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         if (!refname) {
 110                 /*
 111                  * FIXME: of course this is wrong in multi worktree
 112                  * setting. To be fixed real soon.
 113                  */
 114                 strbuf_addf(sb, "%s/logs", refs->gitcommondir);
 115                 return;
 116         }
 117
 118         switch (ref_type(refname)) {
 119         case REF_TYPE_PER_WORKTREE:
 120         case REF_TYPE_PSEUDOREF:
 121                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 122                 break;
 123         case REF_TYPE_NORMAL:
 124                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 125                 break;
 126         default:
 127                 die("BUG: unknown ref type %d of ref %s",
 128                     ref_type(refname), refname);
 129         }
 130 }
 131
 132 static void files_ref_path(struct files_ref_store *refs,
 133                            struct strbuf *sb,
 134                            const char *refname)
 135 {
 136         switch (ref_type(refname)) {
 137         case REF_TYPE_PER_WORKTREE:
 138         case REF_TYPE_PSEUDOREF:
 139                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 140                 break;
 141         case REF_TYPE_NORMAL:
 142                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 143                 break;
 144         default:
 145                 die("BUG: unknown ref type %d of ref %s",
 146                     ref_type(refname), refname);
 147         }
 148 }
 149
 150 /*
 151  * Read the loose references from the namespace dirname into dir
 152  * (without recursing).  dirname must end with '/'.  dir must be the
 153  * directory entry corresponding to dirname.
 154  */
 155 static void loose_fill_ref_dir(struct ref_store *ref_store,
 156                                struct ref_dir *dir, const char *dirname)
 157 {
 158         struct files_ref_store *refs =
 159                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 160         DIR *d;
 161         struct dirent *de;
 162         int dirnamelen = strlen(dirname);
 163         struct strbuf refname;
 164         struct strbuf path = STRBUF_INIT;
 165         size_t path_baselen;
 166
 167         files_ref_path(refs, &path, dirname);
 168         path_baselen = path.len;
 169
 170         d = opendir(path.buf);
 171         if (!d) {
 172                 strbuf_release(&path);
 173                 return;
 174         }
 175
 176         strbuf_init(&refname, dirnamelen + 257);
 177         strbuf_add(&refname, dirname, dirnamelen);
 178
 179         while ((de = readdir(d)) != NULL) {
 180                 struct object_id oid;
 181                 struct stat st;
 182                 int flag;
 183
 184                 if (de->d_name[0] == '.')
 185                         continue;
 186                 if (ends_with(de->d_name, ".lock"))
 187                         continue;
 188                 strbuf_addstr(&refname, de->d_name);
 189                 strbuf_addstr(&path, de->d_name);
 190                 if (stat(path.buf, &st) < 0) {
 191                         ; /* silently ignore */
 192                 } else if (S_ISDIR(st.st_mode)) {
 193                         strbuf_addch(&refname, '/');
 194                         add_entry_to_dir(dir,
 195                                          create_dir_entry(dir->cache, refname.buf,
 196                                                           refname.len, 1));
 197                 } else {
 198                         if (!refs_resolve_ref_unsafe(&refs->base,
 199                                                      refname.buf,
 200                                                      RESOLVE_REF_READING,
 201                                                      oid.hash, &flag)) {
 202                                 oidclr(&oid);
 203                                 flag |= REF_ISBROKEN;
 204                         } else if (is_null_oid(&oid)) {
 205                                 /*
 206                                  * It is so astronomically unlikely
 207                                  * that NULL_SHA1 is the SHA-1 of an
 208                                  * actual object that we consider its
 209                                  * appearance in a loose reference
 210                                  * file to be repo corruption
 211                                  * (probably due to a software bug).
 212                                  */
 213                                 flag |= REF_ISBROKEN;
 214                         }
 215
 216                         if (check_refname_format(refname.buf,
 217                                                  REFNAME_ALLOW_ONELEVEL)) {
 218                                 if (!refname_is_safe(refname.buf))
 219                                         die("loose refname is dangerous: %s", refname.buf);
 220                                 oidclr(&oid);
 221                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 222                         }
 223                         add_entry_to_dir(dir,
 224                                          create_ref_entry(refname.buf, &oid, flag));
 225                 }
 226                 strbuf_setlen(&refname, dirnamelen);
 227                 strbuf_setlen(&path, path_baselen);
 228         }
 229         strbuf_release(&refname);
 230         strbuf_release(&path);
 231         closedir(d);
 232
 233         /*
 234          * Manually add refs/bisect, which, being per-worktree, might
 235          * not appear in the directory listing for refs/ in the main
 236          * repo.
 237          */
 238         if (!strcmp(dirname, "refs/")) {
 239                 int pos = search_ref_dir(dir, "refs/bisect/", 12);
 240
 241                 if (pos < 0) {
 242                         struct ref_entry *child_entry = create_dir_entry(
 243                                         dir->cache, "refs/bisect/", 12, 1);
 244                         add_entry_to_dir(dir, child_entry);
 245                 }
 246         }
 247 }
 248
 249 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 250 {
 251         if (!refs->loose) {
 252                 /*
 253                  * Mark the top-level directory complete because we
 254                  * are about to read the only subdirectory that can
 255                  * hold references:
 256                  */
 257                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 258
 259                 /* We're going to fill the top level ourselves: */
 260                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 261
 262                 /*
 263                  * Add an incomplete entry for "refs/" (to be filled
 264                  * lazily):
 265                  */
 266                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 267                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 268         }
 269         return refs->loose;
 270 }
 271
 272 static int files_read_raw_ref(struct ref_store *ref_store,
 273                               const char *refname, unsigned char *sha1,
 274                               struct strbuf *referent, unsigned int *type)
 275 {
 276         struct files_ref_store *refs =
 277                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 278         struct strbuf sb_contents = STRBUF_INIT;
 279         struct strbuf sb_path = STRBUF_INIT;
 280         const char *path;
 281         const char *buf;
 282         struct stat st;
 283         int fd;
 284         int ret = -1;
 285         int save_errno;
 286         int remaining_retries = 3;
 287
 288         *type = 0;
 289         strbuf_reset(&sb_path);
 290
 291         files_ref_path(refs, &sb_path, refname);
 292
 293         path = sb_path.buf;
 294
 295 stat_ref:
 296         /*
 297          * We might have to loop back here to avoid a race
 298          * condition: first we lstat() the file, then we try
 299          * to read it as a link or as a file.  But if somebody
 300          * changes the type of the file (file <-> directory
 301          * <-> symlink) between the lstat() and reading, then
 302          * we don't want to report that as an error but rather
 303          * try again starting with the lstat().
 304          *
 305          * We'll keep a count of the retries, though, just to avoid
 306          * any confusing situation sending us into an infinite loop.
 307          */
 308
 309         if (remaining_retries-- <= 0)
 310                 goto out;
 311
 312         if (lstat(path, &st) < 0) {
 313                 if (errno != ENOENT)
 314                         goto out;
 315                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 316                                       sha1, referent, type)) {
 317                         errno = ENOENT;
 318                         goto out;
 319                 }
 320                 ret = 0;
 321                 goto out;
 322         }
 323
 324         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 325         if (S_ISLNK(st.st_mode)) {
 326                 strbuf_reset(&sb_contents);
 327                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 328                         if (errno == ENOENT || errno == EINVAL)
 329                                 /* inconsistent with lstat; retry */
 330                                 goto stat_ref;
 331                         else
 332                                 goto out;
 333                 }
 334                 if (starts_with(sb_contents.buf, "refs/") &&
 335                     !check_refname_format(sb_contents.buf, 0)) {
 336                         strbuf_swap(&sb_contents, referent);
 337                         *type |= REF_ISSYMREF;
 338                         ret = 0;
 339                         goto out;
 340                 }
 341                 /*
 342                  * It doesn't look like a refname; fall through to just
 343                  * treating it like a non-symlink, and reading whatever it
 344                  * points to.
 345                  */
 346         }
 347
 348         /* Is it a directory? */
 349         if (S_ISDIR(st.st_mode)) {
 350                 /*
 351                  * Even though there is a directory where the loose
 352                  * ref is supposed to be, there could still be a
 353                  * packed ref:
 354                  */
 355                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 356                                       sha1, referent, type)) {
 357                         errno = EISDIR;
 358                         goto out;
 359                 }
 360                 ret = 0;
 361                 goto out;
 362         }
 363
 364         /*
 365          * Anything else, just open it and try to use it as
 366          * a ref
 367          */
 368         fd = open(path, O_RDONLY);
 369         if (fd < 0) {
 370                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 371                         /* inconsistent with lstat; retry */
 372                         goto stat_ref;
 373                 else
 374                         goto out;
 375         }
 376         strbuf_reset(&sb_contents);
 377         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 378                 int save_errno = errno;
 379                 close(fd);
 380                 errno = save_errno;
 381                 goto out;
 382         }
 383         close(fd);
 384         strbuf_rtrim(&sb_contents);
 385         buf = sb_contents.buf;
 386         if (starts_with(buf, "ref:")) {
 387                 buf += 4;
 388                 while (isspace(*buf))
 389                         buf++;
 390
 391                 strbuf_reset(referent);
 392                 strbuf_addstr(referent, buf);
 393                 *type |= REF_ISSYMREF;
 394                 ret = 0;
 395                 goto out;
 396         }
 397
 398         /*
 399          * Please note that FETCH_HEAD has additional
 400          * data after the sha.
 401          */
 402         if (get_sha1_hex(buf, sha1) ||
 403             (buf[40] != '\0' && !isspace(buf[40]))) {
 404                 *type |= REF_ISBROKEN;
 405                 errno = EINVAL;
 406                 goto out;
 407         }
 408
 409         ret = 0;
 410
 411 out:
 412         save_errno = errno;
 413         strbuf_release(&sb_path);
 414         strbuf_release(&sb_contents);
 415         errno = save_errno;
 416         return ret;
 417 }
 418
 419 static void unlock_ref(struct ref_lock *lock)
 420 {
 421         rollback_lock_file(&lock->lk);
 422         free(lock->ref_name);
 423         free(lock);
 424 }
 425
 426 /*
 427  * Lock refname, without following symrefs, and set *lock_p to point
 428  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 429  * and type similarly to read_raw_ref().
 430  *
 431  * The caller must verify that refname is a "safe" reference name (in
 432  * the sense of refname_is_safe()) before calling this function.
 433  *
 434  * If the reference doesn't already exist, verify that refname doesn't
 435  * have a D/F conflict with any existing references. extras and skip
 436  * are passed to refs_verify_refname_available() for this check.
 437  *
 438  * If mustexist is not set and the reference is not found or is
 439  * broken, lock the reference anyway but clear sha1.
