refs/files-backend.c

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12
  13 struct ref_lock {
  14         char *ref_name;
  15         struct lock_file lk;
  16         struct object_id old_oid;
  17 };
  18
  19 /*
  20  * Future: need to be in "struct repository"
  21  * when doing a full libification.
  22  */
  23 struct files_ref_store {
  24         struct ref_store base;
  25         unsigned int store_flags;
  26
  27         char *gitdir;
  28         char *gitcommondir;
  29
  30         struct ref_cache *loose;
  31
  32         struct ref_store *packed_ref_store;
  33 };
  34
  35 static void clear_loose_ref_cache(struct files_ref_store *refs)
  36 {
  37         if (refs->loose) {
  38                 free_ref_cache(refs->loose);
  39                 refs->loose = NULL;
  40         }
  41 }
  42
  43 /*
  44  * Create a new submodule ref cache and add it to the internal
  45  * set of caches.
  46  */
  47 static struct ref_store *files_ref_store_create(const char *gitdir,
  48                                                 unsigned int flags)
  49 {
  50         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  51         struct ref_store *ref_store = (struct ref_store *)refs;
  52         struct strbuf sb = STRBUF_INIT;
  53
  54         base_ref_store_init(ref_store, &refs_be_files);
  55         refs->store_flags = flags;
  56
  57         refs->gitdir = xstrdup(gitdir);
  58         get_common_dir_noenv(&sb, gitdir);
  59         refs->gitcommondir = strbuf_detach(&sb, NULL);
  60         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
  61         refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
  62         strbuf_release(&sb);
  63
  64         return ref_store;
  65 }
  66
  67 /*
  68  * Die if refs is not the main ref store. caller is used in any
  69  * necessary error messages.
  70  */
  71 static void files_assert_main_repository(struct files_ref_store *refs,
  72                                          const char *caller)
  73 {
  74         if (refs->store_flags & REF_STORE_MAIN)
  75                 return;
  76
  77         die("BUG: operation %s only allowed for main ref store", caller);
  78 }
  79
  80 /*
  81  * Downcast ref_store to files_ref_store. Die if ref_store is not a
  82  * files_ref_store. required_flags is compared with ref_store's
  83  * store_flags to ensure the ref_store has all required capabilities.
  84  * "caller" is used in any necessary error messages.
  85  */
  86 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
  87                                               unsigned int required_flags,
  88                                               const char *caller)
  89 {
  90         struct files_ref_store *refs;
  91
  92         if (ref_store->be != &refs_be_files)
  93                 die("BUG: ref_store is type \"%s\" not \"files\" in %s",
  94                     ref_store->be->name, caller);
  95
  96         refs = (struct files_ref_store *)ref_store;
  97
  98         if ((refs->store_flags & required_flags) != required_flags)
  99                 die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
 100                     caller, required_flags, refs->store_flags);
 101
 102         return refs;
 103 }
 104
 105 static void files_reflog_path(struct files_ref_store *refs,
 106                               struct strbuf *sb,
 107                               const char *refname)
 108 {
 109         switch (ref_type(refname)) {
 110         case REF_TYPE_PER_WORKTREE:
 111         case REF_TYPE_PSEUDOREF:
 112                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 113                 break;
 114         case REF_TYPE_NORMAL:
 115                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 116                 break;
 117         default:
 118                 die("BUG: unknown ref type %d of ref %s",
 119                     ref_type(refname), refname);
 120         }
 121 }
 122
 123 static void files_ref_path(struct files_ref_store *refs,
 124                            struct strbuf *sb,
 125                            const char *refname)
 126 {
 127         switch (ref_type(refname)) {
 128         case REF_TYPE_PER_WORKTREE:
 129         case REF_TYPE_PSEUDOREF:
 130                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 131                 break;
 132         case REF_TYPE_NORMAL:
 133                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 134                 break;
 135         default:
 136                 die("BUG: unknown ref type %d of ref %s",
 137                     ref_type(refname), refname);
 138         }
 139 }
 140
 141 /*
 142  * Read the loose references from the namespace dirname into dir
 143  * (without recursing).  dirname must end with '/'.  dir must be the
 144  * directory entry corresponding to dirname.
 145  */
 146 static void loose_fill_ref_dir(struct ref_store *ref_store,
 147                                struct ref_dir *dir, const char *dirname)
 148 {
 149         struct files_ref_store *refs =
 150                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 151         DIR *d;
 152         struct dirent *de;
 153         int dirnamelen = strlen(dirname);
 154         struct strbuf refname;
 155         struct strbuf path = STRBUF_INIT;
 156         size_t path_baselen;
 157
 158         files_ref_path(refs, &path, dirname);
 159         path_baselen = path.len;
 160
 161         d = opendir(path.buf);
 162         if (!d) {
 163                 strbuf_release(&path);
 164                 return;
 165         }
 166
 167         strbuf_init(&refname, dirnamelen + 257);
 168         strbuf_add(&refname, dirname, dirnamelen);
 169
 170         while ((de = readdir(d)) != NULL) {
 171                 struct object_id oid;
 172                 struct stat st;
 173                 int flag;
 174
 175                 if (de->d_name[0] == '.')
 176                         continue;
 177                 if (ends_with(de->d_name, ".lock"))
 178                         continue;
 179                 strbuf_addstr(&refname, de->d_name);
 180                 strbuf_addstr(&path, de->d_name);
 181                 if (stat(path.buf, &st) < 0) {
 182                         ; /* silently ignore */
 183                 } else if (S_ISDIR(st.st_mode)) {
 184                         strbuf_addch(&refname, '/');
 185                         add_entry_to_dir(dir,
 186                                          create_dir_entry(dir->cache, refname.buf,
 187                                                           refname.len, 1));
 188                 } else {
 189                         if (!refs_resolve_ref_unsafe(&refs->base,
 190                                                      refname.buf,
 191                                                      RESOLVE_REF_READING,
 192                                                      oid.hash, &flag)) {
 193                                 oidclr(&oid);
 194                                 flag |= REF_ISBROKEN;
 195                         } else if (is_null_oid(&oid)) {
 196                                 /*
 197                                  * It is so astronomically unlikely
 198                                  * that NULL_SHA1 is the SHA-1 of an
 199                                  * actual object that we consider its
 200                                  * appearance in a loose reference
 201                                  * file to be repo corruption
 202                                  * (probably due to a software bug).
 203                                  */
 204                                 flag |= REF_ISBROKEN;
 205                         }
 206
 207                         if (check_refname_format(refname.buf,
 208                                                  REFNAME_ALLOW_ONELEVEL)) {
 209                                 if (!refname_is_safe(refname.buf))
 210                                         die("loose refname is dangerous: %s", refname.buf);
 211                                 oidclr(&oid);
 212                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 213                         }
 214                         add_entry_to_dir(dir,
 215                                          create_ref_entry(refname.buf, &oid, flag));
 216                 }
 217                 strbuf_setlen(&refname, dirnamelen);
 218                 strbuf_setlen(&path, path_baselen);
 219         }
 220         strbuf_release(&refname);
 221         strbuf_release(&path);
 222         closedir(d);
 223
 224         /*
 225          * Manually add refs/bisect, which, being per-worktree, might
 226          * not appear in the directory listing for refs/ in the main
 227          * repo.
 228          */
 229         if (!strcmp(dirname, "refs/")) {
 230                 int pos = search_ref_dir(dir, "refs/bisect/", 12);
 231
 232                 if (pos < 0) {
 233                         struct ref_entry *child_entry = create_dir_entry(
 234                                         dir->cache, "refs/bisect/", 12, 1);
 235                         add_entry_to_dir(dir, child_entry);
 236                 }
 237         }
 238 }
 239
 240 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 241 {
 242         if (!refs->loose) {
 243                 /*
 244                  * Mark the top-level directory complete because we
 245                  * are about to read the only subdirectory that can
 246                  * hold references:
 247                  */
 248                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 249
 250                 /* We're going to fill the top level ourselves: */
 251                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 252
 253                 /*
 254                  * Add an incomplete entry for "refs/" (to be filled
 255                  * lazily):
 256                  */
 257                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 258                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 259         }
 260         return refs->loose;
 261 }
 262
 263 static int files_read_raw_ref(struct ref_store *ref_store,
 264                               const char *refname, unsigned char *sha1,
 265                               struct strbuf *referent, unsigned int *type)
 266 {
 267         struct files_ref_store *refs =
 268                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 269         struct strbuf sb_contents = STRBUF_INIT;
 270         struct strbuf sb_path = STRBUF_INIT;
 271         const char *path;
 272         const char *buf;
 273         struct stat st;
 274         int fd;
 275         int ret = -1;
 276         int save_errno;
 277         int remaining_retries = 3;
 278
 279         *type = 0;
 280         strbuf_reset(&sb_path);
 281
 282         files_ref_path(refs, &sb_path, refname);
 283
 284         path = sb_path.buf;
 285
 286 stat_ref:
 287         /*
 288          * We might have to loop back here to avoid a race
 289          * condition: first we lstat() the file, then we try
 290          * to read it as a link or as a file.  But if somebody
 291          * changes the type of the file (file <-> directory
 292          * <-> symlink) between the lstat() and reading, then
 293          * we don't want to report that as an error but rather
 294          * try again starting with the lstat().
 295          *
 296          * We'll keep a count of the retries, though, just to avoid
 297          * any confusing situation sending us into an infinite loop.
 298          */
 299
 300         if (remaining_retries-- <= 0)
 301                 goto out;
 302
 303         if (lstat(path, &st) < 0) {
 304                 if (errno != ENOENT)
 305                         goto out;
 306                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 307                                       sha1, referent, type)) {
 308                         errno = ENOENT;
 309                         goto out;
 310                 }
 311                 ret = 0;
 312                 goto out;
 313         }
 314
 315         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 316         if (S_ISLNK(st.st_mode)) {
 317                 strbuf_reset(&sb_contents);
 318                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 319                         if (errno == ENOENT || errno == EINVAL)
 320                                 /* inconsistent with lstat; retry */
 321                                 goto stat_ref;
 322                         else
 323                                 goto out;
 324                 }
 325                 if (starts_with(sb_contents.buf, "refs/") &&
 326                     !check_refname_format(sb_contents.buf, 0)) {
 327                         strbuf_swap(&sb_contents, referent);
 328                         *type |= REF_ISSYMREF;
 329                         ret = 0;
 330                         goto out;
 331                 }
 332                 /*
 333                  * It doesn't look like a refname; fall through to just
 334                  * treating it like a non-symlink, and reading whatever it
 335                  * points to.
 336                  */
 337         }
 338
 339         /* Is it a directory? */
 340         if (S_ISDIR(st.st_mode)) {
 341                 /*
 342                  * Even though there is a directory where the loose
 343                  * ref is supposed to be, there could still be a
 344                  * packed ref:
 345                  */
 346                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 347                                       sha1, referent, type)) {
 348                         errno = EISDIR;
 349                         goto out;
 350                 }
 351                 ret = 0;
 352                 goto out;
 353         }
 354
 355         /*
 356          * Anything else, just open it and try to use it as
 357          * a ref
 358          */
 359         fd = open(path, O_RDONLY);
 360         if (fd < 0) {
 361                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 362                         /* inconsistent with lstat; retry */
 363                         goto stat_ref;
 364                 else
 365                         goto out;
 366         }
 367         strbuf_reset(&sb_contents);
 368         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 369                 int save_errno = errno;
 370                 close(fd);
 371                 errno = save_errno;
 372                 goto out;
 373         }
 374         close(fd);
 375         strbuf_rtrim(&sb_contents);
 376         buf = sb_contents.buf;
 377         if (starts_with(buf, "ref:")) {
 378                 buf += 4;
 379                 while (isspace(*buf))
 380                         buf++;
 381
 382                 strbuf_reset(referent);
 383                 strbuf_addstr(referent, buf);
 384                 *type |= REF_ISSYMREF;
 385                 ret = 0;
 386                 goto out;
 387         }
 388
 389         /*
 390          * Please note that FETCH_HEAD has additional
 391          * data after the sha.
 392          */
 393         if (get_sha1_hex(buf, sha1) ||
 394             (buf[40] != '\0' && !isspace(buf[40]))) {
 395                 *type |= REF_ISBROKEN;
 396                 errno = EINVAL;
 397                 goto out;
 398         }
 399
 400         ret = 0;
 401
 402 out:
 403         save_errno = errno;
 404         strbuf_release(&sb_path);
 405         strbuf_release(&sb_contents);
 406         errno = save_errno;
 407         return ret;
 408 }
 409
 410 static void unlock_ref(struct ref_lock *lock)
 411 {
 412         rollback_lock_file(&lock->lk);
 413         free(lock->ref_name);
 414         free(lock);
 415 }
 416
 417 /*
 418  * Lock refname, without following symrefs, and set *lock_p to point
 419  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 420  * and type similarly to read_raw_ref().
