refs/files-backend.c

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12 #include "../chdir-notify.h"
  13 #include "worktree.h"
  14
  15 /*
  16  * This backend uses the following flags in `ref_update::flags` for
  17  * internal bookkeeping purposes. Their numerical values must not
  18  * conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
  19  * REF_HAVE_OLD, or REF_IS_PRUNING, which are also stored in
  20  * `ref_update::flags`.
  21  */
  22
  23 /*
  24  * Used as a flag in ref_update::flags when a loose ref is being
  25  * pruned. This flag must only be used when REF_NO_DEREF is set.
  26  */
  27 #define REF_IS_PRUNING (1 << 4)
  28
  29 /*
  30  * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
  31  * refs (i.e., because the reference is about to be deleted anyway).
  32  */
  33 #define REF_DELETING (1 << 5)
  34
  35 /*
  36  * Used as a flag in ref_update::flags when the lockfile needs to be
  37  * committed.
  38  */
  39 #define REF_NEEDS_COMMIT (1 << 6)
  40
  41 /*
  42  * Used as a flag in ref_update::flags when we want to log a ref
  43  * update but not actually perform it.  This is used when a symbolic
  44  * ref update is split up.
  45  */
  46 #define REF_LOG_ONLY (1 << 7)
  47
  48 /*
  49  * Used as a flag in ref_update::flags when the ref_update was via an
  50  * update to HEAD.
  51  */
  52 #define REF_UPDATE_VIA_HEAD (1 << 8)
  53
  54 /*
  55  * Used as a flag in ref_update::flags when the loose reference has
  56  * been deleted.
  57  */
  58 #define REF_DELETED_LOOSE (1 << 9)
  59
  60 struct ref_lock {
  61         char *ref_name;
  62         struct lock_file lk;
  63         struct object_id old_oid;
  64 };
  65
  66 struct files_ref_store {
  67         struct ref_store base;
  68         unsigned int store_flags;
  69
  70         char *gitdir;
  71         char *gitcommondir;
  72
  73         struct ref_cache *loose;
  74
  75         struct ref_store *packed_ref_store;
  76 };
  77
  78 static void clear_loose_ref_cache(struct files_ref_store *refs)
  79 {
  80         if (refs->loose) {
  81                 free_ref_cache(refs->loose);
  82                 refs->loose = NULL;
  83         }
  84 }
  85
  86 /*
  87  * Create a new submodule ref cache and add it to the internal
  88  * set of caches.
  89  */
  90 static struct ref_store *files_ref_store_create(const char *gitdir,
  91                                                 unsigned int flags)
  92 {
  93         struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  94         struct ref_store *ref_store = (struct ref_store *)refs;
  95         struct strbuf sb = STRBUF_INIT;
  96
  97         base_ref_store_init(ref_store, &refs_be_files);
  98         refs->store_flags = flags;
  99
 100         refs->gitdir = xstrdup(gitdir);
 101         get_common_dir_noenv(&sb, gitdir);
 102         refs->gitcommondir = strbuf_detach(&sb, NULL);
 103         strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
 104         refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
 105         strbuf_release(&sb);
 106
 107         chdir_notify_reparent("files-backend $GIT_DIR",
 108                               &refs->gitdir);
 109         chdir_notify_reparent("files-backend $GIT_COMMONDIR",
 110                               &refs->gitcommondir);
 111
 112         return ref_store;
 113 }
 114
 115 /*
 116  * Die if refs is not the main ref store. caller is used in any
 117  * necessary error messages.
 118  */
 119 static void files_assert_main_repository(struct files_ref_store *refs,
 120                                          const char *caller)
 121 {
 122         if (refs->store_flags & REF_STORE_MAIN)
 123                 return;
 124
 125         BUG("operation %s only allowed for main ref store", caller);
 126 }
 127
 128 /*
 129  * Downcast ref_store to files_ref_store. Die if ref_store is not a
 130  * files_ref_store. required_flags is compared with ref_store's
 131  * store_flags to ensure the ref_store has all required capabilities.
 132  * "caller" is used in any necessary error messages.
 133  */
 134 static struct files_ref_store *files_downcast(struct ref_store *ref_store,
 135                                               unsigned int required_flags,
 136                                               const char *caller)
 137 {
 138         struct files_ref_store *refs;
 139
 140         if (ref_store->be != &refs_be_files)
 141                 BUG("ref_store is type \"%s\" not \"files\" in %s",
 142                     ref_store->be->name, caller);
 143
 144         refs = (struct files_ref_store *)ref_store;
 145
 146         if ((refs->store_flags & required_flags) != required_flags)
 147                 BUG("operation %s requires abilities 0x%x, but only have 0x%x",
 148                     caller, required_flags, refs->store_flags);
 149
 150         return refs;
 151 }
 152
 153 static void files_reflog_path_other_worktrees(struct files_ref_store *refs,
 154                                               struct strbuf *sb,
 155                                               const char *refname)
 156 {
 157         const char *real_ref;
 158         const char *worktree_name;
 159         int length;
 160
 161         if (parse_worktree_ref(refname, &worktree_name, &length, &real_ref))
 162                 BUG("refname %s is not a other-worktree ref", refname);
 163
 164         if (worktree_name)
 165                 strbuf_addf(sb, "%s/worktrees/%.*s/logs/%s", refs->gitcommondir,
 166                             length, worktree_name, real_ref);
 167         else
 168                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir,
 169                             real_ref);
 170 }
 171
 172 static void files_reflog_path(struct files_ref_store *refs,
 173                               struct strbuf *sb,
 174                               const char *refname)
 175 {
 176         switch (ref_type(refname)) {
 177         case REF_TYPE_PER_WORKTREE:
 178         case REF_TYPE_PSEUDOREF:
 179                 strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 180                 break;
 181         case REF_TYPE_OTHER_PSEUDOREF:
 182         case REF_TYPE_MAIN_PSEUDOREF:
 183                 files_reflog_path_other_worktrees(refs, sb, refname);
 184                 break;
 185         case REF_TYPE_NORMAL:
 186                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 187                 break;
 188         default:
 189                 BUG("unknown ref type %d of ref %s",
 190                     ref_type(refname), refname);
 191         }
 192 }
 193
 194 static void files_ref_path(struct files_ref_store *refs,
 195                            struct strbuf *sb,
 196                            const char *refname)
 197 {
 198         switch (ref_type(refname)) {
 199         case REF_TYPE_PER_WORKTREE:
 200         case REF_TYPE_PSEUDOREF:
 201                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 202                 break;
 203         case REF_TYPE_MAIN_PSEUDOREF:
 204                 if (!skip_prefix(refname, "main-worktree/", &refname))
 205                         BUG("ref %s is not a main pseudoref", refname);
 206                 /* fallthrough */
 207         case REF_TYPE_OTHER_PSEUDOREF:
 208         case REF_TYPE_NORMAL:
 209                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 210                 break;
 211         default:
 212                 BUG("unknown ref type %d of ref %s",
 213                     ref_type(refname), refname);
 214         }
 215 }
 216
 217 /*
 218  * Manually add refs/bisect, refs/rewritten and refs/worktree, which, being
 219  * per-worktree, might not appear in the directory listing for
 220  * refs/ in the main repo.
 221  */
 222 static void add_per_worktree_entries_to_dir(struct ref_dir *dir, const char *dirname)
 223 {
 224         const char *prefixes[] = { "refs/bisect/", "refs/worktree/", "refs/rewritten/" };
 225         int ip;
 226
 227         if (strcmp(dirname, "refs/"))
 228                 return;
 229
 230         for (ip = 0; ip < ARRAY_SIZE(prefixes); ip++) {
 231                 const char *prefix = prefixes[ip];
 232                 int prefix_len = strlen(prefix);
 233                 struct ref_entry *child_entry;
 234                 int pos;
 235
 236                 pos = search_ref_dir(dir, prefix, prefix_len);
 237                 if (pos >= 0)
 238                         continue;
 239                 child_entry = create_dir_entry(dir->cache, prefix, prefix_len, 1);
 240                 add_entry_to_dir(dir, child_entry);
 241         }
 242 }
 243
 244 /*
 245  * Read the loose references from the namespace dirname into dir
 246  * (without recursing).  dirname must end with '/'.  dir must be the
 247  * directory entry corresponding to dirname.
 248  */
 249 static void loose_fill_ref_dir(struct ref_store *ref_store,
 250                                struct ref_dir *dir, const char *dirname)
 251 {
 252         struct files_ref_store *refs =
 253                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 254         DIR *d;
 255         struct dirent *de;
 256         int dirnamelen = strlen(dirname);
 257         struct strbuf refname;
 258         struct strbuf path = STRBUF_INIT;
 259         size_t path_baselen;
 260
 261         files_ref_path(refs, &path, dirname);
 262         path_baselen = path.len;
 263
 264         d = opendir(path.buf);
 265         if (!d) {
 266                 strbuf_release(&path);
 267                 return;
 268         }
 269
 270         strbuf_init(&refname, dirnamelen + 257);
 271         strbuf_add(&refname, dirname, dirnamelen);
 272
 273         while ((de = readdir(d)) != NULL) {
 274                 struct object_id oid;
 275                 struct stat st;
 276                 int flag;
 277
 278                 if (de->d_name[0] == '.')
 279                         continue;
 280                 if (ends_with(de->d_name, ".lock"))
 281                         continue;
 282                 strbuf_addstr(&refname, de->d_name);
 283                 strbuf_addstr(&path, de->d_name);
 284                 if (stat(path.buf, &st) < 0) {
 285                         ; /* silently ignore */
 286                 } else if (S_ISDIR(st.st_mode)) {
 287                         strbuf_addch(&refname, '/');
 288                         add_entry_to_dir(dir,
 289                                          create_dir_entry(dir->cache, refname.buf,
 290                                                           refname.len, 1));
 291                 } else {
 292                         if (!refs_resolve_ref_unsafe(&refs->base,
 293                                                      refname.buf,
 294                                                      RESOLVE_REF_READING,
 295                                                      &oid, &flag)) {
 296                                 oidclr(&oid);
 297                                 flag |= REF_ISBROKEN;
 298                         } else if (is_null_oid(&oid)) {
 299                                 /*
 300                                  * It is so astronomically unlikely
 301                                  * that null_oid is the OID of an
 302                                  * actual object that we consider its
 303                                  * appearance in a loose reference
 304                                  * file to be repo corruption
 305                                  * (probably due to a software bug).
 306                                  */
 307                                 flag |= REF_ISBROKEN;
 308                         }
 309
 310                         if (check_refname_format(refname.buf,
 311                                                  REFNAME_ALLOW_ONELEVEL)) {
 312                                 if (!refname_is_safe(refname.buf))
 313                                         die("loose refname is dangerous: %s", refname.buf);
 314                                 oidclr(&oid);
 315                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 316                         }
 317                         add_entry_to_dir(dir,
 318                                          create_ref_entry(refname.buf, &oid, flag));
 319                 }
 320                 strbuf_setlen(&refname, dirnamelen);
 321                 strbuf_setlen(&path, path_baselen);
 322         }
 323         strbuf_release(&refname);
 324         strbuf_release(&path);
 325         closedir(d);
 326
 327         add_per_worktree_entries_to_dir(dir, dirname);
 328 }
 329
 330 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 331 {
 332         if (!refs->loose) {
 333                 /*
 334                  * Mark the top-level directory complete because we
 335                  * are about to read the only subdirectory that can
 336                  * hold references:
 337                  */
 338                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 339
 340                 /* We're going to fill the top level ourselves: */
 341                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 342
 343                 /*
 344                  * Add an incomplete entry for "refs/" (to be filled
 345                  * lazily):
 346                  */
 347                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 348                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 349         }
 350         return refs->loose;
 351 }
 352
 353 static int files_read_raw_ref(struct ref_store *ref_store,
 354                               const char *refname, struct object_id *oid,
 355                               struct strbuf *referent, unsigned int *type)
 356 {
 357         struct files_ref_store *refs =
 358                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 359         struct strbuf sb_contents = STRBUF_INIT;
 360         struct strbuf sb_path = STRBUF_INIT;
 361         const char *path;
 362         const char *buf;
 363         const char *p;
 364         struct stat st;
 365         int fd;
 366         int ret = -1;
 367         int save_errno;
 368         int remaining_retries = 3;
 369
 370         *type = 0;
 371         strbuf_reset(&sb_path);
 372
 373         files_ref_path(refs, &sb_path, refname);
 374
 375         path = sb_path.buf;
 376
 377 stat_ref:
 378         /*
 379          * We might have to loop back here to avoid a race
 380          * condition: first we lstat() the file, then we try
 381          * to read it as a link or as a file.  But if somebody
 382          * changes the type of the file (file <-> directory
 383          * <-> symlink) between the lstat() and reading, then
 384          * we don't want to report that as an error but rather
 385          * try again starting with the lstat().
 386          *
 387          * We'll keep a count of the retries, though, just to avoid
 388          * any confusing situation sending us into an infinite loop.
