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

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12 #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, st.st_size) < 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         struct strbuf sb = STRBUF_INIT;
1586         int ret = 0;
1587
1588         strbuf_addf(&sb, "%s %s %s", oid_to_hex(old_oid), oid_to_hex(new_oid), committer);
1589         if (msg && *msg)
1590                 copy_reflog_msg(&sb, msg);
1591         strbuf_addch(&sb, '\n');
1592         if (write_in_full(fd, sb.buf, sb.len) < 0)
1593                 ret = -1;
1594         strbuf_release(&sb);
1595         return ret;
1596 }
1597
1598 static int files_log_ref_write(struct files_ref_store *refs,
1599                                const char *refname, const struct object_id *old_oid,
1600                                const struct object_id *new_oid, const char *msg,
1601                                int flags, struct strbuf *err)
1602 {
1603         int logfd, result;
1604
1605         if (log_all_ref_updates == LOG_REFS_UNSET)
1606                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1607
1608         result = log_ref_setup(refs, refname,
1609                                flags & REF_FORCE_CREATE_REFLOG,
1610                                &logfd, err);
1611
1612         if (result)
1613                 return result;
1614
1615         if (logfd < 0)
1616                 return 0;
1617         result = log_ref_write_fd(logfd, old_oid, new_oid,
1618                                   git_committer_info(0), msg);
1619         if (result) {
1620                 struct strbuf sb = STRBUF_INIT;
1621                 int save_errno = errno;
1622
1623                 files_reflog_path(refs, &sb, refname);
1624                 strbuf_addf(err, "unable to append to '%s': %s",
1625                             sb.buf, strerror(save_errno));
1626                 strbuf_release(&sb);
1627                 close(logfd);
1628                 return -1;
1629         }
1630         if (close(logfd)) {
1631                 struct strbuf sb = STRBUF_INIT;
1632                 int save_errno = errno;
1633
1634                 files_reflog_path(refs, &sb, refname);
1635                 strbuf_addf(err, "unable to append to '%s': %s",
1636                             sb.buf, strerror(save_errno));
1637                 strbuf_release(&sb);
1638                 return -1;
1639         }
1640         return 0;
1641 }
1642
1643 /*
1644  * Write oid into the open lockfile, then close the lockfile. On
1645  * errors, rollback the lockfile, fill in *err and return -1.
1646  */
1647 static int write_ref_to_lockfile(struct ref_lock *lock,
1648                                  const struct object_id *oid, struct strbuf *err)
1649 {
1650         static char term = '\n';
1651         struct object *o;
1652         int fd;
1653
1654         o = parse_object(the_repository, oid);
1655         if (!o) {
1656                 strbuf_addf(err,
1657                             "trying to write ref '%s' with nonexistent object %s",
1658                             lock->ref_name, oid_to_hex(oid));
1659                 unlock_ref(lock);
1660                 return -1;
1661         }
1662         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1663                 strbuf_addf(err,
1664                             "trying to write non-commit object %s to branch '%s'",
1665                             oid_to_hex(oid), lock->ref_name);
1666                 unlock_ref(lock);
1667                 return -1;
1668         }
1669         fd = get_lock_file_fd(&lock->lk);
1670         if (write_in_full(fd, oid_to_hex(oid), the_hash_algo->hexsz) < 0 ||
1671             write_in_full(fd, &term, 1) < 0 ||
1672             close_ref_gently(lock) < 0) {
1673                 strbuf_addf(err,
1674                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1675                 unlock_ref(lock);
1676                 return -1;
1677         }
1678         return 0;
1679 }
1680
1681 /*
1682  * Commit a change to a loose reference that has already been written
1683  * to the loose reference lockfile. Also update the reflogs if
1684  * necessary, using the specified lockmsg (which can be NULL).
1685  */
1686 static int commit_ref_update(struct files_ref_store *refs,
1687                              struct ref_lock *lock,
1688                              const struct object_id *oid, const char *logmsg,
1689                              struct strbuf *err)
1690 {
1691         files_assert_main_repository(refs, "commit_ref_update");
1692
1693         clear_loose_ref_cache(refs);
1694         if (files_log_ref_write(refs, lock->ref_name,
1695                                 &lock->old_oid, oid,
1696                                 logmsg, 0, err)) {
1697                 char *old_msg = strbuf_detach(err, NULL);
1698                 strbuf_addf(err, "cannot update the ref '%s': %s",
1699                             lock->ref_name, old_msg);
1700                 free(old_msg);
1701                 unlock_ref(lock);
1702                 return -1;
1703         }
1704
1705         if (strcmp(lock->ref_name, "HEAD") != 0) {
1706                 /*
1707                  * Special hack: If a branch is updated directly and HEAD
1708                  * points to it (may happen on the remote side of a push
1709                  * for example) then logically the HEAD reflog should be
1710                  * updated too.
1711                  * A generic solution implies reverse symref information,
1712                  * but finding all symrefs pointing to the given branch
1713                  * would be rather costly for this rare event (the direct
1714                  * update of a branch) to be worth it.  So let's cheat and
1715                  * check with HEAD only which should cover 99% of all usage
1716                  * scenarios (even 100% of the default ones).