 421  *
 422  * The caller must verify that refname is a "safe" reference name (in
 423  * the sense of refname_is_safe()) before calling this function.
 424  *
 425  * If the reference doesn't already exist, verify that refname doesn't
 426  * have a D/F conflict with any existing references. extras and skip
 427  * are passed to refs_verify_refname_available() for this check.
 428  *
 429  * If mustexist is not set and the reference is not found or is
 430  * broken, lock the reference anyway but clear sha1.
 431  *
 432  * Return 0 on success. On failure, write an error message to err and
 433  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 434  *
 435  * Implementation note: This function is basically
 436  *
 437  *     lock reference
 438  *     read_raw_ref()
 439  *
 440  * but it includes a lot more code to
 441  * - Deal with possible races with other processes
 442  * - Avoid calling refs_verify_refname_available() when it can be
 443  *   avoided, namely if we were successfully able to read the ref
 444  * - Generate informative error messages in the case of failure
 445  */
 446 static int lock_raw_ref(struct files_ref_store *refs,
 447                         const char *refname, int mustexist,
 448                         const struct string_list *extras,
 449                         const struct string_list *skip,
 450                         struct ref_lock **lock_p,
 451                         struct strbuf *referent,
 452                         unsigned int *type,
 453                         struct strbuf *err)
 454 {
 455         struct ref_lock *lock;
 456         struct strbuf ref_file = STRBUF_INIT;
 457         int attempts_remaining = 3;
 458         int ret = TRANSACTION_GENERIC_ERROR;
 459
 460         assert(err);
 461         files_assert_main_repository(refs, "lock_raw_ref");
 462
 463         *type = 0;
 464
 465         /* First lock the file so it can't change out from under us. */
 466
 467         *lock_p = lock = xcalloc(1, sizeof(*lock));
 468
 469         lock->ref_name = xstrdup(refname);
 470         files_ref_path(refs, &ref_file, refname);
 471
 472 retry:
 473         switch (safe_create_leading_directories(ref_file.buf)) {
 474         case SCLD_OK:
 475                 break; /* success */
 476         case SCLD_EXISTS:
 477                 /*
 478                  * Suppose refname is "refs/foo/bar". We just failed
 479                  * to create the containing directory, "refs/foo",
 480                  * because there was a non-directory in the way. This
 481                  * indicates a D/F conflict, probably because of
 482                  * another reference such as "refs/foo". There is no
 483                  * reason to expect this error to be transitory.
 484                  */
 485                 if (refs_verify_refname_available(&refs->base, refname,
 486                                                   extras, skip, err)) {
 487                         if (mustexist) {
 488                                 /*
 489                                  * To the user the relevant error is
 490                                  * that the "mustexist" reference is
 491                                  * missing:
 492                                  */
 493                                 strbuf_reset(err);
 494                                 strbuf_addf(err, "unable to resolve reference '%s'",
 495                                             refname);
 496                         } else {
 497                                 /*
 498                                  * The error message set by
 499                                  * refs_verify_refname_available() is
 500                                  * OK.
 501                                  */
 502                                 ret = TRANSACTION_NAME_CONFLICT;
 503                         }
 504                 } else {
 505                         /*
 506                          * The file that is in the way isn't a loose
 507                          * reference. Report it as a low-level
 508                          * failure.
 509                          */
 510                         strbuf_addf(err, "unable to create lock file %s.lock; "
 511                                     "non-directory in the way",
 512                                     ref_file.buf);
 513                 }
 514                 goto error_return;
 515         case SCLD_VANISHED:
 516                 /* Maybe another process was tidying up. Try again. */
 517                 if (--attempts_remaining > 0)
 518                         goto retry;
 519                 /* fall through */
 520         default:
 521                 strbuf_addf(err, "unable to create directory for %s",
 522                             ref_file.buf);
 523                 goto error_return;
 524         }
 525
 526         if (hold_lock_file_for_update_timeout(
 527                             &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 528                             get_files_ref_lock_timeout_ms()) < 0) {
 529                 if (errno == ENOENT && --attempts_remaining > 0) {
 530                         /*
 531                          * Maybe somebody just deleted one of the
 532                          * directories leading to ref_file.  Try
 533                          * again:
 534                          */
 535                         goto retry;
 536                 } else {
 537                         unable_to_lock_message(ref_file.buf, errno, err);
 538                         goto error_return;
 539                 }
 540         }
 541
 542         /*
 543          * Now we hold the lock and can read the reference without
 544          * fear that its value will change.
 545          */
 546
 547         if (files_read_raw_ref(&refs->base, refname,
 548                                lock->old_oid.hash, referent, type)) {
 549                 if (errno == ENOENT) {
 550                         if (mustexist) {
 551                                 /* Garden variety missing reference. */
 552                                 strbuf_addf(err, "unable to resolve reference '%s'",
 553                                             refname);
 554                                 goto error_return;
 555                         } else {
 556                                 /*
 557                                  * Reference is missing, but that's OK. We
 558                                  * know that there is not a conflict with
 559                                  * another loose reference because
 560                                  * (supposing that we are trying to lock
 561                                  * reference "refs/foo/bar"):
 562                                  *
 563                                  * - We were successfully able to create
 564                                  *   the lockfile refs/foo/bar.lock, so we
 565                                  *   know there cannot be a loose reference
 566                                  *   named "refs/foo".
 567                                  *
 568                                  * - We got ENOENT and not EISDIR, so we
 569                                  *   know that there cannot be a loose
 570                                  *   reference named "refs/foo/bar/baz".
 571                                  */
 572                         }
 573                 } else if (errno == EISDIR) {
 574                         /*
 575                          * There is a directory in the way. It might have
 576                          * contained references that have been deleted. If
 577                          * we don't require that the reference already
 578                          * exists, try to remove the directory so that it
 579                          * doesn't cause trouble when we want to rename the
 580                          * lockfile into place later.
 581                          */
 582                         if (mustexist) {
 583                                 /* Garden variety missing reference. */
 584                                 strbuf_addf(err, "unable to resolve reference '%s'",
 585                                             refname);
 586                                 goto error_return;
 587                         } else if (remove_dir_recursively(&ref_file,
 588                                                           REMOVE_DIR_EMPTY_ONLY)) {
 589                                 if (refs_verify_refname_available(
 590                                                     &refs->base, refname,
 591                                                     extras, skip, err)) {
 592                                         /*
 593                                          * The error message set by
 594                                          * verify_refname_available() is OK.
 595                                          */
 596                                         ret = TRANSACTION_NAME_CONFLICT;
 597                                         goto error_return;
 598                                 } else {
 599                                         /*
 600                                          * We can't delete the directory,
 601                                          * but we also don't know of any
 602                                          * references that it should
 603                                          * contain.
 604                                          */
 605                                         strbuf_addf(err, "there is a non-empty directory '%s' "
 606                                                     "blocking reference '%s'",
 607                                                     ref_file.buf, refname);
 608                                         goto error_return;
 609                                 }
 610                         }
 611                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 612                         strbuf_addf(err, "unable to resolve reference '%s': "
 613                                     "reference broken", refname);
 614                         goto error_return;
 615                 } else {
 616                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 617                                     refname, strerror(errno));
 618                         goto error_return;
 619                 }
 620
 621                 /*
 622                  * If the ref did not exist and we are creating it,
 623                  * make sure there is no existing packed ref that
 624                  * conflicts with refname:
 625                  */
 626                 if (refs_verify_refname_available(
 627                                     refs->packed_ref_store, refname,
 628                                     extras, skip, err))
 629                         goto error_return;
 630         }
 631
 632         ret = 0;
 633         goto out;
 634
 635 error_return:
 636         unlock_ref(lock);
 637         *lock_p = NULL;
 638
 639 out:
 640         strbuf_release(&ref_file);
 641         return ret;
 642 }
 643
 644 static int files_peel_ref(struct ref_store *ref_store,
 645                           const char *refname, unsigned char *sha1)
 646 {
 647         struct files_ref_store *refs =
 648                 files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
 649                                "peel_ref");
 650         int flag;
 651         unsigned char base[20];
 652
 653         if (current_ref_iter && current_ref_iter->refname == refname) {
 654                 struct object_id peeled;
 655
 656                 if (ref_iterator_peel(current_ref_iter, &peeled))
 657                         return -1;
 658                 hashcpy(sha1, peeled.hash);
 659                 return 0;
 660         }
 661
 662         if (refs_read_ref_full(ref_store, refname,
 663                                RESOLVE_REF_READING, base, &flag))
 664                 return -1;
 665
 666         /*
 667          * If the reference is packed, read its ref_entry from the
 668          * cache in the hope that we already know its peeled value.
 669          * We only try this optimization on packed references because
 670          * (a) forcing the filling of the loose reference cache could
 671          * be expensive and (b) loose references anyway usually do not
 672          * have REF_KNOWS_PEELED.
 673          */
 674         if (flag & REF_ISPACKED &&
 675             !refs_peel_ref(refs->packed_ref_store, refname, sha1))
 676                 return 0;
 677
 678         return peel_object(base, sha1);
 679 }
 680
 681 struct files_ref_iterator {
 682         struct ref_iterator base;
 683
 684         struct ref_iterator *iter0;
 685         unsigned int flags;
 686 };
 687
 688 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 689 {
 690         struct files_ref_iterator *iter =
 691                 (struct files_ref_iterator *)ref_iterator;
 692         int ok;
 693
 694         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 695                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 696                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 697                         continue;
 698
 699                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 700                     !ref_resolves_to_object(iter->iter0->refname,
 701                                             iter->iter0->oid,
 702                                             iter->iter0->flags))
 703                         continue;
 704
 705                 iter->base.refname = iter->iter0->refname;
 706                 iter->base.oid = iter->iter0->oid;
 707                 iter->base.flags = iter->iter0->flags;
 708                 return ITER_OK;
 709         }
 710
 711         iter->iter0 = NULL;
 712         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 713                 ok = ITER_ERROR;
 714
 715         return ok;
 716 }
 717
 718 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 719                                    struct object_id *peeled)
 720 {
 721         struct files_ref_iterator *iter =
 722                 (struct files_ref_iterator *)ref_iterator;
 723
 724         return ref_iterator_peel(iter->iter0, peeled);
 725 }
 726
 727 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 728 {
 729         struct files_ref_iterator *iter =
 730                 (struct files_ref_iterator *)ref_iterator;
 731         int ok = ITER_DONE;
 732
 733         if (iter->iter0)
 734                 ok = ref_iterator_abort(iter->iter0);
 735
 736         base_ref_iterator_free(ref_iterator);
 737         return ok;
 738 }
 739
 740 static struct ref_iterator_vtable files_ref_iterator_vtable = {
 741         files_ref_iterator_advance,
 742         files_ref_iterator_peel,
 743         files_ref_iterator_abort
 744 };
 745
 746 static struct ref_iterator *files_ref_iterator_begin(
 747                 struct ref_store *ref_store,
 748                 const char *prefix, unsigned int flags)
 749 {
 750         struct files_ref_store *refs;
 751         struct ref_iterator *loose_iter, *packed_iter;
 752         struct files_ref_iterator *iter;
 753         struct ref_iterator *ref_iterator;
 754         unsigned int required_flags = REF_STORE_READ;
 755
 756         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 757                 required_flags |= REF_STORE_ODB;
 758
 759         refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 760
 761         iter = xcalloc(1, sizeof(*iter));
 762         ref_iterator = &iter->base;
 763         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
 764
 765         /*
 766          * We must make sure that all loose refs are read before
 767          * accessing the packed-refs file; this avoids a race
 768          * condition if loose refs are migrated to the packed-refs
 769          * file by a simultaneous process, but our in-memory view is
 770          * from before the migration. We ensure this as follows:
 771          * First, we call start the loose refs iteration with its
 772          * `prime_ref` argument set to true. This causes the loose
 773          * references in the subtree to be pre-read into the cache.
 774          * (If they've already been read, that's OK; we only need to
 775          * guarantee that they're read before the packed refs, not
 776          * *how much* before.) After that, we call
 777          * packed_ref_iterator_begin(), which internally checks
 778          * whether the packed-ref cache is up to date with what is on
 779          * disk, and re-reads it if not.