 440  *
 441  * Return 0 on success. On failure, write an error message to err and
 442  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 443  *
 444  * Implementation note: This function is basically
 445  *
 446  *     lock reference
 447  *     read_raw_ref()
 448  *
 449  * but it includes a lot more code to
 450  * - Deal with possible races with other processes
 451  * - Avoid calling refs_verify_refname_available() when it can be
 452  *   avoided, namely if we were successfully able to read the ref
 453  * - Generate informative error messages in the case of failure
 454  */
 455 static int lock_raw_ref(struct files_ref_store *refs,
 456                         const char *refname, int mustexist,
 457                         const struct string_list *extras,
 458                         const struct string_list *skip,
 459                         struct ref_lock **lock_p,
 460                         struct strbuf *referent,
 461                         unsigned int *type,
 462                         struct strbuf *err)
 463 {
 464         struct ref_lock *lock;
 465         struct strbuf ref_file = STRBUF_INIT;
 466         int attempts_remaining = 3;
 467         int ret = TRANSACTION_GENERIC_ERROR;
 468
 469         assert(err);
 470         files_assert_main_repository(refs, "lock_raw_ref");
 471
 472         *type = 0;
 473
 474         /* First lock the file so it can't change out from under us. */
 475
 476         *lock_p = lock = xcalloc(1, sizeof(*lock));
 477
 478         lock->ref_name = xstrdup(refname);
 479         files_ref_path(refs, &ref_file, refname);
 480
 481 retry:
 482         switch (safe_create_leading_directories(ref_file.buf)) {
 483         case SCLD_OK:
 484                 break; /* success */
 485         case SCLD_EXISTS:
 486                 /*
 487                  * Suppose refname is "refs/foo/bar". We just failed
 488                  * to create the containing directory, "refs/foo",
 489                  * because there was a non-directory in the way. This
 490                  * indicates a D/F conflict, probably because of
 491                  * another reference such as "refs/foo". There is no
 492                  * reason to expect this error to be transitory.
 493                  */
 494                 if (refs_verify_refname_available(&refs->base, refname,
 495                                                   extras, skip, err)) {
 496                         if (mustexist) {
 497                                 /*
 498                                  * To the user the relevant error is
 499                                  * that the "mustexist" reference is
 500                                  * missing:
 501                                  */
 502                                 strbuf_reset(err);
 503                                 strbuf_addf(err, "unable to resolve reference '%s'",
 504                                             refname);
 505                         } else {
 506                                 /*
 507                                  * The error message set by
 508                                  * refs_verify_refname_available() is
 509                                  * OK.
 510                                  */
 511                                 ret = TRANSACTION_NAME_CONFLICT;
 512                         }
 513                 } else {
 514                         /*
 515                          * The file that is in the way isn't a loose
 516                          * reference. Report it as a low-level
 517                          * failure.
 518                          */
 519                         strbuf_addf(err, "unable to create lock file %s.lock; "
 520                                     "non-directory in the way",
 521                                     ref_file.buf);
 522                 }
 523                 goto error_return;
 524         case SCLD_VANISHED:
 525                 /* Maybe another process was tidying up. Try again. */
 526                 if (--attempts_remaining > 0)
 527                         goto retry;
 528                 /* fall through */
 529         default:
 530                 strbuf_addf(err, "unable to create directory for %s",
 531                             ref_file.buf);
 532                 goto error_return;
 533         }
 534
 535         if (hold_lock_file_for_update_timeout(
 536                             &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 537                             get_files_ref_lock_timeout_ms()) < 0) {
 538                 if (errno == ENOENT && --attempts_remaining > 0) {
 539                         /*
 540                          * Maybe somebody just deleted one of the
 541                          * directories leading to ref_file.  Try
 542                          * again:
 543                          */
 544                         goto retry;
 545                 } else {
 546                         unable_to_lock_message(ref_file.buf, errno, err);
 547                         goto error_return;
 548                 }
 549         }
 550
 551         /*
 552          * Now we hold the lock and can read the reference without
 553          * fear that its value will change.
 554          */
 555
 556         if (files_read_raw_ref(&refs->base, refname,
 557                                lock->old_oid.hash, referent, type)) {
 558                 if (errno == ENOENT) {
 559                         if (mustexist) {
 560                                 /* Garden variety missing reference. */
 561                                 strbuf_addf(err, "unable to resolve reference '%s'",
 562                                             refname);
 563                                 goto error_return;
 564                         } else {
 565                                 /*
 566                                  * Reference is missing, but that's OK. We
 567                                  * know that there is not a conflict with
 568                                  * another loose reference because
 569                                  * (supposing that we are trying to lock
 570                                  * reference "refs/foo/bar"):
 571                                  *
 572                                  * - We were successfully able to create
 573                                  *   the lockfile refs/foo/bar.lock, so we
 574                                  *   know there cannot be a loose reference
 575                                  *   named "refs/foo".
 576                                  *
 577                                  * - We got ENOENT and not EISDIR, so we
 578                                  *   know that there cannot be a loose
 579                                  *   reference named "refs/foo/bar/baz".
 580                                  */
 581                         }
 582                 } else if (errno == EISDIR) {
 583                         /*
 584                          * There is a directory in the way. It might have
 585                          * contained references that have been deleted. If
 586                          * we don't require that the reference already
 587                          * exists, try to remove the directory so that it
 588                          * doesn't cause trouble when we want to rename the
 589                          * lockfile into place later.
 590                          */
 591                         if (mustexist) {
 592                                 /* Garden variety missing reference. */
 593                                 strbuf_addf(err, "unable to resolve reference '%s'",
 594                                             refname);
 595                                 goto error_return;
 596                         } else if (remove_dir_recursively(&ref_file,
 597                                                           REMOVE_DIR_EMPTY_ONLY)) {
 598                                 if (refs_verify_refname_available(
 599                                                     &refs->base, refname,
 600                                                     extras, skip, err)) {
 601                                         /*
 602                                          * The error message set by
 603                                          * verify_refname_available() is OK.
 604                                          */
 605                                         ret = TRANSACTION_NAME_CONFLICT;
 606                                         goto error_return;
 607                                 } else {
 608                                         /*
 609                                          * We can't delete the directory,
 610                                          * but we also don't know of any
 611                                          * references that it should
 612                                          * contain.
 613                                          */
 614                                         strbuf_addf(err, "there is a non-empty directory '%s' "
 615                                                     "blocking reference '%s'",
 616                                                     ref_file.buf, refname);
 617                                         goto error_return;
 618                                 }
 619                         }
 620                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 621                         strbuf_addf(err, "unable to resolve reference '%s': "
 622                                     "reference broken", refname);
 623                         goto error_return;
 624                 } else {
 625                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 626                                     refname, strerror(errno));
 627                         goto error_return;
 628                 }
 629
 630                 /*
 631                  * If the ref did not exist and we are creating it,
 632                  * make sure there is no existing packed ref that
 633                  * conflicts with refname:
 634                  */
 635                 if (refs_verify_refname_available(
 636                                     refs->packed_ref_store, refname,
 637                                     extras, skip, err))
 638                         goto error_return;
 639         }
 640
 641         ret = 0;
 642         goto out;
 643
 644 error_return:
 645         unlock_ref(lock);
 646         *lock_p = NULL;
 647
 648 out:
 649         strbuf_release(&ref_file);
 650         return ret;
 651 }
 652
 653 static int files_peel_ref(struct ref_store *ref_store,
 654                           const char *refname, unsigned char *sha1)
 655 {
 656         struct files_ref_store *refs =
 657                 files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
 658                                "peel_ref");
 659         int flag;
 660         unsigned char base[20];
 661
 662         if (current_ref_iter && current_ref_iter->refname == refname) {
 663                 struct object_id peeled;
 664
 665                 if (ref_iterator_peel(current_ref_iter, &peeled))
 666                         return -1;
 667                 hashcpy(sha1, peeled.hash);
 668                 return 0;
 669         }
 670
 671         if (refs_read_ref_full(ref_store, refname,
 672                                RESOLVE_REF_READING, base, &flag))
 673                 return -1;
 674
 675         /*
 676          * If the reference is packed, read its ref_entry from the
 677          * cache in the hope that we already know its peeled value.
 678          * We only try this optimization on packed references because
 679          * (a) forcing the filling of the loose reference cache could
 680          * be expensive and (b) loose references anyway usually do not
 681          * have REF_KNOWS_PEELED.
 682          */
 683         if (flag & REF_ISPACKED &&
 684             !refs_peel_ref(refs->packed_ref_store, refname, sha1))
 685                 return 0;
 686
 687         return peel_object(base, sha1);
 688 }
 689
 690 struct files_ref_iterator {
 691         struct ref_iterator base;
 692
 693         struct ref_iterator *iter0;
 694         unsigned int flags;
 695 };
 696
 697 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 698 {
 699         struct files_ref_iterator *iter =
 700                 (struct files_ref_iterator *)ref_iterator;
 701         int ok;
 702
 703         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 704                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 705                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 706                         continue;
 707
 708                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 709                     !ref_resolves_to_object(iter->iter0->refname,
 710                                             iter->iter0->oid,
 711                                             iter->iter0->flags))
 712                         continue;
 713
 714                 iter->base.refname = iter->iter0->refname;
 715                 iter->base.oid = iter->iter0->oid;
 716                 iter->base.flags = iter->iter0->flags;
 717                 return ITER_OK;
 718         }
 719
 720         iter->iter0 = NULL;
 721         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 722                 ok = ITER_ERROR;
 723
 724         return ok;
 725 }
 726
 727 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 728                                    struct object_id *peeled)
 729 {
 730         struct files_ref_iterator *iter =
 731                 (struct files_ref_iterator *)ref_iterator;
 732
 733         return ref_iterator_peel(iter->iter0, peeled);
 734 }
 735
 736 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 737 {
 738         struct files_ref_iterator *iter =
 739                 (struct files_ref_iterator *)ref_iterator;
 740         int ok = ITER_DONE;
 741
 742         if (iter->iter0)
 743                 ok = ref_iterator_abort(iter->iter0);
 744
 745         base_ref_iterator_free(ref_iterator);
 746         return ok;
 747 }
 748
 749 static struct ref_iterator_vtable files_ref_iterator_vtable = {
 750         files_ref_iterator_advance,
 751         files_ref_iterator_peel,
 752         files_ref_iterator_abort
 753 };
 754
 755 static struct ref_iterator *files_ref_iterator_begin(
 756                 struct ref_store *ref_store,
 757                 const char *prefix, unsigned int flags)
 758 {
 759         struct files_ref_store *refs;
 760         struct ref_iterator *loose_iter, *packed_iter;
 761         struct files_ref_iterator *iter;
 762         struct ref_iterator *ref_iterator;
 763         unsigned int required_flags = REF_STORE_READ;
 764
 765         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 766                 required_flags |= REF_STORE_ODB;
 767
 768         refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 769
 770         iter = xcalloc(1, sizeof(*iter));
 771         ref_iterator = &iter->base;
 772         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
 773
 774         /*
 775          * We must make sure that all loose refs are read before
 776          * accessing the packed-refs file; this avoids a race
 777          * condition if loose refs are migrated to the packed-refs
 778          * file by a simultaneous process, but our in-memory view is
 779          * from before the migration. We ensure this as follows:
 780          * First, we call start the loose refs iteration with its
 781          * `prime_ref` argument set to true. This causes the loose
 782          * references in the subtree to be pre-read into the cache.
 783          * (If they've already been read, that's OK; we only need to
 784          * guarantee that they're read before the packed refs, not
 785          * *how much* before.) After that, we call
 786          * packed_ref_iterator_begin(), which internally checks
 787          * whether the packed-ref cache is up to date with what is on
 788          * disk, and re-reads it if not.
 789          */
 790
 791         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 792                                               prefix, 1);
 793
 794         /*
 795          * The packed-refs file might contain broken references, for
 796          * example an old version of a reference that points at an
 797          * object that has since been garbage-collected. This is OK as
 798          * long as there is a corresponding loose reference that
 799          * overrides it, and we don't want to emit an error message in
 800          * this case. So ask the packed_ref_store for all of its
 801          * references, and (if needed) do our own check for broken
 802          * ones in files_ref_iterator_advance(), after we have merged
 803          * the packed and loose references.
