's cheat and check with HEAD
2544          * only, which should cover 99% of all usage scenarios (even
2545          * 100% of the default ones).
2546          *
2547          * So if HEAD is a symbolic reference, then record the name of
2548          * the reference that it points to. If we see an update of
2549          * head_ref within the transaction, then split_head_update()
2550          * arranges for the reflog of HEAD to be updated, too.
2551          */
2552         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2553                                        RESOLVE_REF_NO_RECURSE,
2554                                        NULL, &head_type);
2555
2556         if (head_ref && !(head_type & REF_ISSYMREF)) {
2557                 FREE_AND_NULL(head_ref);
2558         }
2559
2560         /*
2561          * Acquire all locks, verify old values if provided, check
2562          * that new values are valid, and write new values to the
2563          * lockfiles, ready to be activated. Only keep one lockfile
2564          * open at a time to avoid running out of file descriptors.
2565          * Note that lock_ref_for_update() might append more updates
2566          * to the transaction.
2567          */
2568         for (i = 0; i < transaction->nr; i++) {
2569                 struct ref_update *update = transaction->updates[i];
2570
2571                 ret = lock_ref_for_update(refs, update, transaction,
2572                                           head_ref, &affected_refnames, err);
2573                 if (ret)
2574                         goto cleanup;
2575
2576                 if (update->flags & REF_DELETING &&
2577                     !(update->flags & REF_LOG_ONLY) &&
2578                     !(update->flags & REF_ISPRUNING)) {
2579                         /*
2580                          * This reference has to be deleted from
2581                          * packed-refs if it exists there.
2582                          */
2583                         if (!packed_transaction) {
2584                                 packed_transaction = ref_store_transaction_begin(
2585                                                 refs->packed_ref_store, err);
2586                                 if (!packed_transaction) {
2587                                         ret = TRANSACTION_GENERIC_ERROR;
2588                                         goto cleanup;
2589                                 }
2590
2591                                 backend_data->packed_transaction =
2592                                         packed_transaction;
2593                         }
2594
2595                         ref_transaction_add_update(
2596                                         packed_transaction, update->refname,
2597                                         update->flags & ~REF_HAVE_OLD,
2598                                         &update->new_oid, &update->old_oid,
2599                                         NULL);
2600                 }
2601         }
2602
2603         if (packed_transaction) {
2604                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2605                         ret = TRANSACTION_GENERIC_ERROR;
2606                         goto cleanup;
2607                 }
2608                 backend_data->packed_refs_locked = 1;
2609                 ret = ref_transaction_prepare(packed_transaction, err);
2610         }
2611
2612 cleanup:
2613         free(head_ref);
2614         string_list_clear(&affected_refnames, 0);
2615
2616         if (ret)
2617                 files_transaction_cleanup(refs, transaction);
2618         else
2619                 transaction->state = REF_TRANSACTION_PREPARED;
2620
2621         return ret;
2622 }
2623
2624 static int files_transaction_finish(struct ref_store *ref_store,
2625                                     struct ref_transaction *transaction,
2626                                     struct strbuf *err)
2627 {
2628         struct files_ref_store *refs =
2629                 files_downcast(ref_store, 0, "ref_transaction_finish");
2630         size_t i;
2631         int ret = 0;
2632         struct strbuf sb = STRBUF_INIT;
2633         struct files_transaction_backend_data *backend_data;
2634         struct ref_transaction *packed_transaction;
2635
2636
2637         assert(err);
2638
2639         if (!transaction->nr) {
2640                 transaction->state = REF_TRANSACTION_CLOSED;
2641                 return 0;
2642         }
2643
2644         backend_data = transaction->backend_data;
2645         packed_transaction = backend_data->packed_transaction;
2646
2647         /* Perform updates first so live commits remain referenced */
2648         for (i = 0; i < transaction->nr; i++) {
2649                 struct ref_update *update = transaction->updates[i];
2650                 struct ref_lock *lock = update->backend_data;
2651
2652                 if (update->flags & REF_NEEDS_COMMIT ||
2653                     update->flags & REF_LOG_ONLY) {
2654                         if (files_log_ref_write(refs,
2655                                                 lock->ref_name,
2656                                                 &lock->old_oid,
2657                                                 &update->new_oid,
2658                                                 update->msg, update->flags,
2659                                                 err)) {
2660                                 char *old_msg = strbuf_detach(err, NULL);
2661
2662                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2663                                             lock->ref_name, old_msg);
2664                                 free(old_msg);
2665                                 unlock_ref(lock);
2666                                 update->backend_data = NULL;
2667                                 ret = TRANSACTION_GENERIC_ERROR;
2668                                 goto cleanup;
2669                         }
2670                 }
2671                 if (update->flags & REF_NEEDS_COMMIT) {
2672                         clear_loose_ref_cache(refs);
2673                         if (commit_ref(lock)) {
2674                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2675                                 unlock_ref(lock);
2676                                 update->backend_data = NULL;
2677                                 ret = TRANSACTION_GENERIC_ERROR;
2678                                 goto cleanup;
2679                         }
2680                 }
2681         }
2682
2683         /*
2684          * Now that updates are safely completed, we can perform
2685          * deletes. First delete the reflogs of any references that
2686          * will be deleted, since (in the unexpected event of an
2687          * error) leaving a reference without a reflog is less bad
2688          * than leaving a reflog without a reference (the latter is a
2689          * mildly invalid repository state):
2690          */
2691         for (i = 0; i < transaction->nr; i++) {
2692                 struct ref_update *update = transaction->updates[i];
2693                 if (update->flags & REF_DELETING &&
2694                     !(update->flags & REF_LOG_ONLY) &&
2695                     !(update->flags & REF_ISPRUNING)) {
2696                         strbuf_reset(&sb);
2697                         files_reflog_path(refs, &sb, update->refname);
2698                         if (!unlink_or_warn(sb.buf))
2699                                 try_remove_empty_parents(refs, update->refname,
2700                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2701                 }
2702         }
2703
2704         /*
2705          * Perform deletes now that updates are safely completed.