 780          */
 781
 782         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 783                                               prefix, 1);
 784
 785         /*
 786          * The packed-refs file might contain broken references, for
 787          * example an old version of a reference that points at an
 788          * object that has since been garbage-collected. This is OK as
 789          * long as there is a corresponding loose reference that
 790          * overrides it, and we don't want to emit an error message in
 791          * this case. So ask the packed_ref_store for all of its
 792          * references, and (if needed) do our own check for broken
 793          * ones in files_ref_iterator_advance(), after we have merged
 794          * the packed and loose references.
 795          */
 796         packed_iter = refs_ref_iterator_begin(
 797                         refs->packed_ref_store, prefix, 0,
 798                         DO_FOR_EACH_INCLUDE_BROKEN);
 799
 800         iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
 801         iter->flags = flags;
 802
 803         return ref_iterator;
 804 }
 805
 806 /*
 807  * Verify that the reference locked by lock has the value old_sha1.
 808  * Fail if the reference doesn't exist and mustexist is set. Return 0
 809  * on success. On error, write an error message to err, set errno, and
 810  * return a negative value.
 811  */
 812 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 813                        const unsigned char *old_sha1, int mustexist,
 814                        struct strbuf *err)
 815 {
 816         assert(err);
 817
 818         if (refs_read_ref_full(ref_store, lock->ref_name,
 819                                mustexist ? RESOLVE_REF_READING : 0,
 820                                lock->old_oid.hash, NULL)) {
 821                 if (old_sha1) {
 822                         int save_errno = errno;
 823                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 824                         errno = save_errno;
 825                         return -1;
 826                 } else {
 827                         oidclr(&lock->old_oid);
 828                         return 0;
 829                 }
 830         }
 831         if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
 832                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 833                             lock->ref_name,
 834                             oid_to_hex(&lock->old_oid),
 835                             sha1_to_hex(old_sha1));
 836                 errno = EBUSY;
 837                 return -1;
 838         }
 839         return 0;
 840 }
 841
 842 static int remove_empty_directories(struct strbuf *path)
 843 {
 844         /*
 845          * we want to create a file but there is a directory there;
 846          * if that is an empty directory (or a directory that contains
 847          * only empty directories), remove them.
 848          */
 849         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 850 }
 851
 852 static int create_reflock(const char *path, void *cb)
 853 {
 854         struct lock_file *lk = cb;
 855
 856         return hold_lock_file_for_update_timeout(
 857                         lk, path, LOCK_NO_DEREF,
 858                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 859 }
 860
 861 /*
 862  * Locks a ref returning the lock on success and NULL on failure.
 863  * On failure errno is set to something meaningful.
 864  */
 865 static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
 866                                             const char *refname,
 867                                             const unsigned char *old_sha1,
 868                                             const struct string_list *extras,
 869                                             const struct string_list *skip,
 870                                             unsigned int flags, int *type,
 871                                             struct strbuf *err)
 872 {
 873         struct strbuf ref_file = STRBUF_INIT;
 874         struct ref_lock *lock;
 875         int last_errno = 0;
 876         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 877         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 878         int resolved;
 879
 880         files_assert_main_repository(refs, "lock_ref_sha1_basic");
 881         assert(err);
 882
 883         lock = xcalloc(1, sizeof(struct ref_lock));
 884
 885         if (mustexist)
 886                 resolve_flags |= RESOLVE_REF_READING;
 887         if (flags & REF_DELETING)
 888                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 889
 890         files_ref_path(refs, &ref_file, refname);
 891         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 892                                              refname, resolve_flags,
 893                                              lock->old_oid.hash, type);
 894         if (!resolved && errno == EISDIR) {
 895                 /*
 896                  * we are trying to lock foo but we used to
 897                  * have foo/bar which now does not exist;
 898                  * it is normal for the empty directory 'foo'
 899                  * to remain.
 900                  */
 901                 if (remove_empty_directories(&ref_file)) {
 902                         last_errno = errno;
 903                         if (!refs_verify_refname_available(
 904                                             &refs->base,
 905                                             refname, extras, skip, err))
 906                                 strbuf_addf(err, "there are still refs under '%s'",
 907                                             refname);
 908                         goto error_return;
 909                 }
 910                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 911                                                      refname, resolve_flags,
 912                                                      lock->old_oid.hash, type);
 913         }
 914         if (!resolved) {
 915                 last_errno = errno;
 916                 if (last_errno != ENOTDIR ||
 917                     !refs_verify_refname_available(&refs->base, refname,
 918                                                    extras, skip, err))
 919                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 920                                     refname, strerror(last_errno));
 921
 922                 goto error_return;
 923         }
 924
 925         /*
 926          * If the ref did not exist and we are creating it, make sure
 927          * there is no existing packed ref whose name begins with our
 928          * refname, nor a packed ref whose name is a proper prefix of
 929          * our refname.
 930          */
 931         if (is_null_oid(&lock->old_oid) &&
 932             refs_verify_refname_available(refs->packed_ref_store, refname,
 933                                           extras, skip, err)) {
 934                 last_errno = ENOTDIR;
 935                 goto error_return;
 936         }
 937
 938         lock->ref_name = xstrdup(refname);
 939
 940         if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 941                 last_errno = errno;
 942                 unable_to_lock_message(ref_file.buf, errno, err);
 943                 goto error_return;
 944         }
 945
 946         if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
 947                 last_errno = errno;
 948                 goto error_return;
 949         }
 950         goto out;
 951
 952  error_return:
 953         unlock_ref(lock);
 954         lock = NULL;
 955
 956  out:
 957         strbuf_release(&ref_file);
 958         errno = last_errno;
 959         return lock;
 960 }
 961
 962 struct ref_to_prune {
 963         struct ref_to_prune *next;
 964         unsigned char sha1[20];
 965         char name[FLEX_ARRAY];
 966 };
 967
 968 enum {
 969         REMOVE_EMPTY_PARENTS_REF = 0x01,
 970         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 971 };
 972
 973 /*
 974  * Remove empty parent directories associated with the specified
 975  * reference and/or its reflog, but spare [logs/]refs/ and immediate
 976  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 977  * REMOVE_EMPTY_PARENTS_REFLOG.
 978  */
 979 static void try_remove_empty_parents(struct files_ref_store *refs,
 980                                      const char *refname,
 981                                      unsigned int flags)
 982 {
 983         struct strbuf buf = STRBUF_INIT;
 984         struct strbuf sb = STRBUF_INIT;
 985         char *p, *q;
 986         int i;
 987
 988         strbuf_addstr(&buf, refname);
 989         p = buf.buf;
 990         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
 991                 while (*p && *p != '/')
 992                         p++;
 993                 /* tolerate duplicate slashes; see check_refname_format() */
 994                 while (*p == '/')
 995                         p++;
 996         }
 997         q = buf.buf + buf.len;
 998         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
 999                 while (q > p && *q != '/')
1000                         q--;
1001                 while (q > p && *(q-1) == '/')
1002                         q--;
1003                 if (q == p)
1004                         break;
1005                 strbuf_setlen(&buf, q - buf.buf);
1006
1007                 strbuf_reset(&sb);
1008                 files_ref_path(refs, &sb, buf.buf);
1009                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1010                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1011
1012                 strbuf_reset(&sb);
1013                 files_reflog_path(refs, &sb, buf.buf);
1014                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1015                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1016         }
1017         strbuf_release(&buf);
1018         strbuf_release(&sb);
1019 }
1020
1021 /* make sure nobody touched the ref, and unlink */
1022 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1023 {
1024         struct ref_transaction *transaction;
1025         struct strbuf err = STRBUF_INIT;
1026
1027         if (check_refname_format(r->name, 0))
1028                 return;
1029
1030         transaction = ref_store_transaction_begin(&refs->base, &err);
1031         if (!transaction ||
1032             ref_transaction_delete(transaction, r->name, r->sha1,
1033                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
1034             ref_transaction_commit(transaction, &err)) {
1035                 ref_transaction_free(transaction);
1036                 error("%s", err.buf);
1037                 strbuf_release(&err);
1038                 return;
1039         }
1040         ref_transaction_free(transaction);
1041         strbuf_release(&err);
1042 }
1043
1044 /*
1045  * Prune the loose versions of the references in the linked list
1046  * `*refs_to_prune`, freeing the entries in the list as we go.
1047  */
1048 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1049 {
1050         while (*refs_to_prune) {
1051                 struct ref_to_prune *r = *refs_to_prune;
1052                 *refs_to_prune = r->next;
1053                 prune_ref(refs, r);
1054                 free(r);
1055         }
1056 }
1057
1058 /*
1059  * Return true if the specified reference should be packed.
1060  */
1061 static int should_pack_ref(const char *refname,
1062                            const struct object_id *oid, unsigned int ref_flags,
1063                            unsigned int pack_flags)
1064 {
1065         /* Do not pack per-worktree refs: */
1066         if (ref_type(refname) != REF_TYPE_NORMAL)
1067                 return 0;
1068
1069         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1070         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1071                 return 0;
1072
1073         /* Do not pack symbolic refs: */
1074         if (ref_flags & REF_ISSYMREF)
1075                 return 0;
1076
1077         /* Do not pack broken refs: */
1078         if (!ref_resolves_to_object(refname, oid, ref_flags))
1079                 return 0;
1080
1081         return 1;
1082 }
1083
1084 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1085 {
1086         struct files_ref_store *refs =
1087                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1088                                "pack_refs");
1089         struct ref_iterator *iter;
1090         int ok;
1091         struct ref_to_prune *refs_to_prune = NULL;
1092         struct strbuf err = STRBUF_INIT;
1093         struct ref_transaction *transaction;
1094
1095         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1096         if (!transaction)
1097                 return -1;
1098
1099         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1100
1101         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1102         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1103                 /*
1104                  * If the loose reference can be packed, add an entry
1105                  * in the packed ref cache. If the reference should be
1106                  * pruned, also add it to refs_to_prune.
1107                  */
1108                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1109                                      flags))
1110                         continue;
1111
1112                 /*
1113                  * Add a reference creation for this reference to the
1114                  * packed-refs transaction:
1115                  */
1116                 if (ref_transaction_update(transaction, iter->refname,
1117                                            iter->oid->hash, NULL,
1118                                            REF_NODEREF, NULL, &err))
1119                         die("failure preparing to create packed reference %s: %s",
1120                             iter->refname, err.buf);
1121
1122                 /* Schedule the loose reference for pruning if requested. */
1123                 if ((flags & PACK_REFS_PRUNE)) {
1124                         struct ref_to_prune *n;
1125                         FLEX_ALLOC_STR(n, name, iter->refname);
1126                         hashcpy(n->sha1, iter->oid->hash);
1127                         n->next = refs_to_prune;
1128                         refs_to_prune = n;
1129                 }
1130         }
1131         if (ok != ITER_DONE)
1132                 die("error while iterating over references");
1133
1134         if (ref_transaction_commit(transaction, &err))
1135                 die("unable to write new packed-refs: %s", err.buf);
1136
1137         ref_transaction_free(transaction);
1138
1139         packed_refs_unlock(refs->packed_ref_store);
1140
1141         prune_refs(refs, &refs_to_prune);
1142         strbuf_release(&err);
1143         return 0;
1144 }
1145
1146 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1147                              struct string_list *refnames, unsigned int flags)
1148 {
1149         struct files_ref_store *refs =
1150                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1151         struct strbuf err = STRBUF_INIT;
1152         int i, result = 0;
1153
1154         if (!refnames->nr)
1155                 return 0;
1156
1157         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1158                 goto error;
1159
1160         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1161                 packed_refs_unlock(refs->packed_ref_store);
1162                 goto error;
1163         }
1164
1165         packed_refs_unlock(refs->packed_ref_store);
1166
1167         for (i = 0; i < refnames->nr; i++) {
1168                 const char *refname = refnames->items[i].string;
1169
1170                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1171                         result |= error(_("could not remove reference %s"), refname);
1172         }
1173
1174         strbuf_release(&err);
1175         return result;
1176
1177 error:
1178         /*
1179          * If we failed to rewrite the packed-refs file, then it is
1180          * unsafe to try to remove loose refs, because doing so might
1181          * expose an obsolete packed value for a reference that might
1182          * even point at an object that has been garbage collected.
1183          */
1184         if (refnames->nr == 1)
1185                 error(_("could not delete reference %s: %s"),
1186                       refnames->items[0].string, err.buf);
1187         else
1188                 error(_("could not delete references: %s"), err.buf);
1189
1190         strbuf_release(&err);
1191         return -1;
1192 }
1193
1194 /*
1195  * People using contrib's git-new-workdir have .git/logs/refs ->
1196  * /some/other/path/.git/logs/refs, and that may live on another device.
1197  *
1198  * IOW, to avoid cross device rename errors, the temporary renamed log must
1199  * live into logs/refs.
