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