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

   1 #include "../cache.h"
   2 #include "../config.h"
   3 #include "../refs.h"
   4 #include "refs-internal.h"
   5 #include "ref-cache.h"
   6 #include "packed-backend.h"
   7 #include "../iterator.h"
   8 #include "../dir-iterator.h"
   9 #include "../lockfile.h"
  10 #include "../object.h"
  11 #include "../dir.h"
  12 #include "../chdir-notify.h"
  13 #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                 return files_reflog_path_other_worktrees(refs, sb, refname);
 184         case REF_TYPE_NORMAL:
 185                 strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 186                 break;
 187         default:
 188                 BUG("unknown ref type %d of ref %s",
 189                     ref_type(refname), refname);
 190         }
 191 }
 192
 193 static void files_ref_path(struct files_ref_store *refs,
 194                            struct strbuf *sb,
 195                            const char *refname)
 196 {
 197         switch (ref_type(refname)) {
 198         case REF_TYPE_PER_WORKTREE:
 199         case REF_TYPE_PSEUDOREF:
 200                 strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 201                 break;
 202         case REF_TYPE_MAIN_PSEUDOREF:
 203                 if (!skip_prefix(refname, "main-worktree/", &refname))
 204                         BUG("ref %s is not a main pseudoref", refname);
 205                 /* fallthrough */
 206         case REF_TYPE_OTHER_PSEUDOREF:
 207         case REF_TYPE_NORMAL:
 208                 strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 209                 break;
 210         default:
 211                 BUG("unknown ref type %d of ref %s",
 212                     ref_type(refname), refname);
 213         }
 214 }
 215
 216 /*
 217  * Manually add refs/bisect, refs/rewritten and refs/worktree, which, being
 218  * per-worktree, might not appear in the directory listing for
 219  * refs/ in the main repo.
 220  */
 221 static void add_per_worktree_entries_to_dir(struct ref_dir *dir, const char *dirname)
 222 {
 223         const char *prefixes[] = { "refs/bisect/", "refs/worktree/", "refs/rewritten/" };
 224         int ip;
 225
 226         if (strcmp(dirname, "refs/"))
 227                 return;
 228
 229         for (ip = 0; ip < ARRAY_SIZE(prefixes); ip++) {
 230                 const char *prefix = prefixes[ip];
 231                 int prefix_len = strlen(prefix);
 232                 struct ref_entry *child_entry;
 233                 int pos;
 234
 235                 pos = search_ref_dir(dir, prefix, prefix_len);
 236                 if (pos >= 0)
 237                         continue;
 238                 child_entry = create_dir_entry(dir->cache, prefix, prefix_len, 1);
 239                 add_entry_to_dir(dir, child_entry);
 240         }
 241 }
 242
 243 /*
 244  * Read the loose references from the namespace dirname into dir
 245  * (without recursing).  dirname must end with '/'.  dir must be the
 246  * directory entry corresponding to dirname.
 247  */
 248 static void loose_fill_ref_dir(struct ref_store *ref_store,
 249                                struct ref_dir *dir, const char *dirname)
 250 {
 251         struct files_ref_store *refs =
 252                 files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 253         DIR *d;
 254         struct dirent *de;
 255         int dirnamelen = strlen(dirname);
 256         struct strbuf refname;
 257         struct strbuf path = STRBUF_INIT;
 258         size_t path_baselen;
 259
 260         files_ref_path(refs, &path, dirname);
 261         path_baselen = path.len;
 262
 263         d = opendir(path.buf);
 264         if (!d) {
 265                 strbuf_release(&path);
 266                 return;
 267         }
 268
 269         strbuf_init(&refname, dirnamelen + 257);
 270         strbuf_add(&refname, dirname, dirnamelen);
 271
 272         while ((de = readdir(d)) != NULL) {
 273                 struct object_id oid;
 274                 struct stat st;
 275                 int flag;
 276
 277                 if (de->d_name[0] == '.')