1717                  */
1718                 int head_flag;
1719                 const char *head_ref;
1720
1721                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1722                                                    RESOLVE_REF_READING,
1723                                                    NULL, &head_flag);
1724                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1725                     !strcmp(head_ref, lock->ref_name)) {
1726                         struct strbuf log_err = STRBUF_INIT;
1727                         if (files_log_ref_write(refs, "HEAD",
1728                                                 &lock->old_oid, oid,
1729                                                 logmsg, 0, &log_err)) {
1730                                 error("%s", log_err.buf);
1731                                 strbuf_release(&log_err);
1732                         }
1733                 }
1734         }
1735
1736         if (commit_ref(lock)) {
1737                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1738                 unlock_ref(lock);
1739                 return -1;
1740         }
1741
1742         unlock_ref(lock);
1743         return 0;
1744 }
1745
1746 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1747 {
1748         int ret = -1;
1749 #ifndef NO_SYMLINK_HEAD
1750         char *ref_path = get_locked_file_path(&lock->lk);
1751         unlink(ref_path);
1752         ret = symlink(target, ref_path);
1753         free(ref_path);
1754
1755         if (ret)
1756                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1757 #endif
1758         return ret;
1759 }
1760
1761 static void update_symref_reflog(struct files_ref_store *refs,
1762                                  struct ref_lock *lock, const char *refname,
1763                                  const char *target, const char *logmsg)
1764 {
1765         struct strbuf err = STRBUF_INIT;
1766         struct object_id new_oid;
1767         if (logmsg &&
1768             !refs_read_ref_full(&refs->base, target,
1769                                 RESOLVE_REF_READING, &new_oid, NULL) &&
1770             files_log_ref_write(refs, refname, &lock->old_oid,
1771                                 &new_oid, logmsg, 0, &err)) {
1772                 error("%s", err.buf);
1773                 strbuf_release(&err);
1774         }
1775 }
1776
1777 static int create_symref_locked(struct files_ref_store *refs,
1778                                 struct ref_lock *lock, const char *refname,
1779                                 const char *target, const char *logmsg)
1780 {
1781         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1782                 update_symref_reflog(refs, lock, refname, target, logmsg);
1783                 return 0;
1784         }
1785
1786         if (!fdopen_lock_file(&lock->lk, "w"))
1787                 return error("unable to fdopen %s: %s",
1788                              lock->lk.tempfile->filename.buf, strerror(errno));
1789
1790         update_symref_reflog(refs, lock, refname, target, logmsg);
1791
1792         /* no error check; commit_ref will check ferror */
1793         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1794         if (commit_ref(lock) < 0)
1795                 return error("unable to write symref for %s: %s", refname,
1796                              strerror(errno));
1797         return 0;
1798 }
1799
1800 static int files_create_symref(struct ref_store *ref_store,
1801                                const char *refname, const char *target,
1802                                const char *logmsg)
1803 {
1804         struct files_ref_store *refs =
1805                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1806         struct strbuf err = STRBUF_INIT;
1807         struct ref_lock *lock;
1808         int ret;
1809
1810         lock = lock_ref_oid_basic(refs, refname, NULL,
1811                                   NULL, NULL, REF_NO_DEREF, NULL,
1812                                   &err);
1813         if (!lock) {
1814                 error("%s", err.buf);
1815                 strbuf_release(&err);
1816                 return -1;
1817         }
1818
1819         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1820         unlock_ref(lock);
1821         return ret;
1822 }
1823
1824 static int files_reflog_exists(struct ref_store *ref_store,
1825                                const char *refname)
1826 {
1827         struct files_ref_store *refs =
1828                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1829         struct strbuf sb = STRBUF_INIT;
1830         struct stat st;
1831         int ret;
1832
1833         files_reflog_path(refs, &sb, refname);
1834         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1835         strbuf_release(&sb);
1836         return ret;
1837 }
1838
1839 static int files_delete_reflog(struct ref_store *ref_store,
1840                                const char *refname)
1841 {
1842         struct files_ref_store *refs =
1843                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1844         struct strbuf sb = STRBUF_INIT;
1845         int ret;
1846
1847         files_reflog_path(refs, &sb, refname);
1848         ret = remove_path(sb.buf);
1849         strbuf_release(&sb);
1850         return ret;
1851 }
1852
1853 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1854 {
1855         struct object_id ooid, noid;
1856         char *email_end, *message;
1857         timestamp_t timestamp;
1858         int tz;
1859         const char *p = sb->buf;
1860
1861         /* old SP new SP name <email> SP time TAB msg LF */
1862         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1863             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1864             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1865             !(email_end = strchr(p, '>')) ||
1866             email_end[1] != ' ' ||
1867             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1868             !message || message[0] != ' ' ||
1869             (message[1] != '+' && message[1] != '-') ||
1870             !isdigit(message[2]) || !isdigit(message[3]) ||
1871             !isdigit(message[4]) || !isdigit(message[5]))
1872                 return 0; /* corrupt? */
1873         email_end[1] = '\0';
1874         tz = strtol(message + 1, NULL, 10);
1875         if (message[6] != '\t')
1876                 message += 6;
1877         else
1878                 message += 7;
1879         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1880 }
1881
1882 static char *find_beginning_of_line(char *bob, char *scan)
1883 {
1884         while (bob < scan && *(--scan) != '\n')
1885                 ; /* keep scanning backwards */
1886         /*
1887          * Return either beginning of the buffer, or LF at the end of
1888          * the previous line.
1889          */
1890         return scan;
1891 }
1892
1893 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1894                                              const char *refname,
1895                                              each_reflog_ent_fn fn,
1896                                              void *cb_data)
1897 {
1898         struct files_ref_store *refs =
1899                 files_downcast(ref_store, REF_STORE_READ,
1900                                "for_each_reflog_ent_reverse");
1901         struct strbuf sb = STRBUF_INIT;
1902         FILE *logfp;
1903         long pos;
1904         int ret = 0, at_tail = 1;
1905
1906         files_reflog_path(refs, &sb, refname);
1907         logfp = fopen(sb.buf, "r");
1908         strbuf_release(&sb);
1909         if (!logfp)
1910                 return -1;
1911
1912         /* Jump to the end */
1913         if (fseek(logfp, 0, SEEK_END) < 0)
1914                 ret = error("cannot seek back reflog for %s: %s",
1915                             refname, strerror(errno));
1916         pos = ftell(logfp);
1917         while (!ret && 0 < pos) {
1918                 int cnt;
1919                 size_t nread;
1920                 char buf[BUFSIZ];
1921                 char *endp, *scanp;
1922
1923                 /* Fill next block from the end */
1924                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1925                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1926                         ret = error("cannot seek back reflog for %s: %s",
1927                                     refname, strerror(errno));
1928                         break;
1929                 }
1930                 nread = fread(buf, cnt, 1, logfp);
1931                 if (nread != 1) {
1932                         ret = error("cannot read %d bytes from reflog for %s: %s",
1933                                     cnt, refname, strerror(errno));
1934                         break;
1935                 }
1936                 pos -= cnt;
1937
1938                 scanp = endp = buf + cnt;
1939                 if (at_tail && scanp[-1] == '\n')
1940                         /* Looking at the final LF at the end of the file */
1941                         scanp--;
1942                 at_tail = 0;
1943
1944                 while (buf < scanp) {
1945                         /*
1946                          * terminating LF of the previous line, or the beginning
1947                          * of the buffer.
1948                          */
1949                         char *bp;
1950
1951                         bp = find_beginning_of_line(buf, scanp);
1952
1953                         if (*bp == '\n') {
1954                                 /*
1955                                  * The newline is the end of the previous line,
1956                                  * so we know we have complete line starting
1957                                  * at (bp + 1). Prefix it onto any prior data
1958                                  * we collected for the line and process it.
1959                                  */
1960                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1961                                 scanp = bp;
1962                                 endp = bp + 1;
1963                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1964                                 strbuf_reset(&sb);
1965                                 if (ret)
1966                                         break;
1967                         } else if (!pos) {
1968                                 /*
1969                                  * We are at the start of the buffer, and the
1970                                  * start of the file; there is no previous
1971                                  * line, and we have everything for this one.
1972                                  * Process it, and we can end the loop.
