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, *overlay_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         /*
 776          * We must make sure that all loose refs are read before
 777          * accessing the packed-refs file; this avoids a race
 778          * condition if loose refs are migrated to the packed-refs
 779          * file by a simultaneous process, but our in-memory view is
 780          * from before the migration. We ensure this as follows:
 781          * First, we call start the loose refs iteration with its
 782          * `prime_ref` argument set to true. This causes the loose
 783          * references in the subtree to be pre-read into the cache.
 784          * (If they've already been read, that's OK; we only need to
 785          * guarantee that they're read before the packed refs, not
 786          * *how much* before.) After that, we call
 787          * packed_ref_iterator_begin(), which internally checks
 788          * whether the packed-ref cache is up to date with what is on
 789          * disk, and re-reads it if not.
 790          */
 791
 792         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 793                                               prefix, 1);
 794
 795         /*
 796          * The packed-refs file might contain broken references, for
 797          * example an old version of a reference that points at an
 798          * object that has since been garbage-collected. This is OK as
 799          * long as there is a corresponding loose reference that
 800          * overrides it, and we don't want to emit an error message in
 801          * this case. So ask the packed_ref_store for all of its
 802          * references, and (if needed) do our own check for broken
 803          * ones in files_ref_iterator_advance(), after we have merged
 804          * the packed and loose references.
 805          */
 806         packed_iter = refs_ref_iterator_begin(
 807                         refs->packed_ref_store, prefix, 0,
 808                         DO_FOR_EACH_INCLUDE_BROKEN);
 809
 810         overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 811
 812         iter = xcalloc(1, sizeof(*iter));
 813         ref_iterator = &iter->base;
 814         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 815                                overlay_iter->ordered);
 816         iter->iter0 = overlay_iter;
 817         iter->flags = flags;
 818
 819         return ref_iterator;
 820 }
 821
 822 /*
 823  * Verify that the reference locked by lock has the value old_sha1.
 824  * Fail if the reference doesn't exist and mustexist is set. Return 0
 825  * on success. On error, write an error message to err, set errno, and
 826  * return a negative value.
 827  */
 828 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 829                        const unsigned char *old_sha1, int mustexist,
 830                        struct strbuf *err)
 831 {
 832         assert(err);
 833
 834         if (refs_read_ref_full(ref_store, lock->ref_name,
 835                                mustexist ? RESOLVE_REF_READING : 0,
 836                                lock->old_oid.hash, NULL)) {
 837                 if (old_sha1) {
 838                         int save_errno = errno;
 839                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 840                         errno = save_errno;
 841                         return -1;
 842                 } else {
 843                         oidclr(&lock->old_oid);
 844                         return 0;
 845                 }
 846         }
 847         if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
 848                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 849                             lock->ref_name,
 850                             oid_to_hex(&lock->old_oid),
 851                             sha1_to_hex(old_sha1));
 852                 errno = EBUSY;
 853                 return -1;
 854         }
 855         return 0;
 856 }
 857
 858 static int remove_empty_directories(struct strbuf *path)
 859 {
 860         /*
 861          * we want to create a file but there is a directory there;
 862          * if that is an empty directory (or a directory that contains
 863          * only empty directories), remove them.
 864          */
 865         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 866 }
 867
 868 static int create_reflock(const char *path, void *cb)
 869 {
 870         struct lock_file *lk = cb;
 871
 872         return hold_lock_file_for_update_timeout(
 873                         lk, path, LOCK_NO_DEREF,
 874                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 875 }
 876
 877 /*
 878  * Locks a ref returning the lock on success and NULL on failure.
 879  * On failure errno is set to something meaningful.
 880  */
 881 static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
 882                                             const char *refname,
 883                                             const unsigned char *old_sha1,
 884                                             const struct string_list *extras,
 885                                             const struct string_list *skip,
 886                                             unsigned int flags, int *type,
 887                                             struct strbuf *err)
 888 {
 889         struct strbuf ref_file = STRBUF_INIT;
 890         struct ref_lock *lock;
 891         int last_errno = 0;
 892         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 893         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 894         int resolved;
 895
 896         files_assert_main_repository(refs, "lock_ref_sha1_basic");
 897         assert(err);
 898
 899         lock = xcalloc(1, sizeof(struct ref_lock));
 900
 901         if (mustexist)
 902                 resolve_flags |= RESOLVE_REF_READING;
 903         if (flags & REF_DELETING)
 904                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 905
 906         files_ref_path(refs, &ref_file, refname);
 907         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 908                                              refname, resolve_flags,
 909                                              lock->old_oid.hash, type);
 910         if (!resolved && errno == EISDIR) {
 911                 /*
 912                  * we are trying to lock foo but we used to
 913                  * have foo/bar which now does not exist;
 914                  * it is normal for the empty directory 'foo'
 915                  * to remain.
 916                  */
 917                 if (remove_empty_directories(&ref_file)) {
 918                         last_errno = errno;
 919                         if (!refs_verify_refname_available(
 920                                             &refs->base,
 921                                             refname, extras, skip, err))
 922                                 strbuf_addf(err, "there are still refs under '%s'",
 923                                             refname);
 924                         goto error_return;
 925                 }
 926                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 927                                                      refname, resolve_flags,
 928                                                      lock->old_oid.hash, type);
 929         }
 930         if (!resolved) {
 931                 last_errno = errno;
 932                 if (last_errno != ENOTDIR ||
 933                     !refs_verify_refname_available(&refs->base, refname,
 934                                                    extras, skip, err))
 935                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 936                                     refname, strerror(last_errno));
 937
 938                 goto error_return;
 939         }
 940
 941         /*
 942          * If the ref did not exist and we are creating it, make sure
 943          * there is no existing packed ref whose name begins with our
 944          * refname, nor a packed ref whose name is a proper prefix of
 945          * our refname.
 946          */
 947         if (is_null_oid(&lock->old_oid) &&
 948             refs_verify_refname_available(refs->packed_ref_store, refname,
 949                                           extras, skip, err)) {
 950                 last_errno = ENOTDIR;
 951                 goto error_return;
 952         }
 953
 954         lock->lk = xcalloc(1, sizeof(struct lock_file));
 955
 956         lock->ref_name = xstrdup(refname);
 957
 958         if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
 959                 last_errno = errno;
 960                 unable_to_lock_message(ref_file.buf, errno, err);
 961                 goto error_return;
 962         }
 963
 964         if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
 965                 last_errno = errno;
 966                 goto error_return;
 967         }
 968         goto out;
 969
 970  error_return:
 971         unlock_ref(lock);
 972         lock = NULL;
 973
 974  out:
 975         strbuf_release(&ref_file);
 976         errno = last_errno;
 977         return lock;
 978 }
 979
 980 struct ref_to_prune {
 981         struct ref_to_prune *next;
 982         unsigned char sha1[20];
 983         char name[FLEX_ARRAY];
 984 };
 985
 986 enum {
 987         REMOVE_EMPTY_PARENTS_REF = 0x01,
 988         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 989 };
 990
 991 /*
 992  * Remove empty parent directories associated with the specified
 993  * reference and/or its reflog, but spare [logs/]refs/ and immediate
 994  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 995  * REMOVE_EMPTY_PARENTS_REFLOG.
 996  */
 997 static void try_remove_empty_parents(struct files_ref_store *refs,
 998                                      const char *refname,
 999                                      unsigned int flags)
1000 {
1001         struct strbuf buf = STRBUF_INIT;
1002         struct strbuf sb = STRBUF_INIT;
1003         char *p, *q;
1004         int i;
1005
1006         strbuf_addstr(&buf, refname);
1007         p = buf.buf;
1008         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1009                 while (*p && *p != '/')
1010                         p++;
1011                 /* tolerate duplicate slashes; see check_refname_format() */
1012                 while (*p == '/')
1013                         p++;
1014         }
1015         q = buf.buf + buf.len;
1016         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1017                 while (q > p && *q != '/')
1018                         q--;
1019                 while (q > p && *(q-1) == '/')
1020                         q--;
1021                 if (q == p)
1022                         break;
1023                 strbuf_setlen(&buf, q - buf.buf);
1024
1025                 strbuf_reset(&sb);
1026                 files_ref_path(refs, &sb, buf.buf);
1027                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1028                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1029
1030                 strbuf_reset(&sb);
1031                 files_reflog_path(refs, &sb, buf.buf);
1032                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1033                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1034         }
1035         strbuf_release(&buf);
1036         strbuf_release(&sb);
1037 }
1038
1039 /* make sure nobody touched the ref, and unlink */
1040 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1041 {
1042         struct ref_transaction *transaction;
1043         struct strbuf err = STRBUF_INIT;
1044
1045         if (check_refname_format(r->name, 0))
1046                 return;
1047
1048         transaction = ref_store_transaction_begin(&refs->base, &err);
1049         if (!transaction ||
1050             ref_transaction_delete(transaction, r->name, r->sha1,
1051                                    REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
1052             ref_transaction_commit(transaction, &err)) {
1053                 ref_transaction_free(transaction);
1054                 error("%s", err.buf);
1055                 strbuf_release(&err);
1056                 return;
1057         }
1058         ref_transaction_free(transaction);
1059         strbuf_release(&err);
1060 }
1061
1062 /*
1063  * Prune the loose versions of the references in the linked list
1064  * `*refs_to_prune`, freeing the entries in the list as we go.
