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

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12
  13 struct ref_lock {
  14         char *ref_name;
  15         struct lock_file lk;
  16         struct object_id old_oid;
  17 };
  18
  19 /*
  20  * Future: need to be in "struct repository"
  21  * when doing a full libification.
  22  */
  23 struct files_ref_store {
  24         struct ref_store base;
  25         unsigned int store_flags;
  26
  27         char *gitdir;
  28         char *gitcommondir;
  29
  30         struct ref_cache *loose;
  31
  32         struct ref_store *packed_ref_store;
  33 };
  34
  35 static void clear_loose_ref_cache(struct files_ref_store *refs)
  36 {
  37         if (refs->loose) {
  38                 free_ref_cache(refs->loose);
  39                 refs->loose = NULL;
  40         }
  41 }
  42
  43 /*
  44  * Create a new submodule ref cache and add it to the internal
  45  * set of caches.
  46  */
  47 static struct ref_store *files_ref_store_create(const char *gitdir,
  48                                                 unsigned int flags)
  49 {
  50         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  51         struct ref_store *ref_store = (struct ref_store *)refs;
  52         struct strbuf sb = STRBUF_INIT;
  53
  54         base_ref_store_init(ref_store, &refs_be_files);
  55         refs->store_flags = flags;
  56
  57         refs->gitdir = xstrdup(gitdir);
  58         get_common_dir_noenv(&sb, gitdir);
  59         refs->gitcommondir = strbuf_detach(&sb, NULL);
  60         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
  61         refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
  62         strbuf_release(&sb);
  63
  64         return ref_store;
  65 }
  66
  67 /*
  68  * Die if refs is not the main ref store. caller is used in any
  69  * necessary error messages.
  70  */
  71 static void files_assert_main_repository(struct files_ref_store *refs,
  72                                          const char *caller)
  73 {
  74         if (refs->store_flags & REF_STORE_MAIN)
  75                 return;
  76
  77         die("BUG: operation %s only allowed for main ref store", caller);
  78 }
  79
  80 /*
  81  * Downcast ref_store to files_ref_store. Die if ref_store is not a
  82  * files_ref_store. required_flags is compared with ref_store's
  83  * store_flags to ensure the ref_store has all required capabilities.
  84  * "caller" is used in any necessary error messages.
  85  */
  86 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
  87                                               unsigned int required_flags,
  88                                               const char *caller)
  89 {
  90         struct files_ref_store *refs;
  91
  92         if (ref_store->be != &refs_be_files)
  93                 die("BUG: ref_store is type \"%s\" not \"files\" in %s",
  94                     ref_store->be->name, caller);
  95
  96         refs = (struct files_ref_store *)ref_store;
  97
  98         if ((refs->store_flags & required_flags) != required_flags)
  99                 die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
 100                     caller, required_flags, refs->store_flags);
 101
 102         return refs;
 103 }
 104
 105 static void files_reflog_path(struct files_ref_store *refs,
 106                               struct strbuf *sb,
 107                               const char *refname)
 108 {
 109         switch (ref_type(refname)) {
 110         case REF_TYPE_PER_WORKTREE:
 111         case REF_TYPE_PSEUDOREF:
 112                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 113                 break;
 114         case REF_TYPE_NORMAL:
 115                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 116                 break;
 117         default:
 118                 die("BUG: unknown ref type %d of ref %s",
 119                     ref_type(refname), refname);
 120         }
 121 }
 122
 123 static void files_ref_path(struct files_ref_store *refs,
 124                            struct strbuf *sb,
 125                            const char *refname)
 126 {
 127         switch (ref_type(refname)) {
 128         case REF_TYPE_PER_WORKTREE:
 129         case REF_TYPE_PSEUDOREF:
 130                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 131                 break;
 132         case REF_TYPE_NORMAL:
 133                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 134                 break;
 135         default:
 136                 die("BUG: unknown ref type %d of ref %s",
 137                     ref_type(refname), refname);
 138         }
 139 }
 140
 141 /*
 142  * Read the loose references from the namespace dirname into dir
 143  * (without recursing).  dirname must end with '/'.  dir must be the
 144  * directory entry corresponding to dirname.
 145  */
 146 static void loose_fill_ref_dir(struct ref_store *ref_store,
 147                                struct ref_dir *dir, const char *dirname)
 148 {
 149         struct files_ref_store *refs =
 150                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 151         DIR *d;
 152         struct dirent *de;
 153         int dirnamelen = strlen(dirname);
 154         struct strbuf refname;
 155         struct strbuf path = STRBUF_INIT;
 156         size_t path_baselen;
 157
 158         files_ref_path(refs, &path, dirname);
 159         path_baselen = path.len;
 160
 161         d = opendir(path.buf);
 162         if (!d) {
 163                 strbuf_release(&path);
 164                 return;
 165         }
 166
 167         strbuf_init(&refname, dirnamelen + 257);
 168         strbuf_add(&refname, dirname, dirnamelen);
 169
 170         while ((de = readdir(d)) != NULL) {
 171                 struct object_id oid;
 172                 struct stat st;
 173                 int flag;
 174
 175                 if (de->d_name[0] == '.')
 176                         continue;
 177                 if (ends_with(de->d_name, ".lock"))
 178                         continue;
 179                 strbuf_addstr(&refname, de->d_name);
 180                 strbuf_addstr(&path, de->d_name);
 181                 if (stat(path.buf, &st) < 0) {
 182                         ; /* silently ignore */
 183                 } else if (S_ISDIR(st.st_mode)) {
 184                         strbuf_addch(&refname, '/');
 185                         add_entry_to_dir(dir,
 186                                          create_dir_entry(dir->cache, refname.buf,
 187                                                           refname.len, 1));
 188                 } else {
 189                         if (!refs_resolve_ref_unsafe(&refs->base,
 190                                                      refname.buf,
 191                                                      RESOLVE_REF_READING,
 192                                                      oid.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 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
1045 {
1046         while (r) {
1047                 prune_ref(refs, r);
1048                 r = r->next;
1049         }
1050 }
1051
1052 /*
1053  * Return true if the specified reference should be packed.
1054  */
1055 static int should_pack_ref(const char *refname,
1056                            const struct object_id *oid, unsigned int ref_flags,
1057                            unsigned int pack_flags)
1058 {
1059         /* Do not pack per-worktree refs: */
1060         if (ref_type(refname) != REF_TYPE_NORMAL)
1061                 return 0;
1062
1063         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1064         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1065                 return 0;
1066
1067         /* Do not pack symbolic refs: */
1068         if (ref_flags & REF_ISSYMREF)
1069                 return 0;
1070
1071         /* Do not pack broken refs: */
1072         if (!ref_resolves_to_object(refname, oid, ref_flags))
1073                 return 0;
1074
1075         return 1;
1076 }
1077
1078 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1079 {
1080         struct files_ref_store *refs =
1081                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1082                                "pack_refs");
1083         struct ref_iterator *iter;
1084         int ok;
1085         struct ref_to_prune *refs_to_prune = NULL;
1086         struct strbuf err = STRBUF_INIT;
1087
1088         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1089
1090         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1091         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1092                 /*
1093                  * If the loose reference can be packed, add an entry
1094                  * in the packed ref cache. If the reference should be
1095                  * pruned, also add it to refs_to_prune.
1096                  */
1097                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1098                                      flags))
1099                         continue;
1100
1101                 /*
1102                  * Create an entry in the packed-refs cache equivalent
1103                  * to the one from the loose ref cache, except that
1104                  * we don't copy the peeled status, because we want it
1105                  * to be re-peeled.
1106                  */
1107                 add_packed_ref(refs->packed_ref_store, iter->refname, iter->oid);
1108
1109                 /* Schedule the loose reference for pruning if requested. */
1110                 if ((flags & PACK_REFS_PRUNE)) {
1111                         struct ref_to_prune *n;
1112                         FLEX_ALLOC_STR(n, name, iter->refname);
1113                         hashcpy(n->sha1, iter->oid->hash);
1114                         n->next = refs_to_prune;
1115                         refs_to_prune = n;
1116                 }
1117         }
1118         if (ok != ITER_DONE)
1119                 die("error while iterating over references");
1120
1121         if (commit_packed_refs(refs->packed_ref_store, &err))
1122                 die("unable to overwrite old ref-pack file: %s", err.buf);
1123         packed_refs_unlock(refs->packed_ref_store);
1124
1125         prune_refs(refs, refs_to_prune);
1126         strbuf_release(&err);
1127         return 0;
1128 }
1129
1130 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1131                              struct string_list *refnames, unsigned int flags)
1132 {
1133         struct files_ref_store *refs =
1134                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1135         struct strbuf err = STRBUF_INIT;
1136         int i, result = 0;
1137
1138         if (!refnames->nr)
1139                 return 0;
1140
1141         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1142                 goto error;
1143
1144         if (repack_without_refs(refs->packed_ref_store, refnames, &err)) {
1145                 packed_refs_unlock(refs->packed_ref_store);
1146                 goto error;
1147         }
1148
1149         packed_refs_unlock(refs->packed_ref_store);
1150
1151         for (i = 0; i < refnames->nr; i++) {
1152                 const char *refname = refnames->items[i].string;
1153
1154                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1155                         result |= error(_("could not remove reference %s"), refname);
1156         }
1157
1158         strbuf_release(&err);
1159         return result;
1160
1161 error:
1162         /*
1163          * If we failed to rewrite the packed-refs file, then it is
1164          * unsafe to try to remove loose refs, because doing so might
1165          * expose an obsolete packed value for a reference that might
1166          * even point at an object that has been garbage collected.