 389          */
 390
 391         if (remaining_retries-- <= 0)
 392                 goto out;
 393
 394         if (lstat(path, &st) < 0) {
 395                 if (errno != ENOENT)
 396                         goto out;
 397                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 398                                       oid, referent, type)) {
 399                         errno = ENOENT;
 400                         goto out;
 401                 }
 402                 ret = 0;
 403                 goto out;
 404         }
 405
 406         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 407         if (S_ISLNK(st.st_mode)) {
 408                 strbuf_reset(&sb_contents);
 409                 if (strbuf_readlink(&sb_contents, path, st.st_size) < 0) {
 410                         if (errno == ENOENT || errno == EINVAL)
 411                                 /* inconsistent with lstat; retry */
 412                                 goto stat_ref;
 413                         else
 414                                 goto out;
 415                 }
 416                 if (starts_with(sb_contents.buf, "refs/") &&
 417                     !check_refname_format(sb_contents.buf, 0)) {
 418                         strbuf_swap(&sb_contents, referent);
 419                         *type |= REF_ISSYMREF;
 420                         ret = 0;
 421                         goto out;
 422                 }
 423                 /*
 424                  * It doesn't look like a refname; fall through to just
 425                  * treating it like a non-symlink, and reading whatever it
 426                  * points to.
 427                  */
 428         }
 429
 430         /* Is it a directory? */
 431         if (S_ISDIR(st.st_mode)) {
 432                 /*
 433                  * Even though there is a directory where the loose
 434                  * ref is supposed to be, there could still be a
 435                  * packed ref:
 436                  */
 437                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 438                                       oid, referent, type)) {
 439                         errno = EISDIR;
 440                         goto out;
 441                 }
 442                 ret = 0;
 443                 goto out;
 444         }
 445
 446         /*
 447          * Anything else, just open it and try to use it as
 448          * a ref
 449          */
 450         fd = open(path, O_RDONLY);
 451         if (fd < 0) {
 452                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 453                         /* inconsistent with lstat; retry */
 454                         goto stat_ref;
 455                 else
 456                         goto out;
 457         }
 458         strbuf_reset(&sb_contents);
 459         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 460                 int save_errno = errno;
 461                 close(fd);
 462                 errno = save_errno;
 463                 goto out;
 464         }
 465         close(fd);
 466         strbuf_rtrim(&sb_contents);
 467         buf = sb_contents.buf;
 468         if (skip_prefix(buf, "ref:", &buf)) {
 469                 while (isspace(*buf))
 470                         buf++;
 471
 472                 strbuf_reset(referent);
 473                 strbuf_addstr(referent, buf);
 474                 *type |= REF_ISSYMREF;
 475                 ret = 0;
 476                 goto out;
 477         }
 478
 479         /*
 480          * Please note that FETCH_HEAD has additional
 481          * data after the sha.
 482          */
 483         if (parse_oid_hex(buf, oid, &p) ||
 484             (*p != '\0' && !isspace(*p))) {
 485                 *type |= REF_ISBROKEN;
 486                 errno = EINVAL;
 487                 goto out;
 488         }
 489
 490         ret = 0;
 491
 492 out:
 493         save_errno = errno;
 494         strbuf_release(&sb_path);
 495         strbuf_release(&sb_contents);
 496         errno = save_errno;
 497         return ret;
 498 }
 499
 500 static void unlock_ref(struct ref_lock *lock)
 501 {
 502         rollback_lock_file(&lock->lk);
 503         free(lock->ref_name);
 504         free(lock);
 505 }
 506
 507 /*
 508  * Lock refname, without following symrefs, and set *lock_p to point
 509  * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 510  * and type similarly to read_raw_ref().
 511  *
 512  * The caller must verify that refname is a "safe" reference name (in
 513  * the sense of refname_is_safe()) before calling this function.
 514  *
 515  * If the reference doesn't already exist, verify that refname doesn't
 516  * have a D/F conflict with any existing references. extras and skip
 517  * are passed to refs_verify_refname_available() for this check.
 518  *
 519  * If mustexist is not set and the reference is not found or is
 520  * broken, lock the reference anyway but clear old_oid.
 521  *
 522  * Return 0 on success. On failure, write an error message to err and
 523  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 524  *
 525  * Implementation note: This function is basically
 526  *
 527  *     lock reference
 528  *     read_raw_ref()
 529  *
 530  * but it includes a lot more code to
 531  * - Deal with possible races with other processes
 532  * - Avoid calling refs_verify_refname_available() when it can be
 533  *   avoided, namely if we were successfully able to read the ref
 534  * - Generate informative error messages in the case of failure
 535  */
 536 static int lock_raw_ref(struct files_ref_store *refs,
 537                         const char *refname, int mustexist,
 538                         const struct string_list *extras,
 539                         const struct string_list *skip,
 540                         struct ref_lock **lock_p,
 541                         struct strbuf *referent,
 542                         unsigned int *type,
 543                         struct strbuf *err)
 544 {
 545         struct ref_lock *lock;
 546         struct strbuf ref_file = STRBUF_INIT;
 547         int attempts_remaining = 3;
 548         int ret = TRANSACTION_GENERIC_ERROR;
 549
 550         assert(err);
 551         files_assert_main_repository(refs, "lock_raw_ref");
 552
 553         *type = 0;
 554
 555         /* First lock the file so it can't change out from under us. */
 556
 557         *lock_p = lock = xcalloc(1, sizeof(*lock));
 558
 559         lock->ref_name = xstrdup(refname);
 560         files_ref_path(refs, &ref_file, refname);
 561
 562 retry:
 563         switch (safe_create_leading_directories(ref_file.buf)) {
 564         case SCLD_OK:
 565                 break; /* success */
 566         case SCLD_EXISTS:
 567                 /*
 568                  * Suppose refname is "refs/foo/bar". We just failed
 569                  * to create the containing directory, "refs/foo",
 570                  * because there was a non-directory in the way. This
 571                  * indicates a D/F conflict, probably because of
 572                  * another reference such as "refs/foo". There is no
 573                  * reason to expect this error to be transitory.
 574                  */
 575                 if (refs_verify_refname_available(&refs->base, refname,
 576                                                   extras, skip, err)) {
 577                         if (mustexist) {
 578                                 /*
 579                                  * To the user the relevant error is
 580                                  * that the "mustexist" reference is
 581                                  * missing:
 582                                  */
 583                                 strbuf_reset(err);
 584                                 strbuf_addf(err, "unable to resolve reference '%s'",
 585                                             refname);
 586                         } else {
 587                                 /*
 588                                  * The error message set by
 589                                  * refs_verify_refname_available() is
 590                                  * OK.
 591                                  */
 592                                 ret = TRANSACTION_NAME_CONFLICT;
 593                         }
 594                 } else {
 595                         /*
 596                          * The file that is in the way isn't a loose
 597                          * reference. Report it as a low-level
 598                          * failure.
 599                          */
 600                         strbuf_addf(err, "unable to create lock file %s.lock; "
 601                                     "non-directory in the way",
 602                                     ref_file.buf);
 603                 }
 604                 goto error_return;
 605         case SCLD_VANISHED:
 606                 /* Maybe another process was tidying up. Try again. */
 607                 if (--attempts_remaining > 0)
 608                         goto retry;
 609                 /* fall through */
 610         default:
 611                 strbuf_addf(err, "unable to create directory for %s",
 612                             ref_file.buf);
 613                 goto error_return;
 614         }
 615
 616         if (hold_lock_file_for_update_timeout(
 617                             &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 618                             get_files_ref_lock_timeout_ms()) < 0) {
 619                 if (errno == ENOENT && --attempts_remaining > 0) {
 620                         /*
 621                          * Maybe somebody just deleted one of the
 622                          * directories leading to ref_file.  Try
 623                          * again:
 624                          */
 625                         goto retry;
 626                 } else {
 627                         unable_to_lock_message(ref_file.buf, errno, err);
 628                         goto error_return;
 629                 }
 630         }
 631
 632         /*
 633          * Now we hold the lock and can read the reference without
 634          * fear that its value will change.
 635          */
 636
 637         if (files_read_raw_ref(&refs->base, refname,
 638                                &lock->old_oid, referent, type)) {
 639                 if (errno == ENOENT) {
 640                         if (mustexist) {
 641                                 /* Garden variety missing reference. */
 642                                 strbuf_addf(err, "unable to resolve reference '%s'",
 643                                             refname);
 644                                 goto error_return;
 645                         } else {
 646                                 /*
 647                                  * Reference is missing, but that's OK. We
 648                                  * know that there is not a conflict with
 649                                  * another loose reference because
 650                                  * (supposing that we are trying to lock
 651                                  * reference "refs/foo/bar"):
 652                                  *
 653                                  * - We were successfully able to create
 654                                  *   the lockfile refs/foo/bar.lock, so we
 655                                  *   know there cannot be a loose reference
 656                                  *   named "refs/foo".
 657                                  *
 658                                  * - We got ENOENT and not EISDIR, so we
 659                                  *   know that there cannot be a loose
 660                                  *   reference named "refs/foo/bar/baz".
 661                                  */
 662                         }
 663                 } else if (errno == EISDIR) {
 664                         /*
 665                          * There is a directory in the way. It might have
 666                          * contained references that have been deleted. If
 667                          * we don't require that the reference already
 668                          * exists, try to remove the directory so that it
 669                          * doesn't cause trouble when we want to rename the
 670                          * lockfile into place later.
 671                          */
 672                         if (mustexist) {
 673                                 /* Garden variety missing reference. */
 674                                 strbuf_addf(err, "unable to resolve reference '%s'",
 675                                             refname);
 676                                 goto error_return;
 677                         } else if (remove_dir_recursively(&ref_file,
 678                                                           REMOVE_DIR_EMPTY_ONLY)) {
 679                                 if (refs_verify_refname_available(
 680                                                     &refs->base, refname,
 681                                                     extras, skip, err)) {
 682                                         /*
 683                                          * The error message set by
 684                                          * verify_refname_available() is OK.
 685                                          */
 686                                         ret = TRANSACTION_NAME_CONFLICT;
 687                                         goto error_return;
 688                                 } else {
 689                                         /*
 690                                          * We can't delete the directory,
 691                                          * but we also don't know of any
 692                                          * references that it should
 693                                          * contain.
 694                                          */
 695                                         strbuf_addf(err, "there is a non-empty directory '%s' "
 696                                                     "blocking reference '%s'",
 697                                                     ref_file.buf, refname);
 698                                         goto error_return;
 699                                 }
 700                         }
 701                 } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 702                         strbuf_addf(err, "unable to resolve reference '%s': "
 703                                     "reference broken", refname);
 704                         goto error_return;
 705                 } else {
 706                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 707                                     refname, strerror(errno));
 708                         goto error_return;
 709                 }
 710
 711                 /*
 712                  * If the ref did not exist and we are creating it,
 713                  * make sure there is no existing packed ref that
 714                  * conflicts with refname:
 715                  */
 716                 if (refs_verify_refname_available(
 717                                     refs->packed_ref_store, refname,
 718                                     extras, skip, err))
 719                         goto error_return;
 720         }
 721
 722         ret = 0;
 723         goto out;
 724
 725 error_return:
 726         unlock_ref(lock);
 727         *lock_p = NULL;
 728
 729 out:
 730         strbuf_release(&ref_file);
 731         return ret;
 732 }
 733
 734 struct files_ref_iterator {
 735         struct ref_iterator base;
 736
 737         struct ref_iterator *iter0;
 738         unsigned int flags;
 739 };
 740
 741 static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 742 {
 743         struct files_ref_iterator *iter =
 744                 (struct files_ref_iterator *)ref_iterator;
 745         int ok;
 746
 747         while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 748                 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 749                     ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 750                         continue;
 751
 752                 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 753                     !ref_resolves_to_object(iter->iter0->refname,
 754                                             iter->iter0->oid,
 755                                             iter->iter0->flags))
 756                         continue;
 757
 758                 iter->base.refname = iter->iter0->refname;
 759                 iter->base.oid = iter->iter0->oid;
 760                 iter->base.flags = iter->iter0->flags;
 761                 return ITER_OK;
 762         }
 763
 764         iter->iter0 = NULL;
 765         if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 766                 ok = ITER_ERROR;
 767
 768         return ok;
 769 }
 770
 771 static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 772                                    struct object_id *peeled)
 773 {
 774         struct files_ref_iterator *iter =
 775                 (struct files_ref_iterator *)ref_iterator;
 776
 777         return ref_iterator_peel(iter->iter0, peeled);
 778 }
 779
 780 static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 781 {
 782         struct files_ref_iterator *iter =
 783                 (struct files_ref_iterator *)ref_iterator;
 784         int ok = ITER_DONE;
 785
 786         if (iter->iter0)
 787                 ok = ref_iterator_abort(iter->iter0);
 788
 789         base_ref_iterator_free(ref_iterator);
 790         return ok;
 791 }
 792
 793 static struct ref_iterator_vtable files_ref_iterator_vtable = {
 794         files_ref_iterator_advance,
 795         files_ref_iterator_peel,
 796         files_ref_iterator_abort
 797 };
 798
 799 static struct ref_iterator *files_ref_iterator_begin(
 800                 struct ref_store *ref_store,
 801                 const char *prefix, unsigned int flags)
 802 {
 803         struct files_ref_store *refs;
 804         struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 805         struct files_ref_iterator *iter;
 806         struct ref_iterator *ref_iterator;
 807         unsigned int required_flags = REF_STORE_READ;
 808
 809         if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 810                 required_flags |= REF_STORE_ODB;
 811
 812         refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 813
 814         /*
 815          * We must make sure that all loose refs are read before
 816          * accessing the packed-refs file; this avoids a race
 817          * condition if loose refs are migrated to the packed-refs
 818          * file by a simultaneous process, but our in-memory view is
 819          * from before the migration. We ensure this as follows:
 820          * First, we call start the loose refs iteration with its
 821          * `prime_ref` argument set to true. This causes the loose
 822          * references in the subtree to be pre-read into the cache.