1065  */
1066 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1067 {
1068         while (*refs_to_prune) {
1069                 struct ref_to_prune *r = *refs_to_prune;
1070                 *refs_to_prune = r->next;
1071                 prune_ref(refs, r);
1072                 free(r);
1073         }
1074 }
1075
1076 /*
1077  * Return true if the specified reference should be packed.
1078  */
1079 static int should_pack_ref(const char *refname,
1080                            const struct object_id *oid, unsigned int ref_flags,
1081                            unsigned int pack_flags)
1082 {
1083         /* Do not pack per-worktree refs: */
1084         if (ref_type(refname) != REF_TYPE_NORMAL)
1085                 return 0;
1086
1087         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1088         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1089                 return 0;
1090
1091         /* Do not pack symbolic refs: */
1092         if (ref_flags & REF_ISSYMREF)
1093                 return 0;
1094
1095         /* Do not pack broken refs: */
1096         if (!ref_resolves_to_object(refname, oid, ref_flags))
1097                 return 0;
1098
1099         return 1;
1100 }
1101
1102 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1103 {
1104         struct files_ref_store *refs =
1105                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1106                                "pack_refs");
1107         struct ref_iterator *iter;
1108         int ok;
1109         struct ref_to_prune *refs_to_prune = NULL;
1110         struct strbuf err = STRBUF_INIT;
1111         struct ref_transaction *transaction;
1112
1113         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1114         if (!transaction)
1115                 return -1;
1116
1117         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1118
1119         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1120         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1121                 /*
1122                  * If the loose reference can be packed, add an entry
1123                  * in the packed ref cache. If the reference should be
1124                  * pruned, also add it to refs_to_prune.
1125                  */
1126                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1127                                      flags))
1128                         continue;
1129
1130                 /*
1131                  * Add a reference creation for this reference to the
1132                  * packed-refs transaction:
1133                  */
1134                 if (ref_transaction_update(transaction, iter->refname,
1135                                            iter->oid->hash, NULL,
1136                                            REF_NODEREF, NULL, &err))
1137                         die("failure preparing to create packed reference %s: %s",
1138                             iter->refname, err.buf);
1139
1140                 /* Schedule the loose reference for pruning if requested. */
1141                 if ((flags & PACK_REFS_PRUNE)) {
1142                         struct ref_to_prune *n;
1143                         FLEX_ALLOC_STR(n, name, iter->refname);
1144                         hashcpy(n->sha1, iter->oid->hash);
1145                         n->next = refs_to_prune;
1146                         refs_to_prune = n;
1147                 }
1148         }
1149         if (ok != ITER_DONE)
1150                 die("error while iterating over references");
1151
1152         if (ref_transaction_commit(transaction, &err))
1153                 die("unable to write new packed-refs: %s", err.buf);
1154
1155         ref_transaction_free(transaction);
1156
1157         packed_refs_unlock(refs->packed_ref_store);
1158
1159         prune_refs(refs, &refs_to_prune);
1160         strbuf_release(&err);
1161         return 0;
1162 }
1163
1164 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1165                              struct string_list *refnames, unsigned int flags)
1166 {
1167         struct files_ref_store *refs =
1168                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1169         struct strbuf err = STRBUF_INIT;
1170         int i, result = 0;
1171
1172         if (!refnames->nr)
1173                 return 0;
1174
1175         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1176                 goto error;
1177
1178         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1179                 packed_refs_unlock(refs->packed_ref_store);
1180                 goto error;
1181         }
1182
1183         packed_refs_unlock(refs->packed_ref_store);
1184
1185         for (i = 0; i < refnames->nr; i++) {
1186                 const char *refname = refnames->items[i].string;
1187
1188                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1189                         result |= error(_("could not remove reference %s"), refname);
1190         }
1191
1192         strbuf_release(&err);
1193         return result;
1194
1195 error:
1196         /*
1197          * If we failed to rewrite the packed-refs file, then it is
1198          * unsafe to try to remove loose refs, because doing so might
1199          * expose an obsolete packed value for a reference that might
1200          * even point at an object that has been garbage collected.
1201          */
1202         if (refnames->nr == 1)
1203                 error(_("could not delete reference %s: %s"),
1204                       refnames->items[0].string, err.buf);
1205         else
1206                 error(_("could not delete references: %s"), err.buf);
1207
1208         strbuf_release(&err);
1209         return -1;
1210 }
1211
1212 /*
1213  * People using contrib's git-new-workdir have .git/logs/refs ->
1214  * /some/other/path/.git/logs/refs, and that may live on another device.
1215  *
1216  * IOW, to avoid cross device rename errors, the temporary renamed log must
1217  * live into logs/refs.
1218  */
1219 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1220
1221 struct rename_cb {
1222         const char *tmp_renamed_log;
1223         int true_errno;
1224 };
1225
1226 static int rename_tmp_log_callback(const char *path, void *cb_data)
1227 {
1228         struct rename_cb *cb = cb_data;
1229
1230         if (rename(cb->tmp_renamed_log, path)) {
1231                 /*
1232                  * rename(a, b) when b is an existing directory ought
1233                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1234                  * Sheesh. Record the true errno for error reporting,
1235                  * but report EISDIR to raceproof_create_file() so
1236                  * that it knows to retry.
1237                  */
1238                 cb->true_errno = errno;
1239                 if (errno == ENOTDIR)
1240                         errno = EISDIR;
1241                 return -1;
1242         } else {
1243                 return 0;
1244         }
1245 }
1246
1247 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1248 {
1249         struct strbuf path = STRBUF_INIT;
1250         struct strbuf tmp = STRBUF_INIT;
1251         struct rename_cb cb;
1252         int ret;
1253
1254         files_reflog_path(refs, &path, newrefname);
1255         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1256         cb.tmp_renamed_log = tmp.buf;
1257         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1258         if (ret) {
1259                 if (errno == EISDIR)
1260                         error("directory not empty: %s", path.buf);
1261                 else
1262                         error("unable to move logfile %s to %s: %s",
1263                               tmp.buf, path.buf,
1264                               strerror(cb.true_errno));
1265         }
1266
1267         strbuf_release(&path);
1268         strbuf_release(&tmp);
1269         return ret;
1270 }
1271
1272 static int write_ref_to_lockfile(struct ref_lock *lock,
1273                                  const struct object_id *oid, struct strbuf *err);
1274 static int commit_ref_update(struct files_ref_store *refs,
1275                              struct ref_lock *lock,
1276                              const struct object_id *oid, const char *logmsg,
1277                              struct strbuf *err);
1278
1279 static int files_rename_ref(struct ref_store *ref_store,
1280                             const char *oldrefname, const char *newrefname,
1281                             const char *logmsg)
1282 {
1283         struct files_ref_store *refs =
1284                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1285         struct object_id oid, orig_oid;
1286         int flag = 0, logmoved = 0;
1287         struct ref_lock *lock;
1288         struct stat loginfo;
1289         struct strbuf sb_oldref = STRBUF_INIT;
1290         struct strbuf sb_newref = STRBUF_INIT;
1291         struct strbuf tmp_renamed_log = STRBUF_INIT;
1292         int log, ret;
1293         struct strbuf err = STRBUF_INIT;
1294
1295         files_reflog_path(refs, &sb_oldref, oldrefname);
1296         files_reflog_path(refs, &sb_newref, newrefname);
1297         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1298
1299         log = !lstat(sb_oldref.buf, &loginfo);
1300         if (log && S_ISLNK(loginfo.st_mode)) {
1301                 ret = error("reflog for %s is a symlink", oldrefname);
1302                 goto out;
1303         }
1304
1305         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1306                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1307                                 orig_oid.hash, &flag)) {
1308                 ret = error("refname %s not found", oldrefname);
1309                 goto out;
1310         }
1311
1312         if (flag & REF_ISSYMREF) {
1313                 ret = error("refname %s is a symbolic ref, renaming it is not supported",
1314                             oldrefname);
1315                 goto out;
1316         }
1317         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1318                 ret = 1;
1319                 goto out;
1320         }
1321
1322         if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1323                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1324                             oldrefname, strerror(errno));
1325                 goto out;
1326         }
1327
1328         if (refs_delete_ref(&refs->base, logmsg, oldrefname,
1329                             orig_oid.hash, REF_NODEREF)) {
1330                 error("unable to delete old %s", oldrefname);
1331                 goto rollback;
1332         }
1333
1334         /*
1335          * Since we are doing a shallow lookup, oid is not the
1336          * correct value to pass to delete_ref as old_oid. But that
1337          * doesn't matter, because an old_oid check wouldn't add to
1338          * the safety anyway; we want to delete the reference whatever
1339          * its current value.