2706          *
2707          * First delete any packed versions of the references, while
2708          * retaining the packed-refs lock:
2709          */
2710         if (packed_transaction) {
2711                 ret = ref_transaction_commit(packed_transaction, err);
2712                 ref_transaction_free(packed_transaction);
2713                 packed_transaction = NULL;
2714                 backend_data->packed_transaction = NULL;
2715                 if (ret)
2716                         goto cleanup;
2717         }
2718
2719         /* Now delete the loose versions of the references: */
2720         for (i = 0; i < transaction->nr; i++) {
2721                 struct ref_update *update = transaction->updates[i];
2722                 struct ref_lock *lock = update->backend_data;
2723
2724                 if (update->flags & REF_DELETING &&
2725                     !(update->flags & REF_LOG_ONLY)) {
2726                         if (!(update->type & REF_ISPACKED) ||
2727                             update->type & REF_ISSYMREF) {
2728                                 /* It is a loose reference. */
2729                                 strbuf_reset(&sb);
2730                                 files_ref_path(refs, &sb, lock->ref_name);
2731                                 if (unlink_or_msg(sb.buf, err)) {
2732                                         ret = TRANSACTION_GENERIC_ERROR;
2733                                         goto cleanup;
2734                                 }
2735                                 update->flags |= REF_DELETED_LOOSE;
2736                         }
2737                 }
2738         }
2739
2740         clear_loose_ref_cache(refs);
2741
2742 cleanup:
2743         files_transaction_cleanup(refs, transaction);
2744
2745         for (i = 0; i < transaction->nr; i++) {
2746                 struct ref_update *update = transaction->updates[i];
2747
2748                 if (update->flags & REF_DELETED_LOOSE) {
2749                         /*
2750                          * The loose reference was deleted. Delete any
2751                          * empty parent directories. (Note that this
2752                          * can only work because we have already
2753                          * removed the lockfile.)
2754                          */
2755                         try_remove_empty_parents(refs, update->refname,
2756                                                  REMOVE_EMPTY_PARENTS_REF);
2757                 }
2758         }
2759
2760         strbuf_release(&sb);
2761         return ret;
2762 }
2763
2764 static int files_transaction_abort(struct ref_store *ref_store,
2765                                    struct ref_transaction *transaction,
2766                                    struct strbuf *err)
2767 {
2768         struct files_ref_store *refs =
2769                 files_downcast(ref_store, 0, "ref_transaction_abort");
2770
2771         files_transaction_cleanup(refs, transaction);
2772         return 0;
2773 }
2774
2775 static int ref_present(const char *refname,
2776                        const struct object_id *oid, int flags, void *cb_data)
2777 {
2778         struct string_list *affected_refnames = cb_data;
2779
2780         return string_list_has_string(affected_refnames, refname);
2781 }
2782
2783 static int files_initial_transaction_commit(struct ref_store *ref_store,
2784                                             struct ref_transaction *transaction,
2785                                             struct strbuf *err)
2786 {
2787         struct files_ref_store *refs =
2788                 files_downcast(ref_store, REF_STORE_WRITE,
2789                                "initial_ref_transaction_commit");
2790         size_t i;
2791         int ret = 0;
2792         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2793         struct ref_transaction *packed_transaction = NULL;
2794
2795         assert(err);
2796
2797         if (transaction->state != REF_TRANSACTION_OPEN)
2798                 die("BUG: commit called for transaction that is not open");
2799
2800         /* Fail if a refname appears more than once in the transaction: */
2801         for (i = 0; i < transaction->nr; i++)
2802                 string_list_append(&affected_refnames,
2803                                    transaction->updates[i]->refname);
2804         string_list_sort(&affected_refnames);
2805         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2806                 ret = TRANSACTION_GENERIC_ERROR;
2807                 goto cleanup;
2808         }
2809
2810         /*
2811          * It's really undefined to call this function in an active
2812          * repository or when there are existing references: we are
2813          * only locking and changing packed-refs, so (1) any
2814          * simultaneous processes might try to change a reference at
2815          * the same time we do, and (2) any existing loose versions of
2816          * the references that we are setting would have precedence
2817          * over our values. But some remote helpers create the remote
2818          * "HEAD" and "master" branches before calling this function,
2819          * so here we really only check that none of the references
2820          * that we are creating already exists.