 278                         continue;
 279                 if (ends_with(de->d_name, ".lock"))
 280                         continue;
 281                 strbuf_addstr(&refname, de->d_name);
 282                 strbuf_addstr(&path, de->d_name);
 283                 if (stat(path.buf, &st) < 0) {
 284                         ; /* silently ignore */
 285                 } else if (S_ISDIR(st.st_mode)) {
 286                         strbuf_addch(&refname, '/');
 287                         add_entry_to_dir(dir,
 288                                          create_dir_entry(dir->cache, refname.buf,
 289                                                           refname.len, 1));
 290                 } else {
 291                         if (!refs_resolve_ref_unsafe(&refs->base,
 292                                                      refname.buf,
 293                                                      RESOLVE_REF_READING,
 294                                                      &oid, &flag)) {
 295                                 oidclr(&oid);
 296                                 flag |= REF_ISBROKEN;
 297                         } else if (is_null_oid(&oid)) {
 298                                 /*
 299                                  * It is so astronomically unlikely
 300                                  * that null_oid is the OID of an
 301                                  * actual object that we consider its
 302                                  * appearance in a loose reference
 303                                  * file to be repo corruption
 304                                  * (probably due to a software bug).
 305                                  */
 306                                 flag |= REF_ISBROKEN;
 307                         }
 308
 309                         if (check_refname_format(refname.buf,
 310                                                  REFNAME_ALLOW_ONELEVEL)) {
 311                                 if (!refname_is_safe(refname.buf))
 312                                         die("loose refname is dangerous: %s", refname.buf);
 313                                 oidclr(&oid);
 314                                 flag |= REF_BAD_NAME | REF_ISBROKEN;
 315                         }
 316                         add_entry_to_dir(dir,
 317                                          create_ref_entry(refname.buf, &oid, flag));
 318                 }
 319                 strbuf_setlen(&refname, dirnamelen);
 320                 strbuf_setlen(&path, path_baselen);
 321         }
 322         strbuf_release(&refname);
 323         strbuf_release(&path);
 324         closedir(d);
 325
 326         add_per_worktree_entries_to_dir(dir, dirname);
 327 }
 328
 329 static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 330 {
 331         if (!refs->loose) {
 332                 /*
 333                  * Mark the top-level directory complete because we
 334                  * are about to read the only subdirectory that can
 335                  * hold references:
 336                  */
 337                 refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 338
 339                 /* We're going to fill the top level ourselves: */
 340                 refs->loose->root->flag &= ~REF_INCOMPLETE;
 341
 342                 /*
 343                  * Add an incomplete entry for "refs/" (to be filled
 344                  * lazily):
 345                  */
 346                 add_entry_to_dir(get_ref_dir(refs->loose->root),
 347                                  create_dir_entry(refs->loose, "refs/", 5, 1));
 348         }
 349         return refs->loose;
 350 }
 351
 352 static int files_read_raw_ref(struct ref_store *ref_store,
 353                               const char *refname, struct object_id *oid,
 354                               struct strbuf *referent, unsigned int *type)
 355 {
 356         struct files_ref_store *refs =
 357                 files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 358         struct strbuf sb_contents = STRBUF_INIT;
 359         struct strbuf sb_path = STRBUF_INIT;
 360         const char *path;
 361         const char *buf;
 362         const char *p;
 363         struct stat st;
 364         int fd;
 365         int ret = -1;
 366         int save_errno;
 367         int remaining_retries = 3;
 368
 369         *type = 0;
 370         strbuf_reset(&sb_path);
 371
 372         files_ref_path(refs, &sb_path, refname);
 373
 374         path = sb_path.buf;
 375
 376 stat_ref:
 377         /*
 378          * We might have to loop back here to avoid a race
 379          * condition: first we lstat() the file, then we try
 380          * to read it as a link or as a file.  But if somebody
 381          * changes the type of the file (file <-> directory
 382          * <-> symlink) between the lstat() and reading, then
 383          * we don't want to report that as an error but rather
 384          * try again starting with the lstat().
 385          *
 386          * We'll keep a count of the retries, though, just to avoid
 387          * any confusing situation sending us into an infinite loop.