 823          * (If they've already been read, that's OK; we only need to
 824          * guarantee that they're read before the packed refs, not
 825          * *how much* before.) After that, we call
 826          * packed_ref_iterator_begin(), which internally checks
 827          * whether the packed-ref cache is up to date with what is on
 828          * disk, and re-reads it if not.
 829          */
 830
 831         loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 832                                               prefix, 1);
 833
 834         /*
 835          * The packed-refs file might contain broken references, for
 836          * example an old version of a reference that points at an
 837          * object that has since been garbage-collected. This is OK as
 838          * long as there is a corresponding loose reference that
 839          * overrides it, and we don't want to emit an error message in
 840          * this case. So ask the packed_ref_store for all of its
 841          * references, and (if needed) do our own check for broken
 842          * ones in files_ref_iterator_advance(), after we have merged
 843          * the packed and loose references.
 844          */
 845         packed_iter = refs_ref_iterator_begin(
 846                         refs->packed_ref_store, prefix, 0,
 847                         DO_FOR_EACH_INCLUDE_BROKEN);
 848
 849         overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 850
 851         iter = xcalloc(1, sizeof(*iter));
 852         ref_iterator = &iter->base;
 853         base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 854                                overlay_iter->ordered);
 855         iter->iter0 = overlay_iter;
 856         iter->flags = flags;
 857
 858         return ref_iterator;
 859 }
 860
 861 /*
 862  * Verify that the reference locked by lock has the value old_oid
 863  * (unless it is NULL).  Fail if the reference doesn't exist and
 864  * mustexist is set. Return 0 on success. On error, write an error
 865  * message to err, set errno, and return a negative value.
 866  */
 867 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 868                        const struct object_id *old_oid, int mustexist,
 869                        struct strbuf *err)
 870 {
 871         assert(err);
 872
 873         if (refs_read_ref_full(ref_store, lock->ref_name,
 874                                mustexist ? RESOLVE_REF_READING : 0,
 875                                &lock->old_oid, NULL)) {
 876                 if (old_oid) {
 877                         int save_errno = errno;
 878                         strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 879                         errno = save_errno;
 880                         return -1;
 881                 } else {
 882                         oidclr(&lock->old_oid);
 883                         return 0;
 884                 }
 885         }
 886         if (old_oid && !oideq(&lock->old_oid, old_oid)) {
 887                 strbuf_addf(err, "ref '%s' is at %s but expected %s",
 888                             lock->ref_name,
 889                             oid_to_hex(&lock->old_oid),
 890                             oid_to_hex(old_oid));
 891                 errno = EBUSY;
 892                 return -1;
 893         }
 894         return 0;
 895 }
 896
 897 static int remove_empty_directories(struct strbuf *path)
 898 {
 899         /*
 900          * we want to create a file but there is a directory there;
 901          * if that is an empty directory (or a directory that contains
 902          * only empty directories), remove them.
 903          */
 904         return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 905 }
 906
 907 static int create_reflock(const char *path, void *cb)
 908 {
 909         struct lock_file *lk = cb;
 910
 911         return hold_lock_file_for_update_timeout(
 912                         lk, path, LOCK_NO_DEREF,
 913                         get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 914 }
 915
 916 /*
 917  * Locks a ref returning the lock on success and NULL on failure.
 918  * On failure errno is set to something meaningful.
 919  */
 920 static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
 921                                            const char *refname,
 922                                            const struct object_id *old_oid,
 923                                            const struct string_list *extras,
 924                                            const struct string_list *skip,
 925                                            unsigned int flags, int *type,
 926                                            struct strbuf *err)
 927 {
 928         struct strbuf ref_file = STRBUF_INIT;
 929         struct ref_lock *lock;
 930         int last_errno = 0;
 931         int mustexist = (old_oid && !is_null_oid(old_oid));
 932         int resolve_flags = RESOLVE_REF_NO_RECURSE;
 933         int resolved;
 934
 935         files_assert_main_repository(refs, "lock_ref_oid_basic");
 936         assert(err);
 937
 938         lock = xcalloc(1, sizeof(struct ref_lock));
 939
 940         if (mustexist)
 941                 resolve_flags |= RESOLVE_REF_READING;
 942         if (flags & REF_DELETING)
 943                 resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 944
 945         files_ref_path(refs, &ref_file, refname);
 946         resolved = !!refs_resolve_ref_unsafe(&refs->base,
 947                                              refname, resolve_flags,
 948                                              &lock->old_oid, type);
 949         if (!resolved && errno == EISDIR) {
 950                 /*
 951                  * we are trying to lock foo but we used to
 952                  * have foo/bar which now does not exist;
 953                  * it is normal for the empty directory 'foo'
 954                  * to remain.
 955                  */
 956                 if (remove_empty_directories(&ref_file)) {
 957                         last_errno = errno;
 958                         if (!refs_verify_refname_available(
 959                                             &refs->base,
 960                                             refname, extras, skip, err))
 961                                 strbuf_addf(err, "there are still refs under '%s'",
 962                                             refname);
 963                         goto error_return;
 964                 }
 965                 resolved = !!refs_resolve_ref_unsafe(&refs->base,
 966                                                      refname, resolve_flags,
 967                                                      &lock->old_oid, type);
 968         }
 969         if (!resolved) {
 970                 last_errno = errno;
 971                 if (last_errno != ENOTDIR ||
 972                     !refs_verify_refname_available(&refs->base, refname,
 973                                                    extras, skip, err))
 974                         strbuf_addf(err, "unable to resolve reference '%s': %s",
 975                                     refname, strerror(last_errno));
 976
 977                 goto error_return;
 978         }
 979
 980         /*
 981          * If the ref did not exist and we are creating it, make sure
 982          * there is no existing packed ref whose name begins with our
 983          * refname, nor a packed ref whose name is a proper prefix of
 984          * our refname.
 985          */
 986         if (is_null_oid(&lock->old_oid) &&
 987             refs_verify_refname_available(refs->packed_ref_store, refname,
 988                                           extras, skip, err)) {
 989                 last_errno = ENOTDIR;
 990                 goto error_return;
 991         }
 992
 993         lock->ref_name = xstrdup(refname);
 994
 995         if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 996                 last_errno = errno;
 997                 unable_to_lock_message(ref_file.buf, errno, err);
 998                 goto error_return;
 999         }
1000
1001         if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
1002                 last_errno = errno;
1003                 goto error_return;
1004         }
1005         goto out;
1006
1007  error_return:
1008         unlock_ref(lock);
1009         lock = NULL;
1010
1011  out:
1012         strbuf_release(&ref_file);
1013         errno = last_errno;
1014         return lock;
1015 }
1016
1017 struct ref_to_prune {
1018         struct ref_to_prune *next;
1019         struct object_id oid;
1020         char name[FLEX_ARRAY];
1021 };
1022
1023 enum {
1024         REMOVE_EMPTY_PARENTS_REF = 0x01,
1025         REMOVE_EMPTY_PARENTS_REFLOG = 0x02
1026 };
1027
1028 /*
1029  * Remove empty parent directories associated with the specified
1030  * reference and/or its reflog, but spare [logs/]refs/ and immediate
1031  * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
1032  * REMOVE_EMPTY_PARENTS_REFLOG.
1033  */
1034 static void try_remove_empty_parents(struct files_ref_store *refs,
1035                                      const char *refname,
1036                                      unsigned int flags)
1037 {
1038         struct strbuf buf = STRBUF_INIT;
1039         struct strbuf sb = STRBUF_INIT;
1040         char *p, *q;
1041         int i;
1042
1043         strbuf_addstr(&buf, refname);
1044         p = buf.buf;
1045         for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1046                 while (*p && *p != '/')
1047                         p++;
1048                 /* tolerate duplicate slashes; see check_refname_format() */
1049                 while (*p == '/')
1050                         p++;
1051         }
1052         q = buf.buf + buf.len;
1053         while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1054                 while (q > p && *q != '/')
1055                         q--;
1056                 while (q > p && *(q-1) == '/')
1057                         q--;
1058                 if (q == p)
1059                         break;
1060                 strbuf_setlen(&buf, q - buf.buf);
1061
1062                 strbuf_reset(&sb);
1063                 files_ref_path(refs, &sb, buf.buf);
1064                 if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1065                         flags &= ~REMOVE_EMPTY_PARENTS_REF;
1066
1067                 strbuf_reset(&sb);
1068                 files_reflog_path(refs, &sb, buf.buf);
1069                 if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1070                         flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1071         }
1072         strbuf_release(&buf);
1073         strbuf_release(&sb);
1074 }
1075
1076 /* make sure nobody touched the ref, and unlink */
1077 static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1078 {
1079         struct ref_transaction *transaction;
1080         struct strbuf err = STRBUF_INIT;
1081         int ret = -1;
1082
1083         if (check_refname_format(r->name, 0))
1084                 return;
1085
1086         transaction = ref_store_transaction_begin(&refs->base, &err);
1087         if (!transaction)
1088                 goto cleanup;
1089         ref_transaction_add_update(
1090                         transaction, r->name,
1091                         REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
1092                         &null_oid, &r->oid, NULL);
1093         if (ref_transaction_commit(transaction, &err))
1094                 goto cleanup;
1095
1096         ret = 0;
1097
1098 cleanup:
1099         if (ret)
1100                 error("%s", err.buf);
1101         strbuf_release(&err);
1102         ref_transaction_free(transaction);
1103         return;
1104 }
1105
1106 /*
1107  * Prune the loose versions of the references in the linked list
1108  * `*refs_to_prune`, freeing the entries in the list as we go.
1109  */
1110 static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1111 {
1112         while (*refs_to_prune) {
1113                 struct ref_to_prune *r = *refs_to_prune;
1114                 *refs_to_prune = r->next;
1115                 prune_ref(refs, r);
1116                 free(r);
1117         }
1118 }
1119
1120 /*
1121  * Return true if the specified reference should be packed.
1122  */
1123 static int should_pack_ref(const char *refname,
1124                            const struct object_id *oid, unsigned int ref_flags,
1125                            unsigned int pack_flags)
1126 {
1127         /* Do not pack per-worktree refs: */
1128         if (ref_type(refname) != REF_TYPE_NORMAL)
1129                 return 0;
1130
1131         /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1132         if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1133                 return 0;
1134
1135         /* Do not pack symbolic refs: */
1136         if (ref_flags & REF_ISSYMREF)
1137                 return 0;
1138
1139         /* Do not pack broken refs: */
1140         if (!ref_resolves_to_object(refname, oid, ref_flags))
1141                 return 0;
1142
1143         return 1;
1144 }
1145
1146 static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1147 {
1148         struct files_ref_store *refs =
1149                 files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1150                                "pack_refs");
1151         struct ref_iterator *iter;
1152         int ok;
1153         struct ref_to_prune *refs_to_prune = NULL;
1154         struct strbuf err = STRBUF_INIT;
1155         struct ref_transaction *transaction;
1156
1157         transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1158         if (!transaction)
1159                 return -1;
1160
1161         packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1162
1163         iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1164         while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1165                 /*
1166                  * If the loose reference can be packed, add an entry
1167                  * in the packed ref cache. If the reference should be
1168                  * pruned, also add it to refs_to_prune.
1169                  */
1170                 if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1171                                      flags))
1172                         continue;
1173
1174                 /*
1175                  * Add a reference creation for this reference to the
1176                  * packed-refs transaction:
1177                  */
1178                 if (ref_transaction_update(transaction, iter->refname,
1179                                            iter->oid, NULL,
1180                                            REF_NO_DEREF, NULL, &err))
1181                         die("failure preparing to create packed reference %s: %s",
1182                             iter->refname, err.buf);
1183
1184                 /* Schedule the loose reference for pruning if requested. */
1185                 if ((flags & PACK_REFS_PRUNE)) {
1186                         struct ref_to_prune *n;
1187                         FLEX_ALLOC_STR(n, name, iter->refname);
1188                         oidcpy(&n->oid, iter->oid);
1189                         n->next = refs_to_prune;
1190                         refs_to_prune = n;
1191                 }
1192         }
1193         if (ok != ITER_DONE)
1194                 die("error while iterating over references");
1195
1196         if (ref_transaction_commit(transaction, &err))
1197                 die("unable to write new packed-refs: %s", err.buf);
1198
1199         ref_transaction_free(transaction);
1200
1201         packed_refs_unlock(refs->packed_ref_store);
1202
1203         prune_refs(refs, &refs_to_prune);
1204         strbuf_release(&err);
1205         return 0;
1206 }
1207
1208 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1209                              struct string_list *refnames, unsigned int flags)
1210 {
1211         struct files_ref_store *refs =
1212                 files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1213         struct strbuf err = STRBUF_INIT;
1214         int i, result = 0;
1215
1216         if (!refnames->nr)
1217                 return 0;
1218
1219         if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1220                 goto error;
1221
1222         if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1223                 packed_refs_unlock(refs->packed_ref_store);
1224                 goto error;
1225         }
1226
1227         packed_refs_unlock(refs->packed_ref_store);
1228
1229         for (i = 0; i < refnames->nr; i++) {
1230                 const char *refname = refnames->items[i].string;
1231
1232                 if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1233                         result |= error(_("could not remove reference %s"), refname);
1234         }
1235
1236         strbuf_release(&err);
1237         return result;
1238
1239 error:
1240         /*
1241          * If we failed to rewrite the packed-refs file, then it is
1242          * unsafe to try to remove loose refs, because doing so might
1243          * expose an obsolete packed value for a reference that might
1244          * even point at an object that has been garbage collected.