1167          */
1168         if (refnames->nr == 1)
1169                 error(_("could not delete reference %s: %s"),
1170                       refnames->items[0].string, err.buf);
1171         else
1172                 error(_("could not delete references: %s"), err.buf);
1173
1174         strbuf_release(&err);
1175         return -1;
1176 }
1177
1178 /*
1179  * People using contrib's git-new-workdir have .git/logs/refs ->
1180  * /some/other/path/.git/logs/refs, and that may live on another device.
1181  *
1182  * IOW, to avoid cross device rename errors, the temporary renamed log must
1183  * live into logs/refs.
1184  */
1185 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1186
1187 struct rename_cb {
1188         const char *tmp_renamed_log;
1189         int true_errno;
1190 };
1191
1192 static int rename_tmp_log_callback(const char *path, void *cb_data)
1193 {
1194         struct rename_cb *cb = cb_data;
1195
1196         if (rename(cb->tmp_renamed_log, path)) {
1197                 /*
1198                  * rename(a, b) when b is an existing directory ought
1199                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1200                  * Sheesh. Record the true errno for error reporting,
1201                  * but report EISDIR to raceproof_create_file() so
1202                  * that it knows to retry.
1203                  */
1204                 cb->true_errno = errno;
1205                 if (errno == ENOTDIR)
1206                         errno = EISDIR;
1207                 return -1;
1208         } else {
1209                 return 0;
1210         }
1211 }
1212
1213 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1214 {
1215         struct strbuf path = STRBUF_INIT;
1216         struct strbuf tmp = STRBUF_INIT;
1217         struct rename_cb cb;
1218         int ret;
1219
1220         files_reflog_path(refs, &path, newrefname);
1221         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1222         cb.tmp_renamed_log = tmp.buf;
1223         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1224         if (ret) {
1225                 if (errno == EISDIR)
1226                         error("directory not empty: %s", path.buf);
1227                 else
1228                         error("unable to move logfile %s to %s: %s",
1229                               tmp.buf, path.buf,
1230                               strerror(cb.true_errno));
1231         }
1232
1233         strbuf_release(&path);
1234         strbuf_release(&tmp);
1235         return ret;
1236 }
1237
1238 static int write_ref_to_lockfile(struct ref_lock *lock,
1239                                  const struct object_id *oid, struct strbuf *err);
1240 static int commit_ref_update(struct files_ref_store *refs,
1241                              struct ref_lock *lock,
1242                              const struct object_id *oid, const char *logmsg,
1243                              struct strbuf *err);
1244
1245 static int files_rename_ref(struct ref_store *ref_store,
1246                             const char *oldrefname, const char *newrefname,
1247                             const char *logmsg)
1248 {
1249         struct files_ref_store *refs =
1250                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1251         struct object_id oid, orig_oid;
1252         int flag = 0, logmoved = 0;
1253         struct ref_lock *lock;
1254         struct stat loginfo;
1255         struct strbuf sb_oldref = STRBUF_INIT;
1256         struct strbuf sb_newref = STRBUF_INIT;
1257         struct strbuf tmp_renamed_log = STRBUF_INIT;
1258         int log, ret;
1259         struct strbuf err = STRBUF_INIT;
1260
1261         files_reflog_path(refs, &sb_oldref, oldrefname);
1262         files_reflog_path(refs, &sb_newref, newrefname);
1263         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1264
1265         log = !lstat(sb_oldref.buf, &loginfo);
1266         if (log && S_ISLNK(loginfo.st_mode)) {
1267                 ret = error("reflog for %s is a symlink", oldrefname);
1268                 goto out;
1269         }
1270
1271         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1272                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1273                                 orig_oid.hash, &flag)) {
1274                 ret = error("refname %s not found", oldrefname);
1275                 goto out;
1276         }
1277
1278         if (flag & REF_ISSYMREF) {
1279                 ret = error("refname %s is a symbolic ref, renaming it is not supported",
1280                             oldrefname);
1281                 goto out;
1282         }
1283         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1284                 ret = 1;
1285                 goto out;
1286         }
1287
1288         if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1289                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1290                             oldrefname, strerror(errno));
1291                 goto out;
1292         }
1293
1294         if (refs_delete_ref(&refs->base, logmsg, oldrefname,
1295                             orig_oid.hash, REF_NODEREF)) {
1296                 error("unable to delete old %s", oldrefname);
1297                 goto rollback;
1298         }
1299
1300         /*
1301          * Since we are doing a shallow lookup, oid is not the
1302          * correct value to pass to delete_ref as old_oid. But that
1303          * doesn't matter, because an old_oid check wouldn't add to
1304          * the safety anyway; we want to delete the reference whatever
1305          * its current value.
1306          */
1307         if (!refs_read_ref_full(&refs->base, newrefname,
1308                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1309                                 oid.hash, NULL) &&
1310             refs_delete_ref(&refs->base, NULL, newrefname,
1311                             NULL, REF_NODEREF)) {
1312                 if (errno == EISDIR) {
1313                         struct strbuf path = STRBUF_INIT;
1314                         int result;
1315
1316                         files_ref_path(refs, &path, newrefname);
1317                         result = remove_empty_directories(&path);
1318                         strbuf_release(&path);
1319
1320                         if (result) {
1321                                 error("Directory not empty: %s", newrefname);
1322                                 goto rollback;
1323                         }
1324                 } else {
1325                         error("unable to delete existing %s", newrefname);
1326                         goto rollback;
1327                 }
1328         }
1329
1330         if (log && rename_tmp_log(refs, newrefname))
1331                 goto rollback;
1332
1333         logmoved = log;
1334
1335         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
1336                                    REF_NODEREF, NULL, &err);
1337         if (!lock) {
1338                 error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1339                 strbuf_release(&err);
1340                 goto rollback;
1341         }
1342         oidcpy(&lock->old_oid, &orig_oid);
1343
1344         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1345             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1346                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1347                 strbuf_release(&err);
1348                 goto rollback;
1349         }
1350
1351         ret = 0;
1352         goto out;
1353
1354  rollback:
1355         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
1356                                    REF_NODEREF, NULL, &err);
1357         if (!lock) {
1358                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1359                 strbuf_release(&err);
1360                 goto rollbacklog;
1361         }
1362
1363         flag = log_all_ref_updates;
1364         log_all_ref_updates = LOG_REFS_NONE;
1365         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1366             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1367                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1368                 strbuf_release(&err);
1369         }
1370         log_all_ref_updates = flag;
1371
1372  rollbacklog:
1373         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1374                 error("unable to restore logfile %s from %s: %s",
1375                         oldrefname, newrefname, strerror(errno));
1376         if (!logmoved && log &&
1377             rename(tmp_renamed_log.buf, sb_oldref.buf))
1378                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1379                         oldrefname, strerror(errno));
1380         ret = 1;
1381  out:
1382         strbuf_release(&sb_newref);
1383         strbuf_release(&sb_oldref);
1384         strbuf_release(&tmp_renamed_log);
1385
1386         return ret;
1387 }
1388
1389 static int close_ref_gently(struct ref_lock *lock)
1390 {
1391         if (close_lock_file_gently(&lock->lk))
1392                 return -1;
1393         return 0;
1394 }
1395
1396 static int commit_ref(struct ref_lock *lock)
1397 {
1398         char *path = get_locked_file_path(&lock->lk);
1399         struct stat st;
1400
1401         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1402                 /*
1403                  * There is a directory at the path we want to rename
1404                  * the lockfile to. Hopefully it is empty; try to
1405                  * delete it.
1406                  */
1407                 size_t len = strlen(path);
1408                 struct strbuf sb_path = STRBUF_INIT;
1409
1410                 strbuf_attach(&sb_path, path, len, len);
1411
1412                 /*
1413                  * If this fails, commit_lock_file() will also fail
1414                  * and will report the problem.