 388          */
 389
 390         if (remaining_retries-- <= 0)
 391                 goto out;
 392
 393         if (lstat(path, &st) < 0) {
 394                 if (errno != ENOENT)
 395                         goto out;
 396                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 397                                       oid, referent, type)) {
 398                         errno = ENOENT;
 399                         goto out;
 400                 }
 401                 ret = 0;
 402                 goto out;
 403         }
 404
 405         /* Follow "normalized" - ie "refs/.." symlinks by hand */
 406         if (S_ISLNK(st.st_mode)) {
 407                 strbuf_reset(&sb_contents);
 408                 if (strbuf_readlink(&sb_contents, path, st.st_size) < 0) {
 409                         if (errno == ENOENT || errno == EINVAL)
 410                                 /* inconsistent with lstat; retry */
 411                                 goto stat_ref;
 412                         else
 413                                 goto out;
 414                 }
 415                 if (starts_with(sb_contents.buf, "refs/") &&
 416                     !check_refname_format(sb_contents.buf, 0)) {
 417                         strbuf_swap(&sb_contents, referent);
 418                         *type |= REF_ISSYMREF;
 419                         ret = 0;
 420                         goto out;
 421                 }
 422                 /*
 423                  * It doesn't look like a refname; fall through to just
 424                  * treating it like a non-symlink, and reading whatever it
 425                  * points to.
 426                  */
 427         }
 428
 429         /* Is it a directory? */
 430         if (S_ISDIR(st.st_mode)) {
 431                 /*
 432                  * Even though there is a directory where the loose
 433                  * ref is supposed to be, there could still be a
 434                  * packed ref:
 435                  */
 436                 if (refs_read_raw_ref(refs->packed_ref_store, refname,
 437                                       oid, referent, type)) {
 438                         errno = EISDIR;
 439                         goto out;
 440                 }
 441                 ret = 0;
 442                 goto out;
 443         }
 444
 445         /*
 446          * Anything else, just open it and try to use it as
 447          * a ref
 448          */
 449         fd = open(path, O_RDONLY);
 450         if (fd < 0) {
 451                 if (errno == ENOENT && !S_ISLNK(st.st_mode))
 452                         /* inconsistent with lstat; retry */
 453                         goto stat_ref;
 454                 else
 455                         goto out;
 456         }
 457         strbuf_reset(&sb_contents);
 458         if (strbuf_read(&sb_contents, fd, 256) < 0) {
 459                 int save_errno = errno;
 460                 close(fd);
 461                 errno = save_errno;
 462                 goto out;
 463         }
 464         close(fd);
 465         strbuf_rtrim(&sb_contents);
 466         buf = sb_contents.buf;
 467         if (starts_with(buf, "ref:")) {
 468                 buf += 4;
 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 oid, 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                                 &oid, 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 files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2146         struct ref_iterator *ref_iterator = &iter->base;
2147         struct strbuf sb = STRBUF_INIT;
2148
2149         base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2150         strbuf_addf(&sb, "%s/logs", gitdir);
2151         iter->dir_iterator = dir_iterator_begin(sb.buf);
2152         iter->ref_store = ref_store;
2153         strbuf_release(&sb);
2154
2155         return ref_iterator;
2156 }
2157
2158 static enum iterator_selection reflog_iterator_select(
2159         struct ref_iterator *iter_worktree,
2160         struct ref_iterator *iter_common,
2161         void *cb_data)
2162 {
2163         if (iter_worktree) {
2164                 /*
2165                  * We're a bit loose here. We probably should ignore
2166                  * common refs if they are accidentally added as
2167                  * per-worktree refs.