1245          */
1246         if (refnames->nr == 1)
1247                 error(_("could not delete reference %s: %s"),
1248                       refnames->items[0].string, err.buf);
1249         else
1250                 error(_("could not delete references: %s"), err.buf);
1251
1252         strbuf_release(&err);
1253         return -1;
1254 }
1255
1256 /*
1257  * People using contrib's git-new-workdir have .git/logs/refs ->
1258  * /some/other/path/.git/logs/refs, and that may live on another device.
1259  *
1260  * IOW, to avoid cross device rename errors, the temporary renamed log must
1261  * live into logs/refs.
1262  */
1263 #define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1264
1265 struct rename_cb {
1266         const char *tmp_renamed_log;
1267         int true_errno;
1268 };
1269
1270 static int rename_tmp_log_callback(const char *path, void *cb_data)
1271 {
1272         struct rename_cb *cb = cb_data;
1273
1274         if (rename(cb->tmp_renamed_log, path)) {
1275                 /*
1276                  * rename(a, b) when b is an existing directory ought
1277                  * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1278                  * Sheesh. Record the true errno for error reporting,
1279                  * but report EISDIR to raceproof_create_file() so
1280                  * that it knows to retry.
1281                  */
1282                 cb->true_errno = errno;
1283                 if (errno == ENOTDIR)
1284                         errno = EISDIR;
1285                 return -1;
1286         } else {
1287                 return 0;
1288         }
1289 }
1290
1291 static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1292 {
1293         struct strbuf path = STRBUF_INIT;
1294         struct strbuf tmp = STRBUF_INIT;
1295         struct rename_cb cb;
1296         int ret;
1297
1298         files_reflog_path(refs, &path, newrefname);
1299         files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1300         cb.tmp_renamed_log = tmp.buf;
1301         ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1302         if (ret) {
1303                 if (errno == EISDIR)
1304                         error("directory not empty: %s", path.buf);
1305                 else
1306                         error("unable to move logfile %s to %s: %s",
1307                               tmp.buf, path.buf,
1308                               strerror(cb.true_errno));
1309         }
1310
1311         strbuf_release(&path);
1312         strbuf_release(&tmp);
1313         return ret;
1314 }
1315
1316 static int write_ref_to_lockfile(struct ref_lock *lock,
1317                                  const struct object_id *oid, struct strbuf *err);
1318 static int commit_ref_update(struct files_ref_store *refs,
1319                              struct ref_lock *lock,
1320                              const struct object_id *oid, const char *logmsg,
1321                              struct strbuf *err);
1322
1323 static int files_copy_or_rename_ref(struct ref_store *ref_store,
1324                             const char *oldrefname, const char *newrefname,
1325                             const char *logmsg, int copy)
1326 {
1327         struct files_ref_store *refs =
1328                 files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1329         struct object_id orig_oid;
1330         int flag = 0, logmoved = 0;
1331         struct ref_lock *lock;
1332         struct stat loginfo;
1333         struct strbuf sb_oldref = STRBUF_INIT;
1334         struct strbuf sb_newref = STRBUF_INIT;
1335         struct strbuf tmp_renamed_log = STRBUF_INIT;
1336         int log, ret;
1337         struct strbuf err = STRBUF_INIT;
1338
1339         files_reflog_path(refs, &sb_oldref, oldrefname);
1340         files_reflog_path(refs, &sb_newref, newrefname);
1341         files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1342
1343         log = !lstat(sb_oldref.buf, &loginfo);
1344         if (log && S_ISLNK(loginfo.st_mode)) {
1345                 ret = error("reflog for %s is a symlink", oldrefname);
1346                 goto out;
1347         }
1348
1349         if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1350                                      RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1351                                 &orig_oid, &flag)) {
1352                 ret = error("refname %s not found", oldrefname);
1353                 goto out;
1354         }
1355
1356         if (flag & REF_ISSYMREF) {
1357                 if (copy)
1358                         ret = error("refname %s is a symbolic ref, copying it is not supported",
1359                                     oldrefname);
1360                 else
1361                         ret = error("refname %s is a symbolic ref, renaming it is not supported",
1362                                     oldrefname);
1363                 goto out;
1364         }
1365         if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1366                 ret = 1;
1367                 goto out;
1368         }
1369
1370         if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1371                 ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1372                             oldrefname, strerror(errno));
1373                 goto out;
1374         }
1375
1376         if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1377                 ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1378                             oldrefname, strerror(errno));
1379                 goto out;
1380         }
1381
1382         if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1383                             &orig_oid, REF_NO_DEREF)) {
1384                 error("unable to delete old %s", oldrefname);
1385                 goto rollback;
1386         }
1387
1388         /*
1389          * Since we are doing a shallow lookup, oid is not the
1390          * correct value to pass to delete_ref as old_oid. But that
1391          * doesn't matter, because an old_oid check wouldn't add to
1392          * the safety anyway; we want to delete the reference whatever
1393          * its current value.
1394          */
1395         if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1396                                 RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1397                                 NULL, NULL) &&
1398             refs_delete_ref(&refs->base, NULL, newrefname,
1399                             NULL, REF_NO_DEREF)) {
1400                 if (errno == EISDIR) {
1401                         struct strbuf path = STRBUF_INIT;
1402                         int result;
1403
1404                         files_ref_path(refs, &path, newrefname);
1405                         result = remove_empty_directories(&path);
1406                         strbuf_release(&path);
1407
1408                         if (result) {
1409                                 error("Directory not empty: %s", newrefname);
1410                                 goto rollback;
1411                         }
1412                 } else {
1413                         error("unable to delete existing %s", newrefname);
1414                         goto rollback;
1415                 }
1416         }
1417
1418         if (log && rename_tmp_log(refs, newrefname))
1419                 goto rollback;
1420
1421         logmoved = log;
1422
1423         lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1424                                   REF_NO_DEREF, NULL, &err);
1425         if (!lock) {
1426                 if (copy)
1427                         error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1428                 else
1429                         error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1430                 strbuf_release(&err);
1431                 goto rollback;
1432         }
1433         oidcpy(&lock->old_oid, &orig_oid);
1434
1435         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1436             commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1437                 error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1438                 strbuf_release(&err);
1439                 goto rollback;
1440         }
1441
1442         ret = 0;
1443         goto out;
1444
1445  rollback:
1446         lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1447                                   REF_NO_DEREF, NULL, &err);
1448         if (!lock) {
1449                 error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1450                 strbuf_release(&err);
1451                 goto rollbacklog;
1452         }
1453
1454         flag = log_all_ref_updates;
1455         log_all_ref_updates = LOG_REFS_NONE;
1456         if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1457             commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1458                 error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1459                 strbuf_release(&err);
1460         }
1461         log_all_ref_updates = flag;
1462
1463  rollbacklog:
1464         if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1465                 error("unable to restore logfile %s from %s: %s",
1466                         oldrefname, newrefname, strerror(errno));
1467         if (!logmoved && log &&
1468             rename(tmp_renamed_log.buf, sb_oldref.buf))
1469                 error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1470                         oldrefname, strerror(errno));
1471         ret = 1;
1472  out:
1473         strbuf_release(&sb_newref);
1474         strbuf_release(&sb_oldref);
1475         strbuf_release(&tmp_renamed_log);
1476
1477         return ret;
1478 }
1479
1480 static int files_rename_ref(struct ref_store *ref_store,
1481                             const char *oldrefname, const char *newrefname,
1482                             const char *logmsg)
1483 {
1484         return files_copy_or_rename_ref(ref_store, oldrefname,
1485                                  newrefname, logmsg, 0);
1486 }
1487
1488 static int files_copy_ref(struct ref_store *ref_store,
1489                             const char *oldrefname, const char *newrefname,
1490                             const char *logmsg)
1491 {
1492         return files_copy_or_rename_ref(ref_store, oldrefname,
1493                                  newrefname, logmsg, 1);
1494 }
1495
1496 static int close_ref_gently(struct ref_lock *lock)
1497 {
1498         if (close_lock_file_gently(&lock->lk))
1499                 return -1;
1500         return 0;
1501 }
1502
1503 static int commit_ref(struct ref_lock *lock)
1504 {
1505         char *path = get_locked_file_path(&lock->lk);
1506         struct stat st;
1507
1508         if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1509                 /*
1510                  * There is a directory at the path we want to rename
1511                  * the lockfile to. Hopefully it is empty; try to
1512                  * delete it.
1513                  */
1514                 size_t len = strlen(path);
1515                 struct strbuf sb_path = STRBUF_INIT;
1516
1517                 strbuf_attach(&sb_path, path, len, len);
1518
1519                 /*
1520                  * If this fails, commit_lock_file() will also fail
1521                  * and will report the problem.
1522                  */
1523                 remove_empty_directories(&sb_path);
1524                 strbuf_release(&sb_path);
1525         } else {
1526                 free(path);
1527         }
1528
1529         if (commit_lock_file(&lock->lk))
1530                 return -1;
1531         return 0;
1532 }
1533
1534 static int open_or_create_logfile(const char *path, void *cb)
1535 {
1536         int *fd = cb;
1537
1538         *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1539         return (*fd < 0) ? -1 : 0;
1540 }
1541
1542 /*
1543  * Create a reflog for a ref. If force_create = 0, only create the
1544  * reflog for certain refs (those for which should_autocreate_reflog
1545  * returns non-zero). Otherwise, create it regardless of the reference
1546  * name. If the logfile already existed or was created, return 0 and
1547  * set *logfd to the file descriptor opened for appending to the file.
1548  * If no logfile exists and we decided not to create one, return 0 and
1549  * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1550  * return -1.
1551  */
1552 static int log_ref_setup(struct files_ref_store *refs,
1553                          const char *refname, int force_create,
1554                          int *logfd, struct strbuf *err)
1555 {
1556         struct strbuf logfile_sb = STRBUF_INIT;
1557         char *logfile;
1558
1559         files_reflog_path(refs, &logfile_sb, refname);
1560         logfile = strbuf_detach(&logfile_sb, NULL);
1561
1562         if (force_create || should_autocreate_reflog(refname)) {
1563                 if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1564                         if (errno == ENOENT)
1565                                 strbuf_addf(err, "unable to create directory for '%s': "
1566                                             "%s", logfile, strerror(errno));
1567                         else if (errno == EISDIR)
1568                                 strbuf_addf(err, "there are still logs under '%s'",
1569                                             logfile);
1570                         else
1571                                 strbuf_addf(err, "unable to append to '%s': %s",
1572                                             logfile, strerror(errno));
1573
1574                         goto error;
1575                 }
1576         } else {
1577                 *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1578                 if (*logfd < 0) {
1579                         if (errno == ENOENT || errno == EISDIR) {
1580                                 /*
1581                                  * The logfile doesn't already exist,
1582                                  * but that is not an error; it only
1583                                  * means that we won't write log
1584                                  * entries to it.
1585                                  */
1586                                 ;
1587                         } else {
1588                                 strbuf_addf(err, "unable to append to '%s': %s",
1589                                             logfile, strerror(errno));
1590                                 goto error;
1591                         }
1592                 }
1593         }
1594
1595         if (*logfd >= 0)
1596                 adjust_shared_perm(logfile);
1597
1598         free(logfile);
1599         return 0;
1600
1601 error:
1602         free(logfile);
1603         return -1;
1604 }
1605
1606 static int files_create_reflog(struct ref_store *ref_store,
1607                                const char *refname, int force_create,
1608                                struct strbuf *err)
1609 {
1610         struct files_ref_store *refs =
1611                 files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1612         int fd;
1613
1614         if (log_ref_setup(refs, refname, force_create, &fd, err))
1615                 return -1;
1616
1617         if (fd >= 0)
1618                 close(fd);
1619
1620         return 0;
1621 }
1622
1623 static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1624                             const struct object_id *new_oid,
1625                             const char *committer, const char *msg)
1626 {
1627         struct strbuf sb = STRBUF_INIT;
1628         int ret = 0;
1629
1630         strbuf_addf(&sb, "%s %s %s", oid_to_hex(old_oid), oid_to_hex(new_oid), committer);
1631         if (msg && *msg)
1632                 copy_reflog_msg(&sb, msg);
1633         strbuf_addch(&sb, '\n');
1634         if (write_in_full(fd, sb.buf, sb.len) < 0)
1635                 ret = -1;
1636         strbuf_release(&sb);
1637         return ret;
1638 }
1639
1640 static int files_log_ref_write(struct files_ref_store *refs,
1641                                const char *refname, const struct object_id *old_oid,
1642                                const struct object_id *new_oid, const char *msg,
1643                                int flags, struct strbuf *err)
1644 {
1645         int logfd, result;
1646
1647         if (log_all_ref_updates == LOG_REFS_UNSET)
1648                 log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1649
1650         result = log_ref_setup(refs, refname,
1651                                flags & REF_FORCE_CREATE_REFLOG,
1652                                &logfd, err);
1653
1654         if (result)
1655                 return result;
1656
1657         if (logfd < 0)
1658                 return 0;
1659         result = log_ref_write_fd(logfd, old_oid, new_oid,
1660                                   git_committer_info(0), msg);
1661         if (result) {
1662                 struct strbuf sb = STRBUF_INIT;
1663                 int save_errno = errno;
1664
1665                 files_reflog_path(refs, &sb, refname);
1666                 strbuf_addf(err, "unable to append to '%s': %s",
1667                             sb.buf, strerror(save_errno));
1668                 strbuf_release(&sb);
1669                 close(logfd);
1670                 return -1;
1671         }
1672         if (close(logfd)) {
1673                 struct strbuf sb = STRBUF_INIT;
1674                 int save_errno = errno;
1675
1676                 files_reflog_path(refs, &sb, refname);
1677                 strbuf_addf(err, "unable to append to '%s': %s",
1678                             sb.buf, strerror(save_errno));
1679                 strbuf_release(&sb);
1680                 return -1;
1681         }
1682         return 0;
1683 }
1684
1685 /*
1686  * Write oid into the open lockfile, then close the lockfile. On
1687  * errors, rollback the lockfile, fill in *err and return -1.
