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 #include "../chdir-notify.h"
  13
  14 /*
  15  * This backend uses the following flags in `ref_update::flags` for
  16  * internal bookkeeping purposes. Their numerical values must not
  17  * conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
  18  * REF_HAVE_OLD, or REF_IS_PRUNING, which are also stored in
  19  * `ref_update::flags`.
  20  */
  21
  22 /*
  23  * Used as a flag in ref_update::flags when a loose ref is being
  24  * pruned. This flag must only be used when REF_NO_DEREF is set.
  25  */
  26 #define REF_IS_PRUNING (1 << 4)
  27
  28 /*
  29  * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
  30  * refs (i.e., because the reference is about to be deleted anyway).
  31  */
  32 #define REF_DELETING (1 << 5)
  33
  34 /*
  35  * Used as a flag in ref_update::flags when the lockfile needs to be
  36  * committed.
  37  */
  38 #define REF_NEEDS_COMMIT (1 << 6)
  39
  40 /*
  41  * Used as a flag in ref_update::flags when we want to log a ref
  42  * update but not actually perform it.  This is used when a symbolic
  43  * ref update is split up.
  44  */
  45 #define REF_LOG_ONLY (1 << 7)
  46
  47 /*
  48  * Used as a flag in ref_update::flags when the ref_update was via an
  49  * update to HEAD.
  50  */
  51 #define REF_UPDATE_VIA_HEAD (1 << 8)
  52
  53 /*
  54  * Used as a flag in ref_update::flags when the loose reference has
  55  * been deleted.
  56  */
  57 #define REF_DELETED_LOOSE (1 << 9)
  58
  59 struct ref_lock {
  60         char *ref_name;
  61         struct lock_file lk;
  62         struct object_id old_oid;
  63 };
  64
  65 struct files_ref_store {
  66         struct ref_store base;
  67         unsigned int store_flags;
  68
  69         char *gitdir;
  70         char *gitcommondir;
  71
  72         struct ref_cache *loose;
  73
  74         struct ref_store *packed_ref_store;
  75 };
  76
  77 static void clear_loose_ref_cache(struct files_ref_store *refs)
  78 {
  79         if (refs->loose) {
  80                 free_ref_cache(refs->loose);
  81                 refs->loose = NULL;
  82         }
  83 }
  84
  85 /*
  86  * Create a new submodule ref cache and add it to the internal
  87  * set of caches.
  88  */
  89 static struct ref_store *files_ref_store_create(const char *gitdir,
  90                                                 unsigned int flags)
  91 {
  92         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  93         struct ref_store *ref_store = (struct ref_store *)refs;
  94         struct strbuf sb = STRBUF_INIT;
  95
  96         base_ref_store_init(ref_store, &refs_be_files);
  97         refs->store_flags = flags;
  98
  99         refs->gitdir = xstrdup(gitdir);
 100         get_common_dir_noenv(&sb, gitdir);
 101         refs->gitcommondir = strbuf_detach(&sb, NULL);
 102         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
 103         refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
 104         strbuf_release(&sb);
 105
 106         chdir_notify_reparent("files-backend $GIT_DIR",
 107                               &refs->gitdir);
 108         chdir_notify_reparent("files-backend $GIT_COMMONDIR",
 109                               &refs->gitcommondir);
 110
 111         return ref_store;
 112 }
 113
 114 /*
 115  * Die if refs is not the main ref store. caller is used in any
 116  * necessary error messages.
 117  */
 118 static void files_assert_main_repository(struct files_ref_store *refs,
 119                                          const char *caller)
 120 {
 121         if (refs->store_flags & REF_STORE_MAIN)
 122                 return;
 123
 124         BUG("operation %s only allowed for main ref store", caller);
 125 }
 126
 127 /*
 128  * Downcast ref_store to files_ref_store. Die if ref_store is not a
 129  * files_ref_store. required_flags is compared with ref_store's
 130  * store_flags to ensure the ref_store has all required capabilities.
 131  * "caller" is used in any necessary error messages.
 132  */
 133 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
 134                                               unsigned int required_flags,
 135                                               const char *caller)
 136 {
 137         struct files_ref_store *refs;
 138
 139         if (ref_store->be != &refs_be_files)
 140                 BUG("ref_store is type \"%s\" not \"files\" in %s",
 141                     ref_store->be->name, caller);
 142
 143         refs = (struct files_ref_store *)ref_store;
 144
 145         if ((refs->store_flags & required_flags) != required_flags)
 146                 BUG("operation %s requires abilities 0x%x, but only have 0x%x",
 147                     caller, required_flags, refs->store_flags);
 148
 149         return refs;
 150 }
 151
 152 static void files_reflog_path(struct files_ref_store *refs,
 153                               struct strbuf *sb,
 154                               const char *refname)
 155 {
 156         switch (ref_type(refname)) {
 157         case REF_TYPE_PER_WORKTREE:
 158         case REF_TYPE_PSEUDOREF:
 159                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 160                 break;
 161         case REF_TYPE_NORMAL:
 162                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 163                 break;
 164         default:
 165                 BUG("unknown ref type %d of ref %s",
 166                     ref_type(refname), refname);
 167         }
 168 }
 169
 170 static void files_ref_path(struct files_ref_store *refs,
 171                            struct strbuf *sb,
 172                            const char *refname)
 173 {
 174         switch (ref_type(refname)) {
 175         case REF_TYPE_PER_WORKTREE:
 176         case REF_TYPE_PSEUDOREF:
 177                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 178                 break;
 179         case REF_TYPE_NORMAL:
 180                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 181                 break;
 182         default:
 183                 BUG("unknown ref type %d of ref %s",
 184                     ref_type(refname), refname);
 185         }
 186 }
 187
 188 /*
 189  * Read the loose references from the namespace dirname into dir
 190  * (without recursing).  dirname must end with '/'.  dir must be the
 191  * directory entry corresponding to dirname.
 192  */
 193 static void loose_fill_ref_dir(struct ref_store *ref_store,
 194                                struct ref_dir *dir, const char *dirname)
 195 {
 196         struct files_ref_store *refs =
 197                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 198         DIR *d;
 199         struct dirent *de;
 200         int dirnamelen = strlen(dirname);
 201         struct strbuf refname;
 202         struct strbuf path = STRBUF_INIT;
 203         size_t path_baselen;
 204
 205         files_ref_path(refs, &path, dirname);
 206         path_baselen = path.len;
 207
 208         d = opendir(path.buf);
 209         if (!d) {
 210                 strbuf_release(&path);
 211                 return;
 212         }
 213
 214         strbuf_init(&refname, dirnamelen + 257);
 215         strbuf_add(&refname, dirname, dirnamelen);
 216
 217         while ((de = readdir(d)) != NULL) {
 218                 struct object_id oid;
 219                 struct stat st;
 220                 int flag;
 221
 222                 if (de->d_name[0] == '.')
 223                         continue;
 224                 if (ends_with(de->d_name, ".lock"))
 225                         continue;
 226                 strbuf_addstr(&refname, de->d_name);
 227                 strbuf_addstr(&path, de->d_name);
 228                 if (stat(path.buf, &st) < 0) {
 229                         ; /* silently ignore */
 230                 } else if (S_ISDIR(st.st_mode)) {
 231                         strbuf_addch(&refname, '/');
 232                         add_entry_to_dir(dir,
 233                                          create_dir_entry(dir->cache, refname.buf,
 234                                                           refname.len, 1));
 235                 } else {
 236                         if (!refs_resolve_ref_unsafe(&refs->base,
 237                                                      refname.buf,
 238                                                      RESOLVE_REF_READING,
 239                                                      &oid, &flag)) {
 240                                 oidclr(&oid);
 241                                 flag |= REF_ISBROKEN;
 242                         } else if (is_null_oid(&oid)) {
 243                                 /*
 244                                  * It is so astronomically unlikely
 245                                  * that null_oid is the OID of an
 246                                  * actual object that we consider its
 247                                  * appearance in a loose reference
 248                                  * file to be repo corruption
 249                                  * (probably due to a software bug).
 250                                  */
 251                                 flag |= REF_ISBROKEN;
 252                         }
 253
 254                         if (check_refname_format(refname.buf,
 255                                                  REFNAME_ALLOW_ONELEVEL)) {
 256                                 if (!refname_is_safe(refname.buf))
 257                                         die("loose refname is dangerous: %s", refname.buf);
 258                                 oidclr(&oid);
 259                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 260                         }
 261                         add_entry_to_dir(dir,
 262                                          create_ref_entry(refname.buf, &oid, flag));
 263                 }
 264                 strbuf_setlen(&refname, dirnamelen);
 265                 strbuf_setlen(&path, path_baselen);
 266         }
 267         strbuf_release(&refname);
 268         strbuf_release(&path);
 269         closedir(d);
 270
 271         /*
 272          * Manually add refs/bisect, which, being per-worktree, might
 273          * not appear in the directory listing for refs/ in the main
 274          * repo.
 275          */
 276         if (!strcmp(dirname, "refs/")) {
 277                 int pos = search_ref_dir(dir, "refs/bisect/", 12);
 278
 279                 if (pos < 0) {
 280                         struct ref_entry *child_entry = create_dir_entry(
 281                                         dir->cache, "refs/bisect/", 12, 1);
 282                         add_entry_to_dir(dir, child_entry);
 283                 }
 284         }
 285 }
 286
 287 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 288 {
 289         if (!refs->loose) {
 290                 /*
 291                  * Mark the top-level directory complete because we
 292                  * are about to read the only subdirectory that can
 293                  * hold references:
 294                  */
 295                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 296
 297                 /* We're going to fill the top level ourselves: */
 298                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 299
 300                 /*
 301                  * Add an incomplete entry for "refs/" (to be filled
 302                  * lazily):
 303                  */
 304                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 305                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 306         }
 307         return refs->loose;
 308 }
 309
 310 static int files_read_raw_ref(struct ref_store *ref_store,
 311                               const char *refname, struct object_id *oid,
 312                               struct strbuf *referent, unsigned int *type)
 313 {
 314         struct files_ref_store *refs =
 315                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 316         struct strbuf sb_contents = STRBUF_INIT;
 317         struct strbuf sb_path = STRBUF_INIT;
 318         const char *path;
 319         const char *buf;
 320         const char *p;
 321         struct stat st;
 322         int fd;
 323         int ret = -1;
 324         int save_errno;
 325         int remaining_retries = 3;
 326
 327         *type = 0;
 328         strbuf_reset(&sb_path);
 329
 330         files_ref_path(refs, &sb_path, refname);
 331
 332         path = sb_path.buf;
 333
 334 stat_ref:
 335         /*
 336          * We might have to loop back here to avoid a race
 337          * condition: first we lstat() the file, then we try
 338          * to read it as a link or as a file.  But if somebody
 339          * changes the type of the file (file <-> directory
 340          * <-> symlink) between the lstat() and reading, then
 341          * we don't want to report that as an error but rather
 342          * try again starting with the lstat().
 343          *
 344          * We'll keep a count of the retries, though, just to avoid
 345          * any confusing situation sending us into an infinite loop.
 346          */
 347
 348         if (remaining_retries-- <= 0)
 349                 goto out;
 350
 351         if (lstat(path, &st) < 0) {
 352                 if (errno != ENOENT)
 353                         goto out;
 354                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 355                                       oid, referent, type)) {
 356                         errno = ENOENT;
 357                         goto out;
 358                 }
 359                 ret = 0;
 360                 goto out;
 361         }
 362
 363         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 364         if (S_ISLNK(st.st_mode)) {
 365                 strbuf_reset(&sb_contents);
 366                 if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 367                         if (errno == ENOENT || errno == EINVAL)
 368                                 /* inconsistent with lstat; retry */
 369                                 goto stat_ref;
 370                         else
 371                                 goto out;
 372                 }
 373                 if (starts_with(sb_contents.buf, "refs/") &&
 374                     !check_refname_format(sb_contents.buf, 0)) {
 375                         strbuf_swap(&sb_contents, referent);
 376                         *type |= REF_ISSYMREF;
 377                         ret = 0;
 378                         goto out;
 379                 }
 380                 /*
 381                  * It doesn't look like a refname; fall through to just
 382                  * treating it like a non-symlink, and reading whatever it
 383                  * points to.