 804          */
 805         packed_iter = refs_ref_iterator_begin(
 806                         refs->packed_ref_store, prefix, 0,
 807                         DO_FOR_EACH_INCLUDE_BROKEN);
 808
 809         iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
 810         iter->flags = flags;
 811
 812         return ref_iterator;
 813 }
 814
 815 /*
 816  * Verify that the reference locked by lock has the value old_sha1.
 817  * Fail if the reference doesn't exist and mustexist is set. Return 0
 818  * on success. On error, write an error message to err, set errno, and
 819  * return a negative value.
 820  */
 821 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 822                        const unsigned char *old_sha1, int mustexist,
 823                        struct strbuf *err)
 824 {
 825         assert(err);
 826
 827         if (refs_read_ref_full(ref_store, lock->ref_name,
 828                                mustexist ? RESOLVE_REF_READING : 0,
 829                                lock->old_oid.hash, NULL)) {
 830                 if (old_sha1) {
 831                         int save_errno = errno;
 832                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 833                         errno = save_errno;
 834                         return -1;
 835                 } else {
 836                         oidclr(&lock->old_oid);
 837                         return 0;
 838                 }
 839         }
 840         if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
 841                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 842                             lock->ref_name,
 843                             oid_to_hex(&lock->old_oid),
 844                             sha1_to_hex(old_sha1));
 845                 errno = EBUSY;
 846                 return -1;
 847         }
 848         return 0;
 849 }
 850
 851 static int remove_empty_directories(struct strbuf *path)
 852 {
 853         /*
 854          * we want to create a file but there is a directory there;
 855          * if that is an empty directory (or a directory that contains
 856          * only empty directories), remove them.
 857          */
 858         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 859 }
 860
 861 static int create_reflock(const char *path, void *cb)
 862 {
 863         struct lock_file *lk = cb;
 864
 865         return hold_lock_file_for_update_timeout(
 866                         lk, path, LOCK_NO_DEREF,
 867                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 868 }
 869
 870 /*
 871  * Locks a ref returning the lock on success and NULL on failure.
 872  * On failure errno is set to something meaningful.
 873  */
 874 static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
 875                                             const char *refname,
 876                                             const unsigned char *old_sha1,
 877                                             const struct string_list *extras,
 878                                             const struct string_list *skip,
 879                                             unsigned int flags, int *type,
 880                                             struct strbuf *err)
 881 {
 882         struct strbuf ref_file = STRBUF_INIT;
 883         struct ref_lock *lock;
 884         int last_errno = 0;
 885         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 886         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 887         int resolved;
 888
 889         files_assert_main_repository(refs, "lock_ref_sha1_basic");
 890         assert(err);
 891
 892         lock = xcalloc(1, sizeof(struct ref_lock));
 893
 894         if (mustexist)
 895                 resolve_flags |= RESOLVE_REF_READING;
 896         if (flags & REF_DELETING)
 897                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 898
 899         files_ref_path(refs, &ref_file, refname);
 900         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 901                                              refname, resolve_flags,
 902                                              lock->old_oid.hash, type);
 903         if (!resolved && errno == EISDIR) {
 904                 /*
 905                  * we are trying to lock foo but we used to
 906                  * have foo/bar which now does not exist;
 907                  * it is normal for the empty directory 'foo'
 908                  * to remain.
 909                  */
 910                 if (remove_empty_directories(&ref_file)) {
 911                         last_errno = errno;
 912                         if (!refs_verify_refname_available(
 913                                             &refs->base,
 914                                             refname, extras, skip, err))
 915                                 strbuf_addf(err, "there are still refs under '%s'",
 916                                             refname);
 917                         goto error_return;
 918                 }
 919                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 920                                                      refname, resolve_flags,
 921                                                      lock->old_oid.hash, type);
 922         }
 923         if (!resolved) {
 924                 last_errno = errno;
 925                 if (last_errno != ENOTDIR ||
 926                     !refs_verify_refname_available(&refs->base, refname,
 927                                                    extras, skip, err))
 928                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 929                                     refname, strerror(last_errno));
 930
 931                 goto error_return;
 932         }
 933
 934         /*
 935          * If the ref did not exist and we are creating it, make sure
 936          * there is no existing packed ref whose name begins with our
 937          * refname, nor a packed ref whose name is a proper prefix of
 938          * our refname.
 939          */
 940         if (is_null_oid(&lock->old_oid) &&
 941             refs_verify_refname_available(refs->packed_ref_store, refname,
 942                                           extras, skip, err)) {
 943                 last_errno = ENOTDIR;
 944                 goto error_return;
 945         }
 946
 947         lock->ref_name = xstrdup(refname);
 948
 949         if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 950                 last_errno = errno;
 951                 unable_to_lock_message(ref_file.buf, errno, err);
 952                 goto error_return;
 953         }
 954
 955         if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
 956                 last_errno = errno;
 957                 goto error_return;
 958         }
 959         goto out;
 960
 961  error_return:
 962         unlock_ref(lock);
 963         lock = NULL;
 964
 965  out:
 966         strbuf_release(&ref_file);
 967         errno = last_errno;
 968         return lock;
 969 }
 970
 971 struct ref_to_prune {
 972         struct ref_to_prune *next;
 973         unsigned char sha1[20];
 974         char name[FLEX_ARRAY];
 975 };
 976
 977 enum {
 978         REMOVE_EMPTY_PARENTS_REF = 0x01,
 979         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 980 };
 981
 982 /*
 983  * Remove empty parent directories associated with the specified
 984  * reference and/or its reflog, but spare [logs/]refs/ and immediate
 985  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 986  * REMOVE_EMPTY_PARENTS_REFLOG.
 987  */
 988 static void try_remove_empty_parents(struct files_ref_store *refs,
 989                                      const char *refname,
 990                                      unsigned int flags)
 991 {
 992         struct strbuf buf = STRBUF_INIT;
 993         struct strbuf sb = STRBUF_INIT;
 994         char *p, *q;
 995         int i;
 996
 997         strbuf_addstr(&buf, refname);
 998         p = buf.buf;
 999         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1000                 while (*p && *p != '/')
1001                         p++;
1002                 /* tolerate duplicate slashes; see check_refname_format() */
1003                 while (*p == '/')
1004                         p++;
1005         }
1006         q = buf.buf + buf.len;
1007         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1008                 while (q > p && *q != '/')
1009                         q--;
1010                 while (q > p && *(q-1) == '/')
1011                         q--;
1012                 if (q == p)
1013                         break;
1014                 strbuf_setlen(&buf, q - buf.buf);
1015
1016                 strbuf_reset(&sb);
1017                 files_ref_path(refs, &sb, buf.buf);
1018                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1019                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1020
1021                 strbuf_reset(&sb);
1022                 files_reflog_path(refs, &sb, buf.buf);
1023                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1024                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1025         }
1026         strbuf_release(&buf);
1027         strbuf_release(&sb);
1028 }
1029
1030 /* make sure nobody touched the ref, and unlink */
1031 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1032 {
1033         struct ref_transaction *transaction;
1034         struct strbuf err = STRBUF_INIT;
1035
1036         if (check_refname_format(r->name, 0))
1037                 return;
1038
1039         transaction = ref_store_transaction_begin(&refs->base, &err);
1040         if (!transaction ||
1041             ref_transaction_delete(transaction, r->name, r->sha1,
1042                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
1043             ref_transaction_commit(transaction, &err)) {
1044                 ref_transaction_free(transaction);
1045                 error("%s", err.buf);
1046                 strbuf_release(&err);
1047                 return;
1048         }
1049         ref_transaction_free(transaction);
1050         strbuf_release(&err);
1051 }
1052
1053 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
1054 {
1055         while (r) {
1056                 prune_ref(refs, r);
1057                 r = r->next;
1058         }
1059 }
1060
1061 /*
1062  * Return true if the specified reference should be packed.
1063  */
1064 static int should_pack_ref(const char *refname,
1065                            const struct object_id *oid, unsigned int ref_flags,
1066                            unsigned int pack_flags)
1067 {
1068         /* Do not pack per-worktree refs: */
1069         if (ref_type(refname) != REF_TYPE_NORMAL)
1070                 return 0;
1071
1072         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1073         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1074                 return 0;
1075
1076         /* Do not pack symbolic refs: */
1077         if (ref_flags & REF_ISSYMREF)
1078                 return 0;
1079
1080         /* Do not pack broken refs: */
1081         if (!ref_resolves_to_object(refname, oid, ref_flags))
1082                 return 0;
1083
1084         return 1;
1085 }
1086
1087 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1088 {
1089         struct files_ref_store *refs =
1090                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1091                                "pack_refs");
1092         struct ref_iterator *iter;
1093         int ok;
1094         struct ref_to_prune *refs_to_prune = NULL;
1095         struct strbuf err = STRBUF_INIT;
1096
1097         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1098
1099         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1100         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1101                 /*
1102                  * If the loose reference can be packed, add an entry
1103                  * in the packed ref cache. If the reference should be
1104                  * pruned, also add it to refs_to_prune.
1105                  */
1106                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1107                                      flags))
1108                         continue;
1109
1110                 /*
1111                  * Create an entry in the packed-refs cache equivalent
1112                  * to the one from the loose ref cache, except that
1113                  * we don't copy the peeled status, because we want it
1114                  * to be re-peeled.
1115                  */
1116                 add_packed_ref(refs->packed_ref_store, iter->refname, iter->oid);
1117
1118                 /* Schedule the loose reference for pruning if requested. */
1119                 if ((flags & PACK_REFS_PRUNE)) {
1120                         struct ref_to_prune *n;
1121                         FLEX_ALLOC_STR(n, name, iter->refname);
1122                         hashcpy(n->sha1, iter->oid->hash);
1123                         n->next = refs_to_prune;
1124                         refs_to_prune = n;
1125                 }
1126         }
1127         if (ok != ITER_DONE)
1128                 die("error while iterating over references");
1129
1130         if (commit_packed_refs(refs->packed_ref_store, &err))
1131                 die("unable to overwrite old ref-pack file: %s", err.buf);
1132         packed_refs_unlock(refs->packed_ref_store);
1133
1134         prune_refs(refs, refs_to_prune);
1135         strbuf_release(&err);
1136         return 0;
1137 }
1138
1139 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1140                              struct string_list *refnames, unsigned int flags)
1141 {
1142         struct files_ref_store *refs =
1143                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1144         struct strbuf err = STRBUF_INIT;
1145         int i, result = 0;
1146
1147         if (!refnames->nr)
1148                 return 0;
1149
1150         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1151                 goto error;
1152
1153         if (repack_without_refs(refs->packed_ref_store, refnames, &err)) {
1154                 packed_refs_unlock(refs->packed_ref_store);
1155                 goto error;
1156         }
1157
1158         packed_refs_unlock(refs->packed_ref_store);
1159
1160         for (i = 0; i < refnames->nr; i++) {
1161                 const char *refname = refnames->items[i].string;
1162
1163                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1164                         result |= error(_("could not remove reference %s"), refname);
1165         }
1166
1167         strbuf_release(&err);
1168         return result;
1169
1170 error:
1171         /*
1172          * If we failed to rewrite the packed-refs file, then it is
1173          * unsafe to try to remove loose refs, because doing so might
1174          * expose an obsolete packed value for a reference that might
1175          * even point at an object that has been garbage collected.
1176          */
1177         if (refnames->nr == 1)
1178                 error(_("could not delete reference %s: %s"),
1179                       refnames->items[0].string, err.buf);
1180         else
1181                 error(_("could not delete references: %s"), err.buf);
1182
1183         strbuf_release(&err);
1184         return -1;
1185 }
1186
1187 /*
1188  * People using contrib's git-new-workdir have .git/logs/refs ->
1189  * /some/other/path/.git/logs/refs, and that may live on another device.