2821          */
2822         if (refs_for_each_rawref(&refs->base, ref_present,
2823                                  &affected_refnames))
2824                 die("BUG: initial ref transaction called with existing refs");
2825
2826         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2827         if (!packed_transaction) {
2828                 ret = TRANSACTION_GENERIC_ERROR;
2829                 goto cleanup;
2830         }
2831
2832         for (i = 0; i < transaction->nr; i++) {
2833                 struct ref_update *update = transaction->updates[i];
2834
2835                 if ((update->flags & REF_HAVE_OLD) &&
2836                     !is_null_oid(&update->old_oid))
2837                         die("BUG: initial ref transaction with old_sha1 set");
2838                 if (refs_verify_refname_available(&refs->base, update->refname,
2839                                                   &affected_refnames, NULL,
2840                                                   err)) {
2841                         ret = TRANSACTION_NAME_CONFLICT;
2842                         goto cleanup;
2843                 }
2844
2845                 /*
2846                  * Add a reference creation for this reference to the
2847                  * packed-refs transaction:
2848                  */
2849                 ref_transaction_add_update(packed_transaction, update->refname,
2850                                            update->flags & ~REF_HAVE_OLD,
2851                                            &update->new_oid, &update->old_oid,
2852                                            NULL);
2853         }
2854
2855         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2856                 ret = TRANSACTION_GENERIC_ERROR;
2857                 goto cleanup;
2858         }
2859
2860         if (initial_ref_transaction_commit(packed_transaction, err)) {
2861                 ret = TRANSACTION_GENERIC_ERROR;
2862                 goto cleanup;
2863         }
2864
2865 cleanup:
2866         if (packed_transaction)
2867                 ref_transaction_free(packed_transaction);
2868         packed_refs_unlock(refs->packed_ref_store);
2869         transaction->state = REF_TRANSACTION_CLOSED;
2870         string_list_clear(&affected_refnames, 0);
2871         return ret;
2872 }
2873
2874 struct expire_reflog_cb {
2875         unsigned int flags;
2876         reflog_expiry_should_prune_fn *should_prune_fn;
2877         void *policy_cb;
2878         FILE *newlog;
2879         struct object_id last_kept_oid;
2880 };
2881
2882 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2883                              const char *email, timestamp_t timestamp, int tz,
2884                              const char *message, void *cb_data)
2885 {
2886         struct expire_reflog_cb *cb = cb_data;
2887         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2888
2889         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2890                 ooid = &cb->last_kept_oid;
2891
2892         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2893                                    message, policy_cb)) {
2894                 if (!cb->newlog)
2895                         printf("would prune %s", message);
2896                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2897                         printf("prune %s", message);
2898         } else {
2899                 if (cb->newlog) {
2900                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2901                                 oid_to_hex(ooid), oid_to_hex(noid),
2902                                 email, timestamp, tz, message);
2903                         oidcpy(&cb->last_kept_oid, noid);
2904                 }
2905                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2906                         printf("keep %s", message);
2907         }
2908         return 0;
2909 }
2910
2911 static int files_reflog_expire(struct ref_store *ref_store,
2912                                const char *refname, const struct object_id *oid,
2913                                unsigned int flags,
2914                                reflog_expiry_prepare_fn prepare_fn,
2915                                reflog_expiry_should_prune_fn should_prune_fn,
2916                                reflog_expiry_cleanup_fn cleanup_fn,
2917                                void *policy_cb_data)
2918 {
2919         struct files_ref_store *refs =
2920                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2921         static struct lock_file reflog_lock;
2922         struct expire_reflog_cb cb;
2923         struct ref_lock *lock;
2924         struct strbuf log_file_sb = STRBUF_INIT;
2925         char *log_file;
2926         int status = 0;
2927         int type;
2928         struct strbuf err = STRBUF_INIT;
2929
2930         memset(&cb, 0, sizeof(cb));
2931         cb.flags = flags;
2932         cb.policy_cb = policy_cb_data;
2933         cb.should_prune_fn = should_prune_fn;
2934
2935         /*
2936          * The reflog file is locked by holding the lock on the
2937          * reference itself, plus we might need to update the
2938          * reference if --updateref was specified:
2939          */
2940         lock = lock_ref_oid_basic(refs, refname, oid,
2941                                   NULL, NULL, REF_NODEREF,
2942                                   &type, &err);
2943         if (!lock) {
2944                 error("cannot lock ref '%s': %s", refname, err.buf);
2945                 strbuf_release(&err);
2946                 return -1;
2947         }
2948         if (!refs_reflog_exists(ref_store, refname)) {
2949                 unlock_ref(lock);
2950                 return 0;
2951         }
2952
2953         files_reflog_path(refs, &log_file_sb, refname);
2954         log_file = strbuf_detach(&log_file_sb, NULL);
2955         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2956                 /*
2957                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2958                  * no locking implications, we use the lock_file
2959                  * machinery here anyway because it does a lot of the
2960                  * work we need, including cleaning up if the program
2961                  * exits unexpectedly.