1415                  */
1416                 remove_empty_directories(&sb_path);
1417                 strbuf_release(&sb_path);
1418         } else {
1419                 free(path);
1420         }
1421
1422         if (commit_lock_file(&lock->lk))
1423                 return -1;
1424         return 0;
1425 }
1426
1427 static int open_or_create_logfile(const char *path, void *cb)
1428 {
1429         int *fd = cb;
1430
1431         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1432         return (*fd < 0) ? -1 : 0;
1433 }
1434
1435 /*
1436  * Create a reflog for a ref. If force_create = 0, only create the
1437  * reflog for certain refs (those for which should_autocreate_reflog
1438  * returns non-zero). Otherwise, create it regardless of the reference
1439  * name. If the logfile already existed or was created, return 0 and
1440  * set *logfd to the file descriptor opened for appending to the file.
1441  * If no logfile exists and we decided not to create one, return 0 and
1442  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1443  * return -1.
1444  */
1445 static int log_ref_setup(struct files_ref_store *refs,
1446                          const char *refname, int force_create,
1447                          int *logfd, struct strbuf *err)
1448 {
1449         struct strbuf logfile_sb = STRBUF_INIT;
1450         char *logfile;
1451
1452         files_reflog_path(refs, &logfile_sb, refname);
1453         logfile = strbuf_detach(&logfile_sb, NULL);
1454
1455         if (force_create || should_autocreate_reflog(refname)) {
1456                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1457                         if (errno == ENOENT)
1458                                 strbuf_addf(err, "unable to create directory for '%s': "
1459                                             "%s", logfile, strerror(errno));
1460                         else if (errno == EISDIR)
1461                                 strbuf_addf(err, "there are still logs under '%s'",
1462                                             logfile);
1463                         else
1464                                 strbuf_addf(err, "unable to append to '%s': %s",
1465                                             logfile, strerror(errno));
1466
1467                         goto error;
1468                 }
1469         } else {
1470                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1471                 if (*logfd < 0) {
1472                         if (errno == ENOENT || errno == EISDIR) {
1473                                 /*
1474                                  * The logfile doesn't already exist,
1475                                  * but that is not an error; it only
1476                                  * means that we won't write log
1477                                  * entries to it.
1478                                  */
1479                                 ;
1480                         } else {
1481                                 strbuf_addf(err, "unable to append to '%s': %s",
1482                                             logfile, strerror(errno));
1483                                 goto error;
1484                         }
1485                 }
1486         }
1487
1488         if (*logfd >= 0)
1489                 adjust_shared_perm(logfile);
1490
1491         free(logfile);
1492         return 0;
1493
1494 error:
1495         free(logfile);
1496         return -1;
1497 }
1498
1499 static int files_create_reflog(struct ref_store *ref_store,
1500                                const char *refname, int force_create,
1501                                struct strbuf *err)
1502 {
1503         struct files_ref_store *refs =
1504                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1505         int fd;
1506
1507         if (log_ref_setup(refs, refname, force_create, &fd, err))
1508                 return -1;
1509
1510         if (fd >= 0)
1511                 close(fd);
1512
1513         return 0;
1514 }
1515
1516 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1517                             const struct object_id *new_oid,
1518                             const char *committer, const char *msg)
1519 {
1520         int msglen, written;
1521         unsigned maxlen, len;
1522         char *logrec;
1523
1524         msglen = msg ? strlen(msg) : 0;
1525         maxlen = strlen(committer) + msglen + 100;
1526         logrec = xmalloc(maxlen);
1527         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1528                         oid_to_hex(old_oid),
1529                         oid_to_hex(new_oid),
1530                         committer);
1531         if (msglen)
1532                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1533
1534         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1535         free(logrec);
1536         if (written != len)
1537                 return -1;
1538
1539         return 0;
1540 }
1541
1542 static int files_log_ref_write(struct files_ref_store *refs,
1543                                const char *refname, const struct object_id *old_oid,
1544                                const struct object_id *new_oid, const char *msg,
1545                                int flags, struct strbuf *err)
1546 {
1547         int logfd, result;
1548
1549         if (log_all_ref_updates == LOG_REFS_UNSET)
1550                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1551
1552         result = log_ref_setup(refs, refname,
1553                                flags & REF_FORCE_CREATE_REFLOG,
1554                                &logfd, err);
1555
1556         if (result)
1557                 return result;
1558
1559         if (logfd < 0)
1560                 return 0;
1561         result = log_ref_write_fd(logfd, old_oid, new_oid,
1562                                   git_committer_info(0), msg);
1563         if (result) {
1564                 struct strbuf sb = STRBUF_INIT;
1565                 int save_errno = errno;
1566
1567                 files_reflog_path(refs, &sb, refname);
1568                 strbuf_addf(err, "unable to append to '%s': %s",
1569                             sb.buf, strerror(save_errno));
1570                 strbuf_release(&sb);
1571                 close(logfd);
1572                 return -1;
1573         }
1574         if (close(logfd)) {
1575                 struct strbuf sb = STRBUF_INIT;
1576                 int save_errno = errno;
1577
1578                 files_reflog_path(refs, &sb, refname);
1579                 strbuf_addf(err, "unable to append to '%s': %s",
1580                             sb.buf, strerror(save_errno));
1581                 strbuf_release(&sb);
1582                 return -1;
1583         }
1584         return 0;
1585 }
1586
1587 /*
1588  * Write sha1 into the open lockfile, then close the lockfile. On
1589  * errors, rollback the lockfile, fill in *err and
1590  * return -1.
1591  */
1592 static int write_ref_to_lockfile(struct ref_lock *lock,
1593                                  const struct object_id *oid, struct strbuf *err)
1594 {
1595         static char term = '\n';
1596         struct object *o;
1597         int fd;
1598
1599         o = parse_object(oid);
1600         if (!o) {
1601                 strbuf_addf(err,
1602                             "trying to write ref '%s' with nonexistent object %s",
1603                             lock->ref_name, oid_to_hex(oid));
1604                 unlock_ref(lock);
1605                 return -1;
1606         }
1607         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1608                 strbuf_addf(err,
1609                             "trying to write non-commit object %s to branch '%s'",
1610                             oid_to_hex(oid), lock->ref_name);
1611                 unlock_ref(lock);
1612                 return -1;
1613         }
1614         fd = get_lock_file_fd(&lock->lk);
1615         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
1616             write_in_full(fd, &term, 1) != 1 ||
1617             close_ref_gently(lock) < 0) {
1618                 strbuf_addf(err,
1619                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1620                 unlock_ref(lock);
1621                 return -1;
1622         }
1623         return 0;
1624 }
1625
1626 /*
1627  * Commit a change to a loose reference that has already been written
1628  * to the loose reference lockfile. Also update the reflogs if
1629  * necessary, using the specified lockmsg (which can be NULL).
1630  */
1631 static int commit_ref_update(struct files_ref_store *refs,
1632                              struct ref_lock *lock,
1633                              const struct object_id *oid, const char *logmsg,
1634                              struct strbuf *err)
1635 {
1636         files_assert_main_repository(refs, "commit_ref_update");
1637
1638         clear_loose_ref_cache(refs);
1639         if (files_log_ref_write(refs, lock->ref_name,
1640                                 &lock->old_oid, oid,
1641                                 logmsg, 0, err)) {
1642                 char *old_msg = strbuf_detach(err, NULL);
1643                 strbuf_addf(err, "cannot update the ref '%s': %s",
1644                             lock->ref_name, old_msg);
1645                 free(old_msg);
1646                 unlock_ref(lock);
1647                 return -1;
1648         }
1649
1650         if (strcmp(lock->ref_name, "HEAD") != 0) {
1651                 /*
1652                  * Special hack: If a branch is updated directly and HEAD
1653                  * points to it (may happen on the remote side of a push
1654                  * for example) then logically the HEAD reflog should be
1655                  * updated too.
1656                  * A generic solution implies reverse symref information,
1657                  * but finding all symrefs pointing to the given branch
1658                  * would be rather costly for this rare event (the direct
1659                  * update of a branch) to be worth it.  So let's cheat and
1660                  * check with HEAD only which should cover 99% of all usage
1661                  * scenarios (even 100% of the default ones).