 384                  */
 385         }
 386
 387         /* Is it a directory? */
 388         if (S_ISDIR(st.st_mode)) {
 389                 /*
 390                  * Even though there is a directory where the loose
 391                  * ref is supposed to be, there could still be a
 392                  * packed ref:
 393                  */
 394                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 395                                       oid, referent, type)) {
 396                         errno = EISDIR;
 397                         goto out;
 398                 }
 399                 ret = 0;
 400                 goto out;
 401         }
 402
 403         /*
 404          * Anything else, just open it and try to use it as
 405          * a ref
 406          */
 407         fd = open(path, O_RDONLY);
 408         if (fd < 0) {
 409                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 410                         /* inconsistent with lstat; retry */
 411                         goto stat_ref;
 412                 else
 413                         goto out;
 414         }
 415         strbuf_reset(&sb_contents);
 416         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 417                 int save_errno = errno;
 418                 close(fd);
 419                 errno = save_errno;
 420                 goto out;
 421         }
 422         close(fd);
 423         strbuf_rtrim(&sb_contents);
 424         buf = sb_contents.buf;
 425         if (starts_with(buf, "ref:")) {
 426                 buf += 4;
 427                 while (isspace(*buf))
 428                         buf++;
 429
 430                 strbuf_reset(referent);
 431                 strbuf_addstr(referent, buf);
 432                 *type |= REF_ISSYMREF;
 433                 ret = 0;
 434                 goto out;
 435         }
 436
 437         /*
 438          * Please note that FETCH_HEAD has additional
 439          * data after the sha.
 440          */
 441         if (parse_oid_hex(buf, oid, &p) ||
 442             (*p != '\0' && !isspace(*p))) {
 443                 *type |= REF_ISBROKEN;
 444                 errno = EINVAL;
 445                 goto out;
 446         }
 447
 448         ret = 0;
 449
 450 out:
 451         save_errno = errno;
 452         strbuf_release(&sb_path);
 453         strbuf_release(&sb_contents);
 454         errno = save_errno;
 455         return ret;
 456 }
 457
 458 static void unlock_ref(struct ref_lock *lock)
 459 {
 460         rollback_lock_file(&lock->lk);
 461         free(lock->ref_name);
 462         free(lock);
 463 }
 464
 465 /*
 466  * Lock refname, without following symrefs, and set *lock_p to point
 467  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 468  * and type similarly to read_raw_ref().
 469  *
 470  * The caller must verify that refname is a "safe" reference name (in
 471  * the sense of refname_is_safe()) before calling this function.
 472  *
 473  * If the reference doesn't already exist, verify that refname doesn't
 474  * have a D/F conflict with any existing references. extras and skip
 475  * are passed to refs_verify_refname_available() for this check.
 476  *
 477  * If mustexist is not set and the reference is not found or is
 478  * broken, lock the reference anyway but clear old_oid.
 479  *
 480  * Return 0 on success. On failure, write an error message to err and
 481  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 482  *
 483  * Implementation note: This function is basically
 484  *
 485  *     lock reference
 486  *     read_raw_ref()
 487  *
 488  * but it includes a lot more code to
 489  * - Deal with possible races with other processes
 490  * - Avoid calling refs_verify_refname_available() when it can be
 491  *   avoided, namely if we were successfully able to read the ref
 492  * - Generate informative error messages in the case of failure
 493  */
 494 static int lock_raw_ref(struct files_ref_store *refs,
 495                         const char *refname, int mustexist,
 496                         const struct string_list *extras,
 497                         const struct string_list *skip,
 498                         struct ref_lock **lock_p,
 499                         struct strbuf *referent,
 500                         unsigned int *type,
 501                         struct strbuf *err)
 502 {
 503         struct ref_lock *lock;
 504         struct strbuf ref_file = STRBUF_INIT;
 505         int attempts_remaining = 3;
 506         int ret = TRANSACTION_GENERIC_ERROR;
 507
 508         assert(err);
 509         files_assert_main_repository(refs, "lock_raw_ref");
 510
 511         *type = 0;
 512
 513         /* First lock the file so it can't change out from under us. */
 514
 515         *lock_p = lock = xcalloc(1, sizeof(*lock));
 516
 517         lock->ref_name = xstrdup(refname);
 518         files_ref_path(refs, &ref_file, refname);
 519
 520 retry:
 521         switch (safe_create_leading_directories(ref_file.buf)) {
 522         case SCLD_OK:
 523                 break; /* success */
 524         case SCLD_EXISTS:
 525                 /*
 526                  * Suppose refname is "refs/foo/bar". We just failed
 527                  * to create the containing directory, "refs/foo",
 528                  * because there was a non-directory in the way. This
 529                  * indicates a D/F conflict, probably because of
 530                  * another reference such as "refs/foo". There is no
 531                  * reason to expect this error to be transitory.
 532                  */
 533                 if (refs_verify_refname_available(&refs->base, refname,
 534                                                   extras, skip, err)) {
 535                         if (mustexist) {
 536                                 /*
 537                                  * To the user the relevant error is
 538                                  * that the "mustexist" reference is
 539                                  * missing:
 540                                  */
 541                                 strbuf_reset(err);
 542                                 strbuf_addf(err, "unable to resolve reference '%s'",
 543                                             refname);
 544                         } else {
 545                                 /*
 546                                  * The error message set by
 547                                  * refs_verify_refname_available() is
 548                                  * OK.
 549                                  */
 550                                 ret = TRANSACTION_NAME_CONFLICT;
 551                         }
 552                 } else {
 553                         /*
 554                          * The file that is in the way isn't a loose
 555                          * reference. Report it as a low-level
 556                          * failure.
 557                          */
 558                         strbuf_addf(err, "unable to create lock file %s.lock; "
 559                                     "non-directory in the way",
 560                                     ref_file.buf);
 561                 }
 562                 goto error_return;
 563         case SCLD_VANISHED:
 564                 /* Maybe another process was tidying up. Try again. */
 565                 if (--attempts_remaining > 0)
 566                         goto retry;
 567                 /* fall through */
 568         default:
 569                 strbuf_addf(err, "unable to create directory for %s",
 570                             ref_file.buf);
 571                 goto error_return;
 572         }
 573
 574         if (hold_lock_file_for_update_timeout(
 575                             &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 576                             get_files_ref_lock_timeout_ms()) < 0) {
 577                 if (errno == ENOENT && --attempts_remaining > 0) {
 578                         /*
 579                          * Maybe somebody just deleted one of the
 580                          * directories leading to ref_file.  Try
 581                          * again:
 582                          */
 583                         goto retry;
 584                 } else {
 585                         unable_to_lock_message(ref_file.buf, errno, err);
 586                         goto error_return;
 587                 }
 588         }
 589
 590         /*
 591          * Now we hold the lock and can read the reference without
 592          * fear that its value will change.
 593          */
 594
 595         if (files_read_raw_ref(&refs->base, refname,
 596                                &lock->old_oid, referent, type)) {
 597                 if (errno == ENOENT) {
 598                         if (mustexist) {
 599                                 /* Garden variety missing reference. */
 600                                 strbuf_addf(err, "unable to resolve reference '%s'",
 601                                             refname);
 602                                 goto error_return;
 603                         } else {
 604                                 /*
 605                                  * Reference is missing, but that's OK. We
 606                                  * know that there is not a conflict with
 607                                  * another loose reference because
 608                                  * (supposing that we are trying to lock
 609                                  * reference "refs/foo/bar"):
 610                                  *
 611                                  * - We were successfully able to create
 612                                  *   the lockfile refs/foo/bar.lock, so we
 613                                  *   know there cannot be a loose reference
 614                                  *   named "refs/foo".
 615                                  *
 616                                  * - We got ENOENT and not EISDIR, so we
 617                                  *   know that there cannot be a loose
 618                                  *   reference named "refs/foo/bar/baz".
 619                                  */
 620                         }
 621                 } else if (errno == EISDIR) {
 622                         /*
 623                          * There is a directory in the way. It might have
 624                          * contained references that have been deleted. If
 625                          * we don't require that the reference already
 626                          * exists, try to remove the directory so that it
 627                          * doesn't cause trouble when we want to rename the
 628                          * lockfile into place later.
 629                          */
 630                         if (mustexist) {
 631                                 /* Garden variety missing reference. */
 632                                 strbuf_addf(err, "unable to resolve reference '%s'",
 633                                             refname);
 634                                 goto error_return;
 635                         } else if (remove_dir_recursively(&ref_file,
 636                                                           REMOVE_DIR_EMPTY_ONLY)) {
 637                                 if (refs_verify_refname_available(
 638                                                     &refs->base, refname,
 639                                                     extras, skip, err)) {
 640                                         /*
 641                                          * The error message set by
 642                                          * verify_refname_available() is OK.
 643                                          */
 644                                         ret = TRANSACTION_NAME_CONFLICT;
 645                                         goto error_return;
 646                                 } else {
 647                                         /*
 648                                          * We can't delete the directory,
 649                                          * but we also don't know of any
 650                                          * references that it should
 651                                          * contain.
 652                                          */
 653                                         strbuf_addf(err, "there is a non-empty directory '%s' "
 654                                                     "blocking reference '%s'",
 655                                                     ref_file.buf, refname);
 656                                         goto error_return;
 657                                 }
 658                         }
 659                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 660                         strbuf_addf(err, "unable to resolve reference '%s': "
 661                                     "reference broken", refname);
 662                         goto error_return;
 663                 } else {
 664                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 665                                     refname, strerror(errno));
 666                         goto error_return;
 667                 }
 668
 669                 /*
 670                  * If the ref did not exist and we are creating it,
 671                  * make sure there is no existing packed ref that
 672                  * conflicts with refname:
 673                  */
 674                 if (refs_verify_refname_available(
 675                                     refs->packed_ref_store, refname,
 676                                     extras, skip, err))
 677                         goto error_return;
 678         }
 679
 680         ret = 0;
 681         goto out;
 682
 683 error_return:
 684         unlock_ref(lock);
 685         *lock_p = NULL;
 686
 687 out:
 688         strbuf_release(&ref_file);
 689         return ret;
 690 }
 691
 692 struct files_ref_iterator {
 693         struct ref_iterator base;
 694
 695         struct ref_iterator *iter0;
 696         unsigned int flags;
 697 };
 698
 699 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 700 {
 701         struct files_ref_iterator *iter =
 702                 (struct files_ref_iterator *)ref_iterator;
 703         int ok;
 704
 705         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 706                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 707                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 708                         continue;
 709
 710                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 711                     !ref_resolves_to_object(iter->iter0->refname,
 712                                             iter->iter0->oid,
 713                                             iter->iter0->flags))
 714                         continue;
 715
 716                 iter->base.refname = iter->iter0->refname;
 717                 iter->base.oid = iter->iter0->oid;
 718                 iter->base.flags = iter->iter0->flags;
 719                 return ITER_OK;
 720         }
 721
 722         iter->iter0 = NULL;
 723         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 724                 ok = ITER_ERROR;
 725
 726         return ok;
 727 }
 728
 729 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 730                                    struct object_id *peeled)
 731 {
 732         struct files_ref_iterator *iter =
 733                 (struct files_ref_iterator *)ref_iterator;
 734
 735         return ref_iterator_peel(iter->iter0, peeled);
 736 }
 737
 738 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 739 {
 740         struct files_ref_iterator *iter =
 741                 (struct files_ref_iterator *)ref_iterator;
 742         int ok = ITER_DONE;
 743
 744         if (iter->iter0)
 745                 ok = ref_iterator_abort(iter->iter0);
 746
 747         base_ref_iterator_free(ref_iterator);
 748         return ok;
 749 }
 750
 751 static struct ref_iterator_vtable files_ref_iterator_vtable = {
 752         files_ref_iterator_advance,
 753         files_ref_iterator_peel,
 754         files_ref_iterator_abort
 755 };
 756
 757 static struct ref_iterator *files_ref_iterator_begin(
 758                 struct ref_store *ref_store,
 759                 const char *prefix, unsigned int flags)
 760 {
 761         struct files_ref_store *refs;
 762         struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 763         struct files_ref_iterator *iter;
 764         struct ref_iterator *ref_iterator;
 765         unsigned int required_flags = REF_STORE_READ;
 766
 767         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 768                 required_flags |= REF_STORE_ODB;
 769
 770         refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 771
 772         /*
 773          * We must make sure that all loose refs are read before
 774          * accessing the packed-refs file; this avoids a race
 775          * condition if loose refs are migrated to the packed-refs
 776          * file by a simultaneous process, but our in-memory view is
 777          * from before the migration. We ensure this as follows:
 778          * First, we call start the loose refs iteration with its
 779          * `prime_ref` argument set to true. This causes the loose
 780          * references in the subtree to be pre-read into the cache.
 781          * (If they've already been read, that's OK; we only need to
 782          * guarantee that they're read before the packed refs, not
 783          * *how much* before.) After that, we call
 784          * packed_ref_iterator_begin(), which internally checks
 785          * whether the packed-ref cache is up to date with what is on
 786          * disk, and re-reads it if not.
 787          */
 788
 789         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 790                                               prefix, 1);
 791
 792         /*
 793          * The packed-refs file might contain broken references, for
 794          * example an old version of a reference that points at an
 795          * object that has since been garbage-collected. This is OK as
 796          * long as there is a corresponding loose reference that
 797          * overrides it, and we don't want to emit an error message in
 798          * this case. So ask the packed_ref_store for all of its
 799          * references, and (if needed) do our own check for broken
 800          * ones in files_ref_iterator_advance(), after we have merged
 801          * the packed and loose references.