2168                  */
2169                 return ITER_SELECT_0;
2170         } else if (iter_common) {
2171                 if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2172                         return ITER_SELECT_1;
2173
2174                 /*
2175                  * The main ref store may contain main worktree's
2176                  * per-worktree refs, which should be ignored
2177                  */
2178                 return ITER_SKIP_1;
2179         } else
2180                 return ITER_DONE;
2181 }
2182
2183 static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2184 {
2185         struct files_ref_store *refs =
2186                 files_downcast(ref_store, REF_STORE_READ,
2187                                "reflog_iterator_begin");
2188
2189         if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2190                 return reflog_iterator_begin(ref_store, refs->gitcommondir);
2191         } else {
2192                 return merge_ref_iterator_begin(
2193                         0,
2194                         reflog_iterator_begin(ref_store, refs->gitdir),
2195                         reflog_iterator_begin(ref_store, refs->gitcommondir),
2196                         reflog_iterator_select, refs);
2197         }
2198 }
2199
2200 /*
2201  * If update is a direct update of head_ref (the reference pointed to
2202  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2203  */
2204 static int split_head_update(struct ref_update *update,
2205                              struct ref_transaction *transaction,
2206                              const char *head_ref,
2207                              struct string_list *affected_refnames,
2208                              struct strbuf *err)
2209 {
2210         struct string_list_item *item;
2211         struct ref_update *new_update;
2212
2213         if ((update->flags & REF_LOG_ONLY) ||
2214             (update->flags & REF_IS_PRUNING) ||
2215             (update->flags & REF_UPDATE_VIA_HEAD))
2216                 return 0;
2217
2218         if (strcmp(update->refname, head_ref))
2219                 return 0;
2220
2221         /*
2222          * First make sure that HEAD is not already in the
2223          * transaction. This check is O(lg N) in the transaction
2224          * size, but it happens at most once per transaction.
2225          */
2226         if (string_list_has_string(affected_refnames, "HEAD")) {
2227                 /* An entry already existed */
2228                 strbuf_addf(err,
2229                             "multiple updates for 'HEAD' (including one "
2230                             "via its referent '%s') are not allowed",
2231                             update->refname);
2232                 return TRANSACTION_NAME_CONFLICT;
2233         }
2234
2235         new_update = ref_transaction_add_update(
2236                         transaction, "HEAD",
2237                         update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2238                         &update->new_oid, &update->old_oid,
2239                         update->msg);
2240
2241         /*
2242          * Add "HEAD". This insertion is O(N) in the transaction
2243          * size, but it happens at most once per transaction.
2244          * Add new_update->refname instead of a literal "HEAD".
2245          */
2246         if (strcmp(new_update->refname, "HEAD"))
2247                 BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2248         item = string_list_insert(affected_refnames, new_update->refname);
2249         item->util = new_update;
2250
2251         return 0;
2252 }
2253
2254 /*
2255  * update is for a symref that points at referent and doesn't have
2256  * REF_NO_DEREF set. Split it into two updates:
2257  * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2258  * - A new, separate update for the referent reference
2259  * Note that the new update will itself be subject to splitting when
2260  * the iteration gets to it.
2261  */
2262 static int split_symref_update(struct files_ref_store *refs,
2263                                struct ref_update *update,
2264                                const char *referent,
2265                                struct ref_transaction *transaction,
2266                                struct string_list *affected_refnames,
2267                                struct strbuf *err)
2268 {
2269         struct string_list_item *item;
2270         struct ref_update *new_update;
2271         unsigned int new_flags;
2272
2273         /*
2274          * First make sure that referent is not already in the
2275          * transaction. This check is O(lg N) in the transaction
2276          * size, but it happens at most once per symref in a
2277          * transaction.
2278          */
2279         if (string_list_has_string(affected_refnames, referent)) {
2280                 /* An entry already exists */
2281                 strbuf_addf(err,
2282                             "multiple updates for '%s' (including one "
2283                             "via symref '%s') are not allowed",
2284                             referent, update->refname);
2285                 return TRANSACTION_NAME_CONFLICT;
2286         }
2287
2288         new_flags = update->flags;
2289         if (!strcmp(update->refname, "HEAD")) {
2290                 /*
2291                  * Record that the new update came via HEAD, so that
2292                  * when we process it, split_head_update() doesn't try
2293                  * to add another reflog update for HEAD. Note that
2294                  * this bit will be propagated if the new_update
2295                  * itself needs to be split.
2296                  */
2297                 new_flags |= REF_UPDATE_VIA_HEAD;
2298         }
2299
2300         new_update = ref_transaction_add_update(
2301                         transaction, referent, new_flags,
2302                         &update->new_oid, &update->old_oid,
2303                         update->msg);
2304
2305         new_update->parent_update = update;
2306
2307         /*
2308          * Change the symbolic ref update to log only. Also, it
2309          * doesn't need to check its old OID value, as that will be
2310          * done when new_update is processed.