1662                  */
1663                 struct object_id head_oid;
1664                 int head_flag;
1665                 const char *head_ref;
1666
1667                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1668                                                    RESOLVE_REF_READING,
1669                                                    head_oid.hash, &head_flag);
1670                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1671                     !strcmp(head_ref, lock->ref_name)) {
1672                         struct strbuf log_err = STRBUF_INIT;
1673                         if (files_log_ref_write(refs, "HEAD",
1674                                                 &lock->old_oid, oid,
1675                                                 logmsg, 0, &log_err)) {
1676                                 error("%s", log_err.buf);
1677                                 strbuf_release(&log_err);
1678                         }
1679                 }
1680         }
1681
1682         if (commit_ref(lock)) {
1683                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1684                 unlock_ref(lock);
1685                 return -1;
1686         }
1687
1688         unlock_ref(lock);
1689         return 0;
1690 }
1691
1692 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1693 {
1694         int ret = -1;
1695 #ifndef NO_SYMLINK_HEAD
1696         char *ref_path = get_locked_file_path(&lock->lk);
1697         unlink(ref_path);
1698         ret = symlink(target, ref_path);
1699         free(ref_path);
1700
1701         if (ret)
1702                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1703 #endif
1704         return ret;
1705 }
1706
1707 static void update_symref_reflog(struct files_ref_store *refs,
1708                                  struct ref_lock *lock, const char *refname,
1709                                  const char *target, const char *logmsg)
1710 {
1711         struct strbuf err = STRBUF_INIT;
1712         struct object_id new_oid;
1713         if (logmsg &&
1714             !refs_read_ref_full(&refs->base, target,
1715                                 RESOLVE_REF_READING, new_oid.hash, NULL) &&
1716             files_log_ref_write(refs, refname, &lock->old_oid,
1717                                 &new_oid, logmsg, 0, &err)) {
1718                 error("%s", err.buf);
1719                 strbuf_release(&err);
1720         }
1721 }
1722
1723 static int create_symref_locked(struct files_ref_store *refs,
1724                                 struct ref_lock *lock, const char *refname,
1725                                 const char *target, const char *logmsg)
1726 {
1727         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1728                 update_symref_reflog(refs, lock, refname, target, logmsg);
1729                 return 0;
1730         }
1731
1732         if (!fdopen_lock_file(&lock->lk, "w"))
1733                 return error("unable to fdopen %s: %s",
1734                              lock->lk.tempfile->filename.buf, strerror(errno));
1735
1736         update_symref_reflog(refs, lock, refname, target, logmsg);
1737
1738         /* no error check; commit_ref will check ferror */
1739         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1740         if (commit_ref(lock) < 0)
1741                 return error("unable to write symref for %s: %s", refname,
1742                              strerror(errno));
1743         return 0;
1744 }
1745
1746 static int files_create_symref(struct ref_store *ref_store,
1747                                const char *refname, const char *target,
1748                                const char *logmsg)
1749 {
1750         struct files_ref_store *refs =
1751                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1752         struct strbuf err = STRBUF_INIT;
1753         struct ref_lock *lock;
1754         int ret;
1755
1756         lock = lock_ref_sha1_basic(refs, refname, NULL,
1757                                    NULL, NULL, REF_NODEREF, NULL,
1758                                    &err);
1759         if (!lock) {
1760                 error("%s", err.buf);
1761                 strbuf_release(&err);
1762                 return -1;
1763         }
1764
1765         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1766         unlock_ref(lock);
1767         return ret;
1768 }
1769
1770 static int files_reflog_exists(struct ref_store *ref_store,
1771                                const char *refname)
1772 {
1773         struct files_ref_store *refs =
1774                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1775         struct strbuf sb = STRBUF_INIT;
1776         struct stat st;
1777         int ret;
1778
1779         files_reflog_path(refs, &sb, refname);
1780         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1781         strbuf_release(&sb);
1782         return ret;
1783 }
1784
1785 static int files_delete_reflog(struct ref_store *ref_store,
1786                                const char *refname)
1787 {
1788         struct files_ref_store *refs =
1789                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1790         struct strbuf sb = STRBUF_INIT;
1791         int ret;
1792
1793         files_reflog_path(refs, &sb, refname);
1794         ret = remove_path(sb.buf);
1795         strbuf_release(&sb);
1796         return ret;
1797 }
1798
1799 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1800 {
1801         struct object_id ooid, noid;
1802         char *email_end, *message;
1803         timestamp_t timestamp;
1804         int tz;
1805         const char *p = sb->buf;
1806
1807         /* old SP new SP name <email> SP time TAB msg LF */
1808         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1809             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1810             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1811             !(email_end = strchr(p, '>')) ||
1812             email_end[1] != ' ' ||
1813             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1814             !message || message[0] != ' ' ||
1815             (message[1] != '+' && message[1] != '-') ||
1816             !isdigit(message[2]) || !isdigit(message[3]) ||
1817             !isdigit(message[4]) || !isdigit(message[5]))
1818                 return 0; /* corrupt? */
1819         email_end[1] = '\0';
1820         tz = strtol(message + 1, NULL, 10);
1821         if (message[6] != '\t')
1822                 message += 6;
1823         else
1824                 message += 7;
1825         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1826 }
1827
1828 static char *find_beginning_of_line(char *bob, char *scan)
1829 {
1830         while (bob < scan && *(--scan) != '\n')
1831                 ; /* keep scanning backwards */
1832         /*
1833          * Return either beginning of the buffer, or LF at the end of
1834          * the previous line.
1835          */
1836         return scan;
1837 }
1838
1839 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1840                                              const char *refname,
1841                                              each_reflog_ent_fn fn,
1842                                              void *cb_data)
1843 {
1844         struct files_ref_store *refs =
1845                 files_downcast(ref_store, REF_STORE_READ,
1846                                "for_each_reflog_ent_reverse");
1847         struct strbuf sb = STRBUF_INIT;
1848         FILE *logfp;
1849         long pos;
1850         int ret = 0, at_tail = 1;
1851
1852         files_reflog_path(refs, &sb, refname);
1853         logfp = fopen(sb.buf, "r");
1854         strbuf_release(&sb);
1855         if (!logfp)
1856                 return -1;
1857
1858         /* Jump to the end */
1859         if (fseek(logfp, 0, SEEK_END) < 0)
1860                 ret = error("cannot seek back reflog for %s: %s",
1861                             refname, strerror(errno));
1862         pos = ftell(logfp);
1863         while (!ret && 0 < pos) {
1864                 int cnt;
1865                 size_t nread;
1866                 char buf[BUFSIZ];
1867                 char *endp, *scanp;
1868
1869                 /* Fill next block from the end */
1870                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1871                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1872                         ret = error("cannot seek back reflog for %s: %s",
1873                                     refname, strerror(errno));
1874                         break;
1875                 }
1876                 nread = fread(buf, cnt, 1, logfp);
1877                 if (nread != 1) {
1878                         ret = error("cannot read %d bytes from reflog for %s: %s",
1879                                     cnt, refname, strerror(errno));
1880                         break;
1881                 }
1882                 pos -= cnt;
1883
1884                 scanp = endp = buf + cnt;
1885                 if (at_tail && scanp[-1] == '\n')
1886                         /* Looking at the final LF at the end of the file */
1887                         scanp--;
1888                 at_tail = 0;
1889
1890                 while (buf < scanp) {
1891                         /*
1892                          * terminating LF of the previous line, or the beginning
1893                          * of the buffer.
1894                          */
1895                         char *bp;
1896
1897                         bp = find_beginning_of_line(buf, scanp);
1898
1899                         if (*bp == '\n') {
1900                                 /*
1901                                  * The newline is the end of the previous line,
1902                                  * so we know we have complete line starting
1903                                  * at (bp + 1). Prefix it onto any prior data
1904                                  * we collected for the line and process it.
1905                                  */
1906                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1907                                 scanp = bp;
1908                                 endp = bp + 1;
1909                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1910                                 strbuf_reset(&sb);
1911                                 if (ret)
1912                                         break;
1913                         } else if (!pos) {
1914                                 /*
1915                                  * We are at the start of the buffer, and the
1916                                  * start of the file; there is no previous
1917                                  * line, and we have everything for this one.
1918                                  * Process it, and we can end the loop.
1919                                  */
1920                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1921                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1922                                 strbuf_reset(&sb);
1923                                 break;
1924                         }
1925
1926                         if (bp == buf) {
1927                                 /*
1928                                  * We are at the start of the buffer, and there
1929                                  * is more file to read backwards. Which means
1930                                  * we are in the middle of a line. Note that we
1931                                  * may get here even if *bp was a newline; that
1932                                  * just means we are at the exact end of the
1933                                  * previous line, rather than some spot in the
1934                                  * middle.
1935                                  *
1936                                  * Save away what we have to be combined with
1937                                  * the data from the next read.