1190  *
1191  * IOW, to avoid cross device rename errors, the temporary renamed log must
1192  * live into logs/refs.
1193  */
1194 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1195
1196 struct rename_cb {
1197         const char *tmp_renamed_log;
1198         int true_errno;
1199 };
1200
1201 static int rename_tmp_log_callback(const char *path, void *cb_data)
1202 {
1203         struct rename_cb *cb = cb_data;
1204
1205         if (rename(cb->tmp_renamed_log, path)) {
1206                 /*
1207                  * rename(a, b) when b is an existing directory ought
1208                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1209                  * Sheesh. Record the true errno for error reporting,
1210                  * but report EISDIR to raceproof_create_file() so
1211                  * that it knows to retry.
1212                  */
1213                 cb->true_errno = errno;
1214                 if (errno == ENOTDIR)
1215                         errno = EISDIR;
1216                 return -1;
1217         } else {
1218                 return 0;
1219         }
1220 }
1221
1222 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1223 {
1224         struct strbuf path = STRBUF_INIT;
1225         struct strbuf tmp = STRBUF_INIT;
1226         struct rename_cb cb;
1227         int ret;
1228
1229         files_reflog_path(refs, &path, newrefname);
1230         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1231         cb.tmp_renamed_log = tmp.buf;
1232         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1233         if (ret) {
1234                 if (errno == EISDIR)
1235                         error("directory not empty: %s", path.buf);
1236                 else
1237                         error("unable to move logfile %s to %s: %s",
1238                               tmp.buf, path.buf,
1239                               strerror(cb.true_errno));
1240         }
1241
1242         strbuf_release(&path);
1243         strbuf_release(&tmp);
1244         return ret;
1245 }
1246
1247 static int write_ref_to_lockfile(struct ref_lock *lock,
1248                                  const struct object_id *oid, struct strbuf *err);
1249 static int commit_ref_update(struct files_ref_store *refs,
1250                              struct ref_lock *lock,
1251                              const struct object_id *oid, const char *logmsg,
1252                              struct strbuf *err);
1253
1254 static int files_rename_ref(struct ref_store *ref_store,
1255                             const char *oldrefname, const char *newrefname,
1256                             const char *logmsg)
1257 {
1258         struct files_ref_store *refs =
1259                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1260         struct object_id oid, orig_oid;
1261         int flag = 0, logmoved = 0;
1262         struct ref_lock *lock;
1263         struct stat loginfo;
1264         struct strbuf sb_oldref = STRBUF_INIT;
1265         struct strbuf sb_newref = STRBUF_INIT;
1266         struct strbuf tmp_renamed_log = STRBUF_INIT;
1267         int log, ret;
1268         struct strbuf err = STRBUF_INIT;
1269
1270         files_reflog_path(refs, &sb_oldref, oldrefname);
1271         files_reflog_path(refs, &sb_newref, newrefname);
1272         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1273
1274         log = !lstat(sb_oldref.buf, &loginfo);
1275         if (log && S_ISLNK(loginfo.st_mode)) {
1276                 ret = error("reflog for %s is a symlink", oldrefname);
1277                 goto out;
1278         }
1279
1280         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1281                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1282                                 orig_oid.hash, &flag)) {
1283                 ret = error("refname %s not found", oldrefname);
1284                 goto out;
1285         }
1286
1287         if (flag & REF_ISSYMREF) {
1288                 ret = error("refname %s is a symbolic ref, renaming it is not supported",
1289                             oldrefname);
1290                 goto out;
1291         }
1292         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1293                 ret = 1;
1294                 goto out;
1295         }
1296
1297         if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1298                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1299                             oldrefname, strerror(errno));
1300                 goto out;
1301         }
1302
1303         if (refs_delete_ref(&refs->base, logmsg, oldrefname,
1304                             orig_oid.hash, REF_NODEREF)) {
1305                 error("unable to delete old %s", oldrefname);
1306                 goto rollback;
1307         }
1308
1309         /*
1310          * Since we are doing a shallow lookup, oid is not the
1311          * correct value to pass to delete_ref as old_oid. But that
1312          * doesn't matter, because an old_oid check wouldn't add to
1313          * the safety anyway; we want to delete the reference whatever
1314          * its current value.
1315          */
1316         if (!refs_read_ref_full(&refs->base, newrefname,
1317                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1318                                 oid.hash, NULL) &&
1319             refs_delete_ref(&refs->base, NULL, newrefname,
1320                             NULL, REF_NODEREF)) {
1321                 if (errno == EISDIR) {
1322                         struct strbuf path = STRBUF_INIT;
1323                         int result;
1324
1325                         files_ref_path(refs, &path, newrefname);
1326                         result = remove_empty_directories(&path);
1327                         strbuf_release(&path);
1328
1329                         if (result) {
1330                                 error("Directory not empty: %s", newrefname);
1331                                 goto rollback;
1332                         }
1333                 } else {
1334                         error("unable to delete existing %s", newrefname);
1335                         goto rollback;
1336                 }
1337         }
1338
1339         if (log && rename_tmp_log(refs, newrefname))
1340                 goto rollback;
1341
1342         logmoved = log;
1343
1344         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
1345                                    REF_NODEREF, NULL, &err);
1346         if (!lock) {
1347                 error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1348                 strbuf_release(&err);
1349                 goto rollback;
1350         }
1351         oidcpy(&lock->old_oid, &orig_oid);
1352
1353         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1354             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1355                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1356                 strbuf_release(&err);
1357                 goto rollback;
1358         }
1359
1360         ret = 0;
1361         goto out;
1362
1363  rollback:
1364         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
1365                                    REF_NODEREF, NULL, &err);
1366         if (!lock) {
1367                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1368                 strbuf_release(&err);
1369                 goto rollbacklog;
1370         }
1371
1372         flag = log_all_ref_updates;
1373         log_all_ref_updates = LOG_REFS_NONE;
1374         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1375             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1376                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1377                 strbuf_release(&err);
1378         }
1379         log_all_ref_updates = flag;
1380
1381  rollbacklog:
1382         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1383                 error("unable to restore logfile %s from %s: %s",
1384                         oldrefname, newrefname, strerror(errno));
1385         if (!logmoved && log &&
1386             rename(tmp_renamed_log.buf, sb_oldref.buf))
1387                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1388                         oldrefname, strerror(errno));
1389         ret = 1;
1390  out:
1391         strbuf_release(&sb_newref);
1392         strbuf_release(&sb_oldref);
1393         strbuf_release(&tmp_renamed_log);
1394
1395         return ret;
1396 }
1397
1398 static int close_ref_gently(struct ref_lock *lock)
1399 {
1400         if (close_lock_file_gently(&lock->lk))
1401                 return -1;
1402         return 0;
1403 }
1404
1405 static int commit_ref(struct ref_lock *lock)
1406 {
1407         char *path = get_locked_file_path(&lock->lk);
1408         struct stat st;
1409
1410         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1411                 /*
1412                  * There is a directory at the path we want to rename
1413                  * the lockfile to. Hopefully it is empty; try to
1414                  * delete it.
1415                  */
1416                 size_t len = strlen(path);
1417                 struct strbuf sb_path = STRBUF_INIT;
1418
1419                 strbuf_attach(&sb_path, path, len, len);
1420
1421                 /*
1422                  * If this fails, commit_lock_file() will also fail
1423                  * and will report the problem.
1424                  */
1425                 remove_empty_directories(&sb_path);
1426                 strbuf_release(&sb_path);
1427         } else {
1428                 free(path);
1429         }
1430
1431         if (commit_lock_file(&lock->lk))
1432                 return -1;
1433         return 0;
1434 }
1435
1436 static int open_or_create_logfile(const char *path, void *cb)
1437 {
1438         int *fd = cb;
1439
1440         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1441         return (*fd < 0) ? -1 : 0;
1442 }
1443
1444 /*
1445  * Create a reflog for a ref. If force_create = 0, only create the
1446  * reflog for certain refs (those for which should_autocreate_reflog
1447  * returns non-zero). Otherwise, create it regardless of the reference
1448  * name. If the logfile already existed or was created, return 0 and
1449  * set *logfd to the file descriptor opened for appending to the file.
1450  * If no logfile exists and we decided not to create one, return 0 and
1451  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1452  * return -1.
1453  */
1454 static int log_ref_setup(struct files_ref_store *refs,
1455                          const char *refname, int force_create,
1456                          int *logfd, struct strbuf *err)
1457 {
1458         struct strbuf logfile_sb = STRBUF_INIT;
1459         char *logfile;
1460
1461         files_reflog_path(refs, &logfile_sb, refname);
1462         logfile = strbuf_detach(&logfile_sb, NULL);
1463
1464         if (force_create || should_autocreate_reflog(refname)) {
1465                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1466                         if (errno == ENOENT)
1467                                 strbuf_addf(err, "unable to create directory for '%s': "
1468                                             "%s", logfile, strerror(errno));
1469                         else if (errno == EISDIR)
1470                                 strbuf_addf(err, "there are still logs under '%s'",
1471                                             logfile);
1472                         else
1473                                 strbuf_addf(err, "unable to append to '%s': %s",
1474                                             logfile, strerror(errno));
1475
1476                         goto error;
1477                 }
1478         } else {
1479                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1480                 if (*logfd < 0) {
1481                         if (errno == ENOENT || errno == EISDIR) {
1482                                 /*
1483                                  * The logfile doesn't already exist,
1484                                  * but that is not an error; it only
1485                                  * means that we won't write log
1486                                  * entries to it.
1487                                  */
1488                                 ;
1489                         } else {
1490                                 strbuf_addf(err, "unable to append to '%s': %s",
1491                                             logfile, strerror(errno));
1492                                 goto error;
1493                         }
1494                 }
1495         }
1496
1497         if (*logfd >= 0)
1498                 adjust_shared_perm(logfile);
1499
1500         free(logfile);
1501         return 0;
1502
1503 error:
1504         free(logfile);
1505         return -1;
1506 }
1507
1508 static int files_create_reflog(struct ref_store *ref_store,
1509                                const char *refname, int force_create,
1510                                struct strbuf *err)
1511 {
1512         struct files_ref_store *refs =
1513                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1514         int fd;
1515
1516         if (log_ref_setup(refs, refname, force_create, &fd, err))
1517                 return -1;
1518
1519         if (fd >= 0)
1520                 close(fd);
1521
1522         return 0;
1523 }
1524
1525 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1526                             const struct object_id *new_oid,
1527                             const char *committer, const char *msg)
1528 {
1529         int msglen, written;
1530         unsigned maxlen, len;
1531         char *logrec;
1532
1533         msglen = msg ? strlen(msg) : 0;
1534         maxlen = strlen(committer) + msglen + 100;
1535         logrec = xmalloc(maxlen);
1536         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1537                         oid_to_hex(old_oid),
1538                         oid_to_hex(new_oid),
1539                         committer);
1540         if (msglen)
1541                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1542
1543         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1544         free(logrec);
1545         if (written != len)
1546                 return -1;
1547
1548         return 0;
1549 }
1550
1551 static int files_log_ref_write(struct files_ref_store *refs,
1552                                const char *refname, const struct object_id *old_oid,
1553                                const struct object_id *new_oid, const char *msg,
1554                                int flags, struct strbuf *err)
1555 {
1556         int logfd, result;
1557
1558         if (log_all_ref_updates == LOG_REFS_UNSET)
1559                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1560
1561         result = log_ref_setup(refs, refname,
1562                                flags & REF_FORCE_CREATE_REFLOG,
1563                                &logfd, err);
1564
1565         if (result)
1566                 return result;
1567
1568         if (logfd < 0)
1569                 return 0;
1570         result = log_ref_write_fd(logfd, old_oid, new_oid,
1571                                   git_committer_info(0), msg);
1572         if (result) {
1573                 struct strbuf sb = STRBUF_INIT;
1574                 int save_errno = errno;
1575
1576                 files_reflog_path(refs, &sb, refname);
1577                 strbuf_addf(err, "unable to append to '%s': %s",
1578                             sb.buf, strerror(save_errno));
1579                 strbuf_release(&sb);
1580                 close(logfd);
1581                 return -1;
1582         }
1583         if (close(logfd)) {
1584                 struct strbuf sb = STRBUF_INIT;
1585                 int save_errno = errno;
1586
1587                 files_reflog_path(refs, &sb, refname);
1588                 strbuf_addf(err, "unable to append to '%s': %s",
1589                             sb.buf, strerror(save_errno));
1590                 strbuf_release(&sb);
1591                 return -1;
1592         }
1593         return 0;
1594 }
1595
1596 /*
1597  * Write sha1 into the open lockfile, then close the lockfile. On
1598  * errors, rollback the lockfile, fill in *err and
1599  * return -1.