1340          */
1341         if (!refs_read_ref_full(&refs->base, newrefname,
1342                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1343                                 oid.hash, NULL) &&
1344             refs_delete_ref(&refs->base, NULL, newrefname,
1345                             NULL, REF_NODEREF)) {
1346                 if (errno == EISDIR) {
1347                         struct strbuf path = STRBUF_INIT;
1348                         int result;
1349
1350                         files_ref_path(refs, &path, newrefname);
1351                         result = remove_empty_directories(&path);
1352                         strbuf_release(&path);
1353
1354                         if (result) {
1355                                 error("Directory not empty: %s", newrefname);
1356                                 goto rollback;
1357                         }
1358                 } else {
1359                         error("unable to delete existing %s", newrefname);
1360                         goto rollback;
1361                 }
1362         }
1363
1364         if (log && rename_tmp_log(refs, newrefname))
1365                 goto rollback;
1366
1367         logmoved = log;
1368
1369         lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
1370                                    REF_NODEREF, NULL, &err);
1371         if (!lock) {
1372                 error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1373                 strbuf_release(&err);
1374                 goto rollback;
1375         }
1376         oidcpy(&lock->old_oid, &orig_oid);
1377
1378         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1379             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1380                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1381                 strbuf_release(&err);
1382                 goto rollback;
1383         }
1384
1385         ret = 0;
1386         goto out;
1387
1388  rollback:
1389         lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
1390                                    REF_NODEREF, NULL, &err);
1391         if (!lock) {
1392                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1393                 strbuf_release(&err);
1394                 goto rollbacklog;
1395         }
1396
1397         flag = log_all_ref_updates;
1398         log_all_ref_updates = LOG_REFS_NONE;
1399         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1400             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1401                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1402                 strbuf_release(&err);
1403         }
1404         log_all_ref_updates = flag;
1405
1406  rollbacklog:
1407         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1408                 error("unable to restore logfile %s from %s: %s",
1409                         oldrefname, newrefname, strerror(errno));
1410         if (!logmoved && log &&
1411             rename(tmp_renamed_log.buf, sb_oldref.buf))
1412                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1413                         oldrefname, strerror(errno));
1414         ret = 1;
1415  out:
1416         strbuf_release(&sb_newref);
1417         strbuf_release(&sb_oldref);
1418         strbuf_release(&tmp_renamed_log);
1419
1420         return ret;
1421 }
1422
1423 static int close_ref(struct ref_lock *lock)
1424 {
1425         if (close_lock_file(lock->lk))
1426                 return -1;
1427         return 0;
1428 }
1429
1430 static int commit_ref(struct ref_lock *lock)
1431 {
1432         char *path = get_locked_file_path(lock->lk);
1433         struct stat st;
1434
1435         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1436                 /*
1437                  * There is a directory at the path we want to rename
1438                  * the lockfile to. Hopefully it is empty; try to
1439                  * delete it.
1440                  */
1441                 size_t len = strlen(path);
1442                 struct strbuf sb_path = STRBUF_INIT;
1443
1444                 strbuf_attach(&sb_path, path, len, len);
1445
1446                 /*
1447                  * If this fails, commit_lock_file() will also fail
1448                  * and will report the problem.
1449                  */
1450                 remove_empty_directories(&sb_path);
1451                 strbuf_release(&sb_path);
1452         } else {
1453                 free(path);
1454         }
1455
1456         if (commit_lock_file(lock->lk))
1457                 return -1;
1458         return 0;
1459 }
1460
1461 static int open_or_create_logfile(const char *path, void *cb)
1462 {
1463         int *fd = cb;
1464
1465         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1466         return (*fd < 0) ? -1 : 0;
1467 }
1468
1469 /*
1470  * Create a reflog for a ref. If force_create = 0, only create the
1471  * reflog for certain refs (those for which should_autocreate_reflog
1472  * returns non-zero). Otherwise, create it regardless of the reference
1473  * name. If the logfile already existed or was created, return 0 and
1474  * set *logfd to the file descriptor opened for appending to the file.
1475  * If no logfile exists and we decided not to create one, return 0 and
1476  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1477  * return -1.
1478  */
1479 static int log_ref_setup(struct files_ref_store *refs,
1480                          const char *refname, int force_create,
1481                          int *logfd, struct strbuf *err)
1482 {
1483         struct strbuf logfile_sb = STRBUF_INIT;
1484         char *logfile;
1485
1486         files_reflog_path(refs, &logfile_sb, refname);
1487         logfile = strbuf_detach(&logfile_sb, NULL);
1488
1489         if (force_create || should_autocreate_reflog(refname)) {
1490                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1491                         if (errno == ENOENT)
1492                                 strbuf_addf(err, "unable to create directory for '%s': "
1493                                             "%s", logfile, strerror(errno));
1494                         else if (errno == EISDIR)
1495                                 strbuf_addf(err, "there are still logs under '%s'",
1496                                             logfile);
1497                         else
1498                                 strbuf_addf(err, "unable to append to '%s': %s",
1499                                             logfile, strerror(errno));
1500
1501                         goto error;
1502                 }
1503         } else {
1504                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1505                 if (*logfd < 0) {
1506                         if (errno == ENOENT || errno == EISDIR) {
1507                                 /*
1508                                  * The logfile doesn't already exist,
1509                                  * but that is not an error; it only
1510                                  * means that we won't write log
1511                                  * entries to it.
1512                                  */
1513                                 ;
1514                         } else {
1515                                 strbuf_addf(err, "unable to append to '%s': %s",
1516                                             logfile, strerror(errno));
1517                                 goto error;
1518                         }
1519                 }
1520         }
1521
1522         if (*logfd >= 0)
1523                 adjust_shared_perm(logfile);
1524
1525         free(logfile);
1526         return 0;
1527
1528 error:
1529         free(logfile);
1530         return -1;
1531 }
1532
1533 static int files_create_reflog(struct ref_store *ref_store,
1534                                const char *refname, int force_create,
1535                                struct strbuf *err)
1536 {
1537         struct files_ref_store *refs =
1538                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1539         int fd;
1540
1541         if (log_ref_setup(refs, refname, force_create, &fd, err))
1542                 return -1;
1543
1544         if (fd >= 0)
1545                 close(fd);
1546
1547         return 0;
1548 }
1549
1550 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1551                             const struct object_id *new_oid,
1552                             const char *committer, const char *msg)
1553 {
1554         int msglen, written;
1555         unsigned maxlen, len;
1556         char *logrec;
1557
1558         msglen = msg ? strlen(msg) : 0;
1559         maxlen = strlen(committer) + msglen + 100;
1560         logrec = xmalloc(maxlen);
1561         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1562                         oid_to_hex(old_oid),
1563                         oid_to_hex(new_oid),
1564                         committer);
1565         if (msglen)
1566                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1567
1568         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1569         free(logrec);
1570         if (written != len)
1571                 return -1;
1572
1573         return 0;
1574 }
1575
1576 static int files_log_ref_write(struct files_ref_store *refs,
1577                                const char *refname, const struct object_id *old_oid,
1578                                const struct object_id *new_oid, const char *msg,
1579                                int flags, struct strbuf *err)
1580 {
1581         int logfd, result;
1582
1583         if (log_all_ref_updates == LOG_REFS_UNSET)
1584                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1585
1586         result = log_ref_setup(refs, refname,
1587                                flags & REF_FORCE_CREATE_REFLOG,
1588                                &logfd, err);
1589
1590         if (result)
1591                 return result;
1592
1593         if (logfd < 0)
1594                 return 0;
1595         result = log_ref_write_fd(logfd, old_oid, new_oid,
1596                                   git_committer_info(0), msg);
1597         if (result) {
1598                 struct strbuf sb = STRBUF_INIT;
1599                 int save_errno = errno;
1600
1601                 files_reflog_path(refs, &sb, refname);
1602                 strbuf_addf(err, "unable to append to '%s': %s",
1603                             sb.buf, strerror(save_errno));
1604                 strbuf_release(&sb);
1605                 close(logfd);
1606                 return -1;
1607         }
1608         if (close(logfd)) {
1609                 struct strbuf sb = STRBUF_INIT;
1610                 int save_errno = errno;
1611
1612                 files_reflog_path(refs, &sb, refname);
1613                 strbuf_addf(err, "unable to append to '%s': %s",
1614                             sb.buf, strerror(save_errno));
1615                 strbuf_release(&sb);
1616                 return -1;
1617         }
1618         return 0;
1619 }
1620
1621 /*
1622  * Write sha1 into the open lockfile, then close the lockfile. On
1623  * errors, rollback the lockfile, fill in *err and
1624  * return -1.
1625  */
1626 static int write_ref_to_lockfile(struct ref_lock *lock,
1627                                  const struct object_id *oid, struct strbuf *err)
1628 {
1629         static char term = '\n';
1630         struct object *o;
1631         int fd;
1632
1633         o = parse_object(oid);
1634         if (!o) {
1635                 strbuf_addf(err,
1636                             "trying to write ref '%s' with nonexistent object %s",
1637                             lock->ref_name, oid_to_hex(oid));
1638                 unlock_ref(lock);
1639                 return -1;
1640         }
1641         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1642                 strbuf_addf(err,
1643                             "trying to write non-commit object %s to branch '%s'",
1644                             oid_to_hex(oid), lock->ref_name);
1645                 unlock_ref(lock);
1646                 return -1;
1647         }
1648         fd = get_lock_file_fd(lock->lk);
1649         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
1650             write_in_full(fd, &term, 1) != 1 ||
1651             close_ref(lock) < 0) {
1652                 strbuf_addf(err,
1653                             "couldn't write '%s'", get_lock_file_path(lock->lk));
1654                 unlock_ref(lock);
1655                 return -1;
1656         }
1657         return 0;
1658 }
1659
1660 /*
1661  * Commit a change to a loose reference that has already been written
1662  * to the loose reference lockfile. Also update the reflogs if
1663  * necessary, using the specified lockmsg (which can be NULL).
