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

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