1973                                  */
1974                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1975                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
1976                                 strbuf_reset(&sb);
1977                                 break;
1978                         }
1979
1980                         if (bp == buf) {
1981                                 /*
1982                                  * We are at the start of the buffer, and there
1983                                  * is more file to read backwards. Which means
1984                                  * we are in the middle of a line. Note that we
1985                                  * may get here even if *bp was a newline; that
1986                                  * just means we are at the exact end of the
1987                                  * previous line, rather than some spot in the
1988                                  * middle.
1989                                  *
1990                                  * Save away what we have to be combined with
1991                                  * the data from the next read.
1992                                  */
1993                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
1994                                 break;
1995                         }
1996                 }
1997
1998         }
1999         if (!ret && sb.len)
2000                 BUG("reverse reflog parser had leftover data");
2001
2002         fclose(logfp);
2003         strbuf_release(&sb);
2004         return ret;
2005 }
2006
2007 static int files_for_each_reflog_ent(struct ref_store *ref_store,
2008                                      const char *refname,
2009                                      each_reflog_ent_fn fn, void *cb_data)
2010 {
2011         struct files_ref_store *refs =
2012                 files_downcast(ref_store, REF_STORE_READ,
2013                                "for_each_reflog_ent");
2014         FILE *logfp;
2015         struct strbuf sb = STRBUF_INIT;
2016         int ret = 0;
2017
2018         files_reflog_path(refs, &sb, refname);
2019         logfp = fopen(sb.buf, "r");
2020         strbuf_release(&sb);
2021         if (!logfp)
2022                 return -1;
2023
2024         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2025                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2026         fclose(logfp);
2027         strbuf_release(&sb);
2028         return ret;
2029 }
2030
2031 struct files_reflog_iterator {
2032         struct ref_iterator base;
2033
2034         struct ref_store *ref_store;
2035         struct dir_iterator *dir_iterator;
2036         struct object_id oid;
2037 };
2038
2039 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2040 {
2041         struct files_reflog_iterator *iter =
2042                 (struct files_reflog_iterator *)ref_iterator;
2043         struct dir_iterator *diter = iter->dir_iterator;
2044         int ok;
2045
2046         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2047                 int flags;
2048
2049                 if (!S_ISREG(diter->st.st_mode))
2050                         continue;
2051                 if (diter->basename[0] == '.')
2052                         continue;
2053                 if (ends_with(diter->basename, ".lock"))
2054                         continue;
2055
2056                 if (refs_read_ref_full(iter->ref_store,
2057                                        diter->relative_path, 0,
2058                                        &iter->oid, &flags)) {
2059                         error("bad ref for %s", diter->path.buf);
2060                         continue;
2061                 }
2062
2063                 iter->base.refname = diter->relative_path;
2064                 iter->base.oid = &iter->oid;
2065                 iter->base.flags = flags;
2066                 return ITER_OK;
2067         }
2068
2069         iter->dir_iterator = NULL;
2070         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2071                 ok = ITER_ERROR;
2072         return ok;
2073 }
2074
2075 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2076                                    struct object_id *peeled)
2077 {
2078         BUG("ref_iterator_peel() called for reflog_iterator");
2079 }
2080
2081 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2082 {
2083         struct files_reflog_iterator *iter =
2084                 (struct files_reflog_iterator *)ref_iterator;
2085         int ok = ITER_DONE;
2086
2087         if (iter->dir_iterator)
2088                 ok = dir_iterator_abort(iter->dir_iterator);
2089
2090         base_ref_iterator_free(ref_iterator);
2091         return ok;
2092 }
2093
2094 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2095         files_reflog_iterator_advance,
2096         files_reflog_iterator_peel,
2097         files_reflog_iterator_abort
2098 };
2099
2100 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2101                                                   const char *gitdir)
2102 {
2103         struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2104         struct ref_iterator *ref_iterator = &iter->base;
2105         struct strbuf sb = STRBUF_INIT;
2106
2107         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2108         strbuf_addf(&sb, "%s/logs", gitdir);
2109         iter->dir_iterator = dir_iterator_begin(sb.buf);
2110         iter->ref_store = ref_store;
2111         strbuf_release(&sb);
2112
2113         return ref_iterator;
2114 }
2115
2116 static enum iterator_selection reflog_iterator_select(
2117         struct ref_iterator *iter_worktree,
2118         struct ref_iterator *iter_common,
2119         void *cb_data)
2120 {
2121         if (iter_worktree) {
2122                 /*
2123                  * We're a bit loose here. We probably should ignore
2124                  * common refs if they are accidentally added as
2125                  * per-worktree refs.
2126                  */
2127                 return ITER_SELECT_0;
2128         } else if (iter_common) {
2129                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2130                         return ITER_SELECT_1;
2131
2132                 /*
2133                  * The main ref store may contain main worktree's
2134                  * per-worktree refs, which should be ignored
2135                  */
2136                 return ITER_SKIP_1;
2137         } else
2138                 return ITER_DONE;
2139 }
2140
2141 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2142 {
2143         struct files_ref_store *refs =
2144                 files_downcast(ref_store, REF_STORE_READ,
2145                                "reflog_iterator_begin");
2146
2147         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2148                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2149         } else {
2150                 return merge_ref_iterator_begin(
2151                         0,
2152                         reflog_iterator_begin(ref_store, refs->gitdir),
2153                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2154                         reflog_iterator_select, refs);
2155         }
2156 }
2157
2158 /*
2159  * If update is a direct update of head_ref (the reference pointed to
2160  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2161  */
2162 static int split_head_update(struct ref_update *update,
2163                              struct ref_transaction *transaction,
2164                              const char *head_ref,
2165                              struct string_list *affected_refnames,
2166                              struct strbuf *err)
2167 {
2168         struct string_list_item *item;
2169         struct ref_update *new_update;
2170
2171         if ((update->flags & REF_LOG_ONLY) ||
2172             (update->flags & REF_IS_PRUNING) ||
2173             (update->flags & REF_UPDATE_VIA_HEAD))
2174                 return 0;
2175
2176         if (strcmp(update->refname, head_ref))
2177                 return 0;
2178
2179         /*
2180          * First make sure that HEAD is not already in the
2181          * transaction. This check is O(lg N) in the transaction
2182          * size, but it happens at most once per transaction.
2183          */
2184         if (string_list_has_string(affected_refnames, "HEAD")) {
2185                 /* An entry already existed */
2186                 strbuf_addf(err,
2187                             "multiple updates for 'HEAD' (including one "
2188                             "via its referent '%s') are not allowed",
2189                             update->refname);
2190                 return TRANSACTION_NAME_CONFLICT;
2191         }
2192
2193         new_update = ref_transaction_add_update(
2194                         transaction, "HEAD",
2195                         update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2196                         &update->new_oid, &update->old_oid,
2197                         update->msg);
2198
2199         /*
2200          * Add "HEAD". This insertion is O(N) in the transaction
2201          * size, but it happens at most once per transaction.