1600  */
1601 static int write_ref_to_lockfile(struct ref_lock *lock,
1602                                  const struct object_id *oid, struct strbuf *err)
1603 {
1604         static char term = '\n';
1605         struct object *o;
1606         int fd;
1607
1608         o = parse_object(oid);
1609         if (!o) {
1610                 strbuf_addf(err,
1611                             "trying to write ref '%s' with nonexistent object %s",
1612                             lock->ref_name, oid_to_hex(oid));
1613                 unlock_ref(lock);
1614                 return -1;
1615         }
1616         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1617                 strbuf_addf(err,
1618                             "trying to write non-commit object %s to branch '%s'",
1619                             oid_to_hex(oid), lock->ref_name);
1620                 unlock_ref(lock);
1621                 return -1;
1622         }
1623         fd = get_lock_file_fd(&lock->lk);
1624         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
1625             write_in_full(fd, &term, 1) != 1 ||
1626             close_ref_gently(lock) < 0) {
1627                 strbuf_addf(err,
1628                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1629                 unlock_ref(lock);
1630                 return -1;
1631         }
1632         return 0;
1633 }
1634
1635 /*
1636  * Commit a change to a loose reference that has already been written
1637  * to the loose reference lockfile. Also update the reflogs if
1638  * necessary, using the specified lockmsg (which can be NULL).
1639  */
1640 static int commit_ref_update(struct files_ref_store *refs,
1641                              struct ref_lock *lock,
1642                              const struct object_id *oid, const char *logmsg,
1643                              struct strbuf *err)
1644 {
1645         files_assert_main_repository(refs, "commit_ref_update");
1646
1647         clear_loose_ref_cache(refs);
1648         if (files_log_ref_write(refs, lock->ref_name,
1649                                 &lock->old_oid, oid,
1650                                 logmsg, 0, err)) {
1651                 char *old_msg = strbuf_detach(err, NULL);
1652                 strbuf_addf(err, "cannot update the ref '%s': %s",
1653                             lock->ref_name, old_msg);
1654                 free(old_msg);
1655                 unlock_ref(lock);
1656                 return -1;
1657         }
1658
1659         if (strcmp(lock->ref_name, "HEAD") != 0) {
1660                 /*
1661                  * Special hack: If a branch is updated directly and HEAD
1662                  * points to it (may happen on the remote side of a push
1663                  * for example) then logically the HEAD reflog should be
1664                  * updated too.
1665                  * A generic solution implies reverse symref information,
1666                  * but finding all symrefs pointing to the given branch
1667                  * would be rather costly for this rare event (the direct
1668                  * update of a branch) to be worth it.  So let's cheat and
1669                  * check with HEAD only which should cover 99% of all usage
1670                  * scenarios (even 100% of the default ones).
1671                  */
1672                 struct object_id head_oid;
1673                 int head_flag;
1674                 const char *head_ref;
1675
1676                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1677                                                    RESOLVE_REF_READING,
1678                                                    head_oid.hash, &head_flag);
1679                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1680                     !strcmp(head_ref, lock->ref_name)) {
1681                         struct strbuf log_err = STRBUF_INIT;
1682                         if (files_log_ref_write(refs, "HEAD",
1683                                                 &lock->old_oid, oid,
1684                                                 logmsg, 0, &log_err)) {
1685                                 error("%s", log_err.buf);
1686                                 strbuf_release(&log_err);
1687                         }
1688                 }
1689         }
1690
1691         if (commit_ref(lock)) {
1692                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1693                 unlock_ref(lock);
1694                 return -1;
1695         }
1696
1697         unlock_ref(lock);
1698         return 0;
1699 }
1700
1701 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1702 {
1703         int ret = -1;
1704 #ifndef NO_SYMLINK_HEAD
1705         char *ref_path = get_locked_file_path(&lock->lk);
1706         unlink(ref_path);
1707         ret = symlink(target, ref_path);
1708         free(ref_path);
1709
1710         if (ret)
1711                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1712 #endif
1713         return ret;
1714 }
1715
1716 static void update_symref_reflog(struct files_ref_store *refs,
1717                                  struct ref_lock *lock, const char *refname,
1718                                  const char *target, const char *logmsg)
1719 {
1720         struct strbuf err = STRBUF_INIT;
1721         struct object_id new_oid;
1722         if (logmsg &&
1723             !refs_read_ref_full(&refs->base, target,
1724                                 RESOLVE_REF_READING, new_oid.hash, NULL) &&
1725             files_log_ref_write(refs, refname, &lock->old_oid,
1726                                 &new_oid, logmsg, 0, &err)) {
1727                 error("%s", err.buf);
1728                 strbuf_release(&err);
1729         }
1730 }
1731
1732 static int create_symref_locked(struct files_ref_store *refs,
1733                                 struct ref_lock *lock, const char *refname,
1734                                 const char *target, const char *logmsg)
1735 {
1736         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1737                 update_symref_reflog(refs, lock, refname, target, logmsg);
1738                 return 0;
1739         }
1740
1741         if (!fdopen_lock_file(&lock->lk, "w"))
1742                 return error("unable to fdopen %s: %s",
1743                              lock->lk.tempfile->filename.buf, strerror(errno));
1744
1745         update_symref_reflog(refs, lock, refname, target, logmsg);
1746
1747         /* no error check; commit_ref will check ferror */
1748         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1749         if (commit_ref(lock) < 0)
1750                 return error("unable to write symref for %s: %s", refname,
1751                              strerror(errno));
1752         return 0;
1753 }
1754
1755 static int files_create_symref(struct ref_store *ref_store,
1756                                const char *refname, const char *target,
1757                                const char *logmsg)
1758 {
1759         struct files_ref_store *refs =
1760                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1761         struct strbuf err = STRBUF_INIT;
1762         struct ref_lock *lock;
1763         int ret;
1764
1765         lock = lock_ref_sha1_basic(refs, refname, NULL,
1766                                    NULL, NULL, REF_NODEREF, NULL,
1767                                    &err);
1768         if (!lock) {
1769                 error("%s", err.buf);
1770                 strbuf_release(&err);
1771                 return -1;
1772         }
1773
1774         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1775         unlock_ref(lock);
1776         return ret;
1777 }
1778
1779 static int files_reflog_exists(struct ref_store *ref_store,
1780                                const char *refname)
1781 {
1782         struct files_ref_store *refs =
1783                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1784         struct strbuf sb = STRBUF_INIT;
1785         struct stat st;
1786         int ret;
1787
1788         files_reflog_path(refs, &sb, refname);
1789         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1790         strbuf_release(&sb);
1791         return ret;
1792 }
1793
1794 static int files_delete_reflog(struct ref_store *ref_store,
1795                                const char *refname)
1796 {
1797         struct files_ref_store *refs =
1798                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1799         struct strbuf sb = STRBUF_INIT;
1800         int ret;
1801
1802         files_reflog_path(refs, &sb, refname);
1803         ret = remove_path(sb.buf);
1804         strbuf_release(&sb);
1805         return ret;
1806 }
1807
1808 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1809 {
1810         struct object_id ooid, noid;
1811         char *email_end, *message;
1812         timestamp_t timestamp;
1813         int tz;
1814         const char *p = sb->buf;
1815
1816         /* old SP new SP name <email> SP time TAB msg LF */
1817         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1818             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1819             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1820             !(email_end = strchr(p, '>')) ||
1821             email_end[1] != ' ' ||
1822             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1823             !message || message[0] != ' ' ||
1824             (message[1] != '+' && message[1] != '-') ||
1825             !isdigit(message[2]) || !isdigit(message[3]) ||
1826             !isdigit(message[4]) || !isdigit(message[5]))
1827                 return 0; /* corrupt? */
1828         email_end[1] = '\0';
1829         tz = strtol(message + 1, NULL, 10);
1830         if (message[6] != '\t')
1831                 message += 6;
1832         else
1833                 message += 7;
1834         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1835 }
1836
1837 static char *find_beginning_of_line(char *bob, char *scan)
1838 {
1839         while (bob < scan && *(--scan) != '\n')
1840                 ; /* keep scanning backwards */
1841         /*
1842          * Return either beginning of the buffer, or LF at the end of
1843          * the previous line.
1844          */
1845         return scan;
1846 }
1847
1848 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1849                                              const char *refname,
1850                                              each_reflog_ent_fn fn,
1851                                              void *cb_data)
1852 {
1853         struct files_ref_store *refs =
1854                 files_downcast(ref_store, REF_STORE_READ,
1855                                "for_each_reflog_ent_reverse");
1856         struct strbuf sb = STRBUF_INIT;
1857         FILE *logfp;
1858         long pos;
1859         int ret = 0, at_tail = 1;
1860
1861         files_reflog_path(refs, &sb, refname);
1862         logfp = fopen(sb.buf, "r");
1863         strbuf_release(&sb);
1864         if (!logfp)
1865                 return -1;
1866
1867         /* Jump to the end */
1868         if (fseek(logfp, 0, SEEK_END) < 0)
1869                 ret = error("cannot seek back reflog for %s: %s",
1870                             refname, strerror(errno));
1871         pos = ftell(logfp);
1872         while (!ret && 0 < pos) {
1873                 int cnt;
1874                 size_t nread;
1875                 char buf[BUFSIZ];
1876                 char *endp, *scanp;
1877
1878                 /* Fill next block from the end */
1879                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1880                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1881                         ret = error("cannot seek back reflog for %s: %s",
1882                                     refname, strerror(errno));
1883                         break;
1884                 }
1885                 nread = fread(buf, cnt, 1, logfp);
1886                 if (nread != 1) {
1887                         ret = error("cannot read %d bytes from reflog for %s: %s",
1888                                     cnt, refname, strerror(errno));
1889                         break;
1890                 }
1891                 pos -= cnt;
1892
1893                 scanp = endp = buf + cnt;
1894                 if (at_tail && scanp[-1] == '\n')
1895                         /* Looking at the final LF at the end of the file */
1896                         scanp--;
1897                 at_tail = 0;
1898
1899                 while (buf < scanp) {
1900                         /*
1901                          * terminating LF of the previous line, or the beginning
1902                          * of the buffer.