1200  */
1201 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1202
1203 struct rename_cb {
1204         const char *tmp_renamed_log;
1205         int true_errno;
1206 };
1207
1208 static int rename_tmp_log_callback(const char *path, void *cb_data)
1209 {
1210         struct rename_cb *cb = cb_data;
1211
1212         if (rename(cb->tmp_renamed_log, path)) {
1213                 /*
1214                  * rename(a, b) when b is an existing directory ought
1215                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1216                  * Sheesh. Record the true errno for error reporting,
1217                  * but report EISDIR to raceproof_create_file() so
1218                  * that it knows to retry.
1219                  */
1220                 cb->true_errno = errno;
1221                 if (errno == ENOTDIR)
1222                         errno = EISDIR;
1223                 return -1;
1224         } else {
1225                 return 0;
1226         }
1227 }
1228
1229 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1230 {
1231         struct strbuf path = STRBUF_INIT;
1232         struct strbuf tmp = STRBUF_INIT;
1233         struct rename_cb cb;
1234         int ret;
1235
1236         files_reflog_path(refs, &path, newrefname);
1237         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1238         cb.tmp_renamed_log = tmp.buf;
1239         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1240         if (ret) {
1241                 if (errno == EISDIR)
1242                         error("directory not empty: %s", path.buf);
1243                 else
1244                         error("unable to move logfile %s to %s: %s",
1245                               tmp.buf, path.buf,
1246                               strerror(cb.true_errno));
1247         }
1248
1249         strbuf_release(&path);
1250         strbuf_release(&tmp);
1251         return ret;
1252 }
1253
1254 static int write_ref_to_lockfile(struct ref_lock *lock,
1255                                  const struct object_id *oid, struct strbuf *err);
1256 static int commit_ref_update(struct files_ref_store *refs,
1257                              struct ref_lock *lock,
1258                              const struct object_id *oid, const char *logmsg,
1259                              struct strbuf *err);
1260
1261 static int files_copy_or_rename_ref(struct ref_store *ref_store,
1262                             const char *oldrefname, const char *newrefname,
1263                             const char *logmsg, int copy)
1264 {
1265         struct files_ref_store *refs =
1266                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1267         struct object_id oid, orig_oid;
1268         int flag = 0, logmoved = 0;
1269         struct ref_lock *lock;
1270         struct stat loginfo;
1271         struct strbuf sb_oldref = STRBUF_INIT;
1272         struct strbuf sb_newref = STRBUF_INIT;
1273         struct strbuf tmp_renamed_log = STRBUF_INIT;
1274         int log, ret;
1275         struct strbuf err = STRBUF_INIT;
1276
1277         files_reflog_path(refs, &sb_oldref, oldrefname);
1278         files_reflog_path(refs, &sb_newref, newrefname);
1279         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1280
1281         log = !lstat(sb_oldref.buf, &loginfo);
1282         if (log && S_ISLNK(loginfo.st_mode)) {
1283                 ret = error("reflog for %s is a symlink", oldrefname);
1284                 goto out;
1285         }
1286
1287         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1288                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1289                                 orig_oid.hash, &flag)) {
1290                 ret = error("refname %s not found", oldrefname);
1291                 goto out;
1292         }
1293
1294         if (flag & REF_ISSYMREF) {
1295                 if (copy)
1296                         ret = error("refname %s is a symbolic ref, copying it is not supported",
1297                                     oldrefname);
1298                 else
1299                         ret = error("refname %s is a symbolic ref, renaming it is not supported",
1300                                     oldrefname);
1301                 goto out;
1302         }
1303         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1304                 ret = 1;
1305                 goto out;
1306         }
1307
1308         if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1309                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1310                             oldrefname, strerror(errno));
1311                 goto out;
1312         }
1313
1314         if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1315                 ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1316                             oldrefname, strerror(errno));
1317                 goto out;
1318         }
1319
1320         if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1321                             orig_oid.hash, REF_NODEREF)) {
1322                 error("unable to delete old %s", oldrefname);
1323                 goto rollback;
1324         }
1325
1326         /*
1327          * Since we are doing a shallow lookup, oid is not the
1328          * correct value to pass to delete_ref as old_oid. But that
1329          * doesn't matter, because an old_oid check wouldn't add to
1330          * the safety anyway; we want to delete the reference whatever
1331          * its current value.
1332          */
1333         if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1334                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1335                                 oid.hash, NULL) &&
1336             refs_delete_ref(&refs->base, NULL, newrefname,
1337                             NULL, REF_NODEREF)) {
1338                 if (errno == EISDIR) {
1339                         struct strbuf path = STRBUF_INIT;
1340                         int result;
1341
1342                         files_ref_path(refs, &path, newrefname);
1343                         result = remove_empty_directories(&path);
1344                         strbuf_release(&path);
1345
1346                         if (result) {
1347                                 error("Directory not empty: %s", newrefname);
1348                                 goto rollback;
1349                         }
1350                 } else {
1351                         error("unable to delete existing %s", newrefname);
1352                         goto rollback;
1353                 }
1354         }
1355
1356         if (log && rename_tmp_log(refs, newrefname))
1357                 goto rollback;
1358
1359         logmoved = log;
1360
1361         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
1362                                    REF_NODEREF, NULL, &err);
1363         if (!lock) {
1364                 if (copy)
1365                         error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1366                 else
1367                         error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1368                 strbuf_release(&err);
1369                 goto rollback;
1370         }
1371         oidcpy(&lock->old_oid, &orig_oid);
1372
1373         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1374             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1375                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1376                 strbuf_release(&err);
1377                 goto rollback;
1378         }
1379
1380         ret = 0;
1381         goto out;
1382
1383  rollback:
1384         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
1385                                    REF_NODEREF, NULL, &err);
1386         if (!lock) {
1387                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1388                 strbuf_release(&err);
1389                 goto rollbacklog;
1390         }
1391
1392         flag = log_all_ref_updates;
1393         log_all_ref_updates = LOG_REFS_NONE;
1394         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1395             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1396                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1397                 strbuf_release(&err);
1398         }
1399         log_all_ref_updates = flag;
1400
1401  rollbacklog:
1402         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1403                 error("unable to restore logfile %s from %s: %s",
1404                         oldrefname, newrefname, strerror(errno));
1405         if (!logmoved && log &&
1406             rename(tmp_renamed_log.buf, sb_oldref.buf))
1407                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1408                         oldrefname, strerror(errno));
1409         ret = 1;
1410  out:
1411         strbuf_release(&sb_newref);
1412         strbuf_release(&sb_oldref);
1413         strbuf_release(&tmp_renamed_log);
1414
1415         return ret;
1416 }
1417
1418 static int files_rename_ref(struct ref_store *ref_store,
1419                             const char *oldrefname, const char *newrefname,
1420                             const char *logmsg)
1421 {
1422         return files_copy_or_rename_ref(ref_store, oldrefname,
1423                                  newrefname, logmsg, 0);
1424 }
1425
1426 static int files_copy_ref(struct ref_store *ref_store,
1427                             const char *oldrefname, const char *newrefname,
1428                             const char *logmsg)
1429 {
1430         return files_copy_or_rename_ref(ref_store, oldrefname,
1431                                  newrefname, logmsg, 1);
1432 }
1433
1434 static int close_ref_gently(struct ref_lock *lock)
1435 {
1436         if (close_lock_file_gently(&lock->lk))
1437                 return -1;
1438         return 0;
1439 }
1440
1441 static int commit_ref(struct ref_lock *lock)
1442 {
1443         char *path = get_locked_file_path(&lock->lk);
1444         struct stat st;
1445
1446         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1447                 /*
1448                  * There is a directory at the path we want to rename
1449                  * the lockfile to. Hopefully it is empty; try to
1450                  * delete it.
1451                  */
1452                 size_t len = strlen(path);
1453                 struct strbuf sb_path = STRBUF_INIT;
1454
1455                 strbuf_attach(&sb_path, path, len, len);
1456
1457                 /*
1458                  * If this fails, commit_lock_file() will also fail
1459                  * and will report the problem.
1460                  */
1461                 remove_empty_directories(&sb_path);
1462                 strbuf_release(&sb_path);
1463         } else {
1464                 free(path);
1465         }
1466
1467         if (commit_lock_file(&lock->lk))
1468                 return -1;
1469         return 0;
1470 }
1471
1472 static int open_or_create_logfile(const char *path, void *cb)
1473 {
1474         int *fd = cb;
1475
1476         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1477         return (*fd < 0) ? -1 : 0;
1478 }
1479
1480 /*
1481  * Create a reflog for a ref. If force_create = 0, only create the
1482  * reflog for certain refs (those for which should_autocreate_reflog
1483  * returns non-zero). Otherwise, create it regardless of the reference
1484  * name. If the logfile already existed or was created, return 0 and
1485  * set *logfd to the file descriptor opened for appending to the file.
1486  * If no logfile exists and we decided not to create one, return 0 and
1487  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1488  * return -1.
1489  */
1490 static int log_ref_setup(struct files_ref_store *refs,
1491                          const char *refname, int force_create,
1492                          int *logfd, struct strbuf *err)
1493 {
1494         struct strbuf logfile_sb = STRBUF_INIT;
1495         char *logfile;
1496
1497         files_reflog_path(refs, &logfile_sb, refname);
1498         logfile = strbuf_detach(&logfile_sb, NULL);
1499
1500         if (force_create || should_autocreate_reflog(refname)) {
1501                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1502                         if (errno == ENOENT)
1503                                 strbuf_addf(err, "unable to create directory for '%s': "
1504                                             "%s", logfile, strerror(errno));
1505                         else if (errno == EISDIR)
1506                                 strbuf_addf(err, "there are still logs under '%s'",
1507                                             logfile);
1508                         else
1509                                 strbuf_addf(err, "unable to append to '%s': %s",
1510                                             logfile, strerror(errno));
1511
1512                         goto error;
1513                 }
1514         } else {
1515                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1516                 if (*logfd < 0) {
1517                         if (errno == ENOENT || errno == EISDIR) {
1518                                 /*
1519                                  * The logfile doesn't already exist,
1520                                  * but that is not an error; it only
1521                                  * means that we won't write log
1522                                  * entries to it.
1523                                  */
1524                                 ;
1525                         } else {
1526                                 strbuf_addf(err, "unable to append to '%s': %s",
1527                                             logfile, strerror(errno));
1528                                 goto error;
1529                         }
1530                 }
1531         }
1532
1533         if (*logfd >= 0)
1534                 adjust_shared_perm(logfile);
1535
1536         free(logfile);
1537         return 0;
1538
1539 error:
1540         free(logfile);
1541         return -1;
1542 }
1543
1544 static int files_create_reflog(struct ref_store *ref_store,
1545                                const char *refname, int force_create,
1546                                struct strbuf *err)
1547 {
1548         struct files_ref_store *refs =
1549                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1550         int fd;
1551
1552         if (log_ref_setup(refs, refname, force_create, &fd, err))
1553                 return -1;
1554
1555         if (fd >= 0)
1556                 close(fd);
1557
1558         return 0;
1559 }
1560
1561 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1562                             const struct object_id *new_oid,
1563                             const char *committer, const char *msg)
1564 {
1565         int msglen, written;
1566         unsigned maxlen, len;
1567         char *logrec;
1568
1569         msglen = msg ? strlen(msg) : 0;
1570         maxlen = strlen(committer) + msglen + 100;
1571         logrec = xmalloc(maxlen);
1572         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1573                         oid_to_hex(old_oid),
1574                         oid_to_hex(new_oid),
1575                         committer);
1576         if (msglen)
1577                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1578
1579         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1580         free(logrec);
1581         if (written < 0)
1582                 return -1;
1583
1584         return 0;
1585 }
1586
1587 static int files_log_ref_write(struct files_ref_store *refs,
1588                                const char *refname, const struct object_id *old_oid,
1589                                const struct object_id *new_oid, const char *msg,
1590                                int flags, struct strbuf *err)
1591 {
1592         int logfd, result;
1593
1594         if (log_all_ref_updates == LOG_REFS_UNSET)
1595                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1596
1597         result = log_ref_setup(refs, refname,
1598                                flags & REF_FORCE_CREATE_REFLOG,
1599                                &logfd, err);
1600
1601         if (result)
1602                 return result;
1603
1604         if (logfd < 0)
1605                 return 0;
1606         result = log_ref_write_fd(logfd, old_oid, new_oid,
1607                                   git_committer_info(0), msg);
1608         if (result) {
1609                 struct strbuf sb = STRBUF_INIT;
1610                 int save_errno = errno;
1611
1612                 files_reflog_path(refs, &sb, refname);
1613                 strbuf_addf(err, "unable to append to '%s': %s",
1614                             sb.buf, strerror(save_errno));
1615                 strbuf_release(&sb);
1616                 close(logfd);
1617                 return -1;
1618         }
1619         if (close(logfd)) {
1620                 struct strbuf sb = STRBUF_INIT;
1621                 int save_errno = errno;
1622
1623                 files_reflog_path(refs, &sb, refname);
1624                 strbuf_addf(err, "unable to append to '%s': %s",
1625                             sb.buf, strerror(save_errno));
1626                 strbuf_release(&sb);
1627                 return -1;
1628         }
1629         return 0;
1630 }
1631
1632 /*
1633  * Write sha1 into the open lockfile, then close the lockfile. On
1634  * errors, rollback the lockfile, fill in *err and
1635  * return -1.