2202          * Add new_update->refname instead of a literal "HEAD".
2203          */
2204         if (strcmp(new_update->refname, "HEAD"))
2205                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2206         item = string_list_insert(affected_refnames, new_update->refname);
2207         item->util = new_update;
2208
2209         return 0;
2210 }
2211
2212 /*
2213  * update is for a symref that points at referent and doesn't have
2214  * REF_NO_DEREF set. Split it into two updates:
2215  * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2216  * - A new, separate update for the referent reference
2217  * Note that the new update will itself be subject to splitting when
2218  * the iteration gets to it.
2219  */
2220 static int split_symref_update(struct files_ref_store *refs,
2221                                struct ref_update *update,
2222                                const char *referent,
2223                                struct ref_transaction *transaction,
2224                                struct string_list *affected_refnames,
2225                                struct strbuf *err)
2226 {
2227         struct string_list_item *item;
2228         struct ref_update *new_update;
2229         unsigned int new_flags;
2230
2231         /*
2232          * First make sure that referent is not already in the
2233          * transaction. This check is O(lg N) in the transaction
2234          * size, but it happens at most once per symref in a
2235          * transaction.
2236          */
2237         if (string_list_has_string(affected_refnames, referent)) {
2238                 /* An entry already exists */
2239                 strbuf_addf(err,
2240                             "multiple updates for '%s' (including one "
2241                             "via symref '%s') are not allowed",
2242                             referent, update->refname);
2243                 return TRANSACTION_NAME_CONFLICT;
2244         }
2245
2246         new_flags = update->flags;
2247         if (!strcmp(update->refname, "HEAD")) {
2248                 /*
2249                  * Record that the new update came via HEAD, so that
2250                  * when we process it, split_head_update() doesn't try
2251                  * to add another reflog update for HEAD. Note that
2252                  * this bit will be propagated if the new_update
2253                  * itself needs to be split.
2254                  */
2255                 new_flags |= REF_UPDATE_VIA_HEAD;
2256         }
2257
2258         new_update = ref_transaction_add_update(
2259                         transaction, referent, new_flags,
2260                         &update->new_oid, &update->old_oid,
2261                         update->msg);
2262
2263         new_update->parent_update = update;
2264
2265         /*
2266          * Change the symbolic ref update to log only. Also, it
2267          * doesn't need to check its old OID value, as that will be
2268          * done when new_update is processed.
2269          */
2270         update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2271         update->flags &= ~REF_HAVE_OLD;
2272
2273         /*
2274          * Add the referent. This insertion is O(N) in the transaction
2275          * size, but it happens at most once per symref in a
2276          * transaction. Make sure to add new_update->refname, which will
2277          * be valid as long as affected_refnames is in use, and NOT
2278          * referent, which might soon be freed by our caller.
2279          */
2280         item = string_list_insert(affected_refnames, new_update->refname);
2281         if (item->util)
2282                 BUG("%s unexpectedly found in affected_refnames",
2283                     new_update->refname);
2284         item->util = new_update;
2285
2286         return 0;
2287 }
2288
2289 /*
2290  * Return the refname under which update was originally requested.
2291  */
2292 static const char *original_update_refname(struct ref_update *update)
2293 {
2294         while (update->parent_update)
2295                 update = update->parent_update;
2296
2297         return update->refname;
2298 }
2299
2300 /*
2301  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2302  * are consistent with oid, which is the reference's current value. If
2303  * everything is OK, return 0; otherwise, write an error message to
2304  * err and return -1.
2305  */
2306 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2307                          struct strbuf *err)
2308 {
2309         if (!(update->flags & REF_HAVE_OLD) ||
2310                    !oidcmp(oid, &update->old_oid))
2311                 return 0;
2312
2313         if (is_null_oid(&update->old_oid))
2314                 strbuf_addf(err, "cannot lock ref '%s': "
2315                             "reference already exists",
2316                             original_update_refname(update));
2317         else if (is_null_oid(oid))
2318                 strbuf_addf(err, "cannot lock ref '%s': "
2319                             "reference is missing but expected %s",
2320                             original_update_refname(update),
2321                             oid_to_hex(&update->old_oid));
2322         else
2323                 strbuf_addf(err, "cannot lock ref '%s': "
2324                             "is at %s but expected %s",
2325                             original_update_refname(update),
2326                             oid_to_hex(oid),
2327                             oid_to_hex(&update->old_oid));
2328
2329         return -1;
2330 }
2331
2332 /*
2333  * Prepare for carrying out update:
2334  * - Lock the reference referred to by update.
2335  * - Read the reference under lock.
2336  * - Check that its old OID value (if specified) is correct, and in
2337  *   any case record it in update->lock->old_oid for later use when
2338  *   writing the reflog.
2339  * - If it is a symref update without REF_NO_DEREF, split it up into a
2340  *   REF_LOG_ONLY update of the symref and add a separate update for
2341  *   the referent to transaction.
2342  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2343  *   update of HEAD.
2344  */
2345 static int lock_ref_for_update(struct files_ref_store *refs,
2346                                struct ref_update *update,
2347                                struct ref_transaction *transaction,
2348                                const char *head_ref,
2349                                struct string_list *affected_refnames,
2350                                struct strbuf *err)
2351 {
2352         struct strbuf referent = STRBUF_INIT;
2353         int mustexist = (update->flags & REF_HAVE_OLD) &&
2354                 !is_null_oid(&update->old_oid);
2355         int ret = 0;
2356         struct ref_lock *lock;
2357
2358         files_assert_main_repository(refs, "lock_ref_for_update");
2359
2360         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2361                 update->flags |= REF_DELETING;
2362
2363         if (head_ref) {
2364                 ret = split_head_update(update, transaction, head_ref,
2365                                         affected_refnames, err);
2366                 if (ret)
2367                         goto out;
2368         }
2369
2370         ret = lock_raw_ref(refs, update->refname, mustexist,
2371                            affected_refnames, NULL,
2372                            &lock, &referent,
2373                            &update->type, err);
2374         if (ret) {
2375                 char *reason;
2376
2377                 reason = strbuf_detach(err, NULL);
2378                 strbuf_addf(err, "cannot lock ref '%s': %s",
2379                             original_update_refname(update), reason);
2380                 free(reason);
2381                 goto out;
2382         }
2383
2384         update->backend_data = lock;
2385
2386         if (update->type & REF_ISSYMREF) {
2387                 if (update->flags & REF_NO_DEREF) {
2388                         /*
2389                          * We won't be reading the referent as part of
2390                          * the transaction, so we have to read it here
2391                          * to record and possibly check old_oid:
2392                          */
2393                         if (refs_read_ref_full(&refs->base,
2394                                                referent.buf, 0,
2395                                                &lock->old_oid, NULL)) {
2396                                 if (update->flags & REF_HAVE_OLD) {
2397                                         strbuf_addf(err, "cannot lock ref '%s': "
2398                                                     "error reading reference",
2399                                                     original_update_refname(update));
2400                                         ret = TRANSACTION_GENERIC_ERROR;
2401                                         goto out;
2402                                 }
2403                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2404                                 ret = TRANSACTION_GENERIC_ERROR;
2405                                 goto out;
2406                         }
2407                 } else {
2408                         /*
2409                          * Create a new update for the reference this
2410                          * symref is pointing at. Also, we will record
2411                          * and verify old_oid for this update as part
2412                          * of processing the split-off update, so we
2413                          * don't have to do it here.