1903                          */
1904                         char *bp;
1905
1906                         bp = find_beginning_of_line(buf, scanp);
1907
1908                         if (*bp == '\n') {
1909                                 /*
1910                                  * The newline is the end of the previous line,
1911                                  * so we know we have complete line starting
1912                                  * at (bp + 1). Prefix it onto any prior data
1913                                  * we collected for the line and process it.
1914                                  */
1915                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1916                                 scanp = bp;
1917                                 endp = bp + 1;
1918                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1919                                 strbuf_reset(&sb);
1920                                 if (ret)
1921                                         break;
1922                         } else if (!pos) {
1923                                 /*
1924                                  * We are at the start of the buffer, and the
1925                                  * start of the file; there is no previous
1926                                  * line, and we have everything for this one.
1927                                  * Process it, and we can end the loop.
1928                                  */
1929                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1930                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1931                                 strbuf_reset(&sb);
1932                                 break;
1933                         }
1934
1935                         if (bp == buf) {
1936                                 /*
1937                                  * We are at the start of the buffer, and there
1938                                  * is more file to read backwards. Which means
1939                                  * we are in the middle of a line. Note that we
1940                                  * may get here even if *bp was a newline; that
1941                                  * just means we are at the exact end of the
1942                                  * previous line, rather than some spot in the
1943                                  * middle.
1944                                  *
1945                                  * Save away what we have to be combined with
1946                                  * the data from the next read.
1947                                  */
1948                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1949                                 break;
1950                         }
1951                 }
1952
1953         }
1954         if (!ret && sb.len)
1955                 die("BUG: reverse reflog parser had leftover data");
1956
1957         fclose(logfp);
1958         strbuf_release(&sb);
1959         return ret;
1960 }
1961
1962 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1963                                      const char *refname,
1964                                      each_reflog_ent_fn fn, void *cb_data)
1965 {
1966         struct files_ref_store *refs =
1967                 files_downcast(ref_store, REF_STORE_READ,
1968                                "for_each_reflog_ent");
1969         FILE *logfp;
1970         struct strbuf sb = STRBUF_INIT;
1971         int ret = 0;
1972
1973         files_reflog_path(refs, &sb, refname);
1974         logfp = fopen(sb.buf, "r");
1975         strbuf_release(&sb);
1976         if (!logfp)
1977                 return -1;
1978
1979         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
1980                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1981         fclose(logfp);
1982         strbuf_release(&sb);
1983         return ret;
1984 }
1985
1986 struct files_reflog_iterator {
1987         struct ref_iterator base;
1988
1989         struct ref_store *ref_store;
1990         struct dir_iterator *dir_iterator;
1991         struct object_id oid;
1992 };
1993
1994 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
1995 {
1996         struct files_reflog_iterator *iter =
1997                 (struct files_reflog_iterator *)ref_iterator;
1998         struct dir_iterator *diter = iter->dir_iterator;
1999         int ok;
2000
2001         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2002                 int flags;
2003
2004                 if (!S_ISREG(diter->st.st_mode))
2005                         continue;
2006                 if (diter->basename[0] == '.')
2007                         continue;
2008                 if (ends_with(diter->basename, ".lock"))
2009                         continue;
2010
2011                 if (refs_read_ref_full(iter->ref_store,
2012                                        diter->relative_path, 0,
2013                                        iter->oid.hash, &flags)) {
2014                         error("bad ref for %s", diter->path.buf);
2015                         continue;
2016                 }
2017
2018                 iter->base.refname = diter->relative_path;
2019                 iter->base.oid = &iter->oid;
2020                 iter->base.flags = flags;
2021                 return ITER_OK;
2022         }
2023
2024         iter->dir_iterator = NULL;
2025         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2026                 ok = ITER_ERROR;
2027         return ok;
2028 }
2029
2030 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2031                                    struct object_id *peeled)
2032 {
2033         die("BUG: ref_iterator_peel() called for reflog_iterator");
2034 }
2035
2036 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2037 {
2038         struct files_reflog_iterator *iter =
2039                 (struct files_reflog_iterator *)ref_iterator;
2040         int ok = ITER_DONE;
2041
2042         if (iter->dir_iterator)
2043                 ok = dir_iterator_abort(iter->dir_iterator);
2044
2045         base_ref_iterator_free(ref_iterator);
2046         return ok;
2047 }
2048
2049 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2050         files_reflog_iterator_advance,
2051         files_reflog_iterator_peel,
2052         files_reflog_iterator_abort
2053 };
2054
2055 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2056 {
2057         struct files_ref_store *refs =
2058                 files_downcast(ref_store, REF_STORE_READ,
2059                                "reflog_iterator_begin");
2060         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2061         struct ref_iterator *ref_iterator = &iter->base;
2062         struct strbuf sb = STRBUF_INIT;
2063
2064         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
2065         files_reflog_path(refs, &sb, NULL);
2066         iter->dir_iterator = dir_iterator_begin(sb.buf);
2067         iter->ref_store = ref_store;
2068         strbuf_release(&sb);
2069         return ref_iterator;
2070 }
2071
2072 /*
2073  * If update is a direct update of head_ref (the reference pointed to
2074  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2075  */
2076 static int split_head_update(struct ref_update *update,
2077                              struct ref_transaction *transaction,
2078                              const char *head_ref,
2079                              struct string_list *affected_refnames,
2080                              struct strbuf *err)
2081 {
2082         struct string_list_item *item;
2083         struct ref_update *new_update;
2084
2085         if ((update->flags & REF_LOG_ONLY) ||
2086             (update->flags & REF_ISPRUNING) ||
2087             (update->flags & REF_UPDATE_VIA_HEAD))
2088                 return 0;
2089
2090         if (strcmp(update->refname, head_ref))
2091                 return 0;
2092
2093         /*
2094          * First make sure that HEAD is not already in the
2095          * transaction. This insertion is O(N) in the transaction
2096          * size, but it happens at most once per transaction.
2097          */
2098         item = string_list_insert(affected_refnames, "HEAD");
2099         if (item->util) {
2100                 /* An entry already existed */
2101                 strbuf_addf(err,
2102                             "multiple updates for 'HEAD' (including one "
2103                             "via its referent '%s') are not allowed",
2104                             update->refname);
2105                 return TRANSACTION_NAME_CONFLICT;
2106         }
2107
2108         new_update = ref_transaction_add_update(
2109                         transaction, "HEAD",
2110                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2111                         update->new_oid.hash, update->old_oid.hash,
2112                         update->msg);
2113
2114         item->util = new_update;
2115
2116         return 0;
2117 }
2118
2119 /*
2120  * update is for a symref that points at referent and doesn't have
2121  * REF_NODEREF set. Split it into two updates:
2122  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2123  * - A new, separate update for the referent reference
2124  * Note that the new update will itself be subject to splitting when
2125  * the iteration gets to it.
2126  */
2127 static int split_symref_update(struct files_ref_store *refs,
2128                                struct ref_update *update,
2129                                const char *referent,
2130                                struct ref_transaction *transaction,
2131                                struct string_list *affected_refnames,
2132                                struct strbuf *err)
2133 {
2134         struct string_list_item *item;
2135         struct ref_update *new_update;
2136         unsigned int new_flags;
2137
2138         /*
2139          * First make sure that referent is not already in the
2140          * transaction. This insertion is O(N) in the transaction
2141          * size, but it happens at most once per symref in a
2142          * transaction.
2143          */
2144         item = string_list_insert(affected_refnames, referent);
2145         if (item->util) {
2146                 /* An entry already existed */
2147                 strbuf_addf(err,
2148                             "multiple updates for '%s' (including one "
2149                             "via symref '%s') are not allowed",
2150                             referent, update->refname);
2151                 return TRANSACTION_NAME_CONFLICT;
2152         }
2153
2154         new_flags = update->flags;
2155         if (!strcmp(update->refname, "HEAD")) {
2156                 /*
2157                  * Record that the new update came via HEAD, so that
2158                  * when we process it, split_head_update() doesn't try
2159                  * to add another reflog update for HEAD. Note that
2160                  * this bit will be propagated if the new_update
2161                  * itself needs to be split.
2162                  */
2163                 new_flags |= REF_UPDATE_VIA_HEAD;
2164         }
2165
2166         new_update = ref_transaction_add_update(
2167                         transaction, referent, new_flags,
2168                         update->new_oid.hash, update->old_oid.hash,
2169                         update->msg);
2170
2171         new_update->parent_update = update;
2172
2173         /*
2174          * Change the symbolic ref update to log only. Also, it
2175          * doesn't need to check its old SHA-1 value, as that will be
2176          * done when new_update is processed.
2177          */
2178         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2179         update->flags &= ~REF_HAVE_OLD;
2180
2181         item->util = new_update;
2182
2183         return 0;
2184 }
2185
2186 /*
2187  * Return the refname under which update was originally requested.
2188  */
2189 static const char *original_update_refname(struct ref_update *update)
2190 {
2191         while (update->parent_update)
2192                 update = update->parent_update;
2193
2194         return update->refname;
2195 }
2196
2197 /*
2198  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2199  * are consistent with oid, which is the reference's current value. If
2200  * everything is OK, return 0; otherwise, write an error message to
2201  * err and return -1.
2202  */
2203 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2204                          struct strbuf *err)
2205 {
2206         if (!(update->flags & REF_HAVE_OLD) ||
2207                    !oidcmp(oid, &update->old_oid))
2208                 return 0;
2209
2210         if (is_null_oid(&update->old_oid))
2211                 strbuf_addf(err, "cannot lock ref '%s': "
2212                             "reference already exists",
2213                             original_update_refname(update));
2214         else if (is_null_oid(oid))
2215                 strbuf_addf(err, "cannot lock ref '%s': "
2216                             "reference is missing but expected %s",
2217                             original_update_refname(update),
2218                             oid_to_hex(&update->old_oid));
2219         else
2220                 strbuf_addf(err, "cannot lock ref '%s': "
2221                             "is at %s but expected %s",
2222                             original_update_refname(update),
2223                             oid_to_hex(oid),
2224                             oid_to_hex(&update->old_oid));
2225
2226         return -1;
2227 }
2228
2229 /*
2230  * Prepare for carrying out update:
2231  * - Lock the reference referred to by update.
2232  * - Read the reference under lock.
2233  * - Check that its old SHA-1 value (if specified) is correct, and in
2234  *   any case record it in update->lock->old_oid for later use when
2235  *   writing the reflog.
2236  * - If it is a symref update without REF_NODEREF, split it up into a
2237  *   REF_LOG_ONLY update of the symref and add a separate update for
2238  *   the referent to transaction.
2239  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2240  *   update of HEAD.