1664  */
1665 static int commit_ref_update(struct files_ref_store *refs,
1666                              struct ref_lock *lock,
1667                              const struct object_id *oid, const char *logmsg,
1668                              struct strbuf *err)
1669 {
1670         files_assert_main_repository(refs, "commit_ref_update");
1671
1672         clear_loose_ref_cache(refs);
1673         if (files_log_ref_write(refs, lock->ref_name,
1674                                 &lock->old_oid, oid,
1675                                 logmsg, 0, err)) {
1676                 char *old_msg = strbuf_detach(err, NULL);
1677                 strbuf_addf(err, "cannot update the ref '%s': %s",
1678                             lock->ref_name, old_msg);
1679                 free(old_msg);
1680                 unlock_ref(lock);
1681                 return -1;
1682         }
1683
1684         if (strcmp(lock->ref_name, "HEAD") != 0) {
1685                 /*
1686                  * Special hack: If a branch is updated directly and HEAD
1687                  * points to it (may happen on the remote side of a push
1688                  * for example) then logically the HEAD reflog should be
1689                  * updated too.
1690                  * A generic solution implies reverse symref information,
1691                  * but finding all symrefs pointing to the given branch
1692                  * would be rather costly for this rare event (the direct
1693                  * update of a branch) to be worth it.  So let's cheat and
1694                  * check with HEAD only which should cover 99% of all usage
1695                  * scenarios (even 100% of the default ones).
1696                  */
1697                 struct object_id head_oid;
1698                 int head_flag;
1699                 const char *head_ref;
1700
1701                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1702                                                    RESOLVE_REF_READING,
1703                                                    head_oid.hash, &head_flag);
1704                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1705                     !strcmp(head_ref, lock->ref_name)) {
1706                         struct strbuf log_err = STRBUF_INIT;
1707                         if (files_log_ref_write(refs, "HEAD",
1708                                                 &lock->old_oid, oid,
1709                                                 logmsg, 0, &log_err)) {
1710                                 error("%s", log_err.buf);
1711                                 strbuf_release(&log_err);
1712                         }
1713                 }
1714         }
1715
1716         if (commit_ref(lock)) {
1717                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1718                 unlock_ref(lock);
1719                 return -1;
1720         }
1721
1722         unlock_ref(lock);
1723         return 0;
1724 }
1725
1726 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1727 {
1728         int ret = -1;
1729 #ifndef NO_SYMLINK_HEAD
1730         char *ref_path = get_locked_file_path(lock->lk);
1731         unlink(ref_path);
1732         ret = symlink(target, ref_path);
1733         free(ref_path);
1734
1735         if (ret)
1736                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1737 #endif
1738         return ret;
1739 }
1740
1741 static void update_symref_reflog(struct files_ref_store *refs,
1742                                  struct ref_lock *lock, const char *refname,
1743                                  const char *target, const char *logmsg)
1744 {
1745         struct strbuf err = STRBUF_INIT;
1746         struct object_id new_oid;
1747         if (logmsg &&
1748             !refs_read_ref_full(&refs->base, target,
1749                                 RESOLVE_REF_READING, new_oid.hash, NULL) &&
1750             files_log_ref_write(refs, refname, &lock->old_oid,
1751                                 &new_oid, logmsg, 0, &err)) {
1752                 error("%s", err.buf);
1753                 strbuf_release(&err);
1754         }
1755 }
1756
1757 static int create_symref_locked(struct files_ref_store *refs,
1758                                 struct ref_lock *lock, const char *refname,
1759                                 const char *target, const char *logmsg)
1760 {
1761         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1762                 update_symref_reflog(refs, lock, refname, target, logmsg);
1763                 return 0;
1764         }
1765
1766         if (!fdopen_lock_file(lock->lk, "w"))
1767                 return error("unable to fdopen %s: %s",
1768                              lock->lk->tempfile.filename.buf, strerror(errno));
1769
1770         update_symref_reflog(refs, lock, refname, target, logmsg);
1771
1772         /* no error check; commit_ref will check ferror */
1773         fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
1774         if (commit_ref(lock) < 0)
1775                 return error("unable to write symref for %s: %s", refname,
1776                              strerror(errno));
1777         return 0;
1778 }
1779
1780 static int files_create_symref(struct ref_store *ref_store,
1781                                const char *refname, const char *target,
1782                                const char *logmsg)
1783 {
1784         struct files_ref_store *refs =
1785                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1786         struct strbuf err = STRBUF_INIT;
1787         struct ref_lock *lock;
1788         int ret;
1789
1790         lock = lock_ref_sha1_basic(refs, refname, NULL,
1791                                    NULL, NULL, REF_NODEREF, NULL,
1792                                    &err);
1793         if (!lock) {
1794                 error("%s", err.buf);
1795                 strbuf_release(&err);
1796                 return -1;
1797         }
1798
1799         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1800         unlock_ref(lock);
1801         return ret;
1802 }
1803
1804 static int files_reflog_exists(struct ref_store *ref_store,
1805                                const char *refname)
1806 {
1807         struct files_ref_store *refs =
1808                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1809         struct strbuf sb = STRBUF_INIT;
1810         struct stat st;
1811         int ret;
1812
1813         files_reflog_path(refs, &sb, refname);
1814         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1815         strbuf_release(&sb);
1816         return ret;
1817 }
1818
1819 static int files_delete_reflog(struct ref_store *ref_store,
1820                                const char *refname)
1821 {
1822         struct files_ref_store *refs =
1823                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1824         struct strbuf sb = STRBUF_INIT;
1825         int ret;
1826
1827         files_reflog_path(refs, &sb, refname);
1828         ret = remove_path(sb.buf);
1829         strbuf_release(&sb);
1830         return ret;
1831 }
1832
1833 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1834 {
1835         struct object_id ooid, noid;
1836         char *email_end, *message;
1837         timestamp_t timestamp;
1838         int tz;
1839         const char *p = sb->buf;
1840
1841         /* old SP new SP name <email> SP time TAB msg LF */
1842         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1843             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1844             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1845             !(email_end = strchr(p, '>')) ||
1846             email_end[1] != ' ' ||
1847             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1848             !message || message[0] != ' ' ||
1849             (message[1] != '+' && message[1] != '-') ||
1850             !isdigit(message[2]) || !isdigit(message[3]) ||
1851             !isdigit(message[4]) || !isdigit(message[5]))
1852                 return 0; /* corrupt? */
1853         email_end[1] = '\0';
1854         tz = strtol(message + 1, NULL, 10);
1855         if (message[6] != '\t')
1856                 message += 6;
1857         else
1858                 message += 7;
1859         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1860 }
1861
1862 static char *find_beginning_of_line(char *bob, char *scan)
1863 {
1864         while (bob < scan && *(--scan) != '\n')
1865                 ; /* keep scanning backwards */
1866         /*
1867          * Return either beginning of the buffer, or LF at the end of
1868          * the previous line.
1869          */
1870         return scan;
1871 }
1872
1873 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1874                                              const char *refname,
1875                                              each_reflog_ent_fn fn,
1876                                              void *cb_data)
1877 {
1878         struct files_ref_store *refs =
1879                 files_downcast(ref_store, REF_STORE_READ,
1880                                "for_each_reflog_ent_reverse");
1881         struct strbuf sb = STRBUF_INIT;
1882         FILE *logfp;
1883         long pos;
1884         int ret = 0, at_tail = 1;
1885
1886         files_reflog_path(refs, &sb, refname);
1887         logfp = fopen(sb.buf, "r");
1888         strbuf_release(&sb);
1889         if (!logfp)
1890                 return -1;
1891
1892         /* Jump to the end */
1893         if (fseek(logfp, 0, SEEK_END) < 0)
1894                 ret = error("cannot seek back reflog for %s: %s",
1895                             refname, strerror(errno));
1896         pos = ftell(logfp);
1897         while (!ret && 0 < pos) {
1898                 int cnt;
1899                 size_t nread;
1900                 char buf[BUFSIZ];
1901                 char *endp, *scanp;
1902
1903                 /* Fill next block from the end */
1904                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1905                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1906                         ret = error("cannot seek back reflog for %s: %s",
1907                                     refname, strerror(errno));
1908                         break;
1909                 }
1910                 nread = fread(buf, cnt, 1, logfp);
1911                 if (nread != 1) {
1912                         ret = error("cannot read %d bytes from reflog for %s: %s",
1913                                     cnt, refname, strerror(errno));
1914                         break;
1915                 }
1916                 pos -= cnt;
1917
1918                 scanp = endp = buf + cnt;
1919                 if (at_tail && scanp[-1] == '\n')
1920                         /* Looking at the final LF at the end of the file */
1921                         scanp--;
1922                 at_tail = 0;
1923
1924                 while (buf < scanp) {
1925                         /*
1926                          * terminating LF of the previous line, or the beginning
1927                          * of the buffer.
1928                          */
1929                         char *bp;
1930
1931                         bp = find_beginning_of_line(buf, scanp);
1932
1933                         if (*bp == '\n') {
1934                                 /*
1935                                  * The newline is the end of the previous line,
1936                                  * so we know we have complete line starting
1937                                  * at (bp + 1). Prefix it onto any prior data
1938                                  * we collected for the line and process it.