1938                                  */
1939                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1940                                 break;
1941                         }
1942                 }
1943
1944         }
1945         if (!ret && sb.len)
1946                 die("BUG: reverse reflog parser had leftover data");
1947
1948         fclose(logfp);
1949         strbuf_release(&sb);
1950         return ret;
1951 }
1952
1953 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1954                                      const char *refname,
1955                                      each_reflog_ent_fn fn, void *cb_data)
1956 {
1957         struct files_ref_store *refs =
1958                 files_downcast(ref_store, REF_STORE_READ,
1959                                "for_each_reflog_ent");
1960         FILE *logfp;
1961         struct strbuf sb = STRBUF_INIT;
1962         int ret = 0;
1963
1964         files_reflog_path(refs, &sb, refname);
1965         logfp = fopen(sb.buf, "r");
1966         strbuf_release(&sb);
1967         if (!logfp)
1968                 return -1;
1969
1970         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
1971                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1972         fclose(logfp);
1973         strbuf_release(&sb);
1974         return ret;
1975 }
1976
1977 struct files_reflog_iterator {
1978         struct ref_iterator base;
1979
1980         struct ref_store *ref_store;
1981         struct dir_iterator *dir_iterator;
1982         struct object_id oid;
1983 };
1984
1985 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
1986 {
1987         struct files_reflog_iterator *iter =
1988                 (struct files_reflog_iterator *)ref_iterator;
1989         struct dir_iterator *diter = iter->dir_iterator;
1990         int ok;
1991
1992         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
1993                 int flags;
1994
1995                 if (!S_ISREG(diter->st.st_mode))
1996                         continue;
1997                 if (diter->basename[0] == '.')
1998                         continue;
1999                 if (ends_with(diter->basename, ".lock"))
2000                         continue;
2001
2002                 if (refs_read_ref_full(iter->ref_store,
2003                                        diter->relative_path, 0,
2004                                        iter->oid.hash, &flags)) {
2005                         error("bad ref for %s", diter->path.buf);
2006                         continue;
2007                 }
2008
2009                 iter->base.refname = diter->relative_path;
2010                 iter->base.oid = &iter->oid;
2011                 iter->base.flags = flags;
2012                 return ITER_OK;
2013         }
2014
2015         iter->dir_iterator = NULL;
2016         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2017                 ok = ITER_ERROR;
2018         return ok;
2019 }
2020
2021 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2022                                    struct object_id *peeled)
2023 {
2024         die("BUG: ref_iterator_peel() called for reflog_iterator");
2025 }
2026
2027 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2028 {
2029         struct files_reflog_iterator *iter =
2030                 (struct files_reflog_iterator *)ref_iterator;
2031         int ok = ITER_DONE;
2032
2033         if (iter->dir_iterator)
2034                 ok = dir_iterator_abort(iter->dir_iterator);
2035
2036         base_ref_iterator_free(ref_iterator);
2037         return ok;
2038 }
2039
2040 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2041         files_reflog_iterator_advance,
2042         files_reflog_iterator_peel,
2043         files_reflog_iterator_abort
2044 };
2045
2046 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2047                                                   const char *gitdir)
2048 {
2049         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2050         struct ref_iterator *ref_iterator = &iter->base;
2051         struct strbuf sb = STRBUF_INIT;
2052
2053         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
2054         strbuf_addf(&sb, "%s/logs", gitdir);
2055         iter->dir_iterator = dir_iterator_begin(sb.buf);
2056         iter->ref_store = ref_store;
2057         strbuf_release(&sb);
2058
2059         return ref_iterator;
2060 }
2061
2062 static enum iterator_selection reflog_iterator_select(
2063         struct ref_iterator *iter_worktree,
2064         struct ref_iterator *iter_common,
2065         void *cb_data)
2066 {
2067         if (iter_worktree) {
2068                 /*
2069                  * We're a bit loose here. We probably should ignore
2070                  * common refs if they are accidentally added as
2071                  * per-worktree refs.
2072                  */
2073                 return ITER_SELECT_0;
2074         } else if (iter_common) {
2075                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2076                         return ITER_SELECT_1;
2077
2078                 /*
2079                  * The main ref store may contain main worktree's
2080                  * per-worktree refs, which should be ignored
2081                  */
2082                 return ITER_SKIP_1;
2083         } else
2084                 return ITER_DONE;
2085 }
2086
2087 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2088 {
2089         struct files_ref_store *refs =
2090                 files_downcast(ref_store, REF_STORE_READ,
2091                                "reflog_iterator_begin");
2092
2093         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2094                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2095         } else {
2096                 return merge_ref_iterator_begin(
2097                         reflog_iterator_begin(ref_store, refs->gitdir),
2098                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2099                         reflog_iterator_select, refs);
2100         }
2101 }
2102
2103 /*
2104  * If update is a direct update of head_ref (the reference pointed to
2105  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2106  */
2107 static int split_head_update(struct ref_update *update,
2108                              struct ref_transaction *transaction,
2109                              const char *head_ref,
2110                              struct string_list *affected_refnames,
2111                              struct strbuf *err)
2112 {
2113         struct string_list_item *item;
2114         struct ref_update *new_update;
2115
2116         if ((update->flags & REF_LOG_ONLY) ||
2117             (update->flags & REF_ISPRUNING) ||
2118             (update->flags & REF_UPDATE_VIA_HEAD))
2119                 return 0;
2120
2121         if (strcmp(update->refname, head_ref))
2122                 return 0;
2123
2124         /*
2125          * First make sure that HEAD is not already in the
2126          * transaction. This check is O(lg N) in the transaction
2127          * size, but it happens at most once per transaction.
2128          */
2129         if (string_list_has_string(affected_refnames, "HEAD")) {
2130                 /* An entry already existed */
2131                 strbuf_addf(err,
2132                             "multiple updates for 'HEAD' (including one "
2133                             "via its referent '%s') are not allowed",
2134                             update->refname);
2135                 return TRANSACTION_NAME_CONFLICT;
2136         }
2137
2138         new_update = ref_transaction_add_update(
2139                         transaction, "HEAD",
2140                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2141                         update->new_oid.hash, update->old_oid.hash,
2142                         update->msg);
2143
2144         /*
2145          * Add "HEAD". This insertion is O(N) in the transaction
2146          * size, but it happens at most once per transaction.
2147          * Add new_update->refname instead of a literal "HEAD".
2148          */
2149         if (strcmp(new_update->refname, "HEAD"))
2150                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2151         item = string_list_insert(affected_refnames, new_update->refname);
2152         item->util = new_update;
2153
2154         return 0;
2155 }
2156
2157 /*
2158  * update is for a symref that points at referent and doesn't have
2159  * REF_NODEREF set. Split it into two updates:
2160  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2161  * - A new, separate update for the referent reference
2162  * Note that the new update will itself be subject to splitting when
2163  * the iteration gets to it.
2164  */
2165 static int split_symref_update(struct files_ref_store *refs,
2166                                struct ref_update *update,
2167                                const char *referent,
2168                                struct ref_transaction *transaction,
2169                                struct string_list *affected_refnames,
2170                                struct strbuf *err)
2171 {
2172         struct string_list_item *item;
2173         struct ref_update *new_update;
2174         unsigned int new_flags;
2175
2176         /*
2177          * First make sure that referent is not already in the
2178          * transaction. This check is O(lg N) in the transaction
2179          * size, but it happens at most once per symref in a
2180          * transaction.
2181          */
2182         if (string_list_has_string(affected_refnames, referent)) {
2183                 /* An entry already exists */
2184                 strbuf_addf(err,
2185                             "multiple updates for '%s' (including one "
2186                             "via symref '%s') are not allowed",
2187                             referent, update->refname);
2188                 return TRANSACTION_NAME_CONFLICT;
2189         }
2190
2191         new_flags = update->flags;
2192         if (!strcmp(update->refname, "HEAD")) {
2193                 /*
2194                  * Record that the new update came via HEAD, so that
2195                  * when we process it, split_head_update() doesn't try
2196                  * to add another reflog update for HEAD. Note that
2197                  * this bit will be propagated if the new_update
2198                  * itself needs to be split.
2199                  */
2200                 new_flags |= REF_UPDATE_VIA_HEAD;
2201         }
2202
2203         new_update = ref_transaction_add_update(
2204                         transaction, referent, new_flags,
2205                         update->new_oid.hash, update->old_oid.hash,
2206                         update->msg);
2207
2208         new_update->parent_update = update;
2209
2210         /*
2211          * Change the symbolic ref update to log only. Also, it
2212          * doesn't need to check its old SHA-1 value, as that will be
2213          * done when new_update is processed.
2214          */
2215         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2216         update->flags &= ~REF_HAVE_OLD;
2217
2218         /*
2219          * Add the referent. This insertion is O(N) in the transaction
2220          * size, but it happens at most once per symref in a
2221          * transaction. Make sure to add new_update->refname, which will
2222          * be valid as long as affected_refnames is in use, and NOT
2223          * referent, which might soon be freed by our caller.
2224          */
2225         item = string_list_insert(affected_refnames, new_update->refname);
2226         if (item->util)
2227                 BUG("%s unexpectedly found in affected_refnames",
2228                     new_update->refname);
2229         item->util = new_update;
2230
2231         return 0;
2232 }
2233
2234 /*
2235  * Return the refname under which update was originally requested.