2414                          */
2415                         ret = split_symref_update(refs, update,
2416                                                   referent.buf, transaction,
2417                                                   affected_refnames, err);
2418                         if (ret)
2419                                 goto out;
2420                 }
2421         } else {
2422                 struct ref_update *parent_update;
2423
2424                 if (check_old_oid(update, &lock->old_oid, err)) {
2425                         ret = TRANSACTION_GENERIC_ERROR;
2426                         goto out;
2427                 }
2428
2429                 /*
2430                  * If this update is happening indirectly because of a
2431                  * symref update, record the old OID in the parent
2432                  * update:
2433                  */
2434                 for (parent_update = update->parent_update;
2435                      parent_update;
2436                      parent_update = parent_update->parent_update) {
2437                         struct ref_lock *parent_lock = parent_update->backend_data;
2438                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2439                 }
2440         }
2441
2442         if ((update->flags & REF_HAVE_NEW) &&
2443             !(update->flags & REF_DELETING) &&
2444             !(update->flags & REF_LOG_ONLY)) {
2445                 if (!(update->type & REF_ISSYMREF) &&
2446                     !oidcmp(&lock->old_oid, &update->new_oid)) {
2447                         /*
2448                          * The reference already has the desired
2449                          * value, so we don't need to write it.
2450                          */
2451                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2452                                                  err)) {
2453                         char *write_err = strbuf_detach(err, NULL);
2454
2455                         /*
2456                          * The lock was freed upon failure of
2457                          * write_ref_to_lockfile():
2458                          */
2459                         update->backend_data = NULL;
2460                         strbuf_addf(err,
2461                                     "cannot update ref '%s': %s",
2462                                     update->refname, write_err);
2463                         free(write_err);
2464                         ret = TRANSACTION_GENERIC_ERROR;
2465                         goto out;
2466                 } else {
2467                         update->flags |= REF_NEEDS_COMMIT;
2468                 }
2469         }
2470         if (!(update->flags & REF_NEEDS_COMMIT)) {
2471                 /*
2472                  * We didn't call write_ref_to_lockfile(), so
2473                  * the lockfile is still open. Close it to
2474                  * free up the file descriptor:
2475                  */
2476                 if (close_ref_gently(lock)) {
2477                         strbuf_addf(err, "couldn't close '%s.lock'",
2478                                     update->refname);
2479                         ret = TRANSACTION_GENERIC_ERROR;
2480                         goto out;
2481                 }
2482         }
2483
2484 out:
2485         strbuf_release(&referent);
2486         return ret;
2487 }
2488
2489 struct files_transaction_backend_data {
2490         struct ref_transaction *packed_transaction;
2491         int packed_refs_locked;
2492 };
2493
2494 /*
2495  * Unlock any references in `transaction` that are still locked, and
2496  * mark the transaction closed.
2497  */
2498 static void files_transaction_cleanup(struct files_ref_store *refs,
2499                                       struct ref_transaction *transaction)
2500 {
2501         size_t i;
2502         struct files_transaction_backend_data *backend_data =
2503                 transaction->backend_data;
2504         struct strbuf err = STRBUF_INIT;
2505
2506         for (i = 0; i < transaction->nr; i++) {
2507                 struct ref_update *update = transaction->updates[i];
2508                 struct ref_lock *lock = update->backend_data;
2509
2510                 if (lock) {
2511                         unlock_ref(lock);
2512                         update->backend_data = NULL;
2513                 }
2514         }
2515
2516         if (backend_data->packed_transaction &&
2517             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2518                 error("error aborting transaction: %s", err.buf);
2519                 strbuf_release(&err);
2520         }
2521
2522         if (backend_data->packed_refs_locked)
2523                 packed_refs_unlock(refs->packed_ref_store);
2524
2525         free(backend_data);
2526
2527         transaction->state = REF_TRANSACTION_CLOSED;
2528 }
2529
2530 static int files_transaction_prepare(struct ref_store *ref_store,
2531                                      struct ref_transaction *transaction,
2532                                      struct strbuf *err)
2533 {
2534         struct files_ref_store *refs =
2535                 files_downcast(ref_store, REF_STORE_WRITE,
2536                                "ref_transaction_prepare");
2537         size_t i;
2538         int ret = 0;
2539         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2540         char *head_ref = NULL;
2541         int head_type;
2542         struct files_transaction_backend_data *backend_data;
2543         struct ref_transaction *packed_transaction = NULL;
2544
2545         assert(err);
2546
2547         if (!transaction->nr)
2548                 goto cleanup;
2549
2550         backend_data = xcalloc(1, sizeof(*backend_data));
2551         transaction->backend_data = backend_data;
2552
2553         /*
2554          * Fail if a refname appears more than once in the
2555          * transaction. (If we end up splitting up any updates using
2556          * split_symref_update() or split_head_update(), those
2557          * functions will check that the new updates don't have the
2558          * same refname as any existing ones.) Also fail if any of the
2559          * updates use REF_IS_PRUNING without REF_NO_DEREF.
2560          */
2561         for (i = 0; i < transaction->nr; i++) {
2562                 struct ref_update *update = transaction->updates[i];
2563                 struct string_list_item *item =
2564                         string_list_append(&affected_refnames, update->refname);
2565
2566                 if ((update->flags & REF_IS_PRUNING) &&
2567                     !(update->flags & REF_NO_DEREF))
2568                         BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2569
2570                 /*
2571                  * We store a pointer to update in item->util, but at
2572                  * the moment we never use the value of this field
2573                  * except to check whether it is non-NULL.