1688  */
1689 static int write_ref_to_lockfile(struct ref_lock *lock,
1690                                  const struct object_id *oid, struct strbuf *err)
1691 {
1692         static char term = '\n';
1693         struct object *o;
1694         int fd;
1695
1696         o = parse_object(the_repository, oid);
1697         if (!o) {
1698                 strbuf_addf(err,
1699                             "trying to write ref '%s' with nonexistent object %s",
1700                             lock->ref_name, oid_to_hex(oid));
1701                 unlock_ref(lock);
1702                 return -1;
1703         }
1704         if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1705                 strbuf_addf(err,
1706                             "trying to write non-commit object %s to branch '%s'",
1707                             oid_to_hex(oid), lock->ref_name);
1708                 unlock_ref(lock);
1709                 return -1;
1710         }
1711         fd = get_lock_file_fd(&lock->lk);
1712         if (write_in_full(fd, oid_to_hex(oid), the_hash_algo->hexsz) < 0 ||
1713             write_in_full(fd, &term, 1) < 0 ||
1714             close_ref_gently(lock) < 0) {
1715                 strbuf_addf(err,
1716                             "couldn't write '%s'", get_lock_file_path(&lock->lk));
1717                 unlock_ref(lock);
1718                 return -1;
1719         }
1720         return 0;
1721 }
1722
1723 /*
1724  * Commit a change to a loose reference that has already been written
1725  * to the loose reference lockfile. Also update the reflogs if
1726  * necessary, using the specified lockmsg (which can be NULL).
1727  */
1728 static int commit_ref_update(struct files_ref_store *refs,
1729                              struct ref_lock *lock,
1730                              const struct object_id *oid, const char *logmsg,
1731                              struct strbuf *err)
1732 {
1733         files_assert_main_repository(refs, "commit_ref_update");
1734
1735         clear_loose_ref_cache(refs);
1736         if (files_log_ref_write(refs, lock->ref_name,
1737                                 &lock->old_oid, oid,
1738                                 logmsg, 0, err)) {
1739                 char *old_msg = strbuf_detach(err, NULL);
1740                 strbuf_addf(err, "cannot update the ref '%s': %s",
1741                             lock->ref_name, old_msg);
1742                 free(old_msg);
1743                 unlock_ref(lock);
1744                 return -1;
1745         }
1746
1747         if (strcmp(lock->ref_name, "HEAD") != 0) {
1748                 /*
1749                  * Special hack: If a branch is updated directly and HEAD
1750                  * points to it (may happen on the remote side of a push
1751                  * for example) then logically the HEAD reflog should be
1752                  * updated too.
1753                  * A generic solution implies reverse symref information,
1754                  * but finding all symrefs pointing to the given branch
1755                  * would be rather costly for this rare event (the direct
1756                  * update of a branch) to be worth it.  So let's cheat and
1757                  * check with HEAD only which should cover 99% of all usage
1758                  * scenarios (even 100% of the default ones).
1759                  */
1760                 int head_flag;
1761                 const char *head_ref;
1762
1763                 head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1764                                                    RESOLVE_REF_READING,
1765                                                    NULL, &head_flag);
1766                 if (head_ref && (head_flag & REF_ISSYMREF) &&
1767                     !strcmp(head_ref, lock->ref_name)) {
1768                         struct strbuf log_err = STRBUF_INIT;
1769                         if (files_log_ref_write(refs, "HEAD",
1770                                                 &lock->old_oid, oid,
1771                                                 logmsg, 0, &log_err)) {
1772                                 error("%s", log_err.buf);
1773                                 strbuf_release(&log_err);
1774                         }
1775                 }
1776         }
1777
1778         if (commit_ref(lock)) {
1779                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1780                 unlock_ref(lock);
1781                 return -1;
1782         }
1783
1784         unlock_ref(lock);
1785         return 0;
1786 }
1787
1788 static int create_ref_symlink(struct ref_lock *lock, const char *target)
1789 {
1790         int ret = -1;
1791 #ifndef NO_SYMLINK_HEAD
1792         char *ref_path = get_locked_file_path(&lock->lk);
1793         unlink(ref_path);
1794         ret = symlink(target, ref_path);
1795         free(ref_path);
1796
1797         if (ret)
1798                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1799 #endif
1800         return ret;
1801 }
1802
1803 static void update_symref_reflog(struct files_ref_store *refs,
1804                                  struct ref_lock *lock, const char *refname,
1805                                  const char *target, const char *logmsg)
1806 {
1807         struct strbuf err = STRBUF_INIT;
1808         struct object_id new_oid;
1809         if (logmsg &&
1810             !refs_read_ref_full(&refs->base, target,
1811                                 RESOLVE_REF_READING, &new_oid, NULL) &&
1812             files_log_ref_write(refs, refname, &lock->old_oid,
1813                                 &new_oid, logmsg, 0, &err)) {
1814                 error("%s", err.buf);
1815                 strbuf_release(&err);
1816         }
1817 }
1818
1819 static int create_symref_locked(struct files_ref_store *refs,
1820                                 struct ref_lock *lock, const char *refname,
1821                                 const char *target, const char *logmsg)
1822 {
1823         if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1824                 update_symref_reflog(refs, lock, refname, target, logmsg);
1825                 return 0;
1826         }
1827
1828         if (!fdopen_lock_file(&lock->lk, "w"))
1829                 return error("unable to fdopen %s: %s",
1830                              lock->lk.tempfile->filename.buf, strerror(errno));
1831
1832         update_symref_reflog(refs, lock, refname, target, logmsg);
1833
1834         /* no error check; commit_ref will check ferror */
1835         fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1836         if (commit_ref(lock) < 0)
1837                 return error("unable to write symref for %s: %s", refname,
1838                              strerror(errno));
1839         return 0;
1840 }
1841
1842 static int files_create_symref(struct ref_store *ref_store,
1843                                const char *refname, const char *target,
1844                                const char *logmsg)
1845 {
1846         struct files_ref_store *refs =
1847                 files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1848         struct strbuf err = STRBUF_INIT;
1849         struct ref_lock *lock;
1850         int ret;
1851
1852         lock = lock_ref_oid_basic(refs, refname, NULL,
1853                                   NULL, NULL, REF_NO_DEREF, NULL,
1854                                   &err);
1855         if (!lock) {
1856                 error("%s", err.buf);
1857                 strbuf_release(&err);
1858                 return -1;
1859         }
1860
1861         ret = create_symref_locked(refs, lock, refname, target, logmsg);
1862         unlock_ref(lock);
1863         return ret;
1864 }
1865
1866 static int files_reflog_exists(struct ref_store *ref_store,
1867                                const char *refname)
1868 {
1869         struct files_ref_store *refs =
1870                 files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1871         struct strbuf sb = STRBUF_INIT;
1872         struct stat st;
1873         int ret;
1874
1875         files_reflog_path(refs, &sb, refname);
1876         ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1877         strbuf_release(&sb);
1878         return ret;
1879 }
1880
1881 static int files_delete_reflog(struct ref_store *ref_store,
1882                                const char *refname)
1883 {
1884         struct files_ref_store *refs =
1885                 files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1886         struct strbuf sb = STRBUF_INIT;
1887         int ret;
1888
1889         files_reflog_path(refs, &sb, refname);
1890         ret = remove_path(sb.buf);
1891         strbuf_release(&sb);
1892         return ret;
1893 }
1894
1895 static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1896 {
1897         struct object_id ooid, noid;
1898         char *email_end, *message;
1899         timestamp_t timestamp;
1900         int tz;
1901         const char *p = sb->buf;
1902
1903         /* old SP new SP name <email> SP time TAB msg LF */
1904         if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1905             parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1906             parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1907             !(email_end = strchr(p, '>')) ||
1908             email_end[1] != ' ' ||
1909             !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1910             !message || message[0] != ' ' ||
1911             (message[1] != '+' && message[1] != '-') ||
1912             !isdigit(message[2]) || !isdigit(message[3]) ||
1913             !isdigit(message[4]) || !isdigit(message[5]))
1914                 return 0; /* corrupt? */
1915         email_end[1] = '\0';
1916         tz = strtol(message + 1, NULL, 10);
1917         if (message[6] != '\t')
1918                 message += 6;
1919         else
1920                 message += 7;
1921         return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1922 }
1923
1924 static char *find_beginning_of_line(char *bob, char *scan)
1925 {
1926         while (bob < scan && *(--scan) != '\n')
1927                 ; /* keep scanning backwards */
1928         /*
1929          * Return either beginning of the buffer, or LF at the end of
1930          * the previous line.
1931          */
1932         return scan;
1933 }
1934
1935 static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1936                                              const char *refname,
1937                                              each_reflog_ent_fn fn,
1938                                              void *cb_data)
1939 {
1940         struct files_ref_store *refs =
1941                 files_downcast(ref_store, REF_STORE_READ,
1942                                "for_each_reflog_ent_reverse");
1943         struct strbuf sb = STRBUF_INIT;
1944         FILE *logfp;
1945         long pos;
1946         int ret = 0, at_tail = 1;
1947
1948         files_reflog_path(refs, &sb, refname);
1949         logfp = fopen(sb.buf, "r");
1950         strbuf_release(&sb);
1951         if (!logfp)
1952                 return -1;
1953
1954         /* Jump to the end */
1955         if (fseek(logfp, 0, SEEK_END) < 0)
1956                 ret = error("cannot seek back reflog for %s: %s",
1957                             refname, strerror(errno));
1958         pos = ftell(logfp);
1959         while (!ret && 0 < pos) {
1960                 int cnt;
1961                 size_t nread;
1962                 char buf[BUFSIZ];
1963                 char *endp, *scanp;
1964
1965                 /* Fill next block from the end */
1966                 cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1967                 if (fseek(logfp, pos - cnt, SEEK_SET)) {
1968                         ret = error("cannot seek back reflog for %s: %s",
1969                                     refname, strerror(errno));
1970                         break;
1971                 }
1972                 nread = fread(buf, cnt, 1, logfp);
1973                 if (nread != 1) {
1974                         ret = error("cannot read %d bytes from reflog for %s: %s",
1975                                     cnt, refname, strerror(errno));
1976                         break;
1977                 }
1978                 pos -= cnt;
1979
1980                 scanp = endp = buf + cnt;
1981                 if (at_tail && scanp[-1] == '\n')
1982                         /* Looking at the final LF at the end of the file */
1983                         scanp--;
1984                 at_tail = 0;
1985
1986                 while (buf < scanp) {
1987                         /*
1988                          * terminating LF of the previous line, or the beginning
1989                          * of the buffer.
1990                          */
1991                         char *bp;
1992
1993                         bp = find_beginning_of_line(buf, scanp);
1994
1995                         if (*bp == '\n') {
1996                                 /*
1997                                  * The newline is the end of the previous line,
1998                                  * so we know we have complete line starting
1999                                  * at (bp + 1). Prefix it onto any prior data
2000                                  * we collected for the line and process it.
2001                                  */
2002                                 strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
2003                                 scanp = bp;
2004                                 endp = bp + 1;
2005                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2006                                 strbuf_reset(&sb);
2007                                 if (ret)
2008                                         break;
2009                         } else if (!pos) {
2010                                 /*
2011                                  * We are at the start of the buffer, and the
2012                                  * start of the file; there is no previous
2013                                  * line, and we have everything for this one.
2014                                  * Process it, and we can end the loop.
2015                                  */
2016                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
2017                                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2018                                 strbuf_reset(&sb);
2019                                 break;
2020                         }
2021
2022                         if (bp == buf) {
2023                                 /*
2024                                  * We are at the start of the buffer, and there
2025                                  * is more file to read backwards. Which means
2026                                  * we are in the middle of a line. Note that we
2027                                  * may get here even if *bp was a newline; that
2028                                  * just means we are at the exact end of the
2029                                  * previous line, rather than some spot in the
2030                                  * middle.
2031                                  *
2032                                  * Save away what we have to be combined with
2033                                  * the data from the next read.