2236  */
2237 static const char *original_update_refname(struct ref_update *update)
2238 {
2239         while (update->parent_update)
2240                 update = update->parent_update;
2241
2242         return update->refname;
2243 }
2244
2245 /*
2246  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2247  * are consistent with oid, which is the reference's current value. If
2248  * everything is OK, return 0; otherwise, write an error message to
2249  * err and return -1.
2250  */
2251 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2252                          struct strbuf *err)
2253 {
2254         if (!(update->flags & REF_HAVE_OLD) ||
2255                    !oidcmp(oid, &update->old_oid))
2256                 return 0;
2257
2258         if (is_null_oid(&update->old_oid))
2259                 strbuf_addf(err, "cannot lock ref '%s': "
2260                             "reference already exists",
2261                             original_update_refname(update));
2262         else if (is_null_oid(oid))
2263                 strbuf_addf(err, "cannot lock ref '%s': "
2264                             "reference is missing but expected %s",
2265                             original_update_refname(update),
2266                             oid_to_hex(&update->old_oid));
2267         else
2268                 strbuf_addf(err, "cannot lock ref '%s': "
2269                             "is at %s but expected %s",
2270                             original_update_refname(update),
2271                             oid_to_hex(oid),
2272                             oid_to_hex(&update->old_oid));
2273
2274         return -1;
2275 }
2276
2277 /*
2278  * Prepare for carrying out update:
2279  * - Lock the reference referred to by update.
2280  * - Read the reference under lock.
2281  * - Check that its old SHA-1 value (if specified) is correct, and in
2282  *   any case record it in update->lock->old_oid for later use when
2283  *   writing the reflog.
2284  * - If it is a symref update without REF_NODEREF, split it up into a
2285  *   REF_LOG_ONLY update of the symref and add a separate update for
2286  *   the referent to transaction.
2287  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2288  *   update of HEAD.
2289  */
2290 static int lock_ref_for_update(struct files_ref_store *refs,
2291                                struct ref_update *update,
2292                                struct ref_transaction *transaction,
2293                                const char *head_ref,
2294                                struct string_list *affected_refnames,
2295                                struct strbuf *err)
2296 {
2297         struct strbuf referent = STRBUF_INIT;
2298         int mustexist = (update->flags & REF_HAVE_OLD) &&
2299                 !is_null_oid(&update->old_oid);
2300         int ret = 0;
2301         struct ref_lock *lock;
2302
2303         files_assert_main_repository(refs, "lock_ref_for_update");
2304
2305         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2306                 update->flags |= REF_DELETING;
2307
2308         if (head_ref) {
2309                 ret = split_head_update(update, transaction, head_ref,
2310                                         affected_refnames, err);
2311                 if (ret)
2312                         goto out;
2313         }
2314
2315         ret = lock_raw_ref(refs, update->refname, mustexist,
2316                            affected_refnames, NULL,
2317                            &lock, &referent,
2318                            &update->type, err);
2319         if (ret) {
2320                 char *reason;
2321
2322                 reason = strbuf_detach(err, NULL);
2323                 strbuf_addf(err, "cannot lock ref '%s': %s",
2324                             original_update_refname(update), reason);
2325                 free(reason);
2326                 goto out;
2327         }
2328
2329         update->backend_data = lock;
2330
2331         if (update->type & REF_ISSYMREF) {
2332                 if (update->flags & REF_NODEREF) {
2333                         /*
2334                          * We won't be reading the referent as part of
2335                          * the transaction, so we have to read it here
2336                          * to record and possibly check old_sha1:
2337                          */
2338                         if (refs_read_ref_full(&refs->base,
2339                                                referent.buf, 0,
2340                                                lock->old_oid.hash, NULL)) {
2341                                 if (update->flags & REF_HAVE_OLD) {
2342                                         strbuf_addf(err, "cannot lock ref '%s': "
2343                                                     "error reading reference",
2344                                                     original_update_refname(update));
2345                                         ret = TRANSACTION_GENERIC_ERROR;
2346                                         goto out;
2347                                 }
2348                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2349                                 ret = TRANSACTION_GENERIC_ERROR;
2350                                 goto out;
2351                         }
2352                 } else {
2353                         /*
2354                          * Create a new update for the reference this
2355                          * symref is pointing at. Also, we will record
2356                          * and verify old_sha1 for this update as part
2357                          * of processing the split-off update, so we
2358                          * don't have to do it here.
2359                          */
2360                         ret = split_symref_update(refs, update,
2361                                                   referent.buf, transaction,
2362                                                   affected_refnames, err);
2363                         if (ret)
2364                                 goto out;
2365                 }
2366         } else {
2367                 struct ref_update *parent_update;
2368
2369                 if (check_old_oid(update, &lock->old_oid, err)) {
2370                         ret = TRANSACTION_GENERIC_ERROR;
2371                         goto out;
2372                 }
2373
2374                 /*
2375                  * If this update is happening indirectly because of a
2376                  * symref update, record the old SHA-1 in the parent
2377                  * update:
2378                  */
2379                 for (parent_update = update->parent_update;
2380                      parent_update;
2381                      parent_update = parent_update->parent_update) {
2382                         struct ref_lock *parent_lock = parent_update->backend_data;
2383                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2384                 }
2385         }
2386
2387         if ((update->flags & REF_HAVE_NEW) &&
2388             !(update->flags & REF_DELETING) &&
2389             !(update->flags & REF_LOG_ONLY)) {
2390                 if (!(update->type & REF_ISSYMREF) &&
2391                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2392                         /*
2393                          * The reference already has the desired
2394                          * value, so we don't need to write it.
2395                          */
2396                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2397                                                  err)) {
2398                         char *write_err = strbuf_detach(err, NULL);
2399
2400                         /*
2401                          * The lock was freed upon failure of
2402                          * write_ref_to_lockfile():
2403                          */
2404                         update->backend_data = NULL;
2405                         strbuf_addf(err,
2406                                     "cannot update ref '%s': %s",
2407                                     update->refname, write_err);
2408                         free(write_err);
2409                         ret = TRANSACTION_GENERIC_ERROR;
2410                         goto out;
2411                 } else {
2412                         update->flags |= REF_NEEDS_COMMIT;
2413                 }
2414         }
2415         if (!(update->flags & REF_NEEDS_COMMIT)) {
2416                 /*
2417                  * We didn't call write_ref_to_lockfile(), so
2418                  * the lockfile is still open. Close it to
2419                  * free up the file descriptor:
2420                  */
2421                 if (close_ref_gently(lock)) {
2422                         strbuf_addf(err, "couldn't close '%s.lock'",
2423                                     update->refname);
2424                         ret = TRANSACTION_GENERIC_ERROR;
2425                         goto out;
2426                 }
2427         }
2428
2429 out:
2430         strbuf_release(&referent);
2431         return ret;
2432 }
2433
2434 /*
2435  * Unlock any references in `transaction` that are still locked, and
2436  * mark the transaction closed.
2437  */
2438 static void files_transaction_cleanup(struct ref_transaction *transaction)
2439 {
2440         size_t i;
2441
2442         for (i = 0; i < transaction->nr; i++) {
2443                 struct ref_update *update = transaction->updates[i];
2444                 struct ref_lock *lock = update->backend_data;
2445
2446                 if (lock) {
2447                         unlock_ref(lock);
2448                         update->backend_data = NULL;
2449                 }
2450         }
2451
2452         transaction->state = REF_TRANSACTION_CLOSED;
2453 }
2454
2455 static int files_transaction_prepare(struct ref_store *ref_store,
2456                                      struct ref_transaction *transaction,
2457                                      struct strbuf *err)
2458 {
2459         struct files_ref_store *refs =
2460                 files_downcast(ref_store, REF_STORE_WRITE,
2461                                "ref_transaction_prepare");
2462         size_t i;
2463         int ret = 0;
2464         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2465         char *head_ref = NULL;
2466         int head_type;
2467         struct object_id head_oid;
2468
2469         assert(err);
2470
2471         if (!transaction->nr)
2472                 goto cleanup;
2473
2474         /*
2475          * Fail if a refname appears more than once in the
2476          * transaction. (If we end up splitting up any updates using
2477          * split_symref_update() or split_head_update(), those
2478          * functions will check that the new updates don't have the
2479          * same refname as any existing ones.)
2480          */
2481         for (i = 0; i < transaction->nr; i++) {
2482                 struct ref_update *update = transaction->updates[i];
2483                 struct string_list_item *item =
2484                         string_list_append(&affected_refnames, update->refname);
2485
2486                 /*
2487                  * We store a pointer to update in item->util, but at
2488                  * the moment we never use the value of this field
2489                  * except to check whether it is non-NULL.