1636  */
1637 static int write_ref_to_lockfile(struct ref_lock *lock,
1638                                  const struct object_id *oid, struct strbuf *err)
1639 {
1640         static char term = '\n';
1641         struct object *o;
1642         int fd;
1643
1644         o = parse_object(oid);
1645         if (!o) {
1646                 strbuf_addf(err,
1647                             "trying to write ref '%s' with nonexistent object %s",
1648                             lock->ref_name, oid_to_hex(oid));
1649                 unlock_ref(lock);
1650                 return -1;
1651         }
1652         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1653                 strbuf_addf(err,
1654                             "trying to write non-commit object %s to branch '%s'",
1655                             oid_to_hex(oid), lock->ref_name);
1656                 unlock_ref(lock);
1657                 return -1;
1658         }
1659         fd = get_lock_file_fd(&lock->lk);
1660         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1661             write_in_full(fd, &term, 1) < 0 ||
1662             close_ref_gently(lock) < 0) {
1663                 strbuf_addf(err,
1664                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1665                 unlock_ref(lock);
1666                 return -1;
1667         }
1668         return 0;
1669 }
1670
1671 /*
1672  * Commit a change to a loose reference that has already been written
1673  * to the loose reference lockfile. Also update the reflogs if
1674  * necessary, using the specified lockmsg (which can be NULL).
1675  */
1676 static int commit_ref_update(struct files_ref_store *refs,
1677                              struct ref_lock *lock,
1678                              const struct object_id *oid, const char *logmsg,
1679                              struct strbuf *err)
1680 {
1681         files_assert_main_repository(refs, "commit_ref_update");
1682
1683         clear_loose_ref_cache(refs);
1684         if (files_log_ref_write(refs, lock->ref_name,
1685                                 &lock->old_oid, oid,
1686                                 logmsg, 0, err)) {
1687                 char *old_msg = strbuf_detach(err, NULL);
1688                 strbuf_addf(err, "cannot update the ref '%s': %s",
1689                             lock->ref_name, old_msg);
1690                 free(old_msg);
1691                 unlock_ref(lock);
1692                 return -1;
1693         }
1694
1695         if (strcmp(lock->ref_name, "HEAD") != 0) {
1696                 /*
1697                  * Special hack: If a branch is updated directly and HEAD
1698                  * points to it (may happen on the remote side of a push
1699                  * for example) then logically the HEAD reflog should be
1700                  * updated too.
1701                  * A generic solution implies reverse symref information,
1702                  * but finding all symrefs pointing to the given branch
1703                  * would be rather costly for this rare event (the direct
1704                  * update of a branch) to be worth it.  So let's cheat and
1705                  * check with HEAD only which should cover 99% of all usage
1706                  * scenarios (even 100% of the default ones).
1707                  */
1708                 int head_flag;
1709                 const char *head_ref;
1710
1711                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1712                                                    RESOLVE_REF_READING,
1713                                                    NULL, &head_flag);
1714                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1715                     !strcmp(head_ref, lock->ref_name)) {
1716                         struct strbuf log_err = STRBUF_INIT;
1717                         if (files_log_ref_write(refs, "HEAD",
1718                                                 &lock->old_oid, oid,
1719                                                 logmsg, 0, &log_err)) {
1720                                 error("%s", log_err.buf);
1721                                 strbuf_release(&log_err);
1722                         }
1723                 }
1724         }
1725
1726         if (commit_ref(lock)) {
1727                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1728                 unlock_ref(lock);
1729                 return -1;
1730         }
1731
1732         unlock_ref(lock);
1733         return 0;
1734 }
1735
1736 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1737 {
1738         int ret = -1;
1739 #ifndef NO_SYMLINK_HEAD
1740         char *ref_path = get_locked_file_path(&lock->lk);
1741         unlink(ref_path);
1742         ret = symlink(target, ref_path);
1743         free(ref_path);
1744
1745         if (ret)
1746                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1747 #endif
1748         return ret;
1749 }
1750
1751 static void update_symref_reflog(struct files_ref_store *refs,
1752                                  struct ref_lock *lock, const char *refname,
1753                                  const char *target, const char *logmsg)
1754 {
1755         struct strbuf err = STRBUF_INIT;
1756         struct object_id new_oid;
1757         if (logmsg &&
1758             !refs_read_ref_full(&refs->base, target,
1759                                 RESOLVE_REF_READING, new_oid.hash, NULL) &&
1760             files_log_ref_write(refs, refname, &lock->old_oid,
1761                                 &new_oid, logmsg, 0, &err)) {
1762                 error("%s", err.buf);
1763                 strbuf_release(&err);
1764         }
1765 }
1766
1767 static int create_symref_locked(struct files_ref_store *refs,
1768                                 struct ref_lock *lock, const char *refname,
1769                                 const char *target, const char *logmsg)
1770 {
1771         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1772                 update_symref_reflog(refs, lock, refname, target, logmsg);
1773                 return 0;
1774         }
1775
1776         if (!fdopen_lock_file(&lock->lk, "w"))
1777                 return error("unable to fdopen %s: %s",
1778                              lock->lk.tempfile->filename.buf, strerror(errno));
1779
1780         update_symref_reflog(refs, lock, refname, target, logmsg);
1781
1782         /* no error check; commit_ref will check ferror */
1783         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1784         if (commit_ref(lock) < 0)
1785                 return error("unable to write symref for %s: %s", refname,
1786                              strerror(errno));
1787         return 0;
1788 }
1789
1790 static int files_create_symref(struct ref_store *ref_store,
1791                                const char *refname, const char *target,
1792                                const char *logmsg)
1793 {
1794         struct files_ref_store *refs =
1795                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1796         struct strbuf err = STRBUF_INIT;
1797         struct ref_lock *lock;
1798         int ret;
1799
1800         lock = lock_ref_sha1_basic(refs, refname, NULL,
1801                                    NULL, NULL, REF_NODEREF, NULL,
1802                                    &err);
1803         if (!lock) {
1804                 error("%s", err.buf);
1805                 strbuf_release(&err);
1806                 return -1;
1807         }
1808
1809         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1810         unlock_ref(lock);
1811         return ret;
1812 }
1813
1814 static int files_reflog_exists(struct ref_store *ref_store,
1815                                const char *refname)
1816 {
1817         struct files_ref_store *refs =
1818                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1819         struct strbuf sb = STRBUF_INIT;
1820         struct stat st;
1821         int ret;
1822
1823         files_reflog_path(refs, &sb, refname);
1824         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1825         strbuf_release(&sb);
1826         return ret;
1827 }
1828
1829 static int files_delete_reflog(struct ref_store *ref_store,
1830                                const char *refname)
1831 {
1832         struct files_ref_store *refs =
1833                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1834         struct strbuf sb = STRBUF_INIT;
1835         int ret;
1836
1837         files_reflog_path(refs, &sb, refname);
1838         ret = remove_path(sb.buf);
1839         strbuf_release(&sb);
1840         return ret;
1841 }
1842
1843 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1844 {
1845         struct object_id ooid, noid;
1846         char *email_end, *message;
1847         timestamp_t timestamp;
1848         int tz;
1849         const char *p = sb->buf;
1850
1851         /* old SP new SP name <email> SP time TAB msg LF */
1852         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1853             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1854             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1855             !(email_end = strchr(p, '>')) ||
1856             email_end[1] != ' ' ||
1857             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1858             !message || message[0] != ' ' ||
1859             (message[1] != '+' && message[1] != '-') ||
1860             !isdigit(message[2]) || !isdigit(message[3]) ||
1861             !isdigit(message[4]) || !isdigit(message[5]))
1862                 return 0; /* corrupt? */
1863         email_end[1] = '\0';
1864         tz = strtol(message + 1, NULL, 10);
1865         if (message[6] != '\t')
1866                 message += 6;
1867         else
1868                 message += 7;
1869         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1870 }
1871
1872 static char *find_beginning_of_line(char *bob, char *scan)
1873 {
1874         while (bob < scan && *(--scan) != '\n')
1875                 ; /* keep scanning backwards */
1876         /*
1877          * Return either beginning of the buffer, or LF at the end of
1878          * the previous line.
1879          */
1880         return scan;
1881 }
1882
1883 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1884                                              const char *refname,
1885                                              each_reflog_ent_fn fn,
1886                                              void *cb_data)
1887 {
1888         struct files_ref_store *refs =
1889                 files_downcast(ref_store, REF_STORE_READ,
1890                                "for_each_reflog_ent_reverse");
1891         struct strbuf sb = STRBUF_INIT;
1892         FILE *logfp;
1893         long pos;
1894         int ret = 0, at_tail = 1;
1895
1896         files_reflog_path(refs, &sb, refname);
1897         logfp = fopen(sb.buf, "r");
1898         strbuf_release(&sb);
1899         if (!logfp)
1900                 return -1;
1901
1902         /* Jump to the end */
1903         if (fseek(logfp, 0, SEEK_END) < 0)
1904                 ret = error("cannot seek back reflog for %s: %s",
1905                             refname, strerror(errno));
1906         pos = ftell(logfp);
1907         while (!ret && 0 < pos) {
1908                 int cnt;
1909                 size_t nread;
1910                 char buf[BUFSIZ];
1911                 char *endp, *scanp;
1912
1913                 /* Fill next block from the end */
1914                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1915                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1916                         ret = error("cannot seek back reflog for %s: %s",
1917                                     refname, strerror(errno));
1918                         break;
1919                 }
1920                 nread = fread(buf, cnt, 1, logfp);
1921                 if (nread != 1) {
1922                         ret = error("cannot read %d bytes from reflog for %s: %s",
1923                                     cnt, refname, strerror(errno));
1924                         break;
1925                 }
1926                 pos -= cnt;
1927
1928                 scanp = endp = buf + cnt;
1929                 if (at_tail && scanp[-1] == '\n')
1930                         /* Looking at the final LF at the end of the file */
1931                         scanp--;
1932                 at_tail = 0;
1933
1934                 while (buf < scanp) {
1935                         /*
1936                          * terminating LF of the previous line, or the beginning
1937                          * of the buffer.
1938                          */
1939                         char *bp;
1940
1941                         bp = find_beginning_of_line(buf, scanp);
1942
1943                         if (*bp == '\n') {
1944                                 /*
1945                                  * The newline is the end of the previous line,
1946                                  * so we know we have complete line starting
1947                                  * at (bp + 1). Prefix it onto any prior data
1948                                  * we collected for the line and process it.
1949                                  */
1950                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1951                                 scanp = bp;
1952                                 endp = bp + 1;
1953                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1954                                 strbuf_reset(&sb);
1955                                 if (ret)
1956                                         break;
1957                         } else if (!pos) {
1958                                 /*
1959                                  * We are at the start of the buffer, and the
1960                                  * start of the file; there is no previous
1961                                  * line, and we have everything for this one.
1962                                  * Process it, and we can end the loop.
1963                                  */
1964                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1965                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1966                                 strbuf_reset(&sb);
1967                                 break;
1968                         }
1969
1970                         if (bp == buf) {
1971                                 /*
1972                                  * We are at the start of the buffer, and there
1973                                  * is more file to read backwards. Which means
1974                                  * we are in the middle of a line. Note that we
1975                                  * may get here even if *bp was a newline; that
1976                                  * just means we are at the exact end of the
1977                                  * previous line, rather than some spot in the
1978                                  * middle.
1979                                  *
1980                                  * Save away what we have to be combined with
1981                                  * the data from the next read.