2241  */
2242 static int lock_ref_for_update(struct files_ref_store *refs,
2243                                struct ref_update *update,
2244                                struct ref_transaction *transaction,
2245                                const char *head_ref,
2246                                struct string_list *affected_refnames,
2247                                struct strbuf *err)
2248 {
2249         struct strbuf referent = STRBUF_INIT;
2250         int mustexist = (update->flags & REF_HAVE_OLD) &&
2251                 !is_null_oid(&update->old_oid);
2252         int ret;
2253         struct ref_lock *lock;
2254
2255         files_assert_main_repository(refs, "lock_ref_for_update");
2256
2257         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2258                 update->flags |= REF_DELETING;
2259
2260         if (head_ref) {
2261                 ret = split_head_update(update, transaction, head_ref,
2262                                         affected_refnames, err);
2263                 if (ret)
2264                         return ret;
2265         }
2266
2267         ret = lock_raw_ref(refs, update->refname, mustexist,
2268                            affected_refnames, NULL,
2269                            &lock, &referent,
2270                            &update->type, err);
2271         if (ret) {
2272                 char *reason;
2273
2274                 reason = strbuf_detach(err, NULL);
2275                 strbuf_addf(err, "cannot lock ref '%s': %s",
2276                             original_update_refname(update), reason);
2277                 free(reason);
2278                 return ret;
2279         }
2280
2281         update->backend_data = lock;
2282
2283         if (update->type & REF_ISSYMREF) {
2284                 if (update->flags & REF_NODEREF) {
2285                         /*
2286                          * We won't be reading the referent as part of
2287                          * the transaction, so we have to read it here
2288                          * to record and possibly check old_sha1:
2289                          */
2290                         if (refs_read_ref_full(&refs->base,
2291                                                referent.buf, 0,
2292                                                lock->old_oid.hash, NULL)) {
2293                                 if (update->flags & REF_HAVE_OLD) {
2294                                         strbuf_addf(err, "cannot lock ref '%s': "
2295                                                     "error reading reference",
2296                                                     original_update_refname(update));
2297                                         return -1;
2298                                 }
2299                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2300                                 return TRANSACTION_GENERIC_ERROR;
2301                         }
2302                 } else {
2303                         /*
2304                          * Create a new update for the reference this
2305                          * symref is pointing at. Also, we will record
2306                          * and verify old_sha1 for this update as part
2307                          * of processing the split-off update, so we
2308                          * don't have to do it here.
2309                          */
2310                         ret = split_symref_update(refs, update,
2311                                                   referent.buf, transaction,
2312                                                   affected_refnames, err);
2313                         if (ret)
2314                                 return ret;
2315                 }
2316         } else {
2317                 struct ref_update *parent_update;
2318
2319                 if (check_old_oid(update, &lock->old_oid, err))
2320                         return TRANSACTION_GENERIC_ERROR;
2321
2322                 /*
2323                  * If this update is happening indirectly because of a
2324                  * symref update, record the old SHA-1 in the parent
2325                  * update:
2326                  */
2327                 for (parent_update = update->parent_update;
2328                      parent_update;
2329                      parent_update = parent_update->parent_update) {
2330                         struct ref_lock *parent_lock = parent_update->backend_data;
2331                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2332                 }
2333         }
2334
2335         if ((update->flags & REF_HAVE_NEW) &&
2336             !(update->flags & REF_DELETING) &&
2337             !(update->flags & REF_LOG_ONLY)) {
2338                 if (!(update->type & REF_ISSYMREF) &&
2339                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2340                         /*
2341                          * The reference already has the desired
2342                          * value, so we don't need to write it.
2343                          */
2344                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2345                                                  err)) {
2346                         char *write_err = strbuf_detach(err, NULL);
2347
2348                         /*
2349                          * The lock was freed upon failure of
2350                          * write_ref_to_lockfile():
2351                          */
2352                         update->backend_data = NULL;
2353                         strbuf_addf(err,
2354                                     "cannot update ref '%s': %s",
2355                                     update->refname, write_err);
2356                         free(write_err);
2357                         return TRANSACTION_GENERIC_ERROR;
2358                 } else {
2359                         update->flags |= REF_NEEDS_COMMIT;
2360                 }
2361         }
2362         if (!(update->flags & REF_NEEDS_COMMIT)) {
2363                 /*
2364                  * We didn't call write_ref_to_lockfile(), so
2365                  * the lockfile is still open. Close it to
2366                  * free up the file descriptor:
2367                  */
2368                 if (close_ref_gently(lock)) {
2369                         strbuf_addf(err, "couldn't close '%s.lock'",
2370                                     update->refname);
2371                         return TRANSACTION_GENERIC_ERROR;
2372                 }
2373         }
2374         return 0;
2375 }
2376
2377 /*
2378  * Unlock any references in `transaction` that are still locked, and
2379  * mark the transaction closed.
2380  */
2381 static void files_transaction_cleanup(struct ref_transaction *transaction)
2382 {
2383         size_t i;
2384
2385         for (i = 0; i < transaction->nr; i++) {
2386                 struct ref_update *update = transaction->updates[i];
2387                 struct ref_lock *lock = update->backend_data;
2388
2389                 if (lock) {
2390                         unlock_ref(lock);
2391                         update->backend_data = NULL;
2392                 }
2393         }
2394
2395         transaction->state = REF_TRANSACTION_CLOSED;
2396 }
2397
2398 static int files_transaction_prepare(struct ref_store *ref_store,
2399                                      struct ref_transaction *transaction,
2400                                      struct strbuf *err)
2401 {
2402         struct files_ref_store *refs =
2403                 files_downcast(ref_store, REF_STORE_WRITE,
2404                                "ref_transaction_prepare");
2405         size_t i;
2406         int ret = 0;
2407         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2408         char *head_ref = NULL;
2409         int head_type;
2410         struct object_id head_oid;
2411
2412         assert(err);
2413
2414         if (!transaction->nr)
2415                 goto cleanup;
2416
2417         /*
2418          * Fail if a refname appears more than once in the
2419          * transaction. (If we end up splitting up any updates using
2420          * split_symref_update() or split_head_update(), those
2421          * functions will check that the new updates don't have the
2422          * same refname as any existing ones.)
2423          */
2424         for (i = 0; i < transaction->nr; i++) {
2425                 struct ref_update *update = transaction->updates[i];
2426                 struct string_list_item *item =
2427                         string_list_append(&affected_refnames, update->refname);
2428
2429                 /*
2430                  * We store a pointer to update in item->util, but at
2431                  * the moment we never use the value of this field
2432                  * except to check whether it is non-NULL.
2433                  */
2434                 item->util = update;
2435         }
2436         string_list_sort(&affected_refnames);
2437         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2438                 ret = TRANSACTION_GENERIC_ERROR;
2439                 goto cleanup;
2440         }
2441
2442         /*
2443          * Special hack: If a branch is updated directly and HEAD
2444          * points to it (may happen on the remote side of a push
2445          * for example) then logically the HEAD reflog should be
2446          * updated too.
2447          *
2448          * A generic solution would require reverse symref lookups,
2449          * but finding all symrefs pointing to a given branch would be
2450          * rather costly for this rare event (the direct update of a
2451          * branch) to be worth it. So let's cheat and check with HEAD
2452          * only, which should cover 99% of all usage scenarios (even
2453          * 100% of the default ones).
2454          *
2455          * So if HEAD is a symbolic reference, then record the name of
2456          * the reference that it points to. If we see an update of
2457          * head_ref within the transaction, then split_head_update()
2458          * arranges for the reflog of HEAD to be updated, too.
2459          */
2460         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2461                                        RESOLVE_REF_NO_RECURSE,
2462                                        head_oid.hash, &head_type);
2463
2464         if (head_ref && !(head_type & REF_ISSYMREF)) {
2465                 FREE_AND_NULL(head_ref);
2466         }
2467
2468         /*
2469          * Acquire all locks, verify old values if provided, check
2470          * that new values are valid, and write new values to the
2471          * lockfiles, ready to be activated. Only keep one lockfile
2472          * open at a time to avoid running out of file descriptors.
2473          * Note that lock_ref_for_update() might append more updates
2474          * to the transaction.
2475          */
2476         for (i = 0; i < transaction->nr; i++) {
2477                 struct ref_update *update = transaction->updates[i];
2478
2479                 ret = lock_ref_for_update(refs, update, transaction,
2480                                           head_ref, &affected_refnames, err);
2481                 if (ret)
2482                         break;
2483         }
2484
2485 cleanup:
2486         free(head_ref);
2487         string_list_clear(&affected_refnames, 0);
2488
2489         if (ret)
2490                 files_transaction_cleanup(transaction);
2491         else
2492                 transaction->state = REF_TRANSACTION_PREPARED;
2493
2494         return ret;
2495 }
2496
2497 static int files_transaction_finish(struct ref_store *ref_store,
2498                                     struct ref_transaction *transaction,
2499                                     struct strbuf *err)
2500 {
2501         struct files_ref_store *refs =
2502                 files_downcast(ref_store, 0, "ref_transaction_finish");
2503         size_t i;
2504         int ret = 0;
2505         struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
2506         struct string_list_item *ref_to_delete;
2507         struct strbuf sb = STRBUF_INIT;
2508
2509         assert(err);
2510
2511         if (!transaction->nr) {
2512                 transaction->state = REF_TRANSACTION_CLOSED;
2513                 return 0;
2514         }
2515
2516         /* Perform updates first so live commits remain referenced */
2517         for (i = 0; i < transaction->nr; i++) {
2518                 struct ref_update *update = transaction->updates[i];
2519                 struct ref_lock *lock = update->backend_data;
2520
2521                 if (update->flags & REF_NEEDS_COMMIT ||
2522                     update->flags & REF_LOG_ONLY) {
2523                         if (files_log_ref_write(refs,
2524                                                 lock->ref_name,
2525                                                 &lock->old_oid,
2526                                                 &update->new_oid,
2527                                                 update->msg, update->flags,
2528                                                 err)) {
2529                                 char *old_msg = strbuf_detach(err, NULL);
2530
2531                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2532                                             lock->ref_name, old_msg);
2533                                 free(old_msg);
2534                                 unlock_ref(lock);
2535                                 update->backend_data = NULL;
2536                                 ret = TRANSACTION_GENERIC_ERROR;
2537                                 goto cleanup;
2538                         }
2539                 }
2540                 if (update->flags & REF_NEEDS_COMMIT) {
2541                         clear_loose_ref_cache(refs);
2542                         if (commit_ref(lock)) {
2543                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2544                                 unlock_ref(lock);
2545                                 update->backend_data = NULL;
2546                                 ret = TRANSACTION_GENERIC_ERROR;
2547                                 goto cleanup;
2548                         }
2549                 }
2550         }
2551         /* Perform deletes now that updates are safely completed */
2552         for (i = 0; i < transaction->nr; i++) {
2553                 struct ref_update *update = transaction->updates[i];
2554                 struct ref_lock *lock = update->backend_data;
2555
2556                 if (update->flags & REF_DELETING &&
2557                     !(update->flags & REF_LOG_ONLY)) {
2558                         if (!(update->type & REF_ISPACKED) ||
2559                             update->type & REF_ISSYMREF) {
2560                                 /* It is a loose reference. */
2561                                 strbuf_reset(&sb);
2562                                 files_ref_path(refs, &sb, lock->ref_name);
2563                                 if (unlink_or_msg(sb.buf, err)) {
2564                                         ret = TRANSACTION_GENERIC_ERROR;
2565                                         goto cleanup;
2566                                 }
2567                                 update->flags |= REF_DELETED_LOOSE;
2568                         }
2569
2570                         if (!(update->flags & REF_ISPRUNING))
2571                                 string_list_append(&refs_to_delete,
2572                                                    lock->ref_name);
2573                 }
2574         }
2575
2576         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2577                 ret = TRANSACTION_GENERIC_ERROR;
2578                 goto cleanup;
2579         }
2580
2581         if (repack_without_refs(refs->packed_ref_store, &refs_to_delete, err)) {
2582                 ret = TRANSACTION_GENERIC_ERROR;
2583                 packed_refs_unlock(refs->packed_ref_store);
2584                 goto cleanup;
2585         }
2586
2587         packed_refs_unlock(refs->packed_ref_store);
2588
2589         /* Delete the reflogs of any references that were deleted: */
2590         for_each_string_list_item(ref_to_delete, &refs_to_delete) {
2591                 strbuf_reset(&sb);
2592                 files_reflog_path(refs, &sb, ref_to_delete->string);
2593                 if (!unlink_or_warn(sb.buf))
2594                         try_remove_empty_parents(refs, ref_to_delete->string,
2595                                                  REMOVE_EMPTY_PARENTS_REFLOG);
2596         }
2597
2598         clear_loose_ref_cache(refs);
2599
2600 cleanup:
2601         files_transaction_cleanup(transaction);
2602
2603         for (i = 0; i < transaction->nr; i++) {
2604                 struct ref_update *update = transaction->updates[i];
2605
2606                 if (update->flags & REF_DELETED_LOOSE) {
2607                         /*
2608                          * The loose reference was deleted. Delete any
2609                          * empty parent directories. (Note that this
2610                          * can only work because we have already
2611                          * removed the lockfile.)