2574                  */
2575                 item->util = update;
2576         }
2577         string_list_sort(&affected_refnames);
2578         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2579                 ret = TRANSACTION_GENERIC_ERROR;
2580                 goto cleanup;
2581         }
2582
2583         /*
2584          * Special hack: If a branch is updated directly and HEAD
2585          * points to it (may happen on the remote side of a push
2586          * for example) then logically the HEAD reflog should be
2587          * updated too.
2588          *
2589          * A generic solution would require reverse symref lookups,
2590          * but finding all symrefs pointing to a given branch would be
2591          * rather costly for this rare event (the direct update of a
2592          * branch) to be worth it. So let's cheat and check with HEAD
2593          * only, which should cover 99% of all usage scenarios (even
2594          * 100% of the default ones).
2595          *
2596          * So if HEAD is a symbolic reference, then record the name of
2597          * the reference that it points to. If we see an update of
2598          * head_ref within the transaction, then split_head_update()
2599          * arranges for the reflog of HEAD to be updated, too.
2600          */
2601         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2602                                        RESOLVE_REF_NO_RECURSE,
2603                                        NULL, &head_type);
2604
2605         if (head_ref && !(head_type & REF_ISSYMREF)) {
2606                 FREE_AND_NULL(head_ref);
2607         }
2608
2609         /*
2610          * Acquire all locks, verify old values if provided, check
2611          * that new values are valid, and write new values to the
2612          * lockfiles, ready to be activated. Only keep one lockfile
2613          * open at a time to avoid running out of file descriptors.
2614          * Note that lock_ref_for_update() might append more updates
2615          * to the transaction.
2616          */
2617         for (i = 0; i < transaction->nr; i++) {
2618                 struct ref_update *update = transaction->updates[i];
2619
2620                 ret = lock_ref_for_update(refs, update, transaction,
2621                                           head_ref, &affected_refnames, err);
2622                 if (ret)
2623                         goto cleanup;
2624
2625                 if (update->flags & REF_DELETING &&
2626                     !(update->flags & REF_LOG_ONLY) &&
2627                     !(update->flags & REF_IS_PRUNING)) {
2628                         /*
2629                          * This reference has to be deleted from
2630                          * packed-refs if it exists there.
2631                          */
2632                         if (!packed_transaction) {
2633                                 packed_transaction = ref_store_transaction_begin(
2634                                                 refs->packed_ref_store, err);
2635                                 if (!packed_transaction) {
2636                                         ret = TRANSACTION_GENERIC_ERROR;
2637                                         goto cleanup;
2638                                 }
2639
2640                                 backend_data->packed_transaction =
2641                                         packed_transaction;
2642                         }
2643
2644                         ref_transaction_add_update(
2645                                         packed_transaction, update->refname,
2646                                         REF_HAVE_NEW | REF_NO_DEREF,
2647                                         &update->new_oid, NULL,
2648                                         NULL);
2649                 }
2650         }
2651
2652         if (packed_transaction) {
2653                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2654                         ret = TRANSACTION_GENERIC_ERROR;
2655                         goto cleanup;
2656                 }
2657                 backend_data->packed_refs_locked = 1;
2658
2659                 if (is_packed_transaction_needed(refs->packed_ref_store,
2660                                                  packed_transaction)) {
2661                         ret = ref_transaction_prepare(packed_transaction, err);
2662                 } else {
2663                         /*
2664                          * We can skip rewriting the `packed-refs`
2665                          * file. But we do need to leave it locked, so
2666                          * that somebody else doesn't pack a reference
2667                          * that we are trying to delete.
2668                          */
2669                         if (ref_transaction_abort(packed_transaction, err)) {
2670                                 ret = TRANSACTION_GENERIC_ERROR;
2671                                 goto cleanup;
2672                         }
2673                         backend_data->packed_transaction = NULL;
2674                 }
2675         }
2676
2677 cleanup:
2678         free(head_ref);
2679         string_list_clear(&affected_refnames, 0);
2680
2681         if (ret)
2682                 files_transaction_cleanup(refs, transaction);
2683         else
2684                 transaction->state = REF_TRANSACTION_PREPARED;
2685
2686         return ret;
2687 }
2688
2689 static int files_transaction_finish(struct ref_store *ref_store,
2690                                     struct ref_transaction *transaction,
2691                                     struct strbuf *err)
2692 {
2693         struct files_ref_store *refs =
2694                 files_downcast(ref_store, 0, "ref_transaction_finish");
2695         size_t i;
2696         int ret = 0;
2697         struct strbuf sb = STRBUF_INIT;
2698         struct files_transaction_backend_data *backend_data;
2699         struct ref_transaction *packed_transaction;
2700
2701
2702         assert(err);
2703
2704         if (!transaction->nr) {
2705                 transaction->state = REF_TRANSACTION_CLOSED;
2706                 return 0;
2707         }
2708
2709         backend_data = transaction->backend_data;
2710         packed_transaction = backend_data->packed_transaction;
2711
2712         /* Perform updates first so live commits remain referenced */
2713         for (i = 0; i < transaction->nr; i++) {
2714                 struct ref_update *update = transaction->updates[i];
2715                 struct ref_lock *lock = update->backend_data;
2716
2717                 if (update->flags & REF_NEEDS_COMMIT ||
2718                     update->flags & REF_LOG_ONLY) {
2719                         if (files_log_ref_write(refs,
2720                                                 lock->ref_name,
2721                                                 &lock->old_oid,
2722                                                 &update->new_oid,
2723                                                 update->msg, update->flags,
2724                                                 err)) {
2725                                 char *old_msg = strbuf_detach(err, NULL);
2726
2727                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2728                                             lock->ref_name, old_msg);
2729                                 free(old_msg);
2730                                 unlock_ref(lock);
2731                                 update->backend_data = NULL;
2732                                 ret = TRANSACTION_GENERIC_ERROR;
2733                                 goto cleanup;
2734                         }
2735                 }
2736                 if (update->flags & REF_NEEDS_COMMIT) {
2737                         clear_loose_ref_cache(refs);
2738                         if (commit_ref(lock)) {
2739                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2740                                 unlock_ref(lock);
2741                                 update->backend_data = NULL;
2742                                 ret = TRANSACTION_GENERIC_ERROR;
2743                                 goto cleanup;
2744                         }
2745                 }
2746         }
2747
2748         /*
2749          * Now that updates are safely completed, we can perform
2750          * deletes. First delete the reflogs of any references that
2751          * will be deleted, since (in the unexpected event of an
2752          * error) leaving a reference without a reflog is less bad
2753          * than leaving a reflog without a reference (the latter is a
2754          * mildly invalid repository state):
2755          */
2756         for (i = 0; i < transaction->nr; i++) {
2757                 struct ref_update *update = transaction->updates[i];
2758                 if (update->flags & REF_DELETING &&
2759                     !(update->flags & REF_LOG_ONLY) &&
2760                     !(update->flags & REF_IS_PRUNING)) {
2761                         strbuf_reset(&sb);
2762                         files_reflog_path(refs, &sb, update->refname);
2763                         if (!unlink_or_warn(sb.buf))
2764                                 try_remove_empty_parents(refs, update->refname,
2765                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2766                 }
2767         }
2768
2769         /*
2770          * Perform deletes now that updates are safely completed.