2311          */
2312         update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2313         update->flags &= ~REF_HAVE_OLD;
2314
2315         /*
2316          * Add the referent. This insertion is O(N) in the transaction
2317          * size, but it happens at most once per symref in a
2318          * transaction. Make sure to add new_update->refname, which will
2319          * be valid as long as affected_refnames is in use, and NOT
2320          * referent, which might soon be freed by our caller.
2321          */
2322         item = string_list_insert(affected_refnames, new_update->refname);
2323         if (item->util)
2324                 BUG("%s unexpectedly found in affected_refnames",
2325                     new_update->refname);
2326         item->util = new_update;
2327
2328         return 0;
2329 }
2330
2331 /*
2332  * Return the refname under which update was originally requested.
2333  */
2334 static const char *original_update_refname(struct ref_update *update)
2335 {
2336         while (update->parent_update)
2337                 update = update->parent_update;
2338
2339         return update->refname;
2340 }
2341
2342 /*
2343  * Check whether the REF_HAVE_OLD and old_oid values stored in update
2344  * are consistent with oid, which is the reference's current value. If
2345  * everything is OK, return 0; otherwise, write an error message to
2346  * err and return -1.
2347  */
2348 static int check_old_oid(struct ref_update *update, struct object_id *oid,
2349                          struct strbuf *err)
2350 {
2351         if (!(update->flags & REF_HAVE_OLD) ||
2352                    oideq(oid, &update->old_oid))
2353                 return 0;
2354
2355         if (is_null_oid(&update->old_oid))
2356                 strbuf_addf(err, "cannot lock ref '%s': "
2357                             "reference already exists",
2358                             original_update_refname(update));
2359         else if (is_null_oid(oid))
2360                 strbuf_addf(err, "cannot lock ref '%s': "
2361                             "reference is missing but expected %s",
2362                             original_update_refname(update),
2363                             oid_to_hex(&update->old_oid));
2364         else
2365                 strbuf_addf(err, "cannot lock ref '%s': "
2366                             "is at %s but expected %s",
2367                             original_update_refname(update),
2368                             oid_to_hex(oid),
2369                             oid_to_hex(&update->old_oid));
2370
2371         return -1;
2372 }
2373
2374 /*
2375  * Prepare for carrying out update:
2376  * - Lock the reference referred to by update.
2377  * - Read the reference under lock.
2378  * - Check that its old OID value (if specified) is correct, and in
2379  *   any case record it in update->lock->old_oid for later use when
2380  *   writing the reflog.
2381  * - If it is a symref update without REF_NO_DEREF, split it up into a
2382  *   REF_LOG_ONLY update of the symref and add a separate update for
2383  *   the referent to transaction.
2384  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2385  *   update of HEAD.