 802          */
 803         packed_iter = refs_ref_iterator_begin(
 804                         refs->packed_ref_store, prefix, 0,
 805                         DO_FOR_EACH_INCLUDE_BROKEN);
 806
 807         overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 808
 809         iter = xcalloc(1, sizeof(*iter));
 810         ref_iterator = &iter->base;
 811         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 812                                overlay_iter->ordered);
 813         iter->iter0 = overlay_iter;
 814         iter->flags = flags;
 815
 816         return ref_iterator;
 817 }
 818
 819 /*
 820  * Verify that the reference locked by lock has the value old_oid
 821  * (unless it is NULL).  Fail if the reference doesn't exist and
 822  * mustexist is set. Return 0 on success. On error, write an error
 823  * message to err, set errno, and return a negative value.
 824  */
 825 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 826                        const struct object_id *old_oid, int mustexist,
 827                        struct strbuf *err)
 828 {
 829         assert(err);
 830
 831         if (refs_read_ref_full(ref_store, lock->ref_name,
 832                                mustexist ? RESOLVE_REF_READING : 0,
 833                                &lock->old_oid, NULL)) {
 834                 if (old_oid) {
 835                         int save_errno = errno;
 836                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 837                         errno = save_errno;
 838                         return -1;
 839                 } else {
 840                         oidclr(&lock->old_oid);
 841                         return 0;
 842                 }
 843         }
 844         if (old_oid && oidcmp(&lock->old_oid, old_oid)) {
 845                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 846                             lock->ref_name,
 847                             oid_to_hex(&lock->old_oid),
 848                             oid_to_hex(old_oid));
 849                 errno = EBUSY;
 850                 return -1;
 851         }
 852         return 0;
 853 }
 854
 855 static int remove_empty_directories(struct strbuf *path)
 856 {
 857         /*
 858          * we want to create a file but there is a directory there;
 859          * if that is an empty directory (or a directory that contains
 860          * only empty directories), remove them.
 861          */
 862         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 863 }
 864
 865 static int create_reflock(const char *path, void *cb)
 866 {
 867         struct lock_file *lk = cb;
 868
 869         return hold_lock_file_for_update_timeout(
 870                         lk, path, LOCK_NO_DEREF,
 871                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 872 }
 873
 874 /*
 875  * Locks a ref returning the lock on success and NULL on failure.
 876  * On failure errno is set to something meaningful.
 877  */
 878 static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
 879                                            const char *refname,
 880                                            const struct object_id *old_oid,
 881                                            const struct string_list *extras,
 882                                            const struct string_list *skip,
 883                                            unsigned int flags, int *type,
 884                                            struct strbuf *err)
 885 {
 886         struct strbuf ref_file = STRBUF_INIT;
 887         struct ref_lock *lock;
 888         int last_errno = 0;
 889         int mustexist = (old_oid && !is_null_oid(old_oid));
 890         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 891         int resolved;
 892
 893         files_assert_main_repository(refs, "lock_ref_oid_basic");
 894         assert(err);
 895
 896         lock = xcalloc(1, sizeof(struct ref_lock));
 897
 898         if (mustexist)
 899                 resolve_flags |= RESOLVE_REF_READING;
 900         if (flags & REF_DELETING)
 901                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 902
 903         files_ref_path(refs, &ref_file, refname);
 904         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 905                                              refname, resolve_flags,
 906                                              &lock->old_oid, type);
 907         if (!resolved && errno == EISDIR) {
 908                 /*
 909                  * we are trying to lock foo but we used to
 910                  * have foo/bar which now does not exist;
 911                  * it is normal for the empty directory 'foo'
 912                  * to remain.
 913                  */
 914                 if (remove_empty_directories(&ref_file)) {
 915                         last_errno = errno;
 916                         if (!refs_verify_refname_available(
 917                                             &refs->base,
 918                                             refname, extras, skip, err))
 919                                 strbuf_addf(err, "there are still refs under '%s'",
 920                                             refname);
 921                         goto error_return;
 922                 }
 923                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 924                                                      refname, resolve_flags,
 925                                                      &lock->old_oid, type);
 926         }
 927         if (!resolved) {
 928                 last_errno = errno;
 929                 if (last_errno != ENOTDIR ||
 930                     !refs_verify_refname_available(&refs->base, refname,
 931                                                    extras, skip, err))
 932                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 933                                     refname, strerror(last_errno));
 934
 935                 goto error_return;
 936         }
 937
 938         /*
 939          * If the ref did not exist and we are creating it, make sure
 940          * there is no existing packed ref whose name begins with our
 941          * refname, nor a packed ref whose name is a proper prefix of
 942          * our refname.
 943          */
 944         if (is_null_oid(&lock->old_oid) &&
 945             refs_verify_refname_available(refs->packed_ref_store, refname,
 946                                           extras, skip, err)) {
 947                 last_errno = ENOTDIR;
 948                 goto error_return;
 949         }
 950
 951         lock->ref_name = xstrdup(refname);
 952
 953         if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 954                 last_errno = errno;
 955                 unable_to_lock_message(ref_file.buf, errno, err);
 956                 goto error_return;
 957         }
 958
 959         if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
 960                 last_errno = errno;
 961                 goto error_return;
 962         }
 963         goto out;
 964
 965  error_return:
 966         unlock_ref(lock);
 967         lock = NULL;
 968
 969  out:
 970         strbuf_release(&ref_file);
 971         errno = last_errno;
 972         return lock;
 973 }
 974
 975 struct ref_to_prune {
 976         struct ref_to_prune *next;
 977         struct object_id oid;
 978         char name[FLEX_ARRAY];
 979 };
 980
 981 enum {
 982         REMOVE_EMPTY_PARENTS_REF = 0x01,
 983         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 984 };
 985
 986 /*
 987  * Remove empty parent directories associated with the specified
 988  * reference and/or its reflog, but spare [logs/]refs/ and immediate
 989  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 990  * REMOVE_EMPTY_PARENTS_REFLOG.
 991  */
 992 static void try_remove_empty_parents(struct files_ref_store *refs,
 993                                      const char *refname,
 994                                      unsigned int flags)
 995 {
 996         struct strbuf buf = STRBUF_INIT;
 997         struct strbuf sb = STRBUF_INIT;
 998         char *p, *q;
 999         int i;
1000
1001         strbuf_addstr(&buf, refname);
1002         p = buf.buf;
1003         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1004                 while (*p && *p != '/')
1005                         p++;
1006                 /* tolerate duplicate slashes; see check_refname_format() */
1007                 while (*p == '/')
1008                         p++;
1009         }
1010         q = buf.buf + buf.len;
1011         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1012                 while (q > p && *q != '/')
1013                         q--;
1014                 while (q > p && *(q-1) == '/')
1015                         q--;
1016                 if (q == p)
1017                         break;
1018                 strbuf_setlen(&buf, q - buf.buf);
1019
1020                 strbuf_reset(&sb);
1021                 files_ref_path(refs, &sb, buf.buf);
1022                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1023                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1024
1025                 strbuf_reset(&sb);
1026                 files_reflog_path(refs, &sb, buf.buf);
1027                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1028                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1029         }
1030         strbuf_release(&buf);
1031         strbuf_release(&sb);
1032 }
1033
1034 /* make sure nobody touched the ref, and unlink */
1035 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1036 {
1037         struct ref_transaction *transaction;
1038         struct strbuf err = STRBUF_INIT;
1039         int ret = -1;
1040
1041         if (check_refname_format(r->name, 0))
1042                 return;
1043
1044         transaction = ref_store_transaction_begin(&refs->base, &err);
1045         if (!transaction)
1046                 goto cleanup;
1047         ref_transaction_add_update(
1048                         transaction, r->name,
1049                         REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
1050                         &null_oid, &r->oid, NULL);
1051         if (ref_transaction_commit(transaction, &err))
1052                 goto cleanup;
1053
1054         ret = 0;
1055
1056 cleanup:
1057         if (ret)
1058                 error("%s", err.buf);
1059         strbuf_release(&err);
1060         ref_transaction_free(transaction);
1061         return;
1062 }
1063
1064 /*
1065  * Prune the loose versions of the references in the linked list
1066  * `*refs_to_prune`, freeing the entries in the list as we go.
1067  */
1068 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1069 {
1070         while (*refs_to_prune) {
1071                 struct ref_to_prune *r = *refs_to_prune;
1072                 *refs_to_prune = r->next;
1073                 prune_ref(refs, r);
1074                 free(r);
1075         }
1076 }
1077
1078 /*
1079  * Return true if the specified reference should be packed.
1080  */
1081 static int should_pack_ref(const char *refname,
1082                            const struct object_id *oid, unsigned int ref_flags,
1083                            unsigned int pack_flags)
1084 {
1085         /* Do not pack per-worktree refs: */
1086         if (ref_type(refname) != REF_TYPE_NORMAL)
1087                 return 0;
1088
1089         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1090         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1091                 return 0;
1092
1093         /* Do not pack symbolic refs: */
1094         if (ref_flags & REF_ISSYMREF)
1095                 return 0;
1096
1097         /* Do not pack broken refs: */
1098         if (!ref_resolves_to_object(refname, oid, ref_flags))
1099                 return 0;
1100
1101         return 1;
1102 }
1103
1104 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1105 {
1106         struct files_ref_store *refs =
1107                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1108                                "pack_refs");
1109         struct ref_iterator *iter;
1110         int ok;
1111         struct ref_to_prune *refs_to_prune = NULL;
1112         struct strbuf err = STRBUF_INIT;
1113         struct ref_transaction *transaction;
1114
1115         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1116         if (!transaction)
1117                 return -1;
1118
1119         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1120
1121         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1122         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1123                 /*
1124                  * If the loose reference can be packed, add an entry
1125                  * in the packed ref cache. If the reference should be
1126                  * pruned, also add it to refs_to_prune.
1127                  */
1128                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1129                                      flags))
1130                         continue;
1131
1132                 /*
1133                  * Add a reference creation for this reference to the
1134                  * packed-refs transaction:
1135                  */
1136                 if (ref_transaction_update(transaction, iter->refname,
1137                                            iter->oid, NULL,
1138                                            REF_NO_DEREF, NULL, &err))
1139                         die("failure preparing to create packed reference %s: %s",
1140                             iter->refname, err.buf);
1141
1142                 /* Schedule the loose reference for pruning if requested. */
1143                 if ((flags & PACK_REFS_PRUNE)) {
1144                         struct ref_to_prune *n;
1145                         FLEX_ALLOC_STR(n, name, iter->refname);
1146                         oidcpy(&n->oid, iter->oid);
1147                         n->next = refs_to_prune;
1148                         refs_to_prune = n;
1149                 }
1150         }
1151         if (ok != ITER_DONE)
1152                 die("error while iterating over references");
1153
1154         if (ref_transaction_commit(transaction, &err))
1155                 die("unable to write new packed-refs: %s", err.buf);
1156
1157         ref_transaction_free(transaction);
1158
1159         packed_refs_unlock(refs->packed_ref_store);
1160
1161         prune_refs(refs, &refs_to_prune);
1162         strbuf_release(&err);
1163         return 0;
1164 }
1165
1166 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1167                              struct string_list *refnames, unsigned int flags)
1168 {
1169         struct files_ref_store *refs =
1170                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1171         struct strbuf err = STRBUF_INIT;
1172         int i, result = 0;
1173
1174         if (!refnames->nr)
1175                 return 0;
1176
1177         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1178                 goto error;
1179
1180         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1181                 packed_refs_unlock(refs->packed_ref_store);
1182                 goto error;
1183         }
1184
1185         packed_refs_unlock(refs->packed_ref_store);
1186
1187         for (i = 0; i < refnames->nr; i++) {
1188                 const char *refname = refnames->items[i].string;
1189
1190                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1191                         result |= error(_("could not remove reference %s"), refname);
1192         }
1193
1194         strbuf_release(&err);
1195         return result;
1196
1197 error:
1198         /*
1199          * If we failed to rewrite the packed-refs file, then it is
1200          * unsafe to try to remove loose refs, because doing so might
1201          * expose an obsolete packed value for a reference that might
1202          * even point at an object that has been garbage collected.
1203          */
1204         if (refnames->nr == 1)
1205                 error(_("could not delete reference %s: %s"),
1206                       refnames->items[0].string, err.buf);
1207         else
1208                 error(_("could not delete references: %s"), err.buf);
1209
1210         strbuf_release(&err);
1211         return -1;
1212 }
1213
1214 /*
1215  * People using contrib's git-new-workdir have .git/logs/refs ->
1216  * /some/other/path/.git/logs/refs, and that may live on another device.