2771          *
2772          * First delete any packed versions of the references, while
2773          * retaining the packed-refs lock:
2774          */
2775         if (packed_transaction) {
2776                 ret = ref_transaction_commit(packed_transaction, err);
2777                 ref_transaction_free(packed_transaction);
2778                 packed_transaction = NULL;
2779                 backend_data->packed_transaction = NULL;
2780                 if (ret)
2781                         goto cleanup;
2782         }
2783
2784         /* Now delete the loose versions of the references: */
2785         for (i = 0; i < transaction->nr; i++) {
2786                 struct ref_update *update = transaction->updates[i];
2787                 struct ref_lock *lock = update->backend_data;
2788
2789                 if (update->flags & REF_DELETING &&
2790                     !(update->flags & REF_LOG_ONLY)) {
2791                         if (!(update->type & REF_ISPACKED) ||
2792                             update->type & REF_ISSYMREF) {
2793                                 /* It is a loose reference. */
2794                                 strbuf_reset(&sb);
2795                                 files_ref_path(refs, &sb, lock->ref_name);
2796                                 if (unlink_or_msg(sb.buf, err)) {
2797                                         ret = TRANSACTION_GENERIC_ERROR;
2798                                         goto cleanup;
2799                                 }
2800                                 update->flags |= REF_DELETED_LOOSE;
2801                         }
2802                 }
2803         }
2804
2805         clear_loose_ref_cache(refs);
2806
2807 cleanup:
2808         files_transaction_cleanup(refs, transaction);
2809
2810         for (i = 0; i < transaction->nr; i++) {
2811                 struct ref_update *update = transaction->updates[i];
2812
2813                 if (update->flags & REF_DELETED_LOOSE) {
2814                         /*
2815                          * The loose reference was deleted. Delete any
2816                          * empty parent directories. (Note that this
2817                          * can only work because we have already
2818                          * removed the lockfile.)
2819                          */
2820                         try_remove_empty_parents(refs, update->refname,
2821                                                  REMOVE_EMPTY_PARENTS_REF);
2822                 }
2823         }
2824
2825         strbuf_release(&sb);
2826         return ret;
2827 }
2828
2829 static int files_transaction_abort(struct ref_store *ref_store,
2830                                    struct ref_transaction *transaction,
2831                                    struct strbuf *err)
2832 {
2833         struct files_ref_store *refs =
2834                 files_downcast(ref_store, 0, "ref_transaction_abort");
2835
2836         files_transaction_cleanup(refs, transaction);
2837         return 0;
2838 }
2839
2840 static int ref_present(const char *refname,
2841                        const struct object_id *oid, int flags, void *cb_data)
2842 {
2843         struct string_list *affected_refnames = cb_data;
2844
2845         return string_list_has_string(affected_refnames, refname);
2846 }
2847
2848 static int files_initial_transaction_commit(struct ref_store *ref_store,
2849                                             struct ref_transaction *transaction,
2850                                             struct strbuf *err)
2851 {
2852         struct files_ref_store *refs =
2853                 files_downcast(ref_store, REF_STORE_WRITE,
2854                                "initial_ref_transaction_commit");
2855         size_t i;
2856         int ret = 0;
2857         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2858         struct ref_transaction *packed_transaction = NULL;
2859
2860         assert(err);
2861
2862         if (transaction->state != REF_TRANSACTION_OPEN)
2863                 BUG("commit called for transaction that is not open");
2864
2865         /* Fail if a refname appears more than once in the transaction: */
2866         for (i = 0; i < transaction->nr; i++)
2867                 string_list_append(&affected_refnames,
2868                                    transaction->updates[i]->refname);
2869         string_list_sort(&affected_refnames);
2870         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2871                 ret = TRANSACTION_GENERIC_ERROR;
2872                 goto cleanup;
2873         }
2874
2875         /*
2876          * It's really undefined to call this function in an active
2877          * repository or when there are existing references: we are
2878          * only locking and changing packed-refs, so (1) any
2879          * simultaneous processes might try to change a reference at
2880          * the same time we do, and (2) any existing loose versions of
2881          * the references that we are setting would have precedence
2882          * over our values. But some remote helpers create the remote
2883          * "HEAD" and "master" branches before calling this function,
2884          * so here we really only check that none of the references
2885          * that we are creating already exists.