2612                          */
2613                         try_remove_empty_parents(refs, update->refname,
2614                                                  REMOVE_EMPTY_PARENTS_REF);
2615                 }
2616         }
2617
2618         strbuf_release(&sb);
2619         string_list_clear(&refs_to_delete, 0);
2620         return ret;
2621 }
2622
2623 static int files_transaction_abort(struct ref_store *ref_store,
2624                                    struct ref_transaction *transaction,
2625                                    struct strbuf *err)
2626 {
2627         files_transaction_cleanup(transaction);
2628         return 0;
2629 }
2630
2631 static int ref_present(const char *refname,
2632                        const struct object_id *oid, int flags, void *cb_data)
2633 {
2634         struct string_list *affected_refnames = cb_data;
2635
2636         return string_list_has_string(affected_refnames, refname);
2637 }
2638
2639 static int files_initial_transaction_commit(struct ref_store *ref_store,
2640                                             struct ref_transaction *transaction,
2641                                             struct strbuf *err)
2642 {
2643         struct files_ref_store *refs =
2644                 files_downcast(ref_store, REF_STORE_WRITE,
2645                                "initial_ref_transaction_commit");
2646         size_t i;
2647         int ret = 0;
2648         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2649
2650         assert(err);
2651
2652         if (transaction->state != REF_TRANSACTION_OPEN)
2653                 die("BUG: commit called for transaction that is not open");
2654
2655         /* Fail if a refname appears more than once in the transaction: */
2656         for (i = 0; i < transaction->nr; i++)
2657                 string_list_append(&affected_refnames,
2658                                    transaction->updates[i]->refname);
2659         string_list_sort(&affected_refnames);
2660         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2661                 ret = TRANSACTION_GENERIC_ERROR;
2662                 goto cleanup;
2663         }
2664
2665         /*
2666          * It's really undefined to call this function in an active
2667          * repository or when there are existing references: we are
2668          * only locking and changing packed-refs, so (1) any
2669          * simultaneous processes might try to change a reference at
2670          * the same time we do, and (2) any existing loose versions of
2671          * the references that we are setting would have precedence
2672          * over our values. But some remote helpers create the remote
2673          * "HEAD" and "master" branches before calling this function,
2674          * so here we really only check that none of the references
2675          * that we are creating already exists.
2676          */
2677         if (refs_for_each_rawref(&refs->base, ref_present,
2678                                  &affected_refnames))
2679                 die("BUG: initial ref transaction called with existing refs");
2680
2681         for (i = 0; i < transaction->nr; i++) {
2682                 struct ref_update *update = transaction->updates[i];
2683
2684                 if ((update->flags & REF_HAVE_OLD) &&
2685                     !is_null_oid(&update->old_oid))
2686                         die("BUG: initial ref transaction with old_sha1 set");
2687                 if (refs_verify_refname_available(&refs->base, update->refname,
2688                                                   &affected_refnames, NULL,
2689                                                   err)) {
2690                         ret = TRANSACTION_NAME_CONFLICT;
2691                         goto cleanup;
2692                 }
2693         }
2694
2695         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2696                 ret = TRANSACTION_GENERIC_ERROR;
2697                 goto cleanup;
2698         }
2699
2700         for (i = 0; i < transaction->nr; i++) {
2701                 struct ref_update *update = transaction->updates[i];
2702
2703                 if ((update->flags & REF_HAVE_NEW) &&
2704                     !is_null_oid(&update->new_oid))
2705                         add_packed_ref(refs->packed_ref_store, update->refname,
2706                                        &update->new_oid);
2707         }
2708
2709         if (commit_packed_refs(refs->packed_ref_store, err)) {
2710                 ret = TRANSACTION_GENERIC_ERROR;
2711                 goto cleanup;
2712         }
2713
2714 cleanup:
2715         packed_refs_unlock(refs->packed_ref_store);
2716         transaction->state = REF_TRANSACTION_CLOSED;
2717         string_list_clear(&affected_refnames, 0);
2718         return ret;
2719 }
2720
2721 struct expire_reflog_cb {
2722         unsigned int flags;
2723         reflog_expiry_should_prune_fn *should_prune_fn;
2724         void *policy_cb;
2725         FILE *newlog;
2726         struct object_id last_kept_oid;
2727 };
2728
2729 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2730                              const char *email, timestamp_t timestamp, int tz,
2731                              const char *message, void *cb_data)
2732 {
2733         struct expire_reflog_cb *cb = cb_data;
2734         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2735
2736         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2737                 ooid = &cb->last_kept_oid;
2738
2739         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2740                                    message, policy_cb)) {
2741                 if (!cb->newlog)
2742                         printf("would prune %s", message);
2743                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2744                         printf("prune %s", message);
2745         } else {
2746                 if (cb->newlog) {
2747                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2748                                 oid_to_hex(ooid), oid_to_hex(noid),
2749                                 email, timestamp, tz, message);
2750                         oidcpy(&cb->last_kept_oid, noid);
2751                 }
2752                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2753                         printf("keep %s", message);
2754         }
2755         return 0;
2756 }
2757
2758 static int files_reflog_expire(struct ref_store *ref_store,
2759                                const char *refname, const unsigned char *sha1,
2760                                unsigned int flags,
2761                                reflog_expiry_prepare_fn prepare_fn,
2762                                reflog_expiry_should_prune_fn should_prune_fn,
2763                                reflog_expiry_cleanup_fn cleanup_fn,
2764                                void *policy_cb_data)
2765 {
2766         struct files_ref_store *refs =
2767                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2768         static struct lock_file reflog_lock;
2769         struct expire_reflog_cb cb;
2770         struct ref_lock *lock;
2771         struct strbuf log_file_sb = STRBUF_INIT;
2772         char *log_file;
2773         int status = 0;
2774         int type;
2775         struct strbuf err = STRBUF_INIT;
2776         struct object_id oid;
2777
2778         memset(&cb, 0, sizeof(cb));
2779         cb.flags = flags;
2780         cb.policy_cb = policy_cb_data;
2781         cb.should_prune_fn = should_prune_fn;
2782
2783         /*
2784          * The reflog file is locked by holding the lock on the
2785          * reference itself, plus we might need to update the
2786          * reference if --updateref was specified:
2787          */
2788         lock = lock_ref_sha1_basic(refs, refname, sha1,
2789                                    NULL, NULL, REF_NODEREF,
2790                                    &type, &err);
2791         if (!lock) {
2792                 error("cannot lock ref '%s': %s", refname, err.buf);
2793                 strbuf_release(&err);
2794                 return -1;
2795         }
2796         if (!refs_reflog_exists(ref_store, refname)) {
2797                 unlock_ref(lock);
2798                 return 0;
2799         }
2800
2801         files_reflog_path(refs, &log_file_sb, refname);
2802         log_file = strbuf_detach(&log_file_sb, NULL);
2803         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2804                 /*
2805                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2806                  * no locking implications, we use the lock_file
2807                  * machinery here anyway because it does a lot of the
2808                  * work we need, including cleaning up if the program
2809                  * exits unexpectedly.
2810                  */
2811                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2812                         struct strbuf err = STRBUF_INIT;
2813                         unable_to_lock_message(log_file, errno, &err);
2814                         error("%s", err.buf);
2815                         strbuf_release(&err);
2816                         goto failure;
2817                 }
2818                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
2819                 if (!cb.newlog) {
2820                         error("cannot fdopen %s (%s)",
2821                               get_lock_file_path(&reflog_lock), strerror(errno));
2822                         goto failure;
2823                 }
2824         }
2825
2826         hashcpy(oid.hash, sha1);
2827
2828         (*prepare_fn)(refname, &oid, cb.policy_cb);
2829         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
2830         (*cleanup_fn)(cb.policy_cb);
2831
2832         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2833                 /*
2834                  * It doesn't make sense to adjust a reference pointed
2835                  * to by a symbolic ref based on expiring entries in
2836                  * the symbolic reference's reflog. Nor can we update
2837                  * a reference if there are no remaining reflog
2838                  * entries.
2839                  */
2840                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
2841                         !(type & REF_ISSYMREF) &&
2842                         !is_null_oid(&cb.last_kept_oid);
2843
2844                 if (close_lock_file_gently(&reflog_lock)) {
2845                         status |= error("couldn't write %s: %s", log_file,
2846                                         strerror(errno));
2847                         rollback_lock_file(&reflog_lock);
2848                 } else if (update &&
2849                            (write_in_full(get_lock_file_fd(&lock->lk),
2850                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
2851                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") != 1 ||
2852                             close_ref_gently(lock) < 0)) {
2853                         status |= error("couldn't write %s",
2854                                         get_lock_file_path(&lock->lk));
2855                         rollback_lock_file(&reflog_lock);
2856                 } else if (commit_lock_file(&reflog_lock)) {
2857                         status |= error("unable to write reflog '%s' (%s)",
2858                                         log_file, strerror(errno));
2859                 } else if (update && commit_ref(lock)) {
2860                         status |= error("couldn't set %s", lock->ref_name);
2861                 }
2862         }
2863         free(log_file);
2864         unlock_ref(lock);
2865         return status;
2866
2867  failure:
2868         rollback_lock_file(&reflog_lock);
2869         free(log_file);
2870         unlock_ref(lock);
2871         return -1;
2872 }
2873
2874 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
2875 {
2876         struct files_ref_store *refs =
2877                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
2878         struct strbuf sb = STRBUF_INIT;
2879
2880         /*
2881          * Create .git/refs/{heads,tags}
2882          */
2883         files_ref_path(refs, &sb, "refs/heads");
2884         safe_create_dir(sb.buf, 1);
2885
2886         strbuf_reset(&sb);
2887         files_ref_path(refs, &sb, "refs/tags");
2888         safe_create_dir(sb.buf, 1);
2889
2890         strbuf_release(&sb);
2891         return 0;
2892 }
2893
2894 struct ref_storage_be refs_be_files = {
2895         NULL,
2896         "files",
2897         files_ref_store_create,
2898         files_init_db,
2899         files_transaction_prepare,
2900         files_transaction_finish,
2901         files_transaction_abort,
2902         files_initial_transaction_commit,
2903
2904         files_pack_refs,
2905         files_peel_ref,
2906         files_create_symref,
2907         files_delete_refs,
2908         files_rename_ref,
2909
2910         files_ref_iterator_begin,
2911         files_read_raw_ref,
2912
2913         files_reflog_iterator_begin,
2914         files_for_each_reflog_ent,
2915         files_for_each_reflog_ent_reverse,
2916         files_reflog_exists,
2917         files_create_reflog,
2918         files_delete_reflog,
2919         files_reflog_expire
2920 };