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

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