1939                                  */
1940                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1941                                 scanp = bp;
1942                                 endp = bp + 1;
1943                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1944                                 strbuf_reset(&sb);
1945                                 if (ret)
1946                                         break;
1947                         } else if (!pos) {
1948                                 /*
1949                                  * We are at the start of the buffer, and the
1950                                  * start of the file; there is no previous
1951                                  * line, and we have everything for this one.
1952                                  * Process it, and we can end the loop.
1953                                  */
1954                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1955                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1956                                 strbuf_reset(&sb);
1957                                 break;
1958                         }
1959
1960                         if (bp == buf) {
1961                                 /*
1962                                  * We are at the start of the buffer, and there
1963                                  * is more file to read backwards. Which means
1964                                  * we are in the middle of a line. Note that we
1965                                  * may get here even if *bp was a newline; that
1966                                  * just means we are at the exact end of the
1967                                  * previous line, rather than some spot in the
1968                                  * middle.
1969                                  *
1970                                  * Save away what we have to be combined with
1971                                  * the data from the next read.
1972                                  */
1973                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1974                                 break;
1975                         }
1976                 }
1977
1978         }
1979         if (!ret && sb.len)
1980                 die("BUG: reverse reflog parser had leftover data");
1981
1982         fclose(logfp);
1983         strbuf_release(&sb);
1984         return ret;
1985 }
1986
1987 static int files_for_each_reflog_ent(struct ref_store *ref_store,
1988                                      const char *refname,
1989                                      each_reflog_ent_fn fn, void *cb_data)
1990 {
1991         struct files_ref_store *refs =
1992                 files_downcast(ref_store, REF_STORE_READ,
1993                                "for_each_reflog_ent");
1994         FILE *logfp;
1995         struct strbuf sb = STRBUF_INIT;
1996         int ret = 0;
1997
1998         files_reflog_path(refs, &sb, refname);
1999         logfp = fopen(sb.buf, "r");
2000         strbuf_release(&sb);
2001         if (!logfp)
2002                 return -1;
2003
2004         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2005                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2006         fclose(logfp);
2007         strbuf_release(&sb);
2008         return ret;
2009 }
2010
2011 struct files_reflog_iterator {
2012         struct ref_iterator base;
2013
2014         struct ref_store *ref_store;
2015         struct dir_iterator *dir_iterator;
2016         struct object_id oid;
2017 };
2018
2019 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2020 {
2021         struct files_reflog_iterator *iter =
2022                 (struct files_reflog_iterator *)ref_iterator;
2023         struct dir_iterator *diter = iter->dir_iterator;
2024         int ok;
2025
2026         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2027                 int flags;
2028
2029                 if (!S_ISREG(diter->st.st_mode))
2030                         continue;
2031                 if (diter->basename[0] == '.')
2032                         continue;
2033                 if (ends_with(diter->basename, ".lock"))
2034                         continue;
2035
2036                 if (refs_read_ref_full(iter->ref_store,
2037                                        diter->relative_path, 0,
2038                                        iter->oid.hash, &flags)) {
2039                         error("bad ref for %s", diter->path.buf);
2040                         continue;
2041                 }
2042
2043                 iter->base.refname = diter->relative_path;
2044                 iter->base.oid = &iter->oid;
2045                 iter->base.flags = flags;
2046                 return ITER_OK;
2047         }
2048
2049         iter->dir_iterator = NULL;
2050         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2051                 ok = ITER_ERROR;
2052         return ok;
2053 }
2054
2055 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2056                                    struct object_id *peeled)
2057 {
2058         die("BUG: ref_iterator_peel() called for reflog_iterator");
2059 }
2060
2061 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2062 {
2063         struct files_reflog_iterator *iter =
2064                 (struct files_reflog_iterator *)ref_iterator;
2065         int ok = ITER_DONE;
2066
2067         if (iter->dir_iterator)
2068                 ok = dir_iterator_abort(iter->dir_iterator);
2069
2070         base_ref_iterator_free(ref_iterator);
2071         return ok;
2072 }
2073
2074 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2075         files_reflog_iterator_advance,
2076         files_reflog_iterator_peel,
2077         files_reflog_iterator_abort
2078 };
2079
2080 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2081 {
2082         struct files_ref_store *refs =
2083                 files_downcast(ref_store, REF_STORE_READ,
2084                                "reflog_iterator_begin");
2085         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2086         struct ref_iterator *ref_iterator = &iter->base;
2087         struct strbuf sb = STRBUF_INIT;
2088
2089         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2090         files_reflog_path(refs, &sb, NULL);
2091         iter->dir_iterator = dir_iterator_begin(sb.buf);
2092         iter->ref_store = ref_store;
2093         strbuf_release(&sb);
2094         return ref_iterator;
2095 }
2096
2097 /*
2098  * If update is a direct update of head_ref (the reference pointed to
2099  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2100  */
2101 static int split_head_update(struct ref_update *update,
2102                              struct ref_transaction *transaction,
2103                              const char *head_ref,
2104                              struct string_list *affected_refnames,
2105                              struct strbuf *err)
2106 {
2107         struct string_list_item *item;
2108         struct ref_update *new_update;
2109
2110         if ((update->flags & REF_LOG_ONLY) ||
2111             (update->flags & REF_ISPRUNING) ||
2112             (update->flags & REF_UPDATE_VIA_HEAD))
2113                 return 0;
2114
2115         if (strcmp(update->refname, head_ref))
2116                 return 0;
2117
2118         /*
2119          * First make sure that HEAD is not already in the
2120          * transaction. This insertion is O(N) in the transaction
2121          * size, but it happens at most once per transaction.
2122          */
2123         item = string_list_insert(affected_refnames, "HEAD");
2124         if (item->util) {
2125                 /* An entry already existed */
2126                 strbuf_addf(err,
2127                             "multiple updates for 'HEAD' (including one "
2128                             "via its referent '%s') are not allowed",
2129                             update->refname);
2130                 return TRANSACTION_NAME_CONFLICT;
2131         }
2132
2133         new_update = ref_transaction_add_update(
2134                         transaction, "HEAD",
2135                         update->flags | REF_LOG_ONLY | REF_NODEREF,
2136                         update->new_oid.hash, update->old_oid.hash,
2137                         update->msg);
2138
2139         item->util = new_update;
2140
2141         return 0;
2142 }
2143
2144 /*
2145  * update is for a symref that points at referent and doesn't have
2146  * REF_NODEREF set. Split it into two updates:
2147  * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
2148  * - A new, separate update for the referent reference
2149  * Note that the new update will itself be subject to splitting when
2150  * the iteration gets to it.
2151  */
2152 static int split_symref_update(struct files_ref_store *refs,
2153                                struct ref_update *update,
2154                                const char *referent,
2155                                struct ref_transaction *transaction,
2156                                struct string_list *affected_refnames,
2157                                struct strbuf *err)
2158 {
2159         struct string_list_item *item;
2160         struct ref_update *new_update;
2161         unsigned int new_flags;
2162
2163         /*
2164          * First make sure that referent is not already in the
2165          * transaction. This insertion is O(N) in the transaction
2166          * size, but it happens at most once per symref in a
2167          * transaction.
2168          */
2169         item = string_list_insert(affected_refnames, referent);
2170         if (item->util) {
2171                 /* An entry already existed */
2172                 strbuf_addf(err,
2173                             "multiple updates for '%s' (including one "
2174                             "via symref '%s') are not allowed",
2175                             referent, update->refname);
2176                 return TRANSACTION_NAME_CONFLICT;
2177         }
2178
2179         new_flags = update->flags;
2180         if (!strcmp(update->refname, "HEAD")) {
2181                 /*
2182                  * Record that the new update came via HEAD, so that
2183                  * when we process it, split_head_update() doesn't try
2184                  * to add another reflog update for HEAD. Note that
2185                  * this bit will be propagated if the new_update
2186                  * itself needs to be split.
2187                  */
2188                 new_flags |= REF_UPDATE_VIA_HEAD;
2189         }
2190
2191         new_update = ref_transaction_add_update(
2192                         transaction, referent, new_flags,
2193                         update->new_oid.hash, update->old_oid.hash,
2194                         update->msg);
2195
2196         new_update->parent_update = update;
2197
2198         /*
2199          * Change the symbolic ref update to log only. Also, it
2200          * doesn't need to check its old SHA-1 value, as that will be
2201          * done when new_update is processed.
2202          */
2203         update->flags |= REF_LOG_ONLY | REF_NODEREF;
2204         update->flags &= ~REF_HAVE_OLD;
2205
2206         item->util = new_update;
2207
2208         return 0;
2209 }
2210
2211 /*
2212  * Return the refname under which update was originally requested.
2213  */
2214 static const char *original_update_refname(struct ref_update *update)
2215 {
2216         while (update->parent_update)
2217                 update = update->parent_update;
2218
2219         return update->refname;
2220 }
2221
2222 /*
2223  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2224  * are consistent with oid, which is the reference's current value. If
2225  * everything is OK, return 0; otherwise, write an error message to
2226  * err and return -1.