1982                                  */
1983                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1984                                 break;
1985                         }
1986                 }
1987
1988         }
1989         if (!ret && sb.len)
1990                 die("BUG: reverse reflog parser had leftover data");
1991
1992         fclose(logfp);
1993         strbuf_release(&sb);
1994         return ret;
1995 }
1996
1997 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1998                                      const char *refname,
1999                                      each_reflog_ent_fn fn, void *cb_data)
2000 {
2001         struct files_ref_store *refs =
2002                 files_downcast(ref_store, REF_STORE_READ,
2003                                "for_each_reflog_ent");
2004         FILE *logfp;
2005         struct strbuf sb = STRBUF_INIT;
2006         int ret = 0;
2007
2008         files_reflog_path(refs, &sb, refname);
2009         logfp = fopen(sb.buf, "r");
2010         strbuf_release(&sb);
2011         if (!logfp)
2012                 return -1;
2013
2014         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2015                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2016         fclose(logfp);
2017         strbuf_release(&sb);
2018         return ret;
2019 }
2020
2021 struct files_reflog_iterator {
2022         struct ref_iterator base;
2023
2024         struct ref_store *ref_store;
2025         struct dir_iterator *dir_iterator;
2026         struct object_id oid;
2027 };
2028
2029 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2030 {
2031         struct files_reflog_iterator *iter =
2032                 (struct files_reflog_iterator *)ref_iterator;
2033         struct dir_iterator *diter = iter->dir_iterator;
2034         int ok;
2035
2036         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2037                 int flags;
2038
2039                 if (!S_ISREG(diter->st.st_mode))
2040                         continue;
2041                 if (diter->basename[0] == '.')
2042                         continue;
2043                 if (ends_with(diter->basename, ".lock"))
2044                         continue;
2045
2046                 if (refs_read_ref_full(iter->ref_store,
2047                                        diter->relative_path, 0,
2048                                        iter->oid.hash, &flags)) {
2049                         error("bad ref for %s", diter->path.buf);
2050                         continue;
2051                 }
2052
2053                 iter->base.refname = diter->relative_path;
2054                 iter->base.oid = &iter->oid;
2055                 iter->base.flags = flags;
2056                 return ITER_OK;
2057         }
2058
2059         iter->dir_iterator = NULL;
2060         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2061                 ok = ITER_ERROR;
2062         return ok;
2063 }
2064
2065 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2066                                    struct object_id *peeled)
2067 {
2068         die("BUG: ref_iterator_peel() called for reflog_iterator");
2069 }
2070
2071 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2072 {
2073         struct files_reflog_iterator *iter =
2074                 (struct files_reflog_iterator *)ref_iterator;
2075         int ok = ITER_DONE;
2076
2077         if (iter->dir_iterator)
2078                 ok = dir_iterator_abort(iter->dir_iterator);
2079
2080         base_ref_iterator_free(ref_iterator);
2081         return ok;
2082 }
2083
2084 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2085         files_reflog_iterator_advance,
2086         files_reflog_iterator_peel,
2087         files_reflog_iterator_abort
2088 };
2089
2090 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2091                                                   const char *gitdir)
2092 {
2093         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2094         struct ref_iterator *ref_iterator = &iter->base;
2095         struct strbuf sb = STRBUF_INIT;
2096
2097         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
2098         strbuf_addf(&sb, "%s/logs", gitdir);
2099         iter->dir_iterator = dir_iterator_begin(sb.buf);
2100         iter->ref_store = ref_store;
2101         strbuf_release(&sb);
2102
2103         return ref_iterator;
2104 }
2105
2106 static enum iterator_selection reflog_iterator_select(
2107         struct ref_iterator *iter_worktree,
2108         struct ref_iterator *iter_common,
2109         void *cb_data)
2110 {
2111         if (iter_worktree) {
2112                 /*
2113                  * We're a bit loose here. We probably should ignore
2114                  * common refs if they are accidentally added as
2115                  * per-worktree refs.
2116                  */
2117                 return ITER_SELECT_0;
2118         } else if (iter_common) {
2119                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2120                         return ITER_SELECT_1;
2121
2122                 /*
2123                  * The main ref store may contain main worktree's
2124                  * per-worktree refs, which should be ignored
2125                  */
2126                 return ITER_SKIP_1;
2127         } else
2128                 return ITER_DONE;
2129 }
2130
2131 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2132 {
2133         struct files_ref_store *refs =
2134                 files_downcast(ref_store, REF_STORE_READ,
2135                                "reflog_iterator_begin");
2136
2137         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2138                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2139         } else {
2140                 return merge_ref_iterator_begin(
2141                         reflog_iterator_begin(ref_store, refs->gitdir),
2142                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2143                         reflog_iterator_select, refs);
2144         }
2145 }
2146
2147 /*
2148  * If update is a direct update of head_ref (the reference pointed to
2149  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2150  */
2151 static int split_head_update(struct ref_update *update,
2152                              struct ref_transaction *transaction,
2153                              const char *head_ref,
2154                              struct string_list *affected_refnames,
2155                              struct strbuf *err)
2156 {
2157         struct string_list_item *item;
2158         struct ref_update *new_update;
2159
2160         if ((update->flags & REF_LOG_ONLY) ||
2161             (update->flags & REF_ISPRUNING) ||
2162             (update->flags & REF_UPDATE_VIA_HEAD))
2163                 return 0;
2164
2165         if (strcmp(update->refname, head_ref))
2166                 return 0;
2167
2168         /*
2169          * First make sure that HEAD is not already in the
2170          * transaction. This check is O(lg N) in the transaction
2171          * size, but it happens at most once per transaction.
2172          */
2173         if (string_list_has_string(affected_refnames, "HEAD")) {
2174                 /* An entry already existed */
2175                 strbuf_addf(err,
2176                             "multiple updates for 'HEAD' (including one "
2177                             "via its referent '%s') are not allowed",
2178                             update->refname);
2179                 return TRANSACTION_NAME_CONFLICT;
2180         }
2181
2182         new_update = ref_transaction_add_update(
2183                         transaction, "HEAD",
2184                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2185                         update->new_oid.hash, update->old_oid.hash,
2186                         update->msg);
2187
2188         /*
2189          * Add "HEAD". This insertion is O(N) in the transaction
2190          * size, but it happens at most once per transaction.
2191          * Add new_update->refname instead of a literal "HEAD".
2192          */
2193         if (strcmp(new_update->refname, "HEAD"))
2194                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2195         item = string_list_insert(affected_refnames, new_update->refname);
2196         item->util = new_update;
2197
2198         return 0;
2199 }
2200
2201 /*
2202  * update is for a symref that points at referent and doesn't have
2203  * REF_NODEREF set. Split it into two updates:
2204  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2205  * - A new, separate update for the referent reference
2206  * Note that the new update will itself be subject to splitting when
2207  * the iteration gets to it.
2208  */
2209 static int split_symref_update(struct files_ref_store *refs,
2210                                struct ref_update *update,
2211                                const char *referent,
2212                                struct ref_transaction *transaction,
2213                                struct string_list *affected_refnames,
2214                                struct strbuf *err)
2215 {
2216         struct string_list_item *item;
2217         struct ref_update *new_update;
2218         unsigned int new_flags;
2219
2220         /*
2221          * First make sure that referent is not already in the
2222          * transaction. This check is O(lg N) in the transaction
2223          * size, but it happens at most once per symref in a
2224          * transaction.
2225          */
2226         if (string_list_has_string(affected_refnames, referent)) {
2227                 /* An entry already exists */
2228                 strbuf_addf(err,
2229                             "multiple updates for '%s' (including one "
2230                             "via symref '%s') are not allowed",
2231                             referent, update->refname);
2232                 return TRANSACTION_NAME_CONFLICT;
2233         }
2234
2235         new_flags = update->flags;
2236         if (!strcmp(update->refname, "HEAD")) {
2237                 /*
2238                  * Record that the new update came via HEAD, so that
2239                  * when we process it, split_head_update() doesn't try
2240                  * to add another reflog update for HEAD. Note that
2241                  * this bit will be propagated if the new_update
2242                  * itself needs to be split.
2243                  */
2244                 new_flags |= REF_UPDATE_VIA_HEAD;
2245         }
2246
2247         new_update = ref_transaction_add_update(
2248                         transaction, referent, new_flags,
2249                         update->new_oid.hash, update->old_oid.hash,
2250                         update->msg);
2251
2252         new_update->parent_update = update;
2253
2254         /*
2255          * Change the symbolic ref update to log only. Also, it
2256          * doesn't need to check its old SHA-1 value, as that will be
2257          * done when new_update is processed.
2258          */
2259         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2260         update->flags &= ~REF_HAVE_OLD;
2261
2262         /*
2263          * Add the referent. This insertion is O(N) in the transaction
2264          * size, but it happens at most once per symref in a
2265          * transaction. Make sure to add new_update->refname, which will
2266          * be valid as long as affected_refnames is in use, and NOT
2267          * referent, which might soon be freed by our caller.
2268          */
2269         item = string_list_insert(affected_refnames, new_update->refname);
2270         if (item->util)
2271                 BUG("%s unexpectedly found in affected_refnames",
2272                     new_update->refname);
2273         item->util = new_update;
2274
2275         return 0;
2276 }
2277
2278 /*
2279  * Return the refname under which update was originally requested.
2280  */
2281 static const char *original_update_refname(struct ref_update *update)
2282 {
2283         while (update->parent_update)
2284                 update = update->parent_update;
2285
2286         return update->refname;
2287 }
2288
2289 /*
2290  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2291  * are consistent with oid, which is the reference's current value. If
2292  * everything is OK, return 0; otherwise, write an error message to
2293  * err and return -1.
2294  */
2295 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2296                          struct strbuf *err)
2297 {
2298         if (!(update->flags & REF_HAVE_OLD) ||
2299                    !oidcmp(oid, &update->old_oid))
2300                 return 0;
2301
2302         if (is_null_oid(&update->old_oid))
2303                 strbuf_addf(err, "cannot lock ref '%s': "
2304                             "reference already exists",
2305                             original_update_refname(update));
2306         else if (is_null_oid(oid))
2307                 strbuf_addf(err, "cannot lock ref '%s': "
2308                             "reference is missing but expected %s",
2309                             original_update_refname(update),
2310                             oid_to_hex(&update->old_oid));
2311         else
2312                 strbuf_addf(err, "cannot lock ref '%s': "
2313                             "is at %s but expected %s",
2314                             original_update_refname(update),
2315                             oid_to_hex(oid),
2316                             oid_to_hex(&update->old_oid));
2317
2318         return -1;
2319 }
2320
2321 /*
2322  * Prepare for carrying out update:
2323  * - Lock the reference referred to by update.
2324  * - Read the reference under lock.
2325  * - Check that its old SHA-1 value (if specified) is correct, and in
2326  *   any case record it in update->lock->old_oid for later use when
2327  *   writing the reflog.
2328  * - If it is a symref update without REF_NODEREF, split it up into a
2329  *   REF_LOG_ONLY update of the symref and add a separate update for
2330  *   the referent to transaction.
2331  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2332  *   update of HEAD.
2333  */
2334 static int lock_ref_for_update(struct files_ref_store *refs,
2335                                struct ref_update *update,
2336                                struct ref_transaction *transaction,
2337                                const char *head_ref,
2338                                struct string_list *affected_refnames,
2339                                struct strbuf *err)
2340 {
2341         struct strbuf referent = STRBUF_INIT;
2342         int mustexist = (update->flags & REF_HAVE_OLD) &&
2343                 !is_null_oid(&update->old_oid);
2344         int ret = 0;
2345         struct ref_lock *lock;
2346
2347         files_assert_main_repository(refs, "lock_ref_for_update");
2348
2349         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2350                 update->flags |= REF_DELETING;
2351
2352         if (head_ref) {
2353                 ret = split_head_update(update, transaction, head_ref,
2354                                         affected_refnames, err);
2355                 if (ret)
2356                         goto out;
2357         }
2358
2359         ret = lock_raw_ref(refs, update->refname, mustexist,
2360                            affected_refnames, NULL,
2361                            &lock, &referent,
2362                            &update->type, err);
2363         if (ret) {
2364                 char *reason;
2365
2366                 reason = strbuf_detach(err, NULL);
2367                 strbuf_addf(err, "cannot lock ref '%s': %s",
2368                             original_update_refname(update), reason);
2369                 free(reason);
2370                 goto out;
2371         }
2372
2373         update->backend_data = lock;
2374
2375         if (update->type & REF_ISSYMREF) {
2376                 if (update->flags & REF_NODEREF) {
2377                         /*
2378                          * We won't be reading the referent as part of
2379                          * the transaction, so we have to read it here
2380                          * to record and possibly check old_sha1:
2381                          */
2382                         if (refs_read_ref_full(&refs->base,
2383                                                referent.buf, 0,
2384                                                lock->old_oid.hash, NULL)) {
2385                                 if (update->flags & REF_HAVE_OLD) {
2386                                         strbuf_addf(err, "cannot lock ref '%s': "
2387                                                     "error reading reference",
2388                                                     original_update_refname(update));
2389                                         ret = TRANSACTION_GENERIC_ERROR;
2390                                         goto out;
2391                                 }
2392                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2393                                 ret = TRANSACTION_GENERIC_ERROR;
2394                                 goto out;
2395                         }
2396                 } else {
2397                         /*
2398                          * Create a new update for the reference this
2399                          * symref is pointing at. Also, we will record
2400                          * and verify old_sha1 for this update as part
2401                          * of processing the split-off update, so we
2402                          * don't have to do it here.