2490                  */
2491                 item->util = update;
2492         }
2493         string_list_sort(&affected_refnames);
2494         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2495                 ret = TRANSACTION_GENERIC_ERROR;
2496                 goto cleanup;
2497         }
2498
2499         /*
2500          * Special hack: If a branch is updated directly and HEAD
2501          * points to it (may happen on the remote side of a push
2502          * for example) then logically the HEAD reflog should be
2503          * updated too.
2504          *
2505          * A generic solution would require reverse symref lookups,
2506          * but finding all symrefs pointing to a given branch would be
2507          * rather costly for this rare event (the direct update of a
2508          * branch) to be worth it. So let's cheat and check with HEAD
2509          * only, which should cover 99% of all usage scenarios (even
2510          * 100% of the default ones).
2511          *
2512          * So if HEAD is a symbolic reference, then record the name of
2513          * the reference that it points to. If we see an update of
2514          * head_ref within the transaction, then split_head_update()
2515          * arranges for the reflog of HEAD to be updated, too.
2516          */
2517         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2518                                        RESOLVE_REF_NO_RECURSE,
2519                                        head_oid.hash, &head_type);
2520
2521         if (head_ref && !(head_type & REF_ISSYMREF)) {
2522                 FREE_AND_NULL(head_ref);
2523         }
2524
2525         /*
2526          * Acquire all locks, verify old values if provided, check
2527          * that new values are valid, and write new values to the
2528          * lockfiles, ready to be activated. Only keep one lockfile
2529          * open at a time to avoid running out of file descriptors.
2530          * Note that lock_ref_for_update() might append more updates
2531          * to the transaction.
2532          */
2533         for (i = 0; i < transaction->nr; i++) {
2534                 struct ref_update *update = transaction->updates[i];
2535
2536                 ret = lock_ref_for_update(refs, update, transaction,
2537                                           head_ref, &affected_refnames, err);
2538                 if (ret)
2539                         break;
2540         }
2541
2542 cleanup:
2543         free(head_ref);
2544         string_list_clear(&affected_refnames, 0);
2545
2546         if (ret)
2547                 files_transaction_cleanup(transaction);
2548         else
2549                 transaction->state = REF_TRANSACTION_PREPARED;
2550
2551         return ret;
2552 }
2553
2554 static int files_transaction_finish(struct ref_store *ref_store,
2555                                     struct ref_transaction *transaction,
2556                                     struct strbuf *err)
2557 {
2558         struct files_ref_store *refs =
2559                 files_downcast(ref_store, 0, "ref_transaction_finish");
2560         size_t i;
2561         int ret = 0;
2562         struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
2563         struct string_list_item *ref_to_delete;
2564         struct strbuf sb = STRBUF_INIT;
2565
2566         assert(err);
2567
2568         if (!transaction->nr) {
2569                 transaction->state = REF_TRANSACTION_CLOSED;
2570                 return 0;
2571         }
2572
2573         /* Perform updates first so live commits remain referenced */
2574         for (i = 0; i < transaction->nr; i++) {
2575                 struct ref_update *update = transaction->updates[i];
2576                 struct ref_lock *lock = update->backend_data;
2577
2578                 if (update->flags & REF_NEEDS_COMMIT ||
2579                     update->flags & REF_LOG_ONLY) {
2580                         if (files_log_ref_write(refs,
2581                                                 lock->ref_name,
2582                                                 &lock->old_oid,
2583                                                 &update->new_oid,
2584                                                 update->msg, update->flags,
2585                                                 err)) {
2586                                 char *old_msg = strbuf_detach(err, NULL);
2587
2588                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2589                                             lock->ref_name, old_msg);
2590                                 free(old_msg);
2591                                 unlock_ref(lock);
2592                                 update->backend_data = NULL;
2593                                 ret = TRANSACTION_GENERIC_ERROR;
2594                                 goto cleanup;
2595                         }
2596                 }
2597                 if (update->flags & REF_NEEDS_COMMIT) {
2598                         clear_loose_ref_cache(refs);
2599                         if (commit_ref(lock)) {
2600                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2601                                 unlock_ref(lock);
2602                                 update->backend_data = NULL;
2603                                 ret = TRANSACTION_GENERIC_ERROR;
2604                                 goto cleanup;
2605                         }
2606                 }
2607         }
2608         /* Perform deletes now that updates are safely completed */
2609         for (i = 0; i < transaction->nr; i++) {
2610                 struct ref_update *update = transaction->updates[i];
2611                 struct ref_lock *lock = update->backend_data;
2612
2613                 if (update->flags & REF_DELETING &&
2614                     !(update->flags & REF_LOG_ONLY)) {
2615                         if (!(update->type & REF_ISPACKED) ||
2616                             update->type & REF_ISSYMREF) {
2617                                 /* It is a loose reference. */
2618                                 strbuf_reset(&sb);
2619                                 files_ref_path(refs, &sb, lock->ref_name);
2620                                 if (unlink_or_msg(sb.buf, err)) {
2621                                         ret = TRANSACTION_GENERIC_ERROR;
2622                                         goto cleanup;
2623                                 }
2624                                 update->flags |= REF_DELETED_LOOSE;
2625                         }
2626
2627                         if (!(update->flags & REF_ISPRUNING))
2628                                 string_list_append(&refs_to_delete,
2629                                                    lock->ref_name);
2630                 }
2631         }
2632
2633         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2634                 ret = TRANSACTION_GENERIC_ERROR;
2635                 goto cleanup;
2636         }
2637
2638         if (repack_without_refs(refs->packed_ref_store, &refs_to_delete, err)) {
2639                 ret = TRANSACTION_GENERIC_ERROR;
2640                 packed_refs_unlock(refs->packed_ref_store);
2641                 goto cleanup;
2642         }
2643
2644         packed_refs_unlock(refs->packed_ref_store);
2645
2646         /* Delete the reflogs of any references that were deleted: */
2647         for_each_string_list_item(ref_to_delete, &refs_to_delete) {
2648                 strbuf_reset(&sb);
2649                 files_reflog_path(refs, &sb, ref_to_delete->string);
2650                 if (!unlink_or_warn(sb.buf))
2651                         try_remove_empty_parents(refs, ref_to_delete->string,
2652                                                  REMOVE_EMPTY_PARENTS_REFLOG);
2653         }
2654
2655         clear_loose_ref_cache(refs);
2656
2657 cleanup:
2658         files_transaction_cleanup(transaction);
2659
2660         for (i = 0; i < transaction->nr; i++) {
2661                 struct ref_update *update = transaction->updates[i];
2662
2663                 if (update->flags & REF_DELETED_LOOSE) {
2664                         /*
2665                          * The loose reference was deleted. Delete any
2666                          * empty parent directories. (Note that this
2667                          * can only work because we have already
2668                          * removed the lockfile.)
2669                          */
2670                         try_remove_empty_parents(refs, update->refname,
2671                                                  REMOVE_EMPTY_PARENTS_REF);
2672                 }
2673         }
2674
2675         strbuf_release(&sb);
2676         string_list_clear(&refs_to_delete, 0);
2677         return ret;
2678 }
2679
2680 static int files_transaction_abort(struct ref_store *ref_store,
2681                                    struct ref_transaction *transaction,
2682                                    struct strbuf *err)
2683 {
2684         files_transaction_cleanup(transaction);
2685         return 0;
2686 }
2687
2688 static int ref_present(const char *refname,
2689                        const struct object_id *oid, int flags, void *cb_data)
2690 {
2691         struct string_list *affected_refnames = cb_data;
2692
2693         return string_list_has_string(affected_refnames, refname);
2694 }
2695
2696 static int files_initial_transaction_commit(struct ref_store *ref_store,
2697                                             struct ref_transaction *transaction,
2698                                             struct strbuf *err)
2699 {
2700         struct files_ref_store *refs =
2701                 files_downcast(ref_store, REF_STORE_WRITE,
2702                                "initial_ref_transaction_commit");
2703         size_t i;
2704         int ret = 0;
2705         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2706
2707         assert(err);
2708
2709         if (transaction->state != REF_TRANSACTION_OPEN)
2710                 die("BUG: commit called for transaction that is not open");
2711
2712         /* Fail if a refname appears more than once in the transaction: */
2713         for (i = 0; i < transaction->nr; i++)
2714                 string_list_append(&affected_refnames,
2715                                    transaction->updates[i]->refname);
2716         string_list_sort(&affected_refnames);
2717         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2718                 ret = TRANSACTION_GENERIC_ERROR;
2719                 goto cleanup;
2720         }
2721
2722         /*
2723          * It's really undefined to call this function in an active
2724          * repository or when there are existing references: we are
2725          * only locking and changing packed-refs, so (1) any
2726          * simultaneous processes might try to change a reference at
2727          * the same time we do, and (2) any existing loose versions of
2728          * the references that we are setting would have precedence
2729          * over our values. But some remote helpers create the remote
2730          * "HEAD" and "master" branches before calling this function,
2731          * so here we really only check that none of the references
2732          * that we are creating already exists.