1217  *
1218  * IOW, to avoid cross device rename errors, the temporary renamed log must
1219  * live into logs/refs.
1220  */
1221 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1222
1223 struct rename_cb {
1224         const char *tmp_renamed_log;
1225         int true_errno;
1226 };
1227
1228 static int rename_tmp_log_callback(const char *path, void *cb_data)
1229 {
1230         struct rename_cb *cb = cb_data;
1231
1232         if (rename(cb->tmp_renamed_log, path)) {
1233                 /*
1234                  * rename(a, b) when b is an existing directory ought
1235                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1236                  * Sheesh. Record the true errno for error reporting,
1237                  * but report EISDIR to raceproof_create_file() so
1238                  * that it knows to retry.
1239                  */
1240                 cb->true_errno = errno;
1241                 if (errno == ENOTDIR)
1242                         errno = EISDIR;
1243                 return -1;
1244         } else {
1245                 return 0;
1246         }
1247 }
1248
1249 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1250 {
1251         struct strbuf path = STRBUF_INIT;
1252         struct strbuf tmp = STRBUF_INIT;
1253         struct rename_cb cb;
1254         int ret;
1255
1256         files_reflog_path(refs, &path, newrefname);
1257         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1258         cb.tmp_renamed_log = tmp.buf;
1259         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1260         if (ret) {
1261                 if (errno == EISDIR)
1262                         error("directory not empty: %s", path.buf);
1263                 else
1264                         error("unable to move logfile %s to %s: %s",
1265                               tmp.buf, path.buf,
1266                               strerror(cb.true_errno));
1267         }
1268
1269         strbuf_release(&path);
1270         strbuf_release(&tmp);
1271         return ret;
1272 }
1273
1274 static int write_ref_to_lockfile(struct ref_lock *lock,
1275                                  const struct object_id *oid, struct strbuf *err);
1276 static int commit_ref_update(struct files_ref_store *refs,
1277                              struct ref_lock *lock,
1278                              const struct object_id *oid, const char *logmsg,
1279                              struct strbuf *err);
1280
1281 static int files_copy_or_rename_ref(struct ref_store *ref_store,
1282                             const char *oldrefname, const char *newrefname,
1283                             const char *logmsg, int copy)
1284 {
1285         struct files_ref_store *refs =
1286                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1287         struct object_id oid, orig_oid;
1288         int flag = 0, logmoved = 0;
1289         struct ref_lock *lock;
1290         struct stat loginfo;
1291         struct strbuf sb_oldref = STRBUF_INIT;
1292         struct strbuf sb_newref = STRBUF_INIT;
1293         struct strbuf tmp_renamed_log = STRBUF_INIT;
1294         int log, ret;
1295         struct strbuf err = STRBUF_INIT;
1296
1297         files_reflog_path(refs, &sb_oldref, oldrefname);
1298         files_reflog_path(refs, &sb_newref, newrefname);
1299         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1300
1301         log = !lstat(sb_oldref.buf, &loginfo);
1302         if (log && S_ISLNK(loginfo.st_mode)) {
1303                 ret = error("reflog for %s is a symlink", oldrefname);
1304                 goto out;
1305         }
1306
1307         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1308                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1309                                 &orig_oid, &flag)) {
1310                 ret = error("refname %s not found", oldrefname);
1311                 goto out;
1312         }
1313
1314         if (flag & REF_ISSYMREF) {
1315                 if (copy)
1316                         ret = error("refname %s is a symbolic ref, copying it is not supported",
1317                                     oldrefname);
1318                 else
1319                         ret = error("refname %s is a symbolic ref, renaming it is not supported",
1320                                     oldrefname);
1321                 goto out;
1322         }
1323         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1324                 ret = 1;
1325                 goto out;
1326         }
1327
1328         if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1329                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1330                             oldrefname, strerror(errno));
1331                 goto out;
1332         }
1333
1334         if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1335                 ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1336                             oldrefname, strerror(errno));
1337                 goto out;
1338         }
1339
1340         if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1341                             &orig_oid, REF_NO_DEREF)) {
1342                 error("unable to delete old %s", oldrefname);
1343                 goto rollback;
1344         }
1345
1346         /*
1347          * Since we are doing a shallow lookup, oid is not the
1348          * correct value to pass to delete_ref as old_oid. But that
1349          * doesn't matter, because an old_oid check wouldn't add to
1350          * the safety anyway; we want to delete the reference whatever
1351          * its current value.
1352          */
1353         if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1354                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1355                                 &oid, NULL) &&
1356             refs_delete_ref(&refs->base, NULL, newrefname,
1357                             NULL, REF_NO_DEREF)) {
1358                 if (errno == EISDIR) {
1359                         struct strbuf path = STRBUF_INIT;
1360                         int result;
1361
1362                         files_ref_path(refs, &path, newrefname);
1363                         result = remove_empty_directories(&path);
1364                         strbuf_release(&path);
1365
1366                         if (result) {
1367                                 error("Directory not empty: %s", newrefname);
1368                                 goto rollback;
1369                         }
1370                 } else {
1371                         error("unable to delete existing %s", newrefname);
1372                         goto rollback;
1373                 }
1374         }
1375
1376         if (log && rename_tmp_log(refs, newrefname))
1377                 goto rollback;
1378
1379         logmoved = log;
1380
1381         lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1382                                   REF_NO_DEREF, NULL, &err);
1383         if (!lock) {
1384                 if (copy)
1385                         error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1386                 else
1387                         error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1388                 strbuf_release(&err);
1389                 goto rollback;
1390         }
1391         oidcpy(&lock->old_oid, &orig_oid);
1392
1393         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1394             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1395                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1396                 strbuf_release(&err);
1397                 goto rollback;
1398         }
1399
1400         ret = 0;
1401         goto out;
1402
1403  rollback:
1404         lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1405                                   REF_NO_DEREF, NULL, &err);
1406         if (!lock) {
1407                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1408                 strbuf_release(&err);
1409                 goto rollbacklog;
1410         }
1411
1412         flag = log_all_ref_updates;
1413         log_all_ref_updates = LOG_REFS_NONE;
1414         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1415             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1416                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1417                 strbuf_release(&err);
1418         }
1419         log_all_ref_updates = flag;
1420
1421  rollbacklog:
1422         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1423                 error("unable to restore logfile %s from %s: %s",
1424                         oldrefname, newrefname, strerror(errno));
1425         if (!logmoved && log &&
1426             rename(tmp_renamed_log.buf, sb_oldref.buf))
1427                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1428                         oldrefname, strerror(errno));
1429         ret = 1;
1430  out:
1431         strbuf_release(&sb_newref);
1432         strbuf_release(&sb_oldref);
1433         strbuf_release(&tmp_renamed_log);
1434
1435         return ret;
1436 }
1437
1438 static int files_rename_ref(struct ref_store *ref_store,
1439                             const char *oldrefname, const char *newrefname,
1440                             const char *logmsg)
1441 {
1442         return files_copy_or_rename_ref(ref_store, oldrefname,
1443                                  newrefname, logmsg, 0);
1444 }
1445
1446 static int files_copy_ref(struct ref_store *ref_store,
1447                             const char *oldrefname, const char *newrefname,
1448                             const char *logmsg)
1449 {
1450         return files_copy_or_rename_ref(ref_store, oldrefname,
1451                                  newrefname, logmsg, 1);
1452 }
1453
1454 static int close_ref_gently(struct ref_lock *lock)
1455 {
1456         if (close_lock_file_gently(&lock->lk))
1457                 return -1;
1458         return 0;
1459 }
1460
1461 static int commit_ref(struct ref_lock *lock)
1462 {
1463         char *path = get_locked_file_path(&lock->lk);
1464         struct stat st;
1465
1466         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1467                 /*
1468                  * There is a directory at the path we want to rename
1469                  * the lockfile to. Hopefully it is empty; try to
1470                  * delete it.
1471                  */
1472                 size_t len = strlen(path);
1473                 struct strbuf sb_path = STRBUF_INIT;
1474
1475                 strbuf_attach(&sb_path, path, len, len);
1476
1477                 /*
1478                  * If this fails, commit_lock_file() will also fail
1479                  * and will report the problem.
1480                  */
1481                 remove_empty_directories(&sb_path);
1482                 strbuf_release(&sb_path);
1483         } else {
1484                 free(path);
1485         }
1486
1487         if (commit_lock_file(&lock->lk))
1488                 return -1;
1489         return 0;
1490 }
1491
1492 static int open_or_create_logfile(const char *path, void *cb)
1493 {
1494         int *fd = cb;
1495
1496         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1497         return (*fd < 0) ? -1 : 0;
1498 }
1499
1500 /*
1501  * Create a reflog for a ref. If force_create = 0, only create the
1502  * reflog for certain refs (those for which should_autocreate_reflog
1503  * returns non-zero). Otherwise, create it regardless of the reference
1504  * name. If the logfile already existed or was created, return 0 and
1505  * set *logfd to the file descriptor opened for appending to the file.
1506  * If no logfile exists and we decided not to create one, return 0 and
1507  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1508  * return -1.
1509  */
1510 static int log_ref_setup(struct files_ref_store *refs,
1511                          const char *refname, int force_create,
1512                          int *logfd, struct strbuf *err)
1513 {
1514         struct strbuf logfile_sb = STRBUF_INIT;
1515         char *logfile;
1516
1517         files_reflog_path(refs, &logfile_sb, refname);
1518         logfile = strbuf_detach(&logfile_sb, NULL);
1519
1520         if (force_create || should_autocreate_reflog(refname)) {
1521                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1522                         if (errno == ENOENT)
1523                                 strbuf_addf(err, "unable to create directory for '%s': "
1524                                             "%s", logfile, strerror(errno));
1525                         else if (errno == EISDIR)
1526                                 strbuf_addf(err, "there are still logs under '%s'",
1527                                             logfile);
1528                         else
1529                                 strbuf_addf(err, "unable to append to '%s': %s",
1530                                             logfile, strerror(errno));
1531
1532                         goto error;
1533                 }
1534         } else {
1535                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1536                 if (*logfd < 0) {
1537                         if (errno == ENOENT || errno == EISDIR) {
1538                                 /*
1539                                  * The logfile doesn't already exist,
1540                                  * but that is not an error; it only
1541                                  * means that we won't write log
1542                                  * entries to it.
1543                                  */
1544                                 ;
1545                         } else {
1546                                 strbuf_addf(err, "unable to append to '%s': %s",
1547                                             logfile, strerror(errno));
1548                                 goto error;
1549                         }
1550                 }
1551         }
1552
1553         if (*logfd >= 0)
1554                 adjust_shared_perm(logfile);
1555
1556         free(logfile);
1557         return 0;
1558
1559 error:
1560         free(logfile);
1561         return -1;
1562 }
1563
1564 static int files_create_reflog(struct ref_store *ref_store,
1565                                const char *refname, int force_create,
1566                                struct strbuf *err)
1567 {
1568         struct files_ref_store *refs =
1569                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1570         int fd;
1571
1572         if (log_ref_setup(refs, refname, force_create, &fd, err))
1573                 return -1;
1574
1575         if (fd >= 0)
1576                 close(fd);
1577
1578         return 0;
1579 }
1580
1581 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1582                             const struct object_id *new_oid,
1583                             const char *committer, const char *msg)
1584 {
1585         int msglen, written;
1586         unsigned maxlen, len;
1587         char *logrec;
1588
1589         msglen = msg ? strlen(msg) : 0;
1590         maxlen = strlen(committer) + msglen + 100;
1591         logrec = xmalloc(maxlen);
1592         len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1593                         oid_to_hex(old_oid),
1594                         oid_to_hex(new_oid),
1595                         committer);
1596         if (msglen)
1597                 len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1598
1599         written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1600         free(logrec);
1601         if (written < 0)
1602                 return -1;
1603
1604         return 0;
1605 }
1606
1607 static int files_log_ref_write(struct files_ref_store *refs,
1608                                const char *refname, const struct object_id *old_oid,
1609                                const struct object_id *new_oid, const char *msg,
1610                                int flags, struct strbuf *err)
1611 {
1612         int logfd, result;
1613
1614         if (log_all_ref_updates == LOG_REFS_UNSET)
1615                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1616
1617         result = log_ref_setup(refs, refname,
1618                                flags & REF_FORCE_CREATE_REFLOG,
1619                                &logfd, err);
1620
1621         if (result)
1622                 return result;
1623
1624         if (logfd < 0)
1625                 return 0;
1626         result = log_ref_write_fd(logfd, old_oid, new_oid,
1627                                   git_committer_info(0), msg);
1628         if (result) {
1629                 struct strbuf sb = STRBUF_INIT;
1630                 int save_errno = errno;
1631
1632                 files_reflog_path(refs, &sb, refname);
1633                 strbuf_addf(err, "unable to append to '%s': %s",
1634                             sb.buf, strerror(save_errno));
1635                 strbuf_release(&sb);
1636                 close(logfd);
1637                 return -1;
1638         }
1639         if (close(logfd)) {
1640                 struct strbuf sb = STRBUF_INIT;
1641                 int save_errno = errno;
1642
1643                 files_reflog_path(refs, &sb, refname);
1644                 strbuf_addf(err, "unable to append to '%s': %s",
1645                             sb.buf, strerror(save_errno));
1646                 strbuf_release(&sb);
1647                 return -1;
1648         }
1649         return 0;
1650 }
1651
1652 /*
1653  * Write oid into the open lockfile, then close the lockfile. On
1654  * errors, rollback the lockfile, fill in *err and return -1.