2386  */
2387 static int lock_ref_for_update(struct files_ref_store *refs,
2388                                struct ref_update *update,
2389                                struct ref_transaction *transaction,
2390                                const char *head_ref,
2391                                struct string_list *affected_refnames,
2392                                struct strbuf *err)
2393 {
2394         struct strbuf referent = STRBUF_INIT;
2395         int mustexist = (update->flags & REF_HAVE_OLD) &&
2396                 !is_null_oid(&update->old_oid);
2397         int ret = 0;
2398         struct ref_lock *lock;
2399
2400         files_assert_main_repository(refs, "lock_ref_for_update");
2401
2402         if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2403                 update->flags |= REF_DELETING;
2404
2405         if (head_ref) {
2406                 ret = split_head_update(update, transaction, head_ref,
2407                                         affected_refnames, err);
2408                 if (ret)
2409                         goto out;
2410         }
2411
2412         ret = lock_raw_ref(refs, update->refname, mustexist,
2413                            affected_refnames, NULL,
2414                            &lock, &referent,
2415                            &update->type, err);
2416         if (ret) {
2417                 char *reason;
2418
2419                 reason = strbuf_detach(err, NULL);
2420                 strbuf_addf(err, "cannot lock ref '%s': %s",
2421                             original_update_refname(update), reason);
2422                 free(reason);
2423                 goto out;
2424         }
2425
2426         update->backend_data = lock;
2427
2428         if (update->type & REF_ISSYMREF) {
2429                 if (update->flags & REF_NO_DEREF) {
2430                         /*
2431                          * We won't be reading the referent as part of
2432                          * the transaction, so we have to read it here
2433                          * to record and possibly check old_oid:
2434                          */
2435                         if (refs_read_ref_full(&refs->base,
2436                                                referent.buf, 0,
2437                                                &lock->old_oid, NULL)) {
2438                                 if (update->flags & REF_HAVE_OLD) {
2439                                         strbuf_addf(err, "cannot lock ref '%s': "
2440                                                     "error reading reference",
2441                                                     original_update_refname(update));
2442                                         ret = TRANSACTION_GENERIC_ERROR;
2443                                         goto out;
2444                                 }
2445                         } else if (check_old_oid(update, &lock->old_oid, err)) {
2446                                 ret = TRANSACTION_GENERIC_ERROR;
2447                                 goto out;
2448                         }
2449                 } else {
2450                         /*
2451                          * Create a new update for the reference this
2452                          * symref is pointing at. Also, we will record
2453                          * and verify old_oid for this update as part
2454                          * of processing the split-off update, so we
2455                          * don't have to do it here.
2456                          */
2457                         ret = split_symref_update(refs, update,
2458                                                   referent.buf, transaction,
2459                                                   affected_refnames, err);
2460                         if (ret)
2461                                 goto out;
2462                 }
2463         } else {
2464                 struct ref_update *parent_update;
2465
2466                 if (check_old_oid(update, &lock->old_oid, err)) {
2467                         ret = TRANSACTION_GENERIC_ERROR;
2468                         goto out;
2469                 }
2470
2471                 /*
2472                  * If this update is happening indirectly because of a
2473                  * symref update, record the old OID in the parent
2474                  * update:
2475                  */
2476                 for (parent_update = update->parent_update;
2477                      parent_update;
2478                      parent_update = parent_update->parent_update) {
2479                         struct ref_lock *parent_lock = parent_update->backend_data;
2480                         oidcpy(&parent_lock->old_oid, &lock->old_oid);
2481                 }
2482         }
2483
2484         if ((update->flags & REF_HAVE_NEW) &&
2485             !(update->flags & REF_DELETING) &&
2486             !(update->flags & REF_LOG_ONLY)) {
2487                 if (!(update->type & REF_ISSYMREF) &&
2488                     oideq(&lock->old_oid, &update->new_oid)) {
2489                         /*
2490                          * The reference already has the desired
2491                          * value, so we don't need to write it.
2492                          */
2493                 } else if (write_ref_to_lockfile(lock, &update->new_oid,
2494                                                  err)) {
2495                         char *write_err = strbuf_detach(err, NULL);
2496
2497                         /*
2498                          * The lock was freed upon failure of
2499                          * write_ref_to_lockfile():
2500                          */
2501                         update->backend_data = NULL;
2502                         strbuf_addf(err,
2503                                     "cannot update ref '%s': %s",
2504                                     update->refname, write_err);
2505                         free(write_err);
2506                         ret = TRANSACTION_GENERIC_ERROR;
2507                         goto out;
2508                 } else {
2509                         update->flags |= REF_NEEDS_COMMIT;
2510                 }
2511         }
2512         if (!(update->flags & REF_NEEDS_COMMIT)) {
2513                 /*
2514                  * We didn't call write_ref_to_lockfile(), so
2515                  * the lockfile is still open. Close it to
2516                  * free up the file descriptor:
2517                  */
2518                 if (close_ref_gently(lock)) {
2519                         strbuf_addf(err, "couldn't close '%s.lock'",
2520                                     update->refname);
2521                         ret = TRANSACTION_GENERIC_ERROR;
2522                         goto out;
2523                 }
2524         }
2525
2526 out:
2527         strbuf_release(&referent);
2528         return ret;
2529 }
2530
2531 struct files_transaction_backend_data {
2532         struct ref_transaction *packed_transaction;
2533         int packed_refs_locked;
2534 };
2535
2536 /*
2537  * Unlock any references in `transaction` that are still locked, and
2538  * mark the transaction closed.