2034                                  */
2035                                 strbuf_splice(&sb, 0, 0, buf, endp - buf);
2036                                 break;
2037                         }
2038                 }
2039
2040         }
2041         if (!ret && sb.len)
2042                 BUG("reverse reflog parser had leftover data");
2043
2044         fclose(logfp);
2045         strbuf_release(&sb);
2046         return ret;
2047 }
2048
2049 static int files_for_each_reflog_ent(struct ref_store *ref_store,
2050                                      const char *refname,
2051                                      each_reflog_ent_fn fn, void *cb_data)
2052 {
2053         struct files_ref_store *refs =
2054                 files_downcast(ref_store, REF_STORE_READ,
2055                                "for_each_reflog_ent");
2056         FILE *logfp;
2057         struct strbuf sb = STRBUF_INIT;
2058         int ret = 0;
2059
2060         files_reflog_path(refs, &sb, refname);
2061         logfp = fopen(sb.buf, "r");
2062         strbuf_release(&sb);
2063         if (!logfp)
2064                 return -1;
2065
2066         while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2067                 ret = show_one_reflog_ent(&sb, fn, cb_data);
2068         fclose(logfp);
2069         strbuf_release(&sb);
2070         return ret;
2071 }
2072
2073 struct files_reflog_iterator {
2074         struct ref_iterator base;
2075
2076         struct ref_store *ref_store;
2077         struct dir_iterator *dir_iterator;
2078         struct object_id oid;
2079 };
2080
2081 static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2082 {
2083         struct files_reflog_iterator *iter =
2084                 (struct files_reflog_iterator *)ref_iterator;
2085         struct dir_iterator *diter = iter->dir_iterator;
2086         int ok;
2087
2088         while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2089                 int flags;
2090
2091                 if (!S_ISREG(diter->st.st_mode))
2092                         continue;
2093                 if (diter->basename[0] == '.')
2094                         continue;
2095                 if (ends_with(diter->basename, ".lock"))
2096                         continue;
2097
2098                 if (refs_read_ref_full(iter->ref_store,
2099                                        diter->relative_path, 0,
2100                                        &iter->oid, &flags)) {
2101                         error("bad ref for %s", diter->path.buf);
2102                         continue;
2103                 }
2104
2105                 iter->base.refname = diter->relative_path;
2106                 iter->base.oid = &iter->oid;
2107                 iter->base.flags = flags;
2108                 return ITER_OK;
2109         }
2110
2111         iter->dir_iterator = NULL;
2112         if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2113                 ok = ITER_ERROR;
2114         return ok;
2115 }
2116
2117 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2118                                    struct object_id *peeled)
2119 {
2120         BUG("ref_iterator_peel() called for reflog_iterator");
2121 }
2122
2123 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2124 {
2125         struct files_reflog_iterator *iter =
2126                 (struct files_reflog_iterator *)ref_iterator;
2127         int ok = ITER_DONE;
2128
2129         if (iter->dir_iterator)
2130                 ok = dir_iterator_abort(iter->dir_iterator);
2131
2132         base_ref_iterator_free(ref_iterator);
2133         return ok;
2134 }
2135
2136 static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2137         files_reflog_iterator_advance,
2138         files_reflog_iterator_peel,
2139         files_reflog_iterator_abort
2140 };
2141
2142 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2143                                                   const char *gitdir)
2144 {
2145         struct dir_iterator *diter;
2146         struct files_reflog_iterator *iter;
2147         struct ref_iterator *ref_iterator;
2148         struct strbuf sb = STRBUF_INIT;
2149
2150         strbuf_addf(&sb, "%s/logs", gitdir);
2151
2152         diter = dir_iterator_begin(sb.buf, 0);
2153         if (!diter) {
2154                 strbuf_release(&sb);
2155                 return empty_ref_iterator_begin();
2156         }
2157
2158         iter = xcalloc(1, sizeof(*iter));
2159         ref_iterator = &iter->base;
2160
2161         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2162         iter->dir_iterator = diter;
2163         iter->ref_store = ref_store;
2164         strbuf_release(&sb);
2165
2166         return ref_iterator;
2167 }
2168
2169 static enum iterator_selection reflog_iterator_select(
2170         struct ref_iterator *iter_worktree,
2171         struct ref_iterator *iter_common,
2172         void *cb_data)
2173 {
2174         if (iter_worktree) {
2175                 /*
2176                  * We're a bit loose here. We probably should ignore
2177                  * common refs if they are accidentally added as
2178                  * per-worktree refs.
2179                  */
2180                 return ITER_SELECT_0;
2181         } else if (iter_common) {
2182                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2183                         return ITER_SELECT_1;
2184
2185                 /*
2186                  * The main ref store may contain main worktree's
2187                  * per-worktree refs, which should be ignored
2188                  */
2189                 return ITER_SKIP_1;
2190         } else
2191                 return ITER_DONE;
2192 }
2193
2194 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2195 {
2196         struct files_ref_store *refs =
2197                 files_downcast(ref_store, REF_STORE_READ,
2198                                "reflog_iterator_begin");
2199
2200         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2201                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2202         } else {
2203                 return merge_ref_iterator_begin(
2204                         0,
2205                         reflog_iterator_begin(ref_store, refs->gitdir),
2206                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2207                         reflog_iterator_select, refs);
2208         }
2209 }
2210
2211 /*
2212  * If update is a direct update of head_ref (the reference pointed to
2213  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2214  */
2215 static int split_head_update(struct ref_update *update,
2216                              struct ref_transaction *transaction,
2217                              const char *head_ref,
2218                              struct string_list *affected_refnames,
2219                              struct strbuf *err)
2220 {
2221         struct string_list_item *item;
2222         struct ref_update *new_update;
2223
2224         if ((update->flags & REF_LOG_ONLY) ||
2225             (update->flags & REF_IS_PRUNING) ||
2226             (update->flags & REF_UPDATE_VIA_HEAD))
2227                 return 0;
2228
2229         if (strcmp(update->refname, head_ref))
2230                 return 0;
2231
2232         /*
2233          * First make sure that HEAD is not already in the
2234          * transaction. This check is O(lg N) in the transaction
2235          * size, but it happens at most once per transaction.
2236          */
2237         if (string_list_has_string(affected_refnames, "HEAD")) {
2238                 /* An entry already existed */
2239                 strbuf_addf(err,
2240                             "multiple updates for 'HEAD' (including one "
2241                             "via its referent '%s') are not allowed",
2242                             update->refname);
2243                 return TRANSACTION_NAME_CONFLICT;
2244         }
2245
2246         new_update = ref_transaction_add_update(
2247                         transaction, "HEAD",
2248                         update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2249                         &update->new_oid, &update->old_oid,
2250                         update->msg);
2251
2252         /*
2253          * Add "HEAD". This insertion is O(N) in the transaction
2254          * size, but it happens at most once per transaction.
2255          * Add new_update->refname instead of a literal "HEAD".
2256          */
2257         if (strcmp(new_update->refname, "HEAD"))
2258                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2259         item = string_list_insert(affected_refnames, new_update->refname);
2260         item->util = new_update;
2261
2262         return 0;
2263 }
2264
2265 /*
2266  * update is for a symref that points at referent and doesn't have
2267  * REF_NO_DEREF set. Split it into two updates:
2268  * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2269  * - A new, separate update for the referent reference
2270  * Note that the new update will itself be subject to splitting when
2271  * the iteration gets to it.
2272  */
2273 static int split_symref_update(struct ref_update *update,
2274                                const char *referent,
2275                                struct ref_transaction *transaction,
2276                                struct string_list *affected_refnames,
2277                                struct strbuf *err)
2278 {
2279         struct string_list_item *item;
2280         struct ref_update *new_update;
2281         unsigned int new_flags;
2282
2283         /*
2284          * First make sure that referent is not already in the
2285          * transaction. This check is O(lg N) in the transaction
2286          * size, but it happens at most once per symref in a
2287          * transaction.
2288          */
2289         if (string_list_has_string(affected_refnames, referent)) {
2290                 /* An entry already exists */
2291                 strbuf_addf(err,
2292                             "multiple updates for '%s' (including one "
2293                             "via symref '%s') are not allowed",
2294                             referent, update->refname);
2295                 return TRANSACTION_NAME_CONFLICT;
2296         }
2297
2298         new_flags = update->flags;
2299         if (!strcmp(update->refname, "HEAD")) {
2300                 /*
2301                  * Record that the new update came via HEAD, so that
2302                  * when we process it, split_head_update() doesn't try
2303                  * to add another reflog update for HEAD. Note that
2304                  * this bit will be propagated if the new_update
2305                  * itself needs to be split.
2306                  */
2307                 new_flags |= REF_UPDATE_VIA_HEAD;
2308         }
2309
2310         new_update = ref_transaction_add_update(
2311                         transaction, referent, new_flags,
2312                         &update->new_oid, &update->old_oid,
2313                         update->msg);
2314
2315         new_update->parent_update = update;
2316
2317         /*
2318          * Change the symbolic ref update to log only. Also, it
2319          * doesn't need to check its old OID value, as that will be
2320          * done when new_update is processed.
2321          */
2322         update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2323         update->flags &= ~REF_HAVE_OLD;
2324
2325         /*
2326          * Add the referent. This insertion is O(N) in the transaction
2327          * size, but it happens at most once per symref in a
2328          * transaction. Make sure to add new_update->refname, which will
2329          * be valid as long as affected_refnames is in use, and NOT
2330          * referent, which might soon be freed by our caller.
2331          */
2332         item = string_list_insert(affected_refnames, new_update->refname);
2333         if (item->util)
2334                 BUG("%s unexpectedly found in affected_refnames",
2335                     new_update->refname);
2336         item->util = new_update;
2337
2338         return 0;
2339 }
2340
2341 /*
2342  * Return the refname under which update was originally requested.
2343  */
2344 static const char *original_update_refname(struct ref_update *update)
2345 {
2346         while (update->parent_update)
2347                 update = update->parent_update;
2348
2349         return update->refname;
2350 }
2351
2352 /*
2353  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2354  * are consistent with oid, which is the reference's current value. If
2355  * everything is OK, return 0; otherwise, write an error message to
2356  * err and return -1.
2357  */
2358 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2359                          struct strbuf *err)
2360 {
2361         if (!(update->flags & REF_HAVE_OLD) ||
2362                    oideq(oid, &update->old_oid))
2363                 return 0;
2364
2365         if (is_null_oid(&update->old_oid))
2366                 strbuf_addf(err, "cannot lock ref '%s': "
2367                             "reference already exists",
2368                             original_update_refname(update));
2369         else if (is_null_oid(oid))
2370                 strbuf_addf(err, "cannot lock ref '%s': "
2371                             "reference is missing but expected %s",
2372                             original_update_refname(update),
2373                             oid_to_hex(&update->old_oid));
2374         else
2375                 strbuf_addf(err, "cannot lock ref '%s': "
2376                             "is at %s but expected %s",
2377                             original_update_refname(update),
2378                             oid_to_hex(oid),
2379                             oid_to_hex(&update->old_oid));
2380
2381         return -1;
2382 }
2383
2384 /*
2385  * Prepare for carrying out update:
2386  * - Lock the reference referred to by update.
2387  * - Read the reference under lock.
2388  * - Check that its old OID value (if specified) is correct, and in
2389  *   any case record it in update->lock->old_oid for later use when
2390  *   writing the reflog.
2391  * - If it is a symref update without REF_NO_DEREF, split it up into a
2392  *   REF_LOG_ONLY update of the symref and add a separate update for
2393  *   the referent to transaction.
2394  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2395  *   update of HEAD.
2396  */
2397 static int lock_ref_for_update(struct files_ref_store *refs,
2398                                struct ref_update *update,
2399                                struct ref_transaction *transaction,
2400                                const char *head_ref,
2401                                struct string_list *affected_refnames,
2402                                struct strbuf *err)
2403 {
2404         struct strbuf referent = STRBUF_INIT;
2405         int mustexist = (update->flags & REF_HAVE_OLD) &&
2406                 !is_null_oid(&update->old_oid);
2407         int ret = 0;
2408         struct ref_lock *lock;
2409
2410         files_assert_main_repository(refs, "lock_ref_for_update");
2411
2412         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2413                 update->flags |= REF_DELETING;
2414
2415         if (head_ref) {
2416                 ret = split_head_update(update, transaction, head_ref,
2417                                         affected_refnames, err);
2418                 if (ret)
2419                         goto out;
2420         }
2421
2422         ret = lock_raw_ref(refs, update->refname, mustexist,
2423                            affected_refnames, NULL,
2424                            &lock, &referent,
2425                            &update->type, err);
2426         if (ret) {
2427                 char *reason;
2428
2429                 reason = strbuf_detach(err, NULL);
2430                 strbuf_addf(err, "cannot lock ref '%s': %s",
2431                             original_update_refname(update), reason);
2432                 free(reason);
2433                 goto out;
2434         }
2435
2436         update->backend_data = lock;
2437
2438         if (update->type & REF_ISSYMREF) {
2439                 if (update->flags & REF_NO_DEREF) {
2440                         /*
2441                          * We won't be reading the referent as part of
2442                          * the transaction, so we have to read it here
2443                          * to record and possibly check old_oid:
2444                          */
2445                         if (refs_read_ref_full(&refs->base,
2446                                                referent.buf, 0,
2447                                                &lock->old_oid, NULL)) {
2448                                 if (update->flags & REF_HAVE_OLD) {
2449                                         strbuf_addf(err, "cannot lock ref '%s': "
2450                                                     "error reading reference",
2451                                                     original_update_refname(update));
2452                                         ret = TRANSACTION_GENERIC_ERROR;
2453                                         goto out;
2454                                 }
2455                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2456                                 ret = TRANSACTION_GENERIC_ERROR;
2457                                 goto out;
2458                         }
2459                 } else {
2460                         /*
2461                          * Create a new update for the reference this
2462                          * symref is pointing at. Also, we will record
2463                          * and verify old_oid for this update as part
2464                          * of processing the split-off update, so we
2465                          * don't have to do it here.