2227  */
2228 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2229                          struct strbuf *err)
2230 {
2231         if (!(update->flags & REF_HAVE_OLD) ||
2232                    !oidcmp(oid, &update->old_oid))
2233                 return 0;
2234
2235         if (is_null_oid(&update->old_oid))
2236                 strbuf_addf(err, "cannot lock ref '%s': "
2237                             "reference already exists",
2238                             original_update_refname(update));
2239         else if (is_null_oid(oid))
2240                 strbuf_addf(err, "cannot lock ref '%s': "
2241                             "reference is missing but expected %s",
2242                             original_update_refname(update),
2243                             oid_to_hex(&update->old_oid));
2244         else
2245                 strbuf_addf(err, "cannot lock ref '%s': "
2246                             "is at %s but expected %s",
2247                             original_update_refname(update),
2248                             oid_to_hex(oid),
2249                             oid_to_hex(&update->old_oid));
2250
2251         return -1;
2252 }
2253
2254 /*
2255  * Prepare for carrying out update:
2256  * - Lock the reference referred to by update.
2257  * - Read the reference under lock.
2258  * - Check that its old SHA-1 value (if specified) is correct, and in
2259  *   any case record it in update->lock->old_oid for later use when
2260  *   writing the reflog.
2261  * - If it is a symref update without REF_NODEREF, split it up into a
2262  *   REF_LOG_ONLY update of the symref and add a separate update for
2263  *   the referent to transaction.
2264  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2265  *   update of HEAD.
2266  */
2267 static int lock_ref_for_update(struct files_ref_store *refs,
2268                                struct ref_update *update,
2269                                struct ref_transaction *transaction,
2270                                const char *head_ref,
2271                                struct string_list *affected_refnames,
2272                                struct strbuf *err)
2273 {
2274         struct strbuf referent = STRBUF_INIT;
2275         int mustexist = (update->flags & REF_HAVE_OLD) &&
2276                 !is_null_oid(&update->old_oid);
2277         int ret;
2278         struct ref_lock *lock;
2279
2280         files_assert_main_repository(refs, "lock_ref_for_update");
2281
2282         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2283                 update->flags |= REF_DELETING;
2284
2285         if (head_ref) {
2286                 ret = split_head_update(update, transaction, head_ref,
2287                                         affected_refnames, err);
2288                 if (ret)
2289                         return ret;
2290         }
2291
2292         ret = lock_raw_ref(refs, update->refname, mustexist,
2293                            affected_refnames, NULL,
2294                            &lock, &referent,
2295                            &update->type, err);
2296         if (ret) {
2297                 char *reason;
2298
2299                 reason = strbuf_detach(err, NULL);
2300                 strbuf_addf(err, "cannot lock ref '%s': %s",
2301                             original_update_refname(update), reason);
2302                 free(reason);
2303                 return ret;
2304         }
2305
2306         update->backend_data = lock;
2307
2308         if (update->type & REF_ISSYMREF) {
2309                 if (update->flags & REF_NODEREF) {
2310                         /*
2311                          * We won't be reading the referent as part of
2312                          * the transaction, so we have to read it here
2313                          * to record and possibly check old_sha1:
2314                          */
2315                         if (refs_read_ref_full(&refs->base,
2316                                                referent.buf, 0,
2317                                                lock->old_oid.hash, NULL)) {
2318                                 if (update->flags & REF_HAVE_OLD) {
2319                                         strbuf_addf(err, "cannot lock ref '%s': "
2320                                                     "error reading reference",
2321                                                     original_update_refname(update));
2322                                         return -1;
2323                                 }
2324                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2325                                 return TRANSACTION_GENERIC_ERROR;
2326                         }
2327                 } else {
2328                         /*
2329                          * Create a new update for the reference this
2330                          * symref is pointing at. Also, we will record
2331                          * and verify old_sha1 for this update as part
2332                          * of processing the split-off update, so we
2333                          * don't have to do it here.
2334                          */
2335                         ret = split_symref_update(refs, update,
2336                                                   referent.buf, transaction,
2337                                                   affected_refnames, err);
2338                         if (ret)
2339                                 return ret;
2340                 }
2341         } else {
2342                 struct ref_update *parent_update;
2343
2344                 if (check_old_oid(update, &lock->old_oid, err))
2345                         return TRANSACTION_GENERIC_ERROR;
2346
2347                 /*
2348                  * If this update is happening indirectly because of a
2349                  * symref update, record the old SHA-1 in the parent
2350                  * update:
2351                  */
2352                 for (parent_update = update->parent_update;
2353                      parent_update;
2354                      parent_update = parent_update->parent_update) {
2355                         struct ref_lock *parent_lock = parent_update->backend_data;
2356                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2357                 }
2358         }
2359
2360         if ((update->flags & REF_HAVE_NEW) &&
2361             !(update->flags & REF_DELETING) &&
2362             !(update->flags & REF_LOG_ONLY)) {
2363                 if (!(update->type & REF_ISSYMREF) &&
2364                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2365                         /*
2366                          * The reference already has the desired
2367                          * value, so we don't need to write it.
2368                          */
2369                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2370                                                  err)) {
2371                         char *write_err = strbuf_detach(err, NULL);
2372
2373                         /*
2374                          * The lock was freed upon failure of
2375                          * write_ref_to_lockfile():
2376                          */
2377                         update->backend_data = NULL;
2378                         strbuf_addf(err,
2379                                     "cannot update ref '%s': %s",
2380                                     update->refname, write_err);
2381                         free(write_err);
2382                         return TRANSACTION_GENERIC_ERROR;
2383                 } else {
2384                         update->flags |= REF_NEEDS_COMMIT;
2385                 }
2386         }
2387         if (!(update->flags & REF_NEEDS_COMMIT)) {
2388                 /*
2389                  * We didn't call write_ref_to_lockfile(), so
2390                  * the lockfile is still open. Close it to
2391                  * free up the file descriptor:
2392                  */
2393                 if (close_ref(lock)) {
2394                         strbuf_addf(err, "couldn't close '%s.lock'",
2395                                     update->refname);
2396                         return TRANSACTION_GENERIC_ERROR;
2397                 }
2398         }
2399         return 0;
2400 }
2401
2402 struct files_transaction_backend_data {
2403         struct ref_transaction *packed_transaction;
2404         int packed_refs_locked;
2405 };
2406
2407 /*
2408  * Unlock any references in `transaction` that are still locked, and
2409  * mark the transaction closed.
2410  */
2411 static void files_transaction_cleanup(struct files_ref_store *refs,
2412                                       struct ref_transaction *transaction)
2413 {
2414         size_t i;
2415         struct files_transaction_backend_data *backend_data =
2416                 transaction->backend_data;
2417         struct strbuf err = STRBUF_INIT;
2418
2419         for (i = 0; i < transaction->nr; i++) {
2420                 struct ref_update *update = transaction->updates[i];
2421                 struct ref_lock *lock = update->backend_data;
2422
2423                 if (lock) {
2424                         unlock_ref(lock);
2425                         update->backend_data = NULL;
2426                 }
2427         }
2428
2429         if (backend_data->packed_transaction &&
2430             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2431                 error("error aborting transaction: %s", err.buf);
2432                 strbuf_release(&err);
2433         }
2434
2435         if (backend_data->packed_refs_locked)
2436                 packed_refs_unlock(refs->packed_ref_store);
2437
2438         free(backend_data);
2439
2440         transaction->state = REF_TRANSACTION_CLOSED;
2441 }
2442
2443 static int files_transaction_prepare(struct ref_store *ref_store,
2444                                      struct ref_transaction *transaction,
2445                                      struct strbuf *err)
2446 {
2447         struct files_ref_store *refs =
2448                 files_downcast(ref_store, REF_STORE_WRITE,
2449                                "ref_transaction_prepare");
2450         size_t i;
2451         int ret = 0;
2452         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2453         char *head_ref = NULL;
2454         int head_type;
2455         struct object_id head_oid;
2456         struct files_transaction_backend_data *backend_data;
2457         struct ref_transaction *packed_transaction = NULL;
2458
2459         assert(err);
2460
2461         if (!transaction->nr)
2462                 goto cleanup;
2463
2464         backend_data = xcalloc(1, sizeof(*backend_data));
2465         transaction->backend_data = backend_data;
2466
2467         /*
2468          * Fail if a refname appears more than once in the
2469          * transaction. (If we end up splitting up any updates using
2470          * split_symref_update() or split_head_update(), those
2471          * functions will check that the new updates don't have the
2472          * same refname as any existing ones.)
2473          */
2474         for (i = 0; i < transaction->nr; i++) {
2475                 struct ref_update *update = transaction->updates[i];
2476                 struct string_list_item *item =
2477                         string_list_append(&affected_refnames, update->refname);
2478
2479                 /*
2480                  * We store a pointer to update in item->util, but at
2481                  * the moment we never use the value of this field
2482                  * except to check whether it is non-NULL.
2483                  */
2484                 item->util = update;
2485         }
2486         string_list_sort(&affected_refnames);
2487         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2488                 ret = TRANSACTION_GENERIC_ERROR;
2489                 goto cleanup;
2490         }
2491
2492         /*
2493          * Special hack: If a branch is updated directly and HEAD
2494          * points to it (may happen on the remote side of a push
2495          * for example) then logically the HEAD reflog should be
2496          * updated too.
2497          *
2498          * A generic solution would require reverse symref lookups,
2499          * but finding all symrefs pointing to a given branch would be
2500          * rather costly for this rare event (the direct update of a
2501          * branch) to be worth it. So let's cheat and check with HEAD
2502          * only, which should cover 99% of all usage scenarios (even
2503          * 100% of the default ones).