1655  */
1656 static int write_ref_to_lockfile(struct ref_lock *lock,
1657                                  const struct object_id *oid, struct strbuf *err)
1658 {
1659         static char term = '\n';
1660         struct object *o;
1661         int fd;
1662
1663         o = parse_object(oid);
1664         if (!o) {
1665                 strbuf_addf(err,
1666                             "trying to write ref '%s' with nonexistent object %s",
1667                             lock->ref_name, oid_to_hex(oid));
1668                 unlock_ref(lock);
1669                 return -1;
1670         }
1671         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1672                 strbuf_addf(err,
1673                             "trying to write non-commit object %s to branch '%s'",
1674                             oid_to_hex(oid), lock->ref_name);
1675                 unlock_ref(lock);
1676                 return -1;
1677         }
1678         fd = get_lock_file_fd(&lock->lk);
1679         if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1680             write_in_full(fd, &term, 1) < 0 ||
1681             close_ref_gently(lock) < 0) {
1682                 strbuf_addf(err,
1683                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1684                 unlock_ref(lock);
1685                 return -1;
1686         }
1687         return 0;
1688 }
1689
1690 /*
1691  * Commit a change to a loose reference that has already been written
1692  * to the loose reference lockfile. Also update the reflogs if
1693  * necessary, using the specified lockmsg (which can be NULL).
1694  */
1695 static int commit_ref_update(struct files_ref_store *refs,
1696                              struct ref_lock *lock,
1697                              const struct object_id *oid, const char *logmsg,
1698                              struct strbuf *err)
1699 {
1700         files_assert_main_repository(refs, "commit_ref_update");
1701
1702         clear_loose_ref_cache(refs);
1703         if (files_log_ref_write(refs, lock->ref_name,
1704                                 &lock->old_oid, oid,
1705                                 logmsg, 0, err)) {
1706                 char *old_msg = strbuf_detach(err, NULL);
1707                 strbuf_addf(err, "cannot update the ref '%s': %s",
1708                             lock->ref_name, old_msg);
1709                 free(old_msg);
1710                 unlock_ref(lock);
1711                 return -1;
1712         }
1713
1714         if (strcmp(lock->ref_name, "HEAD") != 0) {
1715                 /*
1716                  * Special hack: If a branch is updated directly and HEAD
1717                  * points to it (may happen on the remote side of a push
1718                  * for example) then logically the HEAD reflog should be
1719                  * updated too.
1720                  * A generic solution implies reverse symref information,
1721                  * but finding all symrefs pointing to the given branch
1722                  * would be rather costly for this rare event (the direct
1723                  * update of a branch) to be worth it.  So let's cheat and
1724                  * check with HEAD only which should cover 99% of all usage
1725                  * scenarios (even 100% of the default ones).
1726                  */
1727                 int head_flag;
1728                 const char *head_ref;
1729
1730                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1731                                                    RESOLVE_REF_READING,
1732                                                    NULL, &head_flag);
1733                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1734                     !strcmp(head_ref, lock->ref_name)) {
1735                         struct strbuf log_err = STRBUF_INIT;
1736                         if (files_log_ref_write(refs, "HEAD",
1737                                                 &lock->old_oid, oid,
1738                                                 logmsg, 0, &log_err)) {
1739                                 error("%s", log_err.buf);
1740                                 strbuf_release(&log_err);
1741                         }
1742                 }
1743         }
1744
1745         if (commit_ref(lock)) {
1746                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1747                 unlock_ref(lock);
1748                 return -1;
1749         }
1750
1751         unlock_ref(lock);
1752         return 0;
1753 }
1754
1755 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1756 {
1757         int ret = -1;
1758 #ifndef NO_SYMLINK_HEAD
1759         char *ref_path = get_locked_file_path(&lock->lk);
1760         unlink(ref_path);
1761         ret = symlink(target, ref_path);
1762         free(ref_path);
1763
1764         if (ret)
1765                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1766 #endif
1767         return ret;
1768 }
1769
1770 static void update_symref_reflog(struct files_ref_store *refs,
1771                                  struct ref_lock *lock, const char *refname,
1772                                  const char *target, const char *logmsg)
1773 {
1774         struct strbuf err = STRBUF_INIT;
1775         struct object_id new_oid;
1776         if (logmsg &&
1777             !refs_read_ref_full(&refs->base, target,
1778                                 RESOLVE_REF_READING, &new_oid, NULL) &&
1779             files_log_ref_write(refs, refname, &lock->old_oid,
1780                                 &new_oid, logmsg, 0, &err)) {
1781                 error("%s", err.buf);
1782                 strbuf_release(&err);
1783         }
1784 }
1785
1786 static int create_symref_locked(struct files_ref_store *refs,
1787                                 struct ref_lock *lock, const char *refname,
1788                                 const char *target, const char *logmsg)
1789 {
1790         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1791                 update_symref_reflog(refs, lock, refname, target, logmsg);
1792                 return 0;
1793         }
1794
1795         if (!fdopen_lock_file(&lock->lk, "w"))
1796                 return error("unable to fdopen %s: %s",
1797                              lock->lk.tempfile->filename.buf, strerror(errno));
1798
1799         update_symref_reflog(refs, lock, refname, target, logmsg);
1800
1801         /* no error check; commit_ref will check ferror */
1802         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1803         if (commit_ref(lock) < 0)
1804                 return error("unable to write symref for %s: %s", refname,
1805                              strerror(errno));
1806         return 0;
1807 }
1808
1809 static int files_create_symref(struct ref_store *ref_store,
1810                                const char *refname, const char *target,
1811                                const char *logmsg)
1812 {
1813         struct files_ref_store *refs =
1814                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1815         struct strbuf err = STRBUF_INIT;
1816         struct ref_lock *lock;
1817         int ret;
1818
1819         lock = lock_ref_oid_basic(refs, refname, NULL,
1820                                   NULL, NULL, REF_NO_DEREF, NULL,
1821                                   &err);
1822         if (!lock) {
1823                 error("%s", err.buf);
1824                 strbuf_release(&err);
1825                 return -1;
1826         }
1827
1828         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1829         unlock_ref(lock);
1830         return ret;
1831 }
1832
1833 static int files_reflog_exists(struct ref_store *ref_store,
1834                                const char *refname)
1835 {
1836         struct files_ref_store *refs =
1837                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1838         struct strbuf sb = STRBUF_INIT;
1839         struct stat st;
1840         int ret;
1841
1842         files_reflog_path(refs, &sb, refname);
1843         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1844         strbuf_release(&sb);
1845         return ret;
1846 }
1847
1848 static int files_delete_reflog(struct ref_store *ref_store,
1849                                const char *refname)
1850 {
1851         struct files_ref_store *refs =
1852                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1853         struct strbuf sb = STRBUF_INIT;
1854         int ret;
1855
1856         files_reflog_path(refs, &sb, refname);
1857         ret = remove_path(sb.buf);
1858         strbuf_release(&sb);
1859         return ret;
1860 }
1861
1862 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1863 {
1864         struct object_id ooid, noid;
1865         char *email_end, *message;
1866         timestamp_t timestamp;
1867         int tz;
1868         const char *p = sb->buf;
1869
1870         /* old SP new SP name <email> SP time TAB msg LF */
1871         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1872             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1873             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1874             !(email_end = strchr(p, '>')) ||
1875             email_end[1] != ' ' ||
1876             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1877             !message || message[0] != ' ' ||
1878             (message[1] != '+' && message[1] != '-') ||
1879             !isdigit(message[2]) || !isdigit(message[3]) ||
1880             !isdigit(message[4]) || !isdigit(message[5]))
1881                 return 0; /* corrupt? */
1882         email_end[1] = '\0';
1883         tz = strtol(message + 1, NULL, 10);
1884         if (message[6] != '\t')
1885                 message += 6;
1886         else
1887                 message += 7;
1888         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1889 }
1890
1891 static char *find_beginning_of_line(char *bob, char *scan)
1892 {
1893         while (bob < scan && *(--scan) != '\n')
1894                 ; /* keep scanning backwards */
1895         /*
1896          * Return either beginning of the buffer, or LF at the end of
1897          * the previous line.
1898          */
1899         return scan;
1900 }
1901
1902 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1903                                              const char *refname,
1904                                              each_reflog_ent_fn fn,
1905                                              void *cb_data)
1906 {
1907         struct files_ref_store *refs =
1908                 files_downcast(ref_store, REF_STORE_READ,
1909                                "for_each_reflog_ent_reverse");
1910         struct strbuf sb = STRBUF_INIT;
1911         FILE *logfp;
1912         long pos;
1913         int ret = 0, at_tail = 1;
1914
1915         files_reflog_path(refs, &sb, refname);
1916         logfp = fopen(sb.buf, "r");
1917         strbuf_release(&sb);
1918         if (!logfp)
1919                 return -1;
1920
1921         /* Jump to the end */
1922         if (fseek(logfp, 0, SEEK_END) < 0)
1923                 ret = error("cannot seek back reflog for %s: %s",
1924                             refname, strerror(errno));
1925         pos = ftell(logfp);
1926         while (!ret && 0 < pos) {
1927                 int cnt;
1928                 size_t nread;
1929                 char buf[BUFSIZ];
1930                 char *endp, *scanp;
1931
1932                 /* Fill next block from the end */
1933                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1934                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1935                         ret = error("cannot seek back reflog for %s: %s",
1936                                     refname, strerror(errno));
1937                         break;
1938                 }
1939                 nread = fread(buf, cnt, 1, logfp);
1940                 if (nread != 1) {
1941                         ret = error("cannot read %d bytes from reflog for %s: %s",
1942                                     cnt, refname, strerror(errno));
1943                         break;
1944                 }
1945                 pos -= cnt;
1946
1947                 scanp = endp = buf + cnt;
1948                 if (at_tail && scanp[-1] == '\n')
1949                         /* Looking at the final LF at the end of the file */
1950                         scanp--;
1951                 at_tail = 0;
1952
1953                 while (buf < scanp) {
1954                         /*
1955                          * terminating LF of the previous line, or the beginning
1956                          * of the buffer.
1957                          */
1958                         char *bp;
1959
1960                         bp = find_beginning_of_line(buf, scanp);
1961
1962                         if (*bp == '\n') {
1963                                 /*
1964                                  * The newline is the end of the previous line,
1965                                  * so we know we have complete line starting
1966                                  * at (bp + 1). Prefix it onto any prior data
1967                                  * we collected for the line and process it.
1968                                  */
1969                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1970                                 scanp = bp;
1971                                 endp = bp + 1;
1972                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1973                                 strbuf_reset(&sb);
1974                                 if (ret)
1975                                         break;
1976                         } else if (!pos) {
1977                                 /*
1978                                  * We are at the start of the buffer, and the
1979                                  * start of the file; there is no previous
1980                                  * line, and we have everything for this one.
1981                                  * Process it, and we can end the loop.
1982                                  */
1983                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1984                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1985                                 strbuf_reset(&sb);
1986                                 break;
1987                         }
1988
1989                         if (bp == buf) {
1990                                 /*
1991                                  * We are at the start of the buffer, and there
1992                                  * is more file to read backwards. Which means
1993                                  * we are in the middle of a line. Note that we
1994                                  * may get here even if *bp was a newline; that
1995                                  * just means we are at the exact end of the
1996                                  * previous line, rather than some spot in the
1997                                  * middle.
1998                                  *
1999                                  * Save away what we have to be combined with
2000                                  * the data from the next read.