2466                          */
2467                         ret = split_symref_update(update,
2468                                                   referent.buf, transaction,
2469                                                   affected_refnames, err);
2470                         if (ret)
2471                                 goto out;
2472                 }
2473         } else {
2474                 struct ref_update *parent_update;
2475
2476                 if (check_old_oid(update, &lock->old_oid, err)) {
2477                         ret = TRANSACTION_GENERIC_ERROR;
2478                         goto out;
2479                 }
2480
2481                 /*
2482                  * If this update is happening indirectly because of a
2483                  * symref update, record the old OID in the parent
2484                  * update:
2485                  */
2486                 for (parent_update = update->parent_update;
2487                      parent_update;
2488                      parent_update = parent_update->parent_update) {
2489                         struct ref_lock *parent_lock = parent_update->backend_data;
2490                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2491                 }
2492         }
2493
2494         if ((update->flags & REF_HAVE_NEW) &&
2495             !(update->flags & REF_DELETING) &&
2496             !(update->flags & REF_LOG_ONLY)) {
2497                 if (!(update->type & REF_ISSYMREF) &&
2498                     oideq(&lock->old_oid, &update->new_oid)) {
2499                         /*
2500                          * The reference already has the desired
2501                          * value, so we don't need to write it.
2502                          */
2503                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2504                                                  err)) {
2505                         char *write_err = strbuf_detach(err, NULL);
2506
2507                         /*
2508                          * The lock was freed upon failure of
2509                          * write_ref_to_lockfile():
2510                          */
2511                         update->backend_data = NULL;
2512                         strbuf_addf(err,
2513                                     "cannot update ref '%s': %s",
2514                                     update->refname, write_err);
2515                         free(write_err);
2516                         ret = TRANSACTION_GENERIC_ERROR;
2517                         goto out;
2518                 } else {
2519                         update->flags |= REF_NEEDS_COMMIT;
2520                 }
2521         }
2522         if (!(update->flags & REF_NEEDS_COMMIT)) {
2523                 /*
2524                  * We didn't call write_ref_to_lockfile(), so
2525                  * the lockfile is still open. Close it to
2526                  * free up the file descriptor:
2527                  */
2528                 if (close_ref_gently(lock)) {
2529                         strbuf_addf(err, "couldn't close '%s.lock'",
2530                                     update->refname);
2531                         ret = TRANSACTION_GENERIC_ERROR;
2532                         goto out;
2533                 }
2534         }
2535
2536 out:
2537         strbuf_release(&referent);
2538         return ret;
2539 }
2540
2541 struct files_transaction_backend_data {
2542         struct ref_transaction *packed_transaction;
2543         int packed_refs_locked;
2544 };
2545
2546 /*
2547  * Unlock any references in `transaction` that are still locked, and
2548  * mark the transaction closed.
2549  */
2550 static void files_transaction_cleanup(struct files_ref_store *refs,
2551                                       struct ref_transaction *transaction)
2552 {
2553         size_t i;
2554         struct files_transaction_backend_data *backend_data =
2555                 transaction->backend_data;
2556         struct strbuf err = STRBUF_INIT;
2557
2558         for (i = 0; i < transaction->nr; i++) {
2559                 struct ref_update *update = transaction->updates[i];
2560                 struct ref_lock *lock = update->backend_data;
2561
2562                 if (lock) {
2563                         unlock_ref(lock);
2564                         update->backend_data = NULL;
2565                 }
2566         }
2567
2568         if (backend_data) {
2569                 if (backend_data->packed_transaction &&
2570                     ref_transaction_abort(backend_data->packed_transaction, &err)) {
2571                         error("error aborting transaction: %s", err.buf);
2572                         strbuf_release(&err);
2573                 }
2574
2575                 if (backend_data->packed_refs_locked)
2576                         packed_refs_unlock(refs->packed_ref_store);
2577
2578                 free(backend_data);
2579         }
2580
2581         transaction->state = REF_TRANSACTION_CLOSED;
2582 }
2583
2584 static int files_transaction_prepare(struct ref_store *ref_store,
2585                                      struct ref_transaction *transaction,
2586                                      struct strbuf *err)
2587 {
2588         struct files_ref_store *refs =
2589                 files_downcast(ref_store, REF_STORE_WRITE,
2590                                "ref_transaction_prepare");
2591         size_t i;
2592         int ret = 0;
2593         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2594         char *head_ref = NULL;
2595         int head_type;
2596         struct files_transaction_backend_data *backend_data;
2597         struct ref_transaction *packed_transaction = NULL;
2598
2599         assert(err);
2600
2601         if (!transaction->nr)
2602                 goto cleanup;
2603
2604         backend_data = xcalloc(1, sizeof(*backend_data));
2605         transaction->backend_data = backend_data;
2606
2607         /*
2608          * Fail if a refname appears more than once in the
2609          * transaction. (If we end up splitting up any updates using
2610          * split_symref_update() or split_head_update(), those
2611          * functions will check that the new updates don't have the
2612          * same refname as any existing ones.) Also fail if any of the
2613          * updates use REF_IS_PRUNING without REF_NO_DEREF.
2614          */
2615         for (i = 0; i < transaction->nr; i++) {
2616                 struct ref_update *update = transaction->updates[i];
2617                 struct string_list_item *item =
2618                         string_list_append(&affected_refnames, update->refname);
2619
2620                 if ((update->flags & REF_IS_PRUNING) &&
2621                     !(update->flags & REF_NO_DEREF))
2622                         BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2623
2624                 /*
2625                  * We store a pointer to update in item->util, but at
2626                  * the moment we never use the value of this field
2627                  * except to check whether it is non-NULL.
2628                  */
2629                 item->util = update;
2630         }
2631         string_list_sort(&affected_refnames);
2632         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2633                 ret = TRANSACTION_GENERIC_ERROR;
2634                 goto cleanup;
2635         }
2636
2637         /*
2638          * Special hack: If a branch is updated directly and HEAD
2639          * points to it (may happen on the remote side of a push
2640          * for example) then logically the HEAD reflog should be
2641          * updated too.
2642          *
2643          * A generic solution would require reverse symref lookups,
2644          * but finding all symrefs pointing to a given branch would be
2645          * rather costly for this rare event (the direct update of a
2646          * branch) to be worth it. So let's cheat and check with HEAD
2647          * only, which should cover 99% of all usage scenarios (even
2648          * 100% of the default ones).
2649          *
2650          * So if HEAD is a symbolic reference, then record the name of
2651          * the reference that it points to. If we see an update of
2652          * head_ref within the transaction, then split_head_update()
2653          * arranges for the reflog of HEAD to be updated, too.
2654          */
2655         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2656                                        RESOLVE_REF_NO_RECURSE,
2657                                        NULL, &head_type);
2658
2659         if (head_ref && !(head_type & REF_ISSYMREF)) {
2660                 FREE_AND_NULL(head_ref);
2661         }
2662
2663         /*
2664          * Acquire all locks, verify old values if provided, check
2665          * that new values are valid, and write new values to the
2666          * lockfiles, ready to be activated. Only keep one lockfile
2667          * open at a time to avoid running out of file descriptors.
2668          * Note that lock_ref_for_update() might append more updates
2669          * to the transaction.
2670          */
2671         for (i = 0; i < transaction->nr; i++) {
2672                 struct ref_update *update = transaction->updates[i];
2673
2674                 ret = lock_ref_for_update(refs, update, transaction,
2675                                           head_ref, &affected_refnames, err);
2676                 if (ret)
2677                         goto cleanup;
2678
2679                 if (update->flags & REF_DELETING &&
2680                     !(update->flags & REF_LOG_ONLY) &&
2681                     !(update->flags & REF_IS_PRUNING)) {
2682                         /*
2683                          * This reference has to be deleted from
2684                          * packed-refs if it exists there.
2685                          */
2686                         if (!packed_transaction) {
2687                                 packed_transaction = ref_store_transaction_begin(
2688                                                 refs->packed_ref_store, err);
2689                                 if (!packed_transaction) {
2690                                         ret = TRANSACTION_GENERIC_ERROR;
2691                                         goto cleanup;
2692                                 }
2693
2694                                 backend_data->packed_transaction =
2695                                         packed_transaction;
2696                         }
2697
2698                         ref_transaction_add_update(
2699                                         packed_transaction, update->refname,
2700                                         REF_HAVE_NEW | REF_NO_DEREF,
2701                                         &update->new_oid, NULL,
2702                                         NULL);
2703                 }
2704         }
2705
2706         if (packed_transaction) {
2707                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2708                         ret = TRANSACTION_GENERIC_ERROR;
2709                         goto cleanup;
2710                 }
2711                 backend_data->packed_refs_locked = 1;
2712
2713                 if (is_packed_transaction_needed(refs->packed_ref_store,
2714                                                  packed_transaction)) {
2715                         ret = ref_transaction_prepare(packed_transaction, err);
2716                         /*
2717                          * A failure during the prepare step will abort
2718                          * itself, but not free. Do that now, and disconnect
2719                          * from the files_transaction so it does not try to
2720                          * abort us when we hit the cleanup code below.
2721                          */
2722                         if (ret) {
2723                                 ref_transaction_free(packed_transaction);
2724                                 backend_data->packed_transaction = NULL;
2725                         }
2726                 } else {
2727                         /*
2728                          * We can skip rewriting the `packed-refs`
2729                          * file. But we do need to leave it locked, so
2730                          * that somebody else doesn't pack a reference
2731                          * that we are trying to delete.
2732                          *
2733                          * We need to disconnect our transaction from
2734                          * backend_data, since the abort (whether successful or
2735                          * not) will free it.
2736                          */
2737                         backend_data->packed_transaction = NULL;
2738                         if (ref_transaction_abort(packed_transaction, err)) {
2739                                 ret = TRANSACTION_GENERIC_ERROR;
2740                                 goto cleanup;
2741                         }
2742                 }
2743         }
2744
2745 cleanup:
2746         free(head_ref);
2747         string_list_clear(&affected_refnames, 0);
2748
2749         if (ret)
2750                 files_transaction_cleanup(refs, transaction);
2751         else
2752                 transaction->state = REF_TRANSACTION_PREPARED;
2753
2754         return ret;
2755 }
2756
2757 static int files_transaction_finish(struct ref_store *ref_store,
2758                                     struct ref_transaction *transaction,
2759                                     struct strbuf *err)
2760 {
2761         struct files_ref_store *refs =
2762                 files_downcast(ref_store, 0, "ref_transaction_finish");
2763         size_t i;
2764         int ret = 0;
2765         struct strbuf sb = STRBUF_INIT;
2766         struct files_transaction_backend_data *backend_data;
2767         struct ref_transaction *packed_transaction;
2768
2769
2770         assert(err);
2771
2772         if (!transaction->nr) {
2773                 transaction->state = REF_TRANSACTION_CLOSED;
2774                 return 0;
2775         }
2776
2777         backend_data = transaction->backend_data;
2778         packed_transaction = backend_data->packed_transaction;
2779
2780         /* Perform updates first so live commits remain referenced */
2781         for (i = 0; i < transaction->nr; i++) {
2782                 struct ref_update *update = transaction->updates[i];
2783                 struct ref_lock *lock = update->backend_data;
2784
2785                 if (update->flags & REF_NEEDS_COMMIT ||
2786                     update->flags & REF_LOG_ONLY) {
2787                         if (files_log_ref_write(refs,
2788                                                 lock->ref_name,
2789                                                 &lock->old_oid,
2790                                                 &update->new_oid,
2791                                                 update->msg, update->flags,
2792                                                 err)) {
2793                                 char *old_msg = strbuf_detach(err, NULL);
2794
2795                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2796                                             lock->ref_name, old_msg);
2797                                 free(old_msg);
2798                                 unlock_ref(lock);
2799                                 update->backend_data = NULL;
2800                                 ret = TRANSACTION_GENERIC_ERROR;
2801                                 goto cleanup;
2802                         }
2803                 }
2804                 if (update->flags & REF_NEEDS_COMMIT) {
2805                         clear_loose_ref_cache(refs);
2806                         if (commit_ref(lock)) {
2807                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2808                                 unlock_ref(lock);
2809                                 update->backend_data = NULL;
2810                                 ret = TRANSACTION_GENERIC_ERROR;
2811                                 goto cleanup;
2812                         }
2813                 }
2814         }
2815
2816         /*
2817          * Now that updates are safely completed, we can perform
2818          * deletes. First delete the reflogs of any references that
2819          * will be deleted, since (in the unexpected event of an
2820          * error) leaving a reference without a reflog is less bad
2821          * than leaving a reflog without a reference (the latter is a
2822          * mildly invalid repository state):
2823          */
2824         for (i = 0; i < transaction->nr; i++) {
2825                 struct ref_update *update = transaction->updates[i];
2826                 if (update->flags & REF_DELETING &&
2827                     !(update->flags & REF_LOG_ONLY) &&
2828                     !(update->flags & REF_IS_PRUNING)) {
2829                         strbuf_reset(&sb);
2830                         files_reflog_path(refs, &sb, update->refname);
2831                         if (!unlink_or_warn(sb.buf))
2832                                 try_remove_empty_parents(refs, update->refname,
2833                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2834                 }
2835         }
2836
2837         /*
2838          * Perform deletes now that updates are safely completed.
