refs/files-backend.c

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