2001                                  */
2002                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
2003                                 break;
2004                         }
2005                 }
2006
2007         }
2008         if (!ret && sb.len)
2009                 BUG("reverse reflog parser had leftover data");
2010
2011         fclose(logfp);
2012         strbuf_release(&sb);
2013         return ret;
2014 }
2015
2016 static int files_for_each_reflog_ent(struct ref_store *ref_store,
2017                                      const char *refname,
2018                                      each_reflog_ent_fn fn, void *cb_data)
2019 {
2020         struct files_ref_store *refs =
2021                 files_downcast(ref_store, REF_STORE_READ,
2022                                "for_each_reflog_ent");
2023         FILE *logfp;
2024         struct strbuf sb = STRBUF_INIT;
2025         int ret = 0;
2026
2027         files_reflog_path(refs, &sb, refname);
2028         logfp = fopen(sb.buf, "r");
2029         strbuf_release(&sb);
2030         if (!logfp)
2031                 return -1;
2032
2033         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2034                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2035         fclose(logfp);
2036         strbuf_release(&sb);
2037         return ret;
2038 }
2039
2040 struct files_reflog_iterator {
2041         struct ref_iterator base;
2042
2043         struct ref_store *ref_store;
2044         struct dir_iterator *dir_iterator;
2045         struct object_id oid;
2046 };
2047
2048 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2049 {
2050         struct files_reflog_iterator *iter =
2051                 (struct files_reflog_iterator *)ref_iterator;
2052         struct dir_iterator *diter = iter->dir_iterator;
2053         int ok;
2054
2055         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2056                 int flags;
2057
2058                 if (!S_ISREG(diter->st.st_mode))
2059                         continue;
2060                 if (diter->basename[0] == '.')
2061                         continue;
2062                 if (ends_with(diter->basename, ".lock"))
2063                         continue;
2064
2065                 if (refs_read_ref_full(iter->ref_store,
2066                                        diter->relative_path, 0,
2067                                        &iter->oid, &flags)) {
2068                         error("bad ref for %s", diter->path.buf);
2069                         continue;
2070                 }
2071
2072                 iter->base.refname = diter->relative_path;
2073                 iter->base.oid = &iter->oid;
2074                 iter->base.flags = flags;
2075                 return ITER_OK;
2076         }
2077
2078         iter->dir_iterator = NULL;
2079         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2080                 ok = ITER_ERROR;
2081         return ok;
2082 }
2083
2084 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2085                                    struct object_id *peeled)
2086 {
2087         BUG("ref_iterator_peel() called for reflog_iterator");
2088 }
2089
2090 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2091 {
2092         struct files_reflog_iterator *iter =
2093                 (struct files_reflog_iterator *)ref_iterator;
2094         int ok = ITER_DONE;
2095
2096         if (iter->dir_iterator)
2097                 ok = dir_iterator_abort(iter->dir_iterator);
2098
2099         base_ref_iterator_free(ref_iterator);
2100         return ok;
2101 }
2102
2103 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2104         files_reflog_iterator_advance,
2105         files_reflog_iterator_peel,
2106         files_reflog_iterator_abort
2107 };
2108
2109 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2110                                                   const char *gitdir)
2111 {
2112         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2113         struct ref_iterator *ref_iterator = &iter->base;
2114         struct strbuf sb = STRBUF_INIT;
2115
2116         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2117         strbuf_addf(&sb, "%s/logs", gitdir);
2118         iter->dir_iterator = dir_iterator_begin(sb.buf);
2119         iter->ref_store = ref_store;
2120         strbuf_release(&sb);
2121
2122         return ref_iterator;
2123 }
2124
2125 static enum iterator_selection reflog_iterator_select(
2126         struct ref_iterator *iter_worktree,
2127         struct ref_iterator *iter_common,
2128         void *cb_data)
2129 {
2130         if (iter_worktree) {
2131                 /*
2132                  * We're a bit loose here. We probably should ignore
2133                  * common refs if they are accidentally added as
2134                  * per-worktree refs.
2135                  */
2136                 return ITER_SELECT_0;
2137         } else if (iter_common) {
2138                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2139                         return ITER_SELECT_1;
2140
2141                 /*
2142                  * The main ref store may contain main worktree's
2143                  * per-worktree refs, which should be ignored
2144                  */
2145                 return ITER_SKIP_1;
2146         } else
2147                 return ITER_DONE;
2148 }
2149
2150 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2151 {
2152         struct files_ref_store *refs =
2153                 files_downcast(ref_store, REF_STORE_READ,
2154                                "reflog_iterator_begin");
2155
2156         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2157                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2158         } else {
2159                 return merge_ref_iterator_begin(
2160                         0,
2161                         reflog_iterator_begin(ref_store, refs->gitdir),
2162                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2163                         reflog_iterator_select, refs);
2164         }
2165 }
2166
2167 /*
2168  * If update is a direct update of head_ref (the reference pointed to
2169  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2170  */
2171 static int split_head_update(struct ref_update *update,
2172                              struct ref_transaction *transaction,
2173                              const char *head_ref,
2174                              struct string_list *affected_refnames,
2175                              struct strbuf *err)
2176 {
2177         struct string_list_item *item;
2178         struct ref_update *new_update;
2179
2180         if ((update->flags & REF_LOG_ONLY) ||
2181             (update->flags & REF_IS_PRUNING) ||
2182             (update->flags & REF_UPDATE_VIA_HEAD))
2183                 return 0;
2184
2185         if (strcmp(update->refname, head_ref))
2186                 return 0;
2187
2188         /*
2189          * First make sure that HEAD is not already in the
2190          * transaction. This check is O(lg N) in the transaction
2191          * size, but it happens at most once per transaction.
2192          */
2193         if (string_list_has_string(affected_refnames, "HEAD")) {
2194                 /* An entry already existed */
2195                 strbuf_addf(err,
2196                             "multiple updates for 'HEAD' (including one "
2197                             "via its referent '%s') are not allowed",
2198                             update->refname);
2199                 return TRANSACTION_NAME_CONFLICT;
2200         }
2201
2202         new_update = ref_transaction_add_update(
2203                         transaction, "HEAD",
2204                         update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2205                         &update->new_oid, &update->old_oid,
2206                         update->msg);
2207
2208         /*
2209          * Add "HEAD". This insertion is O(N) in the transaction
2210          * size, but it happens at most once per transaction.
2211          * Add new_update->refname instead of a literal "HEAD".
2212          */
2213         if (strcmp(new_update->refname, "HEAD"))
2214                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2215         item = string_list_insert(affected_refnames, new_update->refname);
2216         item->util = new_update;
2217
2218         return 0;
2219 }
2220
2221 /*
2222  * update is for a symref that points at referent and doesn't have
2223  * REF_NO_DEREF set. Split it into two updates:
2224  * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2225  * - A new, separate update for the referent reference
2226  * Note that the new update will itself be subject to splitting when
2227  * the iteration gets to it.
2228  */
2229 static int split_symref_update(struct files_ref_store *refs,
2230                                struct ref_update *update,
2231                                const char *referent,
2232                                struct ref_transaction *transaction,
2233                                struct string_list *affected_refnames,
2234                                struct strbuf *err)
2235 {
2236         struct string_list_item *item;
2237         struct ref_update *new_update;
2238         unsigned int new_flags;
2239
2240         /*
2241          * First make sure that referent is not already in the
2242          * transaction. This check is O(lg N) in the transaction
2243          * size, but it happens at most once per symref in a
2244          * transaction.
2245          */
2246         if (string_list_has_string(affected_refnames, referent)) {
2247                 /* An entry already exists */
2248                 strbuf_addf(err,
2249                             "multiple updates for '%s' (including one "
2250                             "via symref '%s') are not allowed",
2251                             referent, update->refname);
2252                 return TRANSACTION_NAME_CONFLICT;
2253         }
2254
2255         new_flags = update->flags;
2256         if (!strcmp(update->refname, "HEAD")) {
2257                 /*
2258                  * Record that the new update came via HEAD, so that
2259                  * when we process it, split_head_update() doesn't try
2260                  * to add another reflog update for HEAD. Note that
2261                  * this bit will be propagated if the new_update
2262                  * itself needs to be split.
2263                  */
2264                 new_flags |= REF_UPDATE_VIA_HEAD;
2265         }
2266
2267         new_update = ref_transaction_add_update(
2268                         transaction, referent, new_flags,
2269                         &update->new_oid, &update->old_oid,
2270                         update->msg);
2271
2272         new_update->parent_update = update;
2273
2274         /*
2275          * Change the symbolic ref update to log only. Also, it
2276          * doesn't need to check its old OID value, as that will be
2277          * done when new_update is processed.
2278          */
2279         update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2280         update->flags &= ~REF_HAVE_OLD;
2281
2282         /*
2283          * Add the referent. This insertion is O(N) in the transaction
2284          * size, but it happens at most once per symref in a
2285          * transaction. Make sure to add new_update->refname, which will
2286          * be valid as long as affected_refnames is in use, and NOT
2287          * referent, which might soon be freed by our caller.
2288          */
2289         item = string_list_insert(affected_refnames, new_update->refname);
2290         if (item->util)
2291                 BUG("%s unexpectedly found in affected_refnames",
2292                     new_update->refname);
2293         item->util = new_update;
2294
2295         return 0;
2296 }
2297
2298 /*
2299  * Return the refname under which update was originally requested.
2300  */
2301 static const char *original_update_refname(struct ref_update *update)
2302 {
2303         while (update->parent_update)
2304                 update = update->parent_update;
2305
2306         return update->refname;
2307 }
2308
2309 /*
2310  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2311  * are consistent with oid, which is the reference's current value. If
2312  * everything is OK, return 0; otherwise, write an error message to
2313  * err and return -1.
2314  */
2315 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2316                          struct strbuf *err)
2317 {
2318         if (!(update->flags & REF_HAVE_OLD) ||
2319                    !oidcmp(oid, &update->old_oid))
2320                 return 0;
2321
2322         if (is_null_oid(&update->old_oid))
2323                 strbuf_addf(err, "cannot lock ref '%s': "
2324                             "reference already exists",
2325                             original_update_refname(update));
2326         else if (is_null_oid(oid))
2327                 strbuf_addf(err, "cannot lock ref '%s': "
2328                             "reference is missing but expected %s",
2329                             original_update_refname(update),
2330                             oid_to_hex(&update->old_oid));
2331         else
2332                 strbuf_addf(err, "cannot lock ref '%s': "
2333                             "is at %s but expected %s",
2334                             original_update_refname(update),
2335                             oid_to_hex(oid),
2336                             oid_to_hex(&update->old_oid));
2337
2338         return -1;
2339 }
2340
2341 /*
2342  * Prepare for carrying out update:
2343  * - Lock the reference referred to by update.
2344  * - Read the reference under lock.
2345  * - Check that its old OID value (if specified) is correct, and in
2346  *   any case record it in update->lock->old_oid for later use when
2347  *   writing the reflog.
2348  * - If it is a symref update without REF_NO_DEREF, split it up into a
2349  *   REF_LOG_ONLY update of the symref and add a separate update for
2350  *   the referent to transaction.
2351  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2352  *   update of HEAD.
2353  */
2354 static int lock_ref_for_update(struct files_ref_store *refs,
2355                                struct ref_update *update,
2356                                struct ref_transaction *transaction,
2357                                const char *head_ref,
2358                                struct string_list *affected_refnames,
2359                                struct strbuf *err)
2360 {
2361         struct strbuf referent = STRBUF_INIT;
2362         int mustexist = (update->flags & REF_HAVE_OLD) &&
2363                 !is_null_oid(&update->old_oid);
2364         int ret = 0;
2365         struct ref_lock *lock;
2366
2367         files_assert_main_repository(refs, "lock_ref_for_update");
2368
2369         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2370                 update->flags |= REF_DELETING;
2371
2372         if (head_ref) {
2373                 ret = split_head_update(update, transaction, head_ref,
2374                                         affected_refnames, err);
2375                 if (ret)
2376                         goto out;
2377         }
2378
2379         ret = lock_raw_ref(refs, update->refname, mustexist,
2380                            affected_refnames, NULL,
2381                            &lock, &referent,
2382                            &update->type, err);
2383         if (ret) {
2384                 char *reason;
2385
2386                 reason = strbuf_detach(err, NULL);
2387                 strbuf_addf(err, "cannot lock ref '%s': %s",
2388                             original_update_refname(update), reason);
2389                 free(reason);
2390                 goto out;
2391         }
2392
2393         update->backend_data = lock;
2394
2395         if (update->type & REF_ISSYMREF) {
2396                 if (update->flags & REF_NO_DEREF) {
2397                         /*
2398                          * We won't be reading the referent as part of
2399                          * the transaction, so we have to read it here
2400                          * to record and possibly check old_oid:
2401                          */
2402                         if (refs_read_ref_full(&refs->base,
2403                                                referent.buf, 0,
2404                                                &lock->old_oid, NULL)) {
2405                                 if (update->flags & REF_HAVE_OLD) {
2406                                         strbuf_addf(err, "cannot lock ref '%s': "
2407                                                     "error reading reference",
2408                                                     original_update_refname(update));
2409                                         ret = TRANSACTION_GENERIC_ERROR;
2410                                         goto out;
2411                                 }
2412                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2413                                 ret = TRANSACTION_GENERIC_ERROR;
2414                                 goto out;
2415                         }
2416                 } else {
2417                         /*
2418                          * Create a new update for the reference this
2419                          * symref is pointing at. Also, we will record
2420                          * and verify old_oid for this update as part
2421                          * of processing the split-off update, so we
2422                          * don't have to do it here.