2962                  */
2963                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2964                         struct strbuf err = STRBUF_INIT;
2965                         unable_to_lock_message(log_file, errno, &err);
2966                         error("%s", err.buf);
2967                         strbuf_release(&err);
2968                         goto failure;
2969                 }
2970                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
2971                 if (!cb.newlog) {
2972                         error("cannot fdopen %s (%s)",
2973                               get_lock_file_path(&reflog_lock), strerror(errno));
2974                         goto failure;
2975                 }
2976         }
2977
2978         (*prepare_fn)(refname, oid, cb.policy_cb);
2979         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
2980         (*cleanup_fn)(cb.policy_cb);
2981
2982         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2983                 /*
2984                  * It doesn't make sense to adjust a reference pointed
2985                  * to by a symbolic ref based on expiring entries in
2986                  * the symbolic reference's reflog. Nor can we update
2987                  * a reference if there are no remaining reflog
2988                  * entries.
2989                  */
2990                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
2991                         !(type & REF_ISSYMREF) &&
2992                         !is_null_oid(&cb.last_kept_oid);
2993
2994                 if (close_lock_file_gently(&reflog_lock)) {
2995                         status |= error("couldn't write %s: %s", log_file,
2996                                         strerror(errno));
2997                         rollback_lock_file(&reflog_lock);
2998                 } else if (update &&
2999                            (write_in_full(get_lock_file_fd(&lock->lk),
3000                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3001                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3002                             close_ref_gently(lock) < 0)) {
3003                         status |= error("couldn't write %s",
3004                                         get_lock_file_path(&lock->lk));
3005                         rollback_lock_file(&reflog_lock);
3006                 } else if (commit_lock_file(&reflog_lock)) {
3007                         status |= error("unable to write reflog '%s' (%s)",
3008                                         log_file, strerror(errno));
3009                 } else if (update && commit_ref(lock)) {
3010                         status |= error("couldn't set %s", lock->ref_name);
3011                 }
3012         }
3013         free(log_file);
3014         unlock_ref(lock);
3015         return status;
3016
3017  failure:
3018         rollback_lock_file(&reflog_lock);
3019         free(log_file);
3020         unlock_ref(lock);
3021         return -1;
3022 }
3023
3024 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3025 {
3026         struct files_ref_store *refs =
3027                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3028         struct strbuf sb = STRBUF_INIT;
3029
3030         /*
3031          * Create .git/refs/{heads,tags}
3032          */
3033         files_ref_path(refs, &sb, "refs/heads");
3034         safe_create_dir(sb.buf, 1);
3035
3036         strbuf_reset(&sb);
3037         files_ref_path(refs, &sb, "refs/tags");
3038         safe_create_dir(sb.buf, 1);
3039
3040         strbuf_release(&sb);
3041         return 0;
3042 }
3043
3044 struct ref_storage_be refs_be_files = {
3045         NULL,
3046         "files",
3047         files_ref_store_create,
3048         files_init_db,
3049         files_transaction_prepare,
3050         files_transaction_finish,
3051         files_transaction_abort,
3052         files_initial_transaction_commit,
3053
3054         files_pack_refs,
3055         files_create_symref,
3056         files_delete_refs,
3057         files_rename_ref,
3058         files_copy_ref,
3059
3060         files_ref_iterator_begin,
3061         files_read_raw_ref,
3062
3063         files_reflog_iterator_begin,
3064         files_for_each_reflog_ent,
3065         files_for_each_reflog_ent_reverse,
3066         files_reflog_exists,
3067         files_create_reflog,
3068         files_delete_reflog,
3069         files_reflog_expire
3070 };