2403                          */
2404                         ret = split_symref_update(refs, update,
2405                                                   referent.buf, transaction,
2406                                                   affected_refnames, err);
2407                         if (ret)
2408                                 goto out;
2409                 }
2410         } else {
2411                 struct ref_update *parent_update;
2412
2413                 if (check_old_oid(update, &lock->old_oid, err)) {
2414                         ret = TRANSACTION_GENERIC_ERROR;
2415                         goto out;
2416                 }
2417
2418                 /*
2419                  * If this update is happening indirectly because of a
2420                  * symref update, record the old SHA-1 in the parent
2421                  * update:
2422                  */
2423                 for (parent_update = update->parent_update;
2424                      parent_update;
2425                      parent_update = parent_update->parent_update) {
2426                         struct ref_lock *parent_lock = parent_update->backend_data;
2427                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2428                 }
2429         }
2430
2431         if ((update->flags & REF_HAVE_NEW) &&
2432             !(update->flags & REF_DELETING) &&
2433             !(update->flags & REF_LOG_ONLY)) {
2434                 if (!(update->type & REF_ISSYMREF) &&
2435                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2436                         /*
2437                          * The reference already has the desired
2438                          * value, so we don't need to write it.
2439                          */
2440                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2441                                                  err)) {
2442                         char *write_err = strbuf_detach(err, NULL);
2443
2444                         /*
2445                          * The lock was freed upon failure of
2446                          * write_ref_to_lockfile():
2447                          */
2448                         update->backend_data = NULL;
2449                         strbuf_addf(err,
2450                                     "cannot update ref '%s': %s",
2451                                     update->refname, write_err);
2452                         free(write_err);
2453                         ret = TRANSACTION_GENERIC_ERROR;
2454                         goto out;
2455                 } else {
2456                         update->flags |= REF_NEEDS_COMMIT;
2457                 }
2458         }
2459         if (!(update->flags & REF_NEEDS_COMMIT)) {
2460                 /*
2461                  * We didn't call write_ref_to_lockfile(), so
2462                  * the lockfile is still open. Close it to
2463                  * free up the file descriptor:
2464                  */
2465                 if (close_ref_gently(lock)) {
2466                         strbuf_addf(err, "couldn't close '%s.lock'",
2467                                     update->refname);
2468                         ret = TRANSACTION_GENERIC_ERROR;
2469                         goto out;
2470                 }
2471         }
2472
2473 out:
2474         strbuf_release(&referent);
2475         return ret;
2476 }
2477
2478 struct files_transaction_backend_data {
2479         struct ref_transaction *packed_transaction;
2480         int packed_refs_locked;
2481 };
2482
2483 /*
2484  * Unlock any references in `transaction` that are still locked, and
2485  * mark the transaction closed.
2486  */
2487 static void files_transaction_cleanup(struct files_ref_store *refs,
2488                                       struct ref_transaction *transaction)
2489 {
2490         size_t i;
2491         struct files_transaction_backend_data *backend_data =
2492                 transaction->backend_data;
2493         struct strbuf err = STRBUF_INIT;
2494
2495         for (i = 0; i < transaction->nr; i++) {
2496                 struct ref_update *update = transaction->updates[i];
2497                 struct ref_lock *lock = update->backend_data;
2498
2499                 if (lock) {
2500                         unlock_ref(lock);
2501                         update->backend_data = NULL;
2502                 }
2503         }
2504
2505         if (backend_data->packed_transaction &&
2506             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2507                 error("error aborting transaction: %s", err.buf);
2508                 strbuf_release(&err);
2509         }
2510
2511         if (backend_data->packed_refs_locked)
2512                 packed_refs_unlock(refs->packed_ref_store);
2513
2514         free(backend_data);
2515
2516         transaction->state = REF_TRANSACTION_CLOSED;
2517 }
2518
2519 static int files_transaction_prepare(struct ref_store *ref_store,
2520                                      struct ref_transaction *transaction,
2521                                      struct strbuf *err)
2522 {
2523         struct files_ref_store *refs =
2524                 files_downcast(ref_store, REF_STORE_WRITE,
2525                                "ref_transaction_prepare");
2526         size_t i;
2527         int ret = 0;
2528         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2529         char *head_ref = NULL;
2530         int head_type;
2531         struct object_id head_oid;
2532         struct files_transaction_backend_data *backend_data;
2533         struct ref_transaction *packed_transaction = NULL;
2534
2535         assert(err);
2536
2537         if (!transaction->nr)
2538                 goto cleanup;
2539
2540         backend_data = xcalloc(1, sizeof(*backend_data));
2541         transaction->backend_data = backend_data;
2542
2543         /*
2544          * Fail if a refname appears more than once in the
2545          * transaction. (If we end up splitting up any updates using
2546          * split_symref_update() or split_head_update(), those
2547          * functions will check that the new updates don't have the
2548          * same refname as any existing ones.)
2549          */
2550         for (i = 0; i < transaction->nr; i++) {
2551                 struct ref_update *update = transaction->updates[i];
2552                 struct string_list_item *item =
2553                         string_list_append(&affected_refnames, update->refname);
2554
2555                 /*
2556                  * We store a pointer to update in item->util, but at
2557                  * the moment we never use the value of this field
2558                  * except to check whether it is non-NULL.
2559                  */
2560                 item->util = update;
2561         }
2562         string_list_sort(&affected_refnames);
2563         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2564                 ret = TRANSACTION_GENERIC_ERROR;
2565                 goto cleanup;
2566         }
2567
2568         /*
2569          * Special hack: If a branch is updated directly and HEAD
2570          * points to it (may happen on the remote side of a push
2571          * for example) then logically the HEAD reflog should be
2572          * updated too.
2573          *
2574          * A generic solution would require reverse symref lookups,
2575          * but finding all symrefs pointing to a given branch would be
2576          * rather costly for this rare event (the direct update of a
2577          * branch) to be worth it. So let's cheat and check with HEAD
2578          * only, which should cover 99% of all usage scenarios (even
2579          * 100% of the default ones).
2580          *
2581          * So if HEAD is a symbolic reference, then record the name of
2582          * the reference that it points to. If we see an update of
2583          * head_ref within the transaction, then split_head_update()
2584          * arranges for the reflog of HEAD to be updated, too.
2585          */
2586         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2587                                        RESOLVE_REF_NO_RECURSE,
2588                                        head_oid.hash, &head_type);
2589
2590         if (head_ref && !(head_type & REF_ISSYMREF)) {
2591                 FREE_AND_NULL(head_ref);
2592         }
2593
2594         /*
2595          * Acquire all locks, verify old values if provided, check
2596          * that new values are valid, and write new values to the
2597          * lockfiles, ready to be activated. Only keep one lockfile
2598          * open at a time to avoid running out of file descriptors.
2599          * Note that lock_ref_for_update() might append more updates
2600          * to the transaction.
2601          */
2602         for (i = 0; i < transaction->nr; i++) {
2603                 struct ref_update *update = transaction->updates[i];
2604
2605                 ret = lock_ref_for_update(refs, update, transaction,
2606                                           head_ref, &affected_refnames, err);
2607                 if (ret)
2608                         break;
2609
2610                 if (update->flags & REF_DELETING &&
2611                     !(update->flags & REF_LOG_ONLY) &&
2612                     !(update->flags & REF_ISPRUNING)) {
2613                         /*
2614                          * This reference has to be deleted from
2615                          * packed-refs if it exists there.
2616                          */
2617                         if (!packed_transaction) {
2618                                 packed_transaction = ref_store_transaction_begin(
2619                                                 refs->packed_ref_store, err);
2620                                 if (!packed_transaction) {
2621                                         ret = TRANSACTION_GENERIC_ERROR;
2622                                         goto cleanup;
2623                                 }
2624
2625                                 backend_data->packed_transaction =
2626                                         packed_transaction;
2627                         }
2628
2629                         ref_transaction_add_update(
2630                                         packed_transaction, update->refname,
2631                                         update->flags & ~REF_HAVE_OLD,
2632                                         update->new_oid.hash, update->old_oid.hash,
2633                                         NULL);
2634                 }
2635         }
2636
2637         if (packed_transaction) {
2638                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2639                         ret = TRANSACTION_GENERIC_ERROR;
2640                         goto cleanup;
2641                 }
2642                 backend_data->packed_refs_locked = 1;
2643                 ret = ref_transaction_prepare(packed_transaction, err);
2644         }
2645
2646 cleanup:
2647         free(head_ref);
2648         string_list_clear(&affected_refnames, 0);
2649
2650         if (ret)
2651                 files_transaction_cleanup(refs, transaction);
2652         else
2653                 transaction->state = REF_TRANSACTION_PREPARED;
2654
2655         return ret;
2656 }
2657
2658 static int files_transaction_finish(struct ref_store *ref_store,
2659                                     struct ref_transaction *transaction,
2660                                     struct strbuf *err)
2661 {
2662         struct files_ref_store *refs =
2663                 files_downcast(ref_store, 0, "ref_transaction_finish");
2664         size_t i;
2665         int ret = 0;
2666         struct strbuf sb = STRBUF_INIT;
2667         struct files_transaction_backend_data *backend_data;
2668         struct ref_transaction *packed_transaction;
2669
2670
2671         assert(err);
2672
2673         if (!transaction->nr) {
2674                 transaction->state = REF_TRANSACTION_CLOSED;
2675                 return 0;
2676         }
2677
2678         backend_data = transaction->backend_data;
2679         packed_transaction = backend_data->packed_transaction;
2680
2681         /* Perform updates first so live commits remain referenced */
2682         for (i = 0; i < transaction->nr; i++) {
2683                 struct ref_update *update = transaction->updates[i];
2684                 struct ref_lock *lock = update->backend_data;
2685
2686                 if (update->flags & REF_NEEDS_COMMIT ||
2687                     update->flags & REF_LOG_ONLY) {
2688                         if (files_log_ref_write(refs,
2689                                                 lock->ref_name,
2690                                                 &lock->old_oid,
2691                                                 &update->new_oid,
2692                                                 update->msg, update->flags,
2693                                                 err)) {
2694                                 char *old_msg = strbuf_detach(err, NULL);
2695
2696                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2697                                             lock->ref_name, old_msg);
2698                                 free(old_msg);
2699                                 unlock_ref(lock);
2700                                 update->backend_data = NULL;
2701                                 ret = TRANSACTION_GENERIC_ERROR;
2702                                 goto cleanup;
2703                         }
2704                 }
2705                 if (update->flags & REF_NEEDS_COMMIT) {
2706                         clear_loose_ref_cache(refs);
2707                         if (commit_ref(lock)) {
2708                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2709                                 unlock_ref(lock);
2710                                 update->backend_data = NULL;
2711                                 ret = TRANSACTION_GENERIC_ERROR;
2712                                 goto cleanup;
2713                         }
2714                 }
2715         }
2716
2717         /*
2718          * Now that updates are safely completed, we can perform
2719          * deletes. First delete the reflogs of any references that
2720          * will be deleted, since (in the unexpected event of an
2721          * error) leaving a reference without a reflog is less bad
2722          * than leaving a reflog without a reference (the latter is a
2723          * mildly invalid repository state):
2724          */
2725         for (i = 0; i < transaction->nr; i++) {
2726                 struct ref_update *update = transaction->updates[i];
2727                 if (update->flags & REF_DELETING &&
2728                     !(update->flags & REF_LOG_ONLY) &&
2729                     !(update->flags & REF_ISPRUNING)) {
2730                         strbuf_reset(&sb);
2731                         files_reflog_path(refs, &sb, update->refname);
2732                         if (!unlink_or_warn(sb.buf))
2733                                 try_remove_empty_parents(refs, update->refname,
2734                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2735                 }
2736         }
2737
2738         /*
2739          * Perform deletes now that updates are safely completed.