2423                          */
2424                         ret = split_symref_update(refs, update,
2425                                                   referent.buf, transaction,
2426                                                   affected_refnames, err);
2427                         if (ret)
2428                                 goto out;
2429                 }
2430         } else {
2431                 struct ref_update *parent_update;
2432
2433                 if (check_old_oid(update, &lock->old_oid, err)) {
2434                         ret = TRANSACTION_GENERIC_ERROR;
2435                         goto out;
2436                 }
2437
2438                 /*
2439                  * If this update is happening indirectly because of a
2440                  * symref update, record the old OID in the parent
2441                  * update:
2442                  */
2443                 for (parent_update = update->parent_update;
2444                      parent_update;
2445                      parent_update = parent_update->parent_update) {
2446                         struct ref_lock *parent_lock = parent_update->backend_data;
2447                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2448                 }
2449         }
2450
2451         if ((update->flags & REF_HAVE_NEW) &&
2452             !(update->flags & REF_DELETING) &&
2453             !(update->flags & REF_LOG_ONLY)) {
2454                 if (!(update->type & REF_ISSYMREF) &&
2455                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2456                         /*
2457                          * The reference already has the desired
2458                          * value, so we don't need to write it.
2459                          */
2460                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2461                                                  err)) {
2462                         char *write_err = strbuf_detach(err, NULL);
2463
2464                         /*
2465                          * The lock was freed upon failure of
2466                          * write_ref_to_lockfile():
2467                          */
2468                         update->backend_data = NULL;
2469                         strbuf_addf(err,
2470                                     "cannot update ref '%s': %s",
2471                                     update->refname, write_err);
2472                         free(write_err);
2473                         ret = TRANSACTION_GENERIC_ERROR;
2474                         goto out;
2475                 } else {
2476                         update->flags |= REF_NEEDS_COMMIT;
2477                 }
2478         }
2479         if (!(update->flags & REF_NEEDS_COMMIT)) {
2480                 /*
2481                  * We didn't call write_ref_to_lockfile(), so
2482                  * the lockfile is still open. Close it to
2483                  * free up the file descriptor:
2484                  */
2485                 if (close_ref_gently(lock)) {
2486                         strbuf_addf(err, "couldn't close '%s.lock'",
2487                                     update->refname);
2488                         ret = TRANSACTION_GENERIC_ERROR;
2489                         goto out;
2490                 }
2491         }
2492
2493 out:
2494         strbuf_release(&referent);
2495         return ret;
2496 }
2497
2498 struct files_transaction_backend_data {
2499         struct ref_transaction *packed_transaction;
2500         int packed_refs_locked;
2501 };
2502
2503 /*
2504  * Unlock any references in `transaction` that are still locked, and
2505  * mark the transaction closed.
2506  */
2507 static void files_transaction_cleanup(struct files_ref_store *refs,
2508                                       struct ref_transaction *transaction)
2509 {
2510         size_t i;
2511         struct files_transaction_backend_data *backend_data =
2512                 transaction->backend_data;
2513         struct strbuf err = STRBUF_INIT;
2514
2515         for (i = 0; i < transaction->nr; i++) {
2516                 struct ref_update *update = transaction->updates[i];
2517                 struct ref_lock *lock = update->backend_data;
2518
2519                 if (lock) {
2520                         unlock_ref(lock);
2521                         update->backend_data = NULL;
2522                 }
2523         }
2524
2525         if (backend_data->packed_transaction &&
2526             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2527                 error("error aborting transaction: %s", err.buf);
2528                 strbuf_release(&err);
2529         }
2530
2531         if (backend_data->packed_refs_locked)
2532                 packed_refs_unlock(refs->packed_ref_store);
2533
2534         free(backend_data);
2535
2536         transaction->state = REF_TRANSACTION_CLOSED;
2537 }
2538
2539 static int files_transaction_prepare(struct ref_store *ref_store,
2540                                      struct ref_transaction *transaction,
2541                                      struct strbuf *err)
2542 {
2543         struct files_ref_store *refs =
2544                 files_downcast(ref_store, REF_STORE_WRITE,
2545                                "ref_transaction_prepare");
2546         size_t i;
2547         int ret = 0;
2548         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2549         char *head_ref = NULL;
2550         int head_type;
2551         struct files_transaction_backend_data *backend_data;
2552         struct ref_transaction *packed_transaction = NULL;
2553
2554         assert(err);
2555
2556         if (!transaction->nr)
2557                 goto cleanup;
2558
2559         backend_data = xcalloc(1, sizeof(*backend_data));
2560         transaction->backend_data = backend_data;
2561
2562         /*
2563          * Fail if a refname appears more than once in the
2564          * transaction. (If we end up splitting up any updates using
2565          * split_symref_update() or split_head_update(), those
2566          * functions will check that the new updates don't have the
2567          * same refname as any existing ones.) Also fail if any of the
2568          * updates use REF_IS_PRUNING without REF_NO_DEREF.
2569          */
2570         for (i = 0; i < transaction->nr; i++) {
2571                 struct ref_update *update = transaction->updates[i];
2572                 struct string_list_item *item =
2573                         string_list_append(&affected_refnames, update->refname);
2574
2575                 if ((update->flags & REF_IS_PRUNING) &&
2576                     !(update->flags & REF_NO_DEREF))
2577                         BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2578
2579                 /*
2580                  * We store a pointer to update in item->util, but at
2581                  * the moment we never use the value of this field
2582                  * except to check whether it is non-NULL.
2583                  */
2584                 item->util = update;
2585         }
2586         string_list_sort(&affected_refnames);
2587         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2588                 ret = TRANSACTION_GENERIC_ERROR;
2589                 goto cleanup;
2590         }
2591
2592         /*
2593          * Special hack: If a branch is updated directly and HEAD
2594          * points to it (may happen on the remote side of a push
2595          * for example) then logically the HEAD reflog should be
2596          * updated too.
2597          *
2598          * A generic solution would require reverse symref lookups,
2599          * but finding all symrefs pointing to a given branch would be
2600          * rather costly for this rare event (the direct update of a
2601          * branch) to be worth it. So let's cheat and check with HEAD
2602          * only, which should cover 99% of all usage scenarios (even
2603          * 100% of the default ones).
2604          *
2605          * So if HEAD is a symbolic reference, then record the name of
2606          * the reference that it points to. If we see an update of
2607          * head_ref within the transaction, then split_head_update()
2608          * arranges for the reflog of HEAD to be updated, too.
2609          */
2610         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2611                                        RESOLVE_REF_NO_RECURSE,
2612                                        NULL, &head_type);
2613
2614         if (head_ref && !(head_type & REF_ISSYMREF)) {
2615                 FREE_AND_NULL(head_ref);
2616         }
2617
2618         /*
2619          * Acquire all locks, verify old values if provided, check
2620          * that new values are valid, and write new values to the
2621          * lockfiles, ready to be activated. Only keep one lockfile
2622          * open at a time to avoid running out of file descriptors.
2623          * Note that lock_ref_for_update() might append more updates
2624          * to the transaction.
2625          */
2626         for (i = 0; i < transaction->nr; i++) {
2627                 struct ref_update *update = transaction->updates[i];
2628
2629                 ret = lock_ref_for_update(refs, update, transaction,
2630                                           head_ref, &affected_refnames, err);
2631                 if (ret)
2632                         goto cleanup;
2633
2634                 if (update->flags & REF_DELETING &&
2635                     !(update->flags & REF_LOG_ONLY) &&
2636                     !(update->flags & REF_IS_PRUNING)) {
2637                         /*
2638                          * This reference has to be deleted from
2639                          * packed-refs if it exists there.
2640                          */
2641                         if (!packed_transaction) {
2642                                 packed_transaction = ref_store_transaction_begin(
2643                                                 refs->packed_ref_store, err);
2644                                 if (!packed_transaction) {
2645                                         ret = TRANSACTION_GENERIC_ERROR;
2646                                         goto cleanup;
2647                                 }
2648
2649                                 backend_data->packed_transaction =
2650                                         packed_transaction;
2651                         }
2652
2653                         ref_transaction_add_update(
2654                                         packed_transaction, update->refname,
2655                                         REF_HAVE_NEW | REF_NO_DEREF,
2656                                         &update->new_oid, NULL,
2657                                         NULL);
2658                 }
2659         }
2660
2661         if (packed_transaction) {
2662                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2663                         ret = TRANSACTION_GENERIC_ERROR;
2664                         goto cleanup;
2665                 }
2666                 backend_data->packed_refs_locked = 1;
2667
2668                 if (is_packed_transaction_needed(refs->packed_ref_store,
2669                                                  packed_transaction)) {
2670                         ret = ref_transaction_prepare(packed_transaction, err);
2671                 } else {
2672                         /*
2673                          * We can skip rewriting the `packed-refs`
2674                          * file. But we do need to leave it locked, so
2675                          * that somebody else doesn't pack a reference
2676                          * that we are trying to delete.
2677                          */
2678                         if (ref_transaction_abort(packed_transaction, err)) {
2679                                 ret = TRANSACTION_GENERIC_ERROR;
2680                                 goto cleanup;
2681                         }
2682                         backend_data->packed_transaction = NULL;
2683                 }
2684         }
2685
2686 cleanup:
2687         free(head_ref);
2688         string_list_clear(&affected_refnames, 0);
2689
2690         if (ret)
2691                 files_transaction_cleanup(refs, transaction);
2692         else
2693                 transaction->state = REF_TRANSACTION_PREPARED;
2694
2695         return ret;
2696 }
2697
2698 static int files_transaction_finish(struct ref_store *ref_store,
2699                                     struct ref_transaction *transaction,
2700                                     struct strbuf *err)
2701 {
2702         struct files_ref_store *refs =
2703                 files_downcast(ref_store, 0, "ref_transaction_finish");
2704         size_t i;
2705         int ret = 0;
2706         struct strbuf sb = STRBUF_INIT;
2707         struct files_transaction_backend_data *backend_data;
2708         struct ref_transaction *packed_transaction;
2709
2710
2711         assert(err);
2712
2713         if (!transaction->nr) {
2714                 transaction->state = REF_TRANSACTION_CLOSED;
2715                 return 0;
2716         }
2717
2718         backend_data = transaction->backend_data;
2719         packed_transaction = backend_data->packed_transaction;
2720
2721         /* Perform updates first so live commits remain referenced */
2722         for (i = 0; i < transaction->nr; i++) {
2723                 struct ref_update *update = transaction->updates[i];
2724                 struct ref_lock *lock = update->backend_data;
2725
2726                 if (update->flags & REF_NEEDS_COMMIT ||
2727                     update->flags & REF_LOG_ONLY) {
2728                         if (files_log_ref_write(refs,
2729                                                 lock->ref_name,
2730                                                 &lock->old_oid,
2731                                                 &update->new_oid,
2732                                                 update->msg, update->flags,
2733                                                 err)) {
2734                                 char *old_msg = strbuf_detach(err, NULL);
2735
2736                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2737                                             lock->ref_name, old_msg);
2738                                 free(old_msg);
2739                                 unlock_ref(lock);
2740                                 update->backend_data = NULL;
2741                                 ret = TRANSACTION_GENERIC_ERROR;
2742                                 goto cleanup;
2743                         }
2744                 }
2745                 if (update->flags & REF_NEEDS_COMMIT) {
2746                         clear_loose_ref_cache(refs);
2747                         if (commit_ref(lock)) {
2748                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2749                                 unlock_ref(lock);
2750                                 update->backend_data = NULL;
2751                                 ret = TRANSACTION_GENERIC_ERROR;
2752                                 goto cleanup;
2753                         }
2754                 }
2755         }
2756
2757         /*
2758          * Now that updates are safely completed, we can perform
2759          * deletes. First delete the reflogs of any references that
2760          * will be deleted, since (in the unexpected event of an
2761          * error) leaving a reference without a reflog is less bad
2762          * than leaving a reflog without a reference (the latter is a
2763          * mildly invalid repository state):
2764          */
2765         for (i = 0; i < transaction->nr; i++) {
2766                 struct ref_update *update = transaction->updates[i];
2767                 if (update->flags & REF_DELETING &&
2768                     !(update->flags & REF_LOG_ONLY) &&
2769                     !(update->flags & REF_IS_PRUNING)) {
2770                         strbuf_reset(&sb);
2771                         files_reflog_path(refs, &sb, update->refname);
2772                         if (!unlink_or_warn(sb.buf))
2773                                 try_remove_empty_parents(refs, update->refname,
2774                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2775                 }
2776         }
2777
2778         /*
2779          * Perform deletes now that updates are safely completed.