2886          */
2887         if (refs_for_each_rawref(&refs->base, ref_present,
2888                                  &affected_refnames))
2889                 BUG("initial ref transaction called with existing refs");
2890
2891         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2892         if (!packed_transaction) {
2893                 ret = TRANSACTION_GENERIC_ERROR;
2894                 goto cleanup;
2895         }
2896
2897         for (i = 0; i < transaction->nr; i++) {
2898                 struct ref_update *update = transaction->updates[i];
2899
2900                 if ((update->flags & REF_HAVE_OLD) &&
2901                     !is_null_oid(&update->old_oid))
2902                         BUG("initial ref transaction with old_sha1 set");
2903                 if (refs_verify_refname_available(&refs->base, update->refname,
2904                                                   &affected_refnames, NULL,
2905                                                   err)) {
2906                         ret = TRANSACTION_NAME_CONFLICT;
2907                         goto cleanup;
2908                 }
2909
2910                 /*
2911                  * Add a reference creation for this reference to the
2912                  * packed-refs transaction:
2913                  */
2914                 ref_transaction_add_update(packed_transaction, update->refname,
2915                                            update->flags & ~REF_HAVE_OLD,
2916                                            &update->new_oid, &update->old_oid,
2917                                            NULL);
2918         }
2919
2920         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2921                 ret = TRANSACTION_GENERIC_ERROR;
2922                 goto cleanup;
2923         }
2924
2925         if (initial_ref_transaction_commit(packed_transaction, err)) {
2926                 ret = TRANSACTION_GENERIC_ERROR;
2927         }
2928
2929         packed_refs_unlock(refs->packed_ref_store);
2930 cleanup:
2931         if (packed_transaction)
2932                 ref_transaction_free(packed_transaction);
2933         transaction->state = REF_TRANSACTION_CLOSED;
2934         string_list_clear(&affected_refnames, 0);
2935         return ret;
2936 }
2937
2938 struct expire_reflog_cb {
2939         unsigned int flags;
2940         reflog_expiry_should_prune_fn *should_prune_fn;
2941         void *policy_cb;
2942         FILE *newlog;
2943         struct object_id last_kept_oid;
2944 };
2945
2946 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2947                              const char *email, timestamp_t timestamp, int tz,
2948                              const char *message, void *cb_data)
2949 {
2950         struct expire_reflog_cb *cb = cb_data;
2951         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2952
2953         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2954                 ooid = &cb->last_kept_oid;
2955
2956         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2957                                    message, policy_cb)) {
2958                 if (!cb->newlog)
2959                         printf("would prune %s", message);
2960                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2961                         printf("prune %s", message);
2962         } else {
2963                 if (cb->newlog) {
2964                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2965                                 oid_to_hex(ooid), oid_to_hex(noid),
2966                                 email, timestamp, tz, message);
2967                         oidcpy(&cb->last_kept_oid, noid);
2968                 }
2969                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2970                         printf("keep %s", message);
2971         }
2972         return 0;
2973 }
2974
2975 static int files_reflog_expire(struct ref_store *ref_store,
2976                                const char *refname, const struct object_id *oid,
2977                                unsigned int flags,
2978                                reflog_expiry_prepare_fn prepare_fn,
2979                                reflog_expiry_should_prune_fn should_prune_fn,
2980                                reflog_expiry_cleanup_fn cleanup_fn,
2981                                void *policy_cb_data)
2982 {
2983         struct files_ref_store *refs =
2984                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2985         struct lock_file reflog_lock = LOCK_INIT;
2986         struct expire_reflog_cb cb;
2987         struct ref_lock *lock;
2988         struct strbuf log_file_sb = STRBUF_INIT;
2989         char *log_file;
2990         int status = 0;
2991         int type;
2992         struct strbuf err = STRBUF_INIT;
2993
2994         memset(&cb, 0, sizeof(cb));
2995         cb.flags = flags;
2996         cb.policy_cb = policy_cb_data;
2997         cb.should_prune_fn = should_prune_fn;
2998
2999         /*
3000          * The reflog file is locked by holding the lock on the
3001          * reference itself, plus we might need to update the
3002          * reference if --updateref was specified:
3003          */
3004         lock = lock_ref_oid_basic(refs, refname, oid,
3005                                   NULL, NULL, REF_NO_DEREF,
3006                                   &type, &err);
3007         if (!lock) {
3008                 error("cannot lock ref '%s': %s", refname, err.buf);
3009                 strbuf_release(&err);
3010                 return -1;
3011         }
3012         if (!refs_reflog_exists(ref_store, refname)) {
3013                 unlock_ref(lock);
3014                 return 0;
3015         }
3016
3017         files_reflog_path(refs, &log_file_sb, refname);
3018         log_file = strbuf_detach(&log_file_sb, NULL);
3019         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3020                 /*
3021                  * Even though holding $GIT_DIR/logs/$reflog.lock has
3022                  * no locking implications, we use the lock_file
3023                  * machinery here anyway because it does a lot of the
3024                  * work we need, including cleaning up if the program
3025                  * exits unexpectedly.
3026                  */
3027                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3028                         struct strbuf err = STRBUF_INIT;
3029                         unable_to_lock_message(log_file, errno, &err);
3030                         error("%s", err.buf);
3031                         strbuf_release(&err);
3032                         goto failure;
3033                 }
3034                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3035                 if (!cb.newlog) {
3036                         error("cannot fdopen %s (%s)",
3037                               get_lock_file_path(&reflog_lock), strerror(errno));
3038                         goto failure;
3039                 }
3040         }
3041
3042         (*prepare_fn)(refname, oid, cb.policy_cb);
3043         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3044         (*cleanup_fn)(cb.policy_cb);
3045
3046         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3047                 /*
3048                  * It doesn't make sense to adjust a reference pointed
3049                  * to by a symbolic ref based on expiring entries in
3050                  * the symbolic reference's reflog. Nor can we update
3051                  * a reference if there are no remaining reflog
3052                  * entries.
3053                  */
3054                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3055                         !(type & REF_ISSYMREF) &&
3056                         !is_null_oid(&cb.last_kept_oid);
3057
3058                 if (close_lock_file_gently(&reflog_lock)) {
3059                         status |= error("couldn't write %s: %s", log_file,
3060                                         strerror(errno));
3061                         rollback_lock_file(&reflog_lock);
3062                 } else if (update &&
3063                            (write_in_full(get_lock_file_fd(&lock->lk),
3064                                 oid_to_hex(&cb.last_kept_oid), the_hash_algo->hexsz) < 0 ||
3065                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3066                             close_ref_gently(lock) < 0)) {
3067                         status |= error("couldn't write %s",
3068                                         get_lock_file_path(&lock->lk));
3069                         rollback_lock_file(&reflog_lock);
3070                 } else if (commit_lock_file(&reflog_lock)) {
3071                         status |= error("unable to write reflog '%s' (%s)",
3072                                         log_file, strerror(errno));
3073                 } else if (update && commit_ref(lock)) {
3074                         status |= error("couldn't set %s", lock->ref_name);
3075                 }
3076         }
3077         free(log_file);
3078         unlock_ref(lock);
3079         return status;
3080
3081  failure:
3082         rollback_lock_file(&reflog_lock);
3083         free(log_file);
3084         unlock_ref(lock);
3085         return -1;
3086 }
3087
3088 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3089 {
3090         struct files_ref_store *refs =
3091                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3092         struct strbuf sb = STRBUF_INIT;
3093
3094         /*
3095          * Create .git/refs/{heads,tags}
3096          */
3097         files_ref_path(refs, &sb, "refs/heads");
3098         safe_create_dir(sb.buf, 1);
3099
3100         strbuf_reset(&sb);
3101         files_ref_path(refs, &sb, "refs/tags");
3102         safe_create_dir(sb.buf, 1);
3103
3104         strbuf_release(&sb);
3105         return 0;
3106 }
3107
3108 struct ref_storage_be refs_be_files = {
3109         NULL,
3110         "files",
3111         files_ref_store_create,
3112         files_init_db,
3113         files_transaction_prepare,
3114         files_transaction_finish,
3115         files_transaction_abort,
3116         files_initial_transaction_commit,
3117
3118         files_pack_refs,
3119         files_create_symref,
3120         files_delete_refs,
3121         files_rename_ref,
3122         files_copy_ref,
3123
3124         files_ref_iterator_begin,
3125         files_read_raw_ref,
3126
3127         files_reflog_iterator_begin,
3128         files_for_each_reflog_ent,
3129         files_for_each_reflog_ent_reverse,
3130         files_reflog_exists,
3131         files_create_reflog,
3132         files_delete_reflog,
3133         files_reflog_expire
3134 };