2740          *
2741          * First delete any packed versions of the references, while
2742          * retaining the packed-refs lock:
2743          */
2744         if (packed_transaction) {
2745                 ret = ref_transaction_commit(packed_transaction, err);
2746                 ref_transaction_free(packed_transaction);
2747                 packed_transaction = NULL;
2748                 backend_data->packed_transaction = NULL;
2749                 if (ret)
2750                         goto cleanup;
2751         }
2752
2753         /* Now delete the loose versions of the references: */
2754         for (i = 0; i < transaction->nr; i++) {
2755                 struct ref_update *update = transaction->updates[i];
2756                 struct ref_lock *lock = update->backend_data;
2757
2758                 if (update->flags & REF_DELETING &&
2759                     !(update->flags & REF_LOG_ONLY)) {
2760                         if (!(update->type & REF_ISPACKED) ||
2761                             update->type & REF_ISSYMREF) {
2762                                 /* It is a loose reference. */
2763                                 strbuf_reset(&sb);
2764                                 files_ref_path(refs, &sb, lock->ref_name);
2765                                 if (unlink_or_msg(sb.buf, err)) {
2766                                         ret = TRANSACTION_GENERIC_ERROR;
2767                                         goto cleanup;
2768                                 }
2769                                 update->flags |= REF_DELETED_LOOSE;
2770                         }
2771                 }
2772         }
2773
2774         clear_loose_ref_cache(refs);
2775
2776 cleanup:
2777         files_transaction_cleanup(refs, transaction);
2778
2779         for (i = 0; i < transaction->nr; i++) {
2780                 struct ref_update *update = transaction->updates[i];
2781
2782                 if (update->flags & REF_DELETED_LOOSE) {
2783                         /*
2784                          * The loose reference was deleted. Delete any
2785                          * empty parent directories. (Note that this
2786                          * can only work because we have already
2787                          * removed the lockfile.)
2788                          */
2789                         try_remove_empty_parents(refs, update->refname,
2790                                                  REMOVE_EMPTY_PARENTS_REF);
2791                 }
2792         }
2793
2794         strbuf_release(&sb);
2795         return ret;
2796 }
2797
2798 static int files_transaction_abort(struct ref_store *ref_store,
2799                                    struct ref_transaction *transaction,
2800                                    struct strbuf *err)
2801 {
2802         struct files_ref_store *refs =
2803                 files_downcast(ref_store, 0, "ref_transaction_abort");
2804
2805         files_transaction_cleanup(refs, transaction);
2806         return 0;
2807 }
2808
2809 static int ref_present(const char *refname,
2810                        const struct object_id *oid, int flags, void *cb_data)
2811 {
2812         struct string_list *affected_refnames = cb_data;
2813
2814         return string_list_has_string(affected_refnames, refname);
2815 }
2816
2817 static int files_initial_transaction_commit(struct ref_store *ref_store,
2818                                             struct ref_transaction *transaction,
2819                                             struct strbuf *err)
2820 {
2821         struct files_ref_store *refs =
2822                 files_downcast(ref_store, REF_STORE_WRITE,
2823                                "initial_ref_transaction_commit");
2824         size_t i;
2825         int ret = 0;
2826         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2827         struct ref_transaction *packed_transaction = NULL;
2828
2829         assert(err);
2830
2831         if (transaction->state != REF_TRANSACTION_OPEN)
2832                 die("BUG: commit called for transaction that is not open");
2833
2834         /* Fail if a refname appears more than once in the transaction: */
2835         for (i = 0; i < transaction->nr; i++)
2836                 string_list_append(&affected_refnames,
2837                                    transaction->updates[i]->refname);
2838         string_list_sort(&affected_refnames);
2839         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2840                 ret = TRANSACTION_GENERIC_ERROR;
2841                 goto cleanup;
2842         }
2843
2844         /*
2845          * It's really undefined to call this function in an active
2846          * repository or when there are existing references: we are
2847          * only locking and changing packed-refs, so (1) any
2848          * simultaneous processes might try to change a reference at
2849          * the same time we do, and (2) any existing loose versions of
2850          * the references that we are setting would have precedence
2851          * over our values. But some remote helpers create the remote
2852          * "HEAD" and "master" branches before calling this function,
2853          * so here we really only check that none of the references
2854          * that we are creating already exists.
2855          */
2856         if (refs_for_each_rawref(&refs->base, ref_present,
2857                                  &affected_refnames))
2858                 die("BUG: initial ref transaction called with existing refs");
2859
2860         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2861         if (!packed_transaction) {
2862                 ret = TRANSACTION_GENERIC_ERROR;
2863                 goto cleanup;
2864         }
2865
2866         for (i = 0; i < transaction->nr; i++) {
2867                 struct ref_update *update = transaction->updates[i];
2868
2869                 if ((update->flags & REF_HAVE_OLD) &&
2870                     !is_null_oid(&update->old_oid))
2871                         die("BUG: initial ref transaction with old_sha1 set");
2872                 if (refs_verify_refname_available(&refs->base, update->refname,
2873                                                   &affected_refnames, NULL,
2874                                                   err)) {
2875                         ret = TRANSACTION_NAME_CONFLICT;
2876                         goto cleanup;
2877                 }
2878
2879                 /*
2880                  * Add a reference creation for this reference to the
2881                  * packed-refs transaction:
2882                  */
2883                 ref_transaction_add_update(packed_transaction, update->refname,
2884                                            update->flags & ~REF_HAVE_OLD,
2885                                            update->new_oid.hash, update->old_oid.hash,
2886                                            NULL);
2887         }
2888
2889         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2890                 ret = TRANSACTION_GENERIC_ERROR;
2891                 goto cleanup;
2892         }
2893
2894         if (initial_ref_transaction_commit(packed_transaction, err)) {
2895                 ret = TRANSACTION_GENERIC_ERROR;
2896                 goto cleanup;
2897         }
2898
2899 cleanup:
2900         if (packed_transaction)
2901                 ref_transaction_free(packed_transaction);
2902         packed_refs_unlock(refs->packed_ref_store);
2903         transaction->state = REF_TRANSACTION_CLOSED;
2904         string_list_clear(&affected_refnames, 0);
2905         return ret;
2906 }
2907
2908 struct expire_reflog_cb {
2909         unsigned int flags;
2910         reflog_expiry_should_prune_fn *should_prune_fn;
2911         void *policy_cb;
2912         FILE *newlog;
2913         struct object_id last_kept_oid;
2914 };
2915
2916 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2917                              const char *email, timestamp_t timestamp, int tz,
2918                              const char *message, void *cb_data)
2919 {
2920         struct expire_reflog_cb *cb = cb_data;
2921         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2922
2923         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2924                 ooid = &cb->last_kept_oid;
2925
2926         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2927                                    message, policy_cb)) {
2928                 if (!cb->newlog)
2929                         printf("would prune %s", message);
2930                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2931                         printf("prune %s", message);
2932         } else {
2933                 if (cb->newlog) {
2934                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2935                                 oid_to_hex(ooid), oid_to_hex(noid),
2936                                 email, timestamp, tz, message);
2937                         oidcpy(&cb->last_kept_oid, noid);
2938                 }
2939                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2940                         printf("keep %s", message);
2941         }
2942         return 0;
2943 }
2944
2945 static int files_reflog_expire(struct ref_store *ref_store,
2946                                const char *refname, const unsigned char *sha1,
2947                                unsigned int flags,
2948                                reflog_expiry_prepare_fn prepare_fn,
2949                                reflog_expiry_should_prune_fn should_prune_fn,
2950                                reflog_expiry_cleanup_fn cleanup_fn,
2951                                void *policy_cb_data)
2952 {
2953         struct files_ref_store *refs =
2954                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2955         static struct lock_file reflog_lock;
2956         struct expire_reflog_cb cb;
2957         struct ref_lock *lock;
2958         struct strbuf log_file_sb = STRBUF_INIT;
2959         char *log_file;
2960         int status = 0;
2961         int type;
2962         struct strbuf err = STRBUF_INIT;
2963         struct object_id oid;
2964
2965         memset(&cb, 0, sizeof(cb));
2966         cb.flags = flags;
2967         cb.policy_cb = policy_cb_data;
2968         cb.should_prune_fn = should_prune_fn;
2969
2970         /*
2971          * The reflog file is locked by holding the lock on the
2972          * reference itself, plus we might need to update the
2973          * reference if --updateref was specified:
2974          */
2975         lock = lock_ref_sha1_basic(refs, refname, sha1,
2976                                    NULL, NULL, REF_NODEREF,
2977                                    &type, &err);
2978         if (!lock) {
2979                 error("cannot lock ref '%s': %s", refname, err.buf);
2980                 strbuf_release(&err);
2981                 return -1;
2982         }
2983         if (!refs_reflog_exists(ref_store, refname)) {
2984                 unlock_ref(lock);
2985                 return 0;
2986         }
2987
2988         files_reflog_path(refs, &log_file_sb, refname);
2989         log_file = strbuf_detach(&log_file_sb, NULL);
2990         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2991                 /*
2992                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2993                  * no locking implications, we use the lock_file
2994                  * machinery here anyway because it does a lot of the
2995                  * work we need, including cleaning up if the program
2996                  * exits unexpectedly.
2997                  */
2998                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2999                         struct strbuf err = STRBUF_INIT;
3000                         unable_to_lock_message(log_file, errno, &err);
3001                         error("%s", err.buf);
3002                         strbuf_release(&err);
3003                         goto failure;
3004                 }
3005                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3006                 if (!cb.newlog) {
3007                         error("cannot fdopen %s (%s)",
3008                               get_lock_file_path(&reflog_lock), strerror(errno));
3009                         goto failure;
3010                 }
3011         }
3012
3013         hashcpy(oid.hash, sha1);
3014
3015         (*prepare_fn)(refname, &oid, cb.policy_cb);
3016         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3017         (*cleanup_fn)(cb.policy_cb);
3018
3019         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3020                 /*
3021                  * It doesn't make sense to adjust a reference pointed
3022                  * to by a symbolic ref based on expiring entries in
3023                  * the symbolic reference's reflog. Nor can we update
3024                  * a reference if there are no remaining reflog
3025                  * entries.
3026                  */
3027                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3028                         !(type & REF_ISSYMREF) &&
3029                         !is_null_oid(&cb.last_kept_oid);
3030
3031                 if (close_lock_file_gently(&reflog_lock)) {
3032                         status |= error("couldn't write %s: %s", log_file,
3033                                         strerror(errno));
3034                         rollback_lock_file(&reflog_lock);
3035                 } else if (update &&
3036                            (write_in_full(get_lock_file_fd(&lock->lk),
3037                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3038                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3039                             close_ref_gently(lock) < 0)) {
3040                         status |= error("couldn't write %s",
3041                                         get_lock_file_path(&lock->lk));
3042                         rollback_lock_file(&reflog_lock);
3043                 } else if (commit_lock_file(&reflog_lock)) {
3044                         status |= error("unable to write reflog '%s' (%s)",
3045                                         log_file, strerror(errno));
3046                 } else if (update && commit_ref(lock)) {
3047                         status |= error("couldn't set %s", lock->ref_name);
3048                 }
3049         }
3050         free(log_file);
3051         unlock_ref(lock);
3052         return status;
3053
3054  failure:
3055         rollback_lock_file(&reflog_lock);
3056         free(log_file);
3057         unlock_ref(lock);
3058         return -1;
3059 }
3060
3061 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3062 {
3063         struct files_ref_store *refs =
3064                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3065         struct strbuf sb = STRBUF_INIT;
3066
3067         /*
3068          * Create .git/refs/{heads,tags}
3069          */
3070         files_ref_path(refs, &sb, "refs/heads");
3071         safe_create_dir(sb.buf, 1);
3072
3073         strbuf_reset(&sb);
3074         files_ref_path(refs, &sb, "refs/tags");
3075         safe_create_dir(sb.buf, 1);
3076
3077         strbuf_release(&sb);
3078         return 0;
3079 }
3080
3081 struct ref_storage_be refs_be_files = {
3082         NULL,
3083         "files",
3084         files_ref_store_create,
3085         files_init_db,
3086         files_transaction_prepare,
3087         files_transaction_finish,
3088         files_transaction_abort,
3089         files_initial_transaction_commit,
3090
3091         files_pack_refs,
3092         files_peel_ref,
3093         files_create_symref,
3094         files_delete_refs,
3095         files_rename_ref,
3096         files_copy_ref,
3097
3098         files_ref_iterator_begin,
3099         files_read_raw_ref,
3100
3101         files_reflog_iterator_begin,
3102         files_for_each_reflog_ent,
3103         files_for_each_reflog_ent_reverse,
3104         files_reflog_exists,
3105         files_create_reflog,
3106         files_delete_reflog,
3107         files_reflog_expire
3108 };