2504          *
2505          * So if HEAD is a symbolic reference, then record the name of
2506          * the reference that it points to. If we see an update of
2507          * head_ref within the transaction, then split_head_update()
2508          * arranges for the reflog of HEAD to be updated, too.
2509          */
2510         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2511                                        RESOLVE_REF_NO_RECURSE,
2512                                        head_oid.hash, &head_type);
2513
2514         if (head_ref && !(head_type & REF_ISSYMREF)) {
2515                 FREE_AND_NULL(head_ref);
2516         }
2517
2518         /*
2519          * Acquire all locks, verify old values if provided, check
2520          * that new values are valid, and write new values to the
2521          * lockfiles, ready to be activated. Only keep one lockfile
2522          * open at a time to avoid running out of file descriptors.
2523          * Note that lock_ref_for_update() might append more updates
2524          * to the transaction.
2525          */
2526         for (i = 0; i < transaction->nr; i++) {
2527                 struct ref_update *update = transaction->updates[i];
2528
2529                 ret = lock_ref_for_update(refs, update, transaction,
2530                                           head_ref, &affected_refnames, err);
2531                 if (ret)
2532                         break;
2533
2534                 if (update->flags & REF_DELETING &&
2535                     !(update->flags & REF_LOG_ONLY) &&
2536                     !(update->flags & REF_ISPRUNING)) {
2537                         /*
2538                          * This reference has to be deleted from
2539                          * packed-refs if it exists there.
2540                          */
2541                         if (!packed_transaction) {
2542                                 packed_transaction = ref_store_transaction_begin(
2543                                                 refs->packed_ref_store, err);
2544                                 if (!packed_transaction) {
2545                                         ret = TRANSACTION_GENERIC_ERROR;
2546                                         goto cleanup;
2547                                 }
2548
2549                                 backend_data->packed_transaction =
2550                                         packed_transaction;
2551                         }
2552
2553                         ref_transaction_add_update(
2554                                         packed_transaction, update->refname,
2555                                         update->flags & ~REF_HAVE_OLD,
2556                                         update->new_oid.hash, update->old_oid.hash,
2557                                         NULL);
2558                 }
2559         }
2560
2561         if (packed_transaction) {
2562                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2563                         ret = TRANSACTION_GENERIC_ERROR;
2564                         goto cleanup;
2565                 }
2566                 backend_data->packed_refs_locked = 1;
2567                 ret = ref_transaction_prepare(packed_transaction, err);
2568         }
2569
2570 cleanup:
2571         free(head_ref);
2572         string_list_clear(&affected_refnames, 0);
2573
2574         if (ret)
2575                 files_transaction_cleanup(refs, transaction);
2576         else
2577                 transaction->state = REF_TRANSACTION_PREPARED;
2578
2579         return ret;
2580 }
2581
2582 static int files_transaction_finish(struct ref_store *ref_store,
2583                                     struct ref_transaction *transaction,
2584                                     struct strbuf *err)
2585 {
2586         struct files_ref_store *refs =
2587                 files_downcast(ref_store, 0, "ref_transaction_finish");
2588         size_t i;
2589         int ret = 0;
2590         struct strbuf sb = STRBUF_INIT;
2591         struct files_transaction_backend_data *backend_data;
2592         struct ref_transaction *packed_transaction;
2593
2594
2595         assert(err);
2596
2597         if (!transaction->nr) {
2598                 transaction->state = REF_TRANSACTION_CLOSED;
2599                 return 0;
2600         }
2601
2602         backend_data = transaction->backend_data;
2603         packed_transaction = backend_data->packed_transaction;
2604
2605         /* Perform updates first so live commits remain referenced */
2606         for (i = 0; i < transaction->nr; i++) {
2607                 struct ref_update *update = transaction->updates[i];
2608                 struct ref_lock *lock = update->backend_data;
2609
2610                 if (update->flags & REF_NEEDS_COMMIT ||
2611                     update->flags & REF_LOG_ONLY) {
2612                         if (files_log_ref_write(refs,
2613                                                 lock->ref_name,
2614                                                 &lock->old_oid,
2615                                                 &update->new_oid,
2616                                                 update->msg, update->flags,
2617                                                 err)) {
2618                                 char *old_msg = strbuf_detach(err, NULL);
2619
2620                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2621                                             lock->ref_name, old_msg);
2622                                 free(old_msg);
2623                                 unlock_ref(lock);
2624                                 update->backend_data = NULL;
2625                                 ret = TRANSACTION_GENERIC_ERROR;
2626                                 goto cleanup;
2627                         }
2628                 }
2629                 if (update->flags & REF_NEEDS_COMMIT) {
2630                         clear_loose_ref_cache(refs);
2631                         if (commit_ref(lock)) {
2632                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2633                                 unlock_ref(lock);
2634                                 update->backend_data = NULL;
2635                                 ret = TRANSACTION_GENERIC_ERROR;
2636                                 goto cleanup;
2637                         }
2638                 }
2639         }
2640
2641         /*
2642          * Now that updates are safely completed, we can perform
2643          * deletes. First delete the reflogs of any references that
2644          * will be deleted, since (in the unexpected event of an
2645          * error) leaving a reference without a reflog is less bad
2646          * than leaving a reflog without a reference (the latter is a
2647          * mildly invalid repository state):
2648          */
2649         for (i = 0; i < transaction->nr; i++) {
2650                 struct ref_update *update = transaction->updates[i];
2651                 if (update->flags & REF_DELETING &&
2652                     !(update->flags & REF_LOG_ONLY) &&
2653                     !(update->flags & REF_ISPRUNING)) {
2654                         strbuf_reset(&sb);
2655                         files_reflog_path(refs, &sb, update->refname);
2656                         if (!unlink_or_warn(sb.buf))
2657                                 try_remove_empty_parents(refs, update->refname,
2658                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2659                 }
2660         }
2661
2662         /*
2663          * Perform deletes now that updates are safely completed.
2664          *
2665          * First delete any packed versions of the references, while
2666          * retaining the packed-refs lock:
2667          */
2668         if (packed_transaction) {
2669                 ret = ref_transaction_commit(packed_transaction, err);
2670                 ref_transaction_free(packed_transaction);
2671                 packed_transaction = NULL;
2672                 backend_data->packed_transaction = NULL;
2673                 if (ret)
2674                         goto cleanup;
2675         }
2676
2677         /* Now delete the loose versions of the references: */
2678         for (i = 0; i < transaction->nr; i++) {
2679                 struct ref_update *update = transaction->updates[i];
2680                 struct ref_lock *lock = update->backend_data;
2681
2682                 if (update->flags & REF_DELETING &&
2683                     !(update->flags & REF_LOG_ONLY)) {
2684                         if (!(update->type & REF_ISPACKED) ||
2685                             update->type & REF_ISSYMREF) {
2686                                 /* It is a loose reference. */
2687                                 strbuf_reset(&sb);
2688                                 files_ref_path(refs, &sb, lock->ref_name);
2689                                 if (unlink_or_msg(sb.buf, err)) {
2690                                         ret = TRANSACTION_GENERIC_ERROR;
2691                                         goto cleanup;
2692                                 }
2693                                 update->flags |= REF_DELETED_LOOSE;
2694                         }
2695                 }
2696         }
2697
2698         clear_loose_ref_cache(refs);
2699
2700 cleanup:
2701         files_transaction_cleanup(refs, transaction);
2702
2703         for (i = 0; i < transaction->nr; i++) {
2704                 struct ref_update *update = transaction->updates[i];
2705
2706                 if (update->flags & REF_DELETED_LOOSE) {
2707                         /*
2708                          * The loose reference was deleted. Delete any
2709                          * empty parent directories. (Note that this
2710                          * can only work because we have already
2711                          * removed the lockfile.)
2712                          */
2713                         try_remove_empty_parents(refs, update->refname,
2714                                                  REMOVE_EMPTY_PARENTS_REF);
2715                 }
2716         }
2717
2718         strbuf_release(&sb);
2719         return ret;
2720 }
2721
2722 static int files_transaction_abort(struct ref_store *ref_store,
2723                                    struct ref_transaction *transaction,
2724                                    struct strbuf *err)
2725 {
2726         struct files_ref_store *refs =
2727                 files_downcast(ref_store, 0, "ref_transaction_abort");
2728
2729         files_transaction_cleanup(refs, transaction);
2730         return 0;
2731 }
2732
2733 static int ref_present(const char *refname,
2734                        const struct object_id *oid, int flags, void *cb_data)
2735 {
2736         struct string_list *affected_refnames = cb_data;
2737
2738         return string_list_has_string(affected_refnames, refname);
2739 }
2740
2741 static int files_initial_transaction_commit(struct ref_store *ref_store,
2742                                             struct ref_transaction *transaction,
2743                                             struct strbuf *err)
2744 {
2745         struct files_ref_store *refs =
2746                 files_downcast(ref_store, REF_STORE_WRITE,
2747                                "initial_ref_transaction_commit");
2748         size_t i;
2749         int ret = 0;
2750         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2751         struct ref_transaction *packed_transaction = NULL;
2752
2753         assert(err);
2754
2755         if (transaction->state != REF_TRANSACTION_OPEN)
2756                 die("BUG: commit called for transaction that is not open");
2757
2758         /* Fail if a refname appears more than once in the transaction: */
2759         for (i = 0; i < transaction->nr; i++)
2760                 string_list_append(&affected_refnames,
2761                                    transaction->updates[i]->refname);
2762         string_list_sort(&affected_refnames);
2763         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2764                 ret = TRANSACTION_GENERIC_ERROR;
2765                 goto cleanup;
2766         }
2767
2768         /*
2769          * It's really undefined to call this function in an active
2770          * repository or when there are existing references: we are
2771          * only locking and changing packed-refs, so (1) any
2772          * simultaneous processes might try to change a reference at
2773          * the same time we do, and (2) any existing loose versions of
2774          * the references that we are setting would have precedence
2775          * over our values. But some remote helpers create the remote
2776          * "HEAD" and "master" branches before calling this function,
2777          * so here we really only check that none of the references
2778          * that we are creating already exists.