2780          *
2781          * First delete any packed versions of the references, while
2782          * retaining the packed-refs lock:
2783          */
2784         if (packed_transaction) {
2785                 ret = ref_transaction_commit(packed_transaction, err);
2786                 ref_transaction_free(packed_transaction);
2787                 packed_transaction = NULL;
2788                 backend_data->packed_transaction = NULL;
2789                 if (ret)
2790                         goto cleanup;
2791         }
2792
2793         /* Now delete the loose versions of the references: */
2794         for (i = 0; i < transaction->nr; i++) {
2795                 struct ref_update *update = transaction->updates[i];
2796                 struct ref_lock *lock = update->backend_data;
2797
2798                 if (update->flags & REF_DELETING &&
2799                     !(update->flags & REF_LOG_ONLY)) {
2800                         if (!(update->type & REF_ISPACKED) ||
2801                             update->type & REF_ISSYMREF) {
2802                                 /* It is a loose reference. */
2803                                 strbuf_reset(&sb);
2804                                 files_ref_path(refs, &sb, lock->ref_name);
2805                                 if (unlink_or_msg(sb.buf, err)) {
2806                                         ret = TRANSACTION_GENERIC_ERROR;
2807                                         goto cleanup;
2808                                 }
2809                                 update->flags |= REF_DELETED_LOOSE;
2810                         }
2811                 }
2812         }
2813
2814         clear_loose_ref_cache(refs);
2815
2816 cleanup:
2817         files_transaction_cleanup(refs, transaction);
2818
2819         for (i = 0; i < transaction->nr; i++) {
2820                 struct ref_update *update = transaction->updates[i];
2821
2822                 if (update->flags & REF_DELETED_LOOSE) {
2823                         /*
2824                          * The loose reference was deleted. Delete any
2825                          * empty parent directories. (Note that this
2826                          * can only work because we have already
2827                          * removed the lockfile.)
2828                          */
2829                         try_remove_empty_parents(refs, update->refname,
2830                                                  REMOVE_EMPTY_PARENTS_REF);
2831                 }
2832         }
2833
2834         strbuf_release(&sb);
2835         return ret;
2836 }
2837
2838 static int files_transaction_abort(struct ref_store *ref_store,
2839                                    struct ref_transaction *transaction,
2840                                    struct strbuf *err)
2841 {
2842         struct files_ref_store *refs =
2843                 files_downcast(ref_store, 0, "ref_transaction_abort");
2844
2845         files_transaction_cleanup(refs, transaction);
2846         return 0;
2847 }
2848
2849 static int ref_present(const char *refname,
2850                        const struct object_id *oid, int flags, void *cb_data)
2851 {
2852         struct string_list *affected_refnames = cb_data;
2853
2854         return string_list_has_string(affected_refnames, refname);
2855 }
2856
2857 static int files_initial_transaction_commit(struct ref_store *ref_store,
2858                                             struct ref_transaction *transaction,
2859                                             struct strbuf *err)
2860 {
2861         struct files_ref_store *refs =
2862                 files_downcast(ref_store, REF_STORE_WRITE,
2863                                "initial_ref_transaction_commit");
2864         size_t i;
2865         int ret = 0;
2866         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2867         struct ref_transaction *packed_transaction = NULL;
2868
2869         assert(err);
2870
2871         if (transaction->state != REF_TRANSACTION_OPEN)
2872                 BUG("commit called for transaction that is not open");
2873
2874         /* Fail if a refname appears more than once in the transaction: */
2875         for (i = 0; i < transaction->nr; i++)
2876                 string_list_append(&affected_refnames,
2877                                    transaction->updates[i]->refname);
2878         string_list_sort(&affected_refnames);
2879         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2880                 ret = TRANSACTION_GENERIC_ERROR;
2881                 goto cleanup;
2882         }
2883
2884         /*
2885          * It's really undefined to call this function in an active
2886          * repository or when there are existing references: we are
2887          * only locking and changing packed-refs, so (1) any
2888          * simultaneous processes might try to change a reference at
2889          * the same time we do, and (2) any existing loose versions of
2890          * the references that we are setting would have precedence
2891          * over our values. But some remote helpers create the remote
2892          * "HEAD" and "master" branches before calling this function,
2893          * so here we really only check that none of the references
2894          * that we are creating already exists.
2895          */
2896         if (refs_for_each_rawref(&refs->base, ref_present,
2897                                  &affected_refnames))
2898                 BUG("initial ref transaction called with existing refs");
2899
2900         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2901         if (!packed_transaction) {
2902                 ret = TRANSACTION_GENERIC_ERROR;
2903                 goto cleanup;
2904         }
2905
2906         for (i = 0; i < transaction->nr; i++) {
2907                 struct ref_update *update = transaction->updates[i];
2908
2909                 if ((update->flags & REF_HAVE_OLD) &&
2910                     !is_null_oid(&update->old_oid))
2911                         BUG("initial ref transaction with old_sha1 set");
2912                 if (refs_verify_refname_available(&refs->base, update->refname,
2913                                                   &affected_refnames, NULL,
2914                                                   err)) {
2915                         ret = TRANSACTION_NAME_CONFLICT;
2916                         goto cleanup;
2917                 }
2918
2919                 /*
2920                  * Add a reference creation for this reference to the
2921                  * packed-refs transaction:
2922                  */
2923                 ref_transaction_add_update(packed_transaction, update->refname,
2924                                            update->flags & ~REF_HAVE_OLD,
2925                                            &update->new_oid, &update->old_oid,
2926                                            NULL);
2927         }
2928
2929         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2930                 ret = TRANSACTION_GENERIC_ERROR;
2931                 goto cleanup;
2932         }
2933
2934         if (initial_ref_transaction_commit(packed_transaction, err)) {
2935                 ret = TRANSACTION_GENERIC_ERROR;
2936         }
2937
2938         packed_refs_unlock(refs->packed_ref_store);
2939 cleanup:
2940         if (packed_transaction)
2941                 ref_transaction_free(packed_transaction);
2942         transaction->state = REF_TRANSACTION_CLOSED;
2943         string_list_clear(&affected_refnames, 0);
2944         return ret;
2945 }
2946
2947 struct expire_reflog_cb {
2948         unsigned int flags;
2949         reflog_expiry_should_prune_fn *should_prune_fn;
2950         void *policy_cb;
2951         FILE *newlog;
2952         struct object_id last_kept_oid;
2953 };
2954
2955 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2956                              const char *email, timestamp_t timestamp, int tz,
2957                              const char *message, void *cb_data)
2958 {
2959         struct expire_reflog_cb *cb = cb_data;
2960         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2961
2962         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2963                 ooid = &cb->last_kept_oid;
2964
2965         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2966                                    message, policy_cb)) {
2967                 if (!cb->newlog)
2968                         printf("would prune %s", message);
2969                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2970                         printf("prune %s", message);
2971         } else {
2972                 if (cb->newlog) {
2973                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2974                                 oid_to_hex(ooid), oid_to_hex(noid),
2975                                 email, timestamp, tz, message);
2976                         oidcpy(&cb->last_kept_oid, noid);
2977                 }
2978                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2979                         printf("keep %s", message);
2980         }
2981         return 0;
2982 }
2983
2984 static int files_reflog_expire(struct ref_store *ref_store,
2985                                const char *refname, const struct object_id *oid,
2986                                unsigned int flags,
2987                                reflog_expiry_prepare_fn prepare_fn,
2988                                reflog_expiry_should_prune_fn should_prune_fn,
2989                                reflog_expiry_cleanup_fn cleanup_fn,
2990                                void *policy_cb_data)
2991 {
2992         struct files_ref_store *refs =
2993                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2994         struct lock_file reflog_lock = LOCK_INIT;
2995         struct expire_reflog_cb cb;
2996         struct ref_lock *lock;
2997         struct strbuf log_file_sb = STRBUF_INIT;
2998         char *log_file;
2999         int status = 0;
3000         int type;
3001         struct strbuf err = STRBUF_INIT;
3002
3003         memset(&cb, 0, sizeof(cb));
3004         cb.flags = flags;
3005         cb.policy_cb = policy_cb_data;
3006         cb.should_prune_fn = should_prune_fn;
3007
3008         /*
3009          * The reflog file is locked by holding the lock on the
3010          * reference itself, plus we might need to update the
3011          * reference if --updateref was specified:
3012          */
3013         lock = lock_ref_oid_basic(refs, refname, oid,
3014                                   NULL, NULL, REF_NO_DEREF,
3015                                   &type, &err);
3016         if (!lock) {
3017                 error("cannot lock ref '%s': %s", refname, err.buf);
3018                 strbuf_release(&err);
3019                 return -1;
3020         }
3021         if (!refs_reflog_exists(ref_store, refname)) {
3022                 unlock_ref(lock);
3023                 return 0;
3024         }
3025
3026         files_reflog_path(refs, &log_file_sb, refname);
3027         log_file = strbuf_detach(&log_file_sb, NULL);
3028         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3029                 /*
3030                  * Even though holding $GIT_DIR/logs/$reflog.lock has
3031                  * no locking implications, we use the lock_file
3032                  * machinery here anyway because it does a lot of the
3033                  * work we need, including cleaning up if the program
3034                  * exits unexpectedly.
3035                  */
3036                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3037                         struct strbuf err = STRBUF_INIT;
3038                         unable_to_lock_message(log_file, errno, &err);
3039                         error("%s", err.buf);
3040                         strbuf_release(&err);
3041                         goto failure;
3042                 }
3043                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3044                 if (!cb.newlog) {
3045                         error("cannot fdopen %s (%s)",
3046                               get_lock_file_path(&reflog_lock), strerror(errno));
3047                         goto failure;
3048                 }
3049         }
3050
3051         (*prepare_fn)(refname, oid, cb.policy_cb);
3052         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3053         (*cleanup_fn)(cb.policy_cb);
3054
3055         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3056                 /*
3057                  * It doesn't make sense to adjust a reference pointed
3058                  * to by a symbolic ref based on expiring entries in
3059                  * the symbolic reference's reflog. Nor can we update
3060                  * a reference if there are no remaining reflog
3061                  * entries.
3062                  */
3063                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3064                         !(type & REF_ISSYMREF) &&
3065                         !is_null_oid(&cb.last_kept_oid);
3066
3067                 if (close_lock_file_gently(&reflog_lock)) {
3068                         status |= error("couldn't write %s: %s", log_file,
3069                                         strerror(errno));
3070                         rollback_lock_file(&reflog_lock);
3071                 } else if (update &&
3072                            (write_in_full(get_lock_file_fd(&lock->lk),
3073                                 oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3074                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3075                             close_ref_gently(lock) < 0)) {
3076                         status |= error("couldn't write %s",
3077                                         get_lock_file_path(&lock->lk));
3078                         rollback_lock_file(&reflog_lock);
3079                 } else if (commit_lock_file(&reflog_lock)) {
3080                         status |= error("unable to write reflog '%s' (%s)",
3081                                         log_file, strerror(errno));
3082                 } else if (update && commit_ref(lock)) {
3083                         status |= error("couldn't set %s", lock->ref_name);
3084                 }
3085         }
3086         free(log_file);
3087         unlock_ref(lock);
3088         return status;
3089
3090  failure:
3091         rollback_lock_file(&reflog_lock);
3092         free(log_file);
3093         unlock_ref(lock);
3094         return -1;
3095 }
3096
3097 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3098 {
3099         struct files_ref_store *refs =
3100                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3101         struct strbuf sb = STRBUF_INIT;
3102
3103         /*
3104          * Create .git/refs/{heads,tags}
3105          */
3106         files_ref_path(refs, &sb, "refs/heads");
3107         safe_create_dir(sb.buf, 1);
3108
3109         strbuf_reset(&sb);
3110         files_ref_path(refs, &sb, "refs/tags");
3111         safe_create_dir(sb.buf, 1);
3112
3113         strbuf_release(&sb);
3114         return 0;
3115 }
3116
3117 struct ref_storage_be refs_be_files = {
3118         NULL,
3119         "files",
3120         files_ref_store_create,
3121         files_init_db,
3122         files_transaction_prepare,
3123         files_transaction_finish,
3124         files_transaction_abort,
3125         files_initial_transaction_commit,
3126
3127         files_pack_refs,
3128         files_create_symref,
3129         files_delete_refs,
3130         files_rename_ref,
3131         files_copy_ref,
3132
3133         files_ref_iterator_begin,
3134         files_read_raw_ref,
3135
3136         files_reflog_iterator_begin,
3137         files_for_each_reflog_ent,
3138         files_for_each_reflog_ent_reverse,
3139         files_reflog_exists,
3140         files_create_reflog,
3141         files_delete_reflog,
3142         files_reflog_expire
3143 };