2839          *
2840          * First delete any packed versions of the references, while
2841          * retaining the packed-refs lock:
2842          */
2843         if (packed_transaction) {
2844                 ret = ref_transaction_commit(packed_transaction, err);
2845                 ref_transaction_free(packed_transaction);
2846                 packed_transaction = NULL;
2847                 backend_data->packed_transaction = NULL;
2848                 if (ret)
2849                         goto cleanup;
2850         }
2851
2852         /* Now delete the loose versions of the references: */
2853         for (i = 0; i < transaction->nr; i++) {
2854                 struct ref_update *update = transaction->updates[i];
2855                 struct ref_lock *lock = update->backend_data;
2856
2857                 if (update->flags & REF_DELETING &&
2858                     !(update->flags & REF_LOG_ONLY)) {
2859                         if (!(update->type & REF_ISPACKED) ||
2860                             update->type & REF_ISSYMREF) {
2861                                 /* It is a loose reference. */
2862                                 strbuf_reset(&sb);
2863                                 files_ref_path(refs, &sb, lock->ref_name);
2864                                 if (unlink_or_msg(sb.buf, err)) {
2865                                         ret = TRANSACTION_GENERIC_ERROR;
2866                                         goto cleanup;
2867                                 }
2868                                 update->flags |= REF_DELETED_LOOSE;
2869                         }
2870                 }
2871         }
2872
2873         clear_loose_ref_cache(refs);
2874
2875 cleanup:
2876         files_transaction_cleanup(refs, transaction);
2877
2878         for (i = 0; i < transaction->nr; i++) {
2879                 struct ref_update *update = transaction->updates[i];
2880
2881                 if (update->flags & REF_DELETED_LOOSE) {
2882                         /*
2883                          * The loose reference was deleted. Delete any
2884                          * empty parent directories. (Note that this
2885                          * can only work because we have already
2886                          * removed the lockfile.)
2887                          */
2888                         try_remove_empty_parents(refs, update->refname,
2889                                                  REMOVE_EMPTY_PARENTS_REF);
2890                 }
2891         }
2892
2893         strbuf_release(&sb);
2894         return ret;
2895 }
2896
2897 static int files_transaction_abort(struct ref_store *ref_store,
2898                                    struct ref_transaction *transaction,
2899                                    struct strbuf *err)
2900 {
2901         struct files_ref_store *refs =
2902                 files_downcast(ref_store, 0, "ref_transaction_abort");
2903
2904         files_transaction_cleanup(refs, transaction);
2905         return 0;
2906 }
2907
2908 static int ref_present(const char *refname,
2909                        const struct object_id *oid, int flags, void *cb_data)
2910 {
2911         struct string_list *affected_refnames = cb_data;
2912
2913         return string_list_has_string(affected_refnames, refname);
2914 }
2915
2916 static int files_initial_transaction_commit(struct ref_store *ref_store,
2917                                             struct ref_transaction *transaction,
2918                                             struct strbuf *err)
2919 {
2920         struct files_ref_store *refs =
2921                 files_downcast(ref_store, REF_STORE_WRITE,
2922                                "initial_ref_transaction_commit");
2923         size_t i;
2924         int ret = 0;
2925         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2926         struct ref_transaction *packed_transaction = NULL;
2927
2928         assert(err);
2929
2930         if (transaction->state != REF_TRANSACTION_OPEN)
2931                 BUG("commit called for transaction that is not open");
2932
2933         /* Fail if a refname appears more than once in the transaction: */
2934         for (i = 0; i < transaction->nr; i++)
2935                 string_list_append(&affected_refnames,
2936                                    transaction->updates[i]->refname);
2937         string_list_sort(&affected_refnames);
2938         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2939                 ret = TRANSACTION_GENERIC_ERROR;
2940                 goto cleanup;
2941         }
2942
2943         /*
2944          * It's really undefined to call this function in an active
2945          * repository or when there are existing references: we are
2946          * only locking and changing packed-refs, so (1) any
2947          * simultaneous processes might try to change a reference at
2948          * the same time we do, and (2) any existing loose versions of
2949          * the references that we are setting would have precedence
2950          * over our values. But some remote helpers create the remote
2951          * "HEAD" and "master" branches before calling this function,
2952          * so here we really only check that none of the references
2953          * that we are creating already exists.
2954          */
2955         if (refs_for_each_rawref(&refs->base, ref_present,
2956                                  &affected_refnames))
2957                 BUG("initial ref transaction called with existing refs");
2958
2959         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2960         if (!packed_transaction) {
2961                 ret = TRANSACTION_GENERIC_ERROR;
2962                 goto cleanup;
2963         }
2964
2965         for (i = 0; i < transaction->nr; i++) {
2966                 struct ref_update *update = transaction->updates[i];
2967
2968                 if ((update->flags & REF_HAVE_OLD) &&
2969                     !is_null_oid(&update->old_oid))
2970                         BUG("initial ref transaction with old_sha1 set");
2971                 if (refs_verify_refname_available(&refs->base, update->refname,
2972                                                   &affected_refnames, NULL,
2973                                                   err)) {
2974                         ret = TRANSACTION_NAME_CONFLICT;
2975                         goto cleanup;
2976                 }
2977
2978                 /*
2979                  * Add a reference creation for this reference to the
2980                  * packed-refs transaction:
2981                  */
2982                 ref_transaction_add_update(packed_transaction, update->refname,
2983                                            update->flags & ~REF_HAVE_OLD,
2984                                            &update->new_oid, &update->old_oid,
2985                                            NULL);
2986         }
2987
2988         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2989                 ret = TRANSACTION_GENERIC_ERROR;
2990                 goto cleanup;
2991         }
2992
2993         if (initial_ref_transaction_commit(packed_transaction, err)) {
2994                 ret = TRANSACTION_GENERIC_ERROR;
2995         }
2996
2997         packed_refs_unlock(refs->packed_ref_store);
2998 cleanup:
2999         if (packed_transaction)
3000                 ref_transaction_free(packed_transaction);
3001         transaction->state = REF_TRANSACTION_CLOSED;
3002         string_list_clear(&affected_refnames, 0);
3003         return ret;
3004 }
3005
3006 struct expire_reflog_cb {
3007         unsigned int flags;
3008         reflog_expiry_should_prune_fn *should_prune_fn;
3009         void *policy_cb;
3010         FILE *newlog;
3011         struct object_id last_kept_oid;
3012 };
3013
3014 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
3015                              const char *email, timestamp_t timestamp, int tz,
3016                              const char *message, void *cb_data)
3017 {
3018         struct expire_reflog_cb *cb = cb_data;
3019         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
3020
3021         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
3022                 ooid = &cb->last_kept_oid;
3023
3024         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
3025                                    message, policy_cb)) {
3026                 if (!cb->newlog)
3027                         printf("would prune %s", message);
3028                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3029                         printf("prune %s", message);
3030         } else {
3031                 if (cb->newlog) {
3032                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
3033                                 oid_to_hex(ooid), oid_to_hex(noid),
3034                                 email, timestamp, tz, message);
3035                         oidcpy(&cb->last_kept_oid, noid);
3036                 }
3037                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3038                         printf("keep %s", message);
3039         }
3040         return 0;
3041 }
3042
3043 static int files_reflog_expire(struct ref_store *ref_store,
3044                                const char *refname, const struct object_id *oid,
3045                                unsigned int flags,
3046                                reflog_expiry_prepare_fn prepare_fn,
3047                                reflog_expiry_should_prune_fn should_prune_fn,
3048                                reflog_expiry_cleanup_fn cleanup_fn,
3049                                void *policy_cb_data)
3050 {
3051         struct files_ref_store *refs =
3052                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
3053         struct lock_file reflog_lock = LOCK_INIT;
3054         struct expire_reflog_cb cb;
3055         struct ref_lock *lock;
3056         struct strbuf log_file_sb = STRBUF_INIT;
3057         char *log_file;
3058         int status = 0;
3059         int type;
3060         struct strbuf err = STRBUF_INIT;
3061
3062         memset(&cb, 0, sizeof(cb));
3063         cb.flags = flags;
3064         cb.policy_cb = policy_cb_data;
3065         cb.should_prune_fn = should_prune_fn;
3066
3067         /*
3068          * The reflog file is locked by holding the lock on the
3069          * reference itself, plus we might need to update the
3070          * reference if --updateref was specified:
3071          */
3072         lock = lock_ref_oid_basic(refs, refname, oid,
3073                                   NULL, NULL, REF_NO_DEREF,
3074                                   &type, &err);
3075         if (!lock) {
3076                 error("cannot lock ref '%s': %s", refname, err.buf);
3077                 strbuf_release(&err);
3078                 return -1;
3079         }
3080         if (!refs_reflog_exists(ref_store, refname)) {
3081                 unlock_ref(lock);
3082                 return 0;
3083         }
3084
3085         files_reflog_path(refs, &log_file_sb, refname);
3086         log_file = strbuf_detach(&log_file_sb, NULL);
3087         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3088                 /*
3089                  * Even though holding $GIT_DIR/logs/$reflog.lock has
3090                  * no locking implications, we use the lock_file
3091                  * machinery here anyway because it does a lot of the
3092                  * work we need, including cleaning up if the program
3093                  * exits unexpectedly.
3094                  */
3095                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3096                         struct strbuf err = STRBUF_INIT;
3097                         unable_to_lock_message(log_file, errno, &err);
3098                         error("%s", err.buf);
3099                         strbuf_release(&err);
3100                         goto failure;
3101                 }
3102                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3103                 if (!cb.newlog) {
3104                         error("cannot fdopen %s (%s)",
3105                               get_lock_file_path(&reflog_lock), strerror(errno));
3106                         goto failure;
3107                 }
3108         }
3109
3110         (*prepare_fn)(refname, oid, cb.policy_cb);
3111         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3112         (*cleanup_fn)(cb.policy_cb);
3113
3114         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3115                 /*
3116                  * It doesn't make sense to adjust a reference pointed
3117                  * to by a symbolic ref based on expiring entries in
3118                  * the symbolic reference's reflog. Nor can we update
3119                  * a reference if there are no remaining reflog
3120                  * entries.
3121                  */
3122                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3123                         !(type & REF_ISSYMREF) &&
3124                         !is_null_oid(&cb.last_kept_oid);
3125
3126                 if (close_lock_file_gently(&reflog_lock)) {
3127                         status |= error("couldn't write %s: %s", log_file,
3128                                         strerror(errno));
3129                         rollback_lock_file(&reflog_lock);
3130                 } else if (update &&
3131                            (write_in_full(get_lock_file_fd(&lock->lk),
3132                                 oid_to_hex(&cb.last_kept_oid), the_hash_algo->hexsz) < 0 ||
3133                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3134                             close_ref_gently(lock) < 0)) {
3135                         status |= error("couldn't write %s",
3136                                         get_lock_file_path(&lock->lk));
3137                         rollback_lock_file(&reflog_lock);
3138                 } else if (commit_lock_file(&reflog_lock)) {
3139                         status |= error("unable to write reflog '%s' (%s)",
3140                                         log_file, strerror(errno));
3141                 } else if (update && commit_ref(lock)) {
3142                         status |= error("couldn't set %s", lock->ref_name);
3143                 }
3144         }
3145         free(log_file);
3146         unlock_ref(lock);
3147         return status;
3148
3149  failure:
3150         rollback_lock_file(&reflog_lock);
3151         free(log_file);
3152         unlock_ref(lock);
3153         return -1;
3154 }
3155
3156 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3157 {
3158         struct files_ref_store *refs =
3159                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3160         struct strbuf sb = STRBUF_INIT;
3161
3162         /*
3163          * Create .git/refs/{heads,tags}
3164          */
3165         files_ref_path(refs, &sb, "refs/heads");
3166         safe_create_dir(sb.buf, 1);
3167
3168         strbuf_reset(&sb);
3169         files_ref_path(refs, &sb, "refs/tags");
3170         safe_create_dir(sb.buf, 1);
3171
3172         strbuf_release(&sb);
3173         return 0;
3174 }
3175
3176 struct ref_storage_be refs_be_files = {
3177         NULL,
3178         "files",
3179         files_ref_store_create,
3180         files_init_db,
3181         files_transaction_prepare,
3182         files_transaction_finish,
3183         files_transaction_abort,
3184         files_initial_transaction_commit,
3185
3186         files_pack_refs,
3187         files_create_symref,
3188         files_delete_refs,
3189         files_rename_ref,
3190         files_copy_ref,
3191
3192         files_ref_iterator_begin,
3193         files_read_raw_ref,
3194
3195         files_reflog_iterator_begin,
3196         files_for_each_reflog_ent,
3197         files_for_each_reflog_ent_reverse,
3198         files_reflog_exists,
3199         files_create_reflog,
3200         files_delete_reflog,
3201         files_reflog_expire
3202 };