2779          */
2780         if (refs_for_each_rawref(&refs->base, ref_present,
2781                                  &affected_refnames))
2782                 die("BUG: initial ref transaction called with existing refs");
2783
2784         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2785         if (!packed_transaction) {
2786                 ret = TRANSACTION_GENERIC_ERROR;
2787                 goto cleanup;
2788         }
2789
2790         for (i = 0; i < transaction->nr; i++) {
2791                 struct ref_update *update = transaction->updates[i];
2792
2793                 if ((update->flags & REF_HAVE_OLD) &&
2794                     !is_null_oid(&update->old_oid))
2795                         die("BUG: initial ref transaction with old_sha1 set");
2796                 if (refs_verify_refname_available(&refs->base, update->refname,
2797                                                   &affected_refnames, NULL,
2798                                                   err)) {
2799                         ret = TRANSACTION_NAME_CONFLICT;
2800                         goto cleanup;
2801                 }
2802
2803                 /*
2804                  * Add a reference creation for this reference to the
2805                  * packed-refs transaction:
2806                  */
2807                 ref_transaction_add_update(packed_transaction, update->refname,
2808                                            update->flags & ~REF_HAVE_OLD,
2809                                            update->new_oid.hash, update->old_oid.hash,
2810                                            NULL);
2811         }
2812
2813         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2814                 ret = TRANSACTION_GENERIC_ERROR;
2815                 goto cleanup;
2816         }
2817
2818         if (initial_ref_transaction_commit(packed_transaction, err)) {
2819                 ret = TRANSACTION_GENERIC_ERROR;
2820                 goto cleanup;
2821         }
2822
2823 cleanup:
2824         if (packed_transaction)
2825                 ref_transaction_free(packed_transaction);
2826         packed_refs_unlock(refs->packed_ref_store);
2827         transaction->state = REF_TRANSACTION_CLOSED;
2828         string_list_clear(&affected_refnames, 0);
2829         return ret;
2830 }
2831
2832 struct expire_reflog_cb {
2833         unsigned int flags;
2834         reflog_expiry_should_prune_fn *should_prune_fn;
2835         void *policy_cb;
2836         FILE *newlog;
2837         struct object_id last_kept_oid;
2838 };
2839
2840 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2841                              const char *email, timestamp_t timestamp, int tz,
2842                              const char *message, void *cb_data)
2843 {
2844         struct expire_reflog_cb *cb = cb_data;
2845         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2846
2847         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2848                 ooid = &cb->last_kept_oid;
2849
2850         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2851                                    message, policy_cb)) {
2852                 if (!cb->newlog)
2853                         printf("would prune %s", message);
2854                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2855                         printf("prune %s", message);
2856         } else {
2857                 if (cb->newlog) {
2858                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2859                                 oid_to_hex(ooid), oid_to_hex(noid),
2860                                 email, timestamp, tz, message);
2861                         oidcpy(&cb->last_kept_oid, noid);
2862                 }
2863                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2864                         printf("keep %s", message);
2865         }
2866         return 0;
2867 }
2868
2869 static int files_reflog_expire(struct ref_store *ref_store,
2870                                const char *refname, const unsigned char *sha1,
2871                                unsigned int flags,
2872                                reflog_expiry_prepare_fn prepare_fn,
2873                                reflog_expiry_should_prune_fn should_prune_fn,
2874                                reflog_expiry_cleanup_fn cleanup_fn,
2875                                void *policy_cb_data)
2876 {
2877         struct files_ref_store *refs =
2878                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2879         static struct lock_file reflog_lock;
2880         struct expire_reflog_cb cb;
2881         struct ref_lock *lock;
2882         struct strbuf log_file_sb = STRBUF_INIT;
2883         char *log_file;
2884         int status = 0;
2885         int type;
2886         struct strbuf err = STRBUF_INIT;
2887         struct object_id oid;
2888
2889         memset(&cb, 0, sizeof(cb));
2890         cb.flags = flags;
2891         cb.policy_cb = policy_cb_data;
2892         cb.should_prune_fn = should_prune_fn;
2893
2894         /*
2895          * The reflog file is locked by holding the lock on the
2896          * reference itself, plus we might need to update the
2897          * reference if --updateref was specified:
2898          */
2899         lock = lock_ref_sha1_basic(refs, refname, sha1,
2900                                    NULL, NULL, REF_NODEREF,
2901                                    &type, &err);
2902         if (!lock) {
2903                 error("cannot lock ref '%s': %s", refname, err.buf);
2904                 strbuf_release(&err);
2905                 return -1;
2906         }
2907         if (!refs_reflog_exists(ref_store, refname)) {
2908                 unlock_ref(lock);
2909                 return 0;
2910         }
2911
2912         files_reflog_path(refs, &log_file_sb, refname);
2913         log_file = strbuf_detach(&log_file_sb, NULL);
2914         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2915                 /*
2916                  * Even though holding $GIT_DIR/logs/$reflog.lock has
2917                  * no locking implications, we use the lock_file
2918                  * machinery here anyway because it does a lot of the
2919                  * work we need, including cleaning up if the program
2920                  * exits unexpectedly.
2921                  */
2922                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
2923                         struct strbuf err = STRBUF_INIT;
2924                         unable_to_lock_message(log_file, errno, &err);
2925                         error("%s", err.buf);
2926                         strbuf_release(&err);
2927                         goto failure;
2928                 }
2929                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
2930                 if (!cb.newlog) {
2931                         error("cannot fdopen %s (%s)",
2932                               get_lock_file_path(&reflog_lock), strerror(errno));
2933                         goto failure;
2934                 }
2935         }
2936
2937         hashcpy(oid.hash, sha1);
2938
2939         (*prepare_fn)(refname, &oid, cb.policy_cb);
2940         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
2941         (*cleanup_fn)(cb.policy_cb);
2942
2943         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
2944                 /*
2945                  * It doesn't make sense to adjust a reference pointed
2946                  * to by a symbolic ref based on expiring entries in
2947                  * the symbolic reference's reflog. Nor can we update
2948                  * a reference if there are no remaining reflog
2949                  * entries.
2950                  */
2951                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
2952                         !(type & REF_ISSYMREF) &&
2953                         !is_null_oid(&cb.last_kept_oid);
2954
2955                 if (close_lock_file(&reflog_lock)) {
2956                         status |= error("couldn't write %s: %s", log_file,
2957                                         strerror(errno));
2958                 } else if (update &&
2959                            (write_in_full(get_lock_file_fd(lock->lk),
2960                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
2961                             write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
2962                             close_ref(lock) < 0)) {
2963                         status |= error("couldn't write %s",
2964                                         get_lock_file_path(lock->lk));
2965                         rollback_lock_file(&reflog_lock);
2966                 } else if (commit_lock_file(&reflog_lock)) {
2967                         status |= error("unable to write reflog '%s' (%s)",
2968                                         log_file, strerror(errno));
2969                 } else if (update && commit_ref(lock)) {
2970                         status |= error("couldn't set %s", lock->ref_name);
2971                 }
2972         }
2973         free(log_file);
2974         unlock_ref(lock);
2975         return status;
2976
2977  failure:
2978         rollback_lock_file(&reflog_lock);
2979         free(log_file);
2980         unlock_ref(lock);
2981         return -1;
2982 }
2983
2984 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
2985 {
2986         struct files_ref_store *refs =
2987                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
2988         struct strbuf sb = STRBUF_INIT;
2989
2990         /*
2991          * Create .git/refs/{heads,tags}
2992          */
2993         files_ref_path(refs, &sb, "refs/heads");
2994         safe_create_dir(sb.buf, 1);
2995
2996         strbuf_reset(&sb);
2997         files_ref_path(refs, &sb, "refs/tags");
2998         safe_create_dir(sb.buf, 1);
2999
3000         strbuf_release(&sb);
3001         return 0;
3002 }
3003
3004 struct ref_storage_be refs_be_files = {
3005         NULL,
3006         "files",
3007         files_ref_store_create,
3008         files_init_db,
3009         files_transaction_prepare,
3010         files_transaction_finish,
3011         files_transaction_abort,
3012         files_initial_transaction_commit,
3013
3014         files_pack_refs,
3015         files_peel_ref,
3016         files_create_symref,
3017         files_delete_refs,
3018         files_rename_ref,
3019
3020         files_ref_iterator_begin,
3021         files_read_raw_ref,
3022
3023         files_reflog_iterator_begin,
3024         files_for_each_reflog_ent,
3025         files_for_each_reflog_ent_reverse,
3026         files_reflog_exists,
3027         files_create_reflog,
3028         files_delete_reflog,
3029         files_reflog_expire
3030 };