2733          */
2734         if (refs_for_each_rawref(&refs->base, ref_present,
2735                                  &affected_refnames))
2736                 die("BUG: initial ref transaction called with existing refs");
2737
2738         for (i = 0; i < transaction->nr; i++) {
2739                 struct ref_update *update = transaction->updates[i];
2740
2741                 if ((update->flags & REF_HAVE_OLD) &&
2742                     !is_null_oid(&update->old_oid))
2743                         die("BUG: initial ref transaction with old_sha1 set");
2744                 if (refs_verify_refname_available(&refs->base, update->refname,
2745                                                   &affected_refnames, NULL,
2746                                                   err)) {
2747                         ret = TRANSACTION_NAME_CONFLICT;
2748                         goto cleanup;
2749                 }
2750         }
2751
2752         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2753                 ret = TRANSACTION_GENERIC_ERROR;
2754                 goto cleanup;
2755         }
2756
2757         for (i = 0; i < transaction->nr; i++) {
2758                 struct ref_update *update = transaction->updates[i];
2759
2760                 if ((update->flags & REF_HAVE_NEW) &&
2761                     !is_null_oid(&update->new_oid))
2762                         add_packed_ref(refs->packed_ref_store, update->refname,
2763                                        &update->new_oid);
2764         }
2765
2766         if (commit_packed_refs(refs->packed_ref_store, err)) {
2767                 ret = TRANSACTION_GENERIC_ERROR;
2768                 goto cleanup;
2769         }
2770
2771 cleanup:
2772         packed_refs_unlock(refs->packed_ref_store);
2773         transaction->state = REF_TRANSACTION_CLOSED;
2774         string_list_clear(&affected_refnames, 0);
2775         return ret;
2776 }
2777
2778 struct expire_reflog_cb {
2779         unsigned int flags;
2780         reflog_expiry_should_prune_fn *should_prune_fn;
2781         void *policy_cb;
2782         FILE *newlog;
2783         struct object_id last_kept_oid;
2784 };
2785
2786 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2787                              const char *email, timestamp_t timestamp, int tz,
2788                              const char *message, void *cb_data)
2789 {
2790         struct expire_reflog_cb *cb = cb_data;
2791         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2792
2793         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2794                 ooid = &cb->last_kept_oid;
2795
2796         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2797                                    message, policy_cb)) {
2798                 if (!cb->newlog)
2799                         printf("would prune %s", message);
2800                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2801                         printf("prune %s", message);
2802         } else {
2803                 if (cb->newlog) {
2804                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2805                                 oid_to_hex(ooid), oid_to_hex(noid),
2806                                 email, timestamp, tz, message);
2807                         oidcpy(&cb->last_kept_oid, noid);
2808                 }
2809                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2810                         printf("keep %s", message);
2811         }
2812         return 0;
2813 }
2814
2815 static int files_reflog_expire(struct ref_store *ref_store,
2816                                const char *refname, const unsigned char *sha1,
2817                                unsigned int flags,
2818                                reflog_expiry_prepare_fn prepare_fn,
2819                                reflog_expiry_should_prune_fn should_prune_fn,
2820                                reflog_expiry_cleanup_fn cleanup_fn,
2821                                void *policy_cb_data)
2822 {
2823         struct files_ref_store *refs =
2824                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2825         static struct lock_file reflog_lock;
2826         struct expire_reflog_cb cb;
2827         struct ref_lock *lock;
2828         struct strbuf log_file_sb = STRBUF_INIT;
2829         char *log_file;
2830         int status = 0;
2831         int type;
2832         struct strbuf err = STRBUF_INIT;
2833         struct object_id oid;
2834
2835         memset(&cb, 0, sizeof(cb));
2836         cb.flags = flags;
2837         cb.policy_cb = policy_cb_data;
2838         cb.should_prune_fn = should_prune_fn;
2839
2840         /*
2841          * The reflog file is locked by holding the lock on the
2842          * reference itself, plus we might need to update the
2843          * reference if --updateref was specified:
2844          */
2845         lock = lock_ref_sha1_basic(refs, refname, sha1,
2846                                    NULL, NULL, REF_NODEREF,
2847                                    &type, &err);
2848         if (!lock) {
2849                 error("cannot lock ref '%s': %s", refname, err.buf);
2850                 strbuf_release(&err);
2851                 return -1;
2852         }
2853         if (!refs_reflog_exists(ref_store, refname)) {
2854                 unlock_ref(lock);
2855                 return 0;
2856         }
2857
2858         files_reflog_path(refs, &log_file_sb, refname);
2859         log_file = strbuf_detach(&log_file_sb, NULL);
2860         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2861                 /*
2862                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2863                  * no locking implications, we use the lock_file
2864                  * machinery here anyway because it does a lot of the
2865                  * work we need, including cleaning up if the program
2866                  * exits unexpectedly.
2867                  */
2868                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2869                         struct strbuf err = STRBUF_INIT;
2870                         unable_to_lock_message(log_file, errno, &err);
2871                         error("%s", err.buf);
2872                         strbuf_release(&err);
2873                         goto failure;
2874                 }
2875                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
2876                 if (!cb.newlog) {
2877                         error("cannot fdopen %s (%s)",
2878                               get_lock_file_path(&reflog_lock), strerror(errno));
2879                         goto failure;
2880                 }
2881         }
2882
2883         hashcpy(oid.hash, sha1);
2884
2885         (*prepare_fn)(refname, &oid, cb.policy_cb);
2886         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
2887         (*cleanup_fn)(cb.policy_cb);
2888
2889         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2890                 /*
2891                  * It doesn't make sense to adjust a reference pointed
2892                  * to by a symbolic ref based on expiring entries in
2893                  * the symbolic reference's reflog. Nor can we update
2894                  * a reference if there are no remaining reflog
2895                  * entries.
2896                  */
2897                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
2898                         !(type & REF_ISSYMREF) &&
2899                         !is_null_oid(&cb.last_kept_oid);
2900
2901                 if (close_lock_file_gently(&reflog_lock)) {
2902                         status |= error("couldn't write %s: %s", log_file,
2903                                         strerror(errno));
2904                         rollback_lock_file(&reflog_lock);
2905                 } else if (update &&
2906                            (write_in_full(get_lock_file_fd(&lock->lk),
2907                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
2908                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") != 1 ||
2909                             close_ref_gently(lock) < 0)) {
2910                         status |= error("couldn't write %s",
2911                                         get_lock_file_path(&lock->lk));
2912                         rollback_lock_file(&reflog_lock);
2913                 } else if (commit_lock_file(&reflog_lock)) {
2914                         status |= error("unable to write reflog '%s' (%s)",
2915                                         log_file, strerror(errno));
2916                 } else if (update && commit_ref(lock)) {
2917                         status |= error("couldn't set %s", lock->ref_name);
2918                 }
2919         }
2920         free(log_file);
2921         unlock_ref(lock);
2922         return status;
2923
2924  failure:
2925         rollback_lock_file(&reflog_lock);
2926         free(log_file);
2927         unlock_ref(lock);
2928         return -1;
2929 }
2930
2931 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
2932 {
2933         struct files_ref_store *refs =
2934                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
2935         struct strbuf sb = STRBUF_INIT;
2936
2937         /*
2938          * Create .git/refs/{heads,tags}
2939          */
2940         files_ref_path(refs, &sb, "refs/heads");
2941         safe_create_dir(sb.buf, 1);
2942
2943         strbuf_reset(&sb);
2944         files_ref_path(refs, &sb, "refs/tags");
2945         safe_create_dir(sb.buf, 1);
2946
2947         strbuf_release(&sb);
2948         return 0;
2949 }
2950
2951 struct ref_storage_be refs_be_files = {
2952         NULL,
2953         "files",
2954         files_ref_store_create,
2955         files_init_db,
2956         files_transaction_prepare,
2957         files_transaction_finish,
2958         files_transaction_abort,
2959         files_initial_transaction_commit,
2960
2961         files_pack_refs,
2962         files_peel_ref,
2963         files_create_symref,
2964         files_delete_refs,
2965         files_rename_ref,
2966
2967         files_ref_iterator_begin,
2968         files_read_raw_ref,
2969
2970         files_reflog_iterator_begin,
2971         files_for_each_reflog_ent,
2972         files_for_each_reflog_ent_reverse,
2973         files_reflog_exists,
2974         files_create_reflog,
2975         files_delete_reflog,
2976         files_reflog_expire
2977 };