2539  */
2540 static void files_transaction_cleanup(struct files_ref_store *refs,
2541                                       struct ref_transaction *transaction)
2542 {
2543         size_t i;
2544         struct files_transaction_backend_data *backend_data =
2545                 transaction->backend_data;
2546         struct strbuf err = STRBUF_INIT;
2547
2548         for (i = 0; i < transaction->nr; i++) {
2549                 struct ref_update *update = transaction->updates[i];
2550                 struct ref_lock *lock = update->backend_data;
2551
2552                 if (lock) {
2553                         unlock_ref(lock);
2554                         update->backend_data = NULL;
2555                 }
2556         }
2557
2558         if (backend_data->packed_transaction &&
2559             ref_transaction_abort(backend_data->packed_transaction, &err)) {
2560                 error("error aborting transaction: %s", err.buf);
2561                 strbuf_release(&err);
2562         }
2563
2564         if (backend_data->packed_refs_locked)
2565                 packed_refs_unlock(refs->packed_ref_store);
2566
2567         free(backend_data);
2568
2569         transaction->state = REF_TRANSACTION_CLOSED;
2570 }
2571
2572 static int files_transaction_prepare(struct ref_store *ref_store,
2573                                      struct ref_transaction *transaction,
2574                                      struct strbuf *err)
2575 {
2576         struct files_ref_store *refs =
2577                 files_downcast(ref_store, REF_STORE_WRITE,
2578                                "ref_transaction_prepare");
2579         size_t i;
2580         int ret = 0;
2581         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2582         char *head_ref = NULL;
2583         int head_type;
2584         struct files_transaction_backend_data *backend_data;
2585         struct ref_transaction *packed_transaction = NULL;
2586
2587         assert(err);
2588
2589         if (!transaction->nr)
2590                 goto cleanup;
2591
2592         backend_data = xcalloc(1, sizeof(*backend_data));
2593         transaction->backend_data = backend_data;
2594
2595         /*
2596          * Fail if a refname appears more than once in the
2597          * transaction. (If we end up splitting up any updates using
2598          * split_symref_update() or split_head_update(), those
2599          * functions will check that the new updates don't have the
2600          * same refname as any existing ones.) Also fail if any of the
2601          * updates use REF_IS_PRUNING without REF_NO_DEREF.
2602          */
2603         for (i = 0; i < transaction->nr; i++) {
2604                 struct ref_update *update = transaction->updates[i];
2605                 struct string_list_item *item =
2606                         string_list_append(&affected_refnames, update->refname);
2607
2608                 if ((update->flags & REF_IS_PRUNING) &&
2609                     !(update->flags & REF_NO_DEREF))
2610                         BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2611
2612                 /*
2613                  * We store a pointer to update in item->util, but at
2614                  * the moment we never use the value of this field
2615                  * except to check whether it is non-NULL.
2616                  */
2617                 item->util = update;
2618         }
2619         string_list_sort(&affected_refnames);
2620         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2621                 ret = TRANSACTION_GENERIC_ERROR;
2622                 goto cleanup;
2623         }
2624
2625         /*
2626          * Special hack: If a branch is updated directly and HEAD
2627          * points to it (may happen on the remote side of a push
2628          * for example) then logically the HEAD reflog should be
2629          * updated too.
2630          *
2631          * A generic solution would require reverse symref lookups,
2632          * but finding all symrefs pointing to a given branch would be
2633          * rather costly for this rare event (the direct update of a
2634          * branch) to be worth it. So let's cheat and check with HEAD
2635          * only, which should cover 99% of all usage scenarios (even
2636          * 100% of the default ones).
2637          *
2638          * So if HEAD is a symbolic reference, then record the name of
2639          * the reference that it points to. If we see an update of
2640          * head_ref within the transaction, then split_head_update()
2641          * arranges for the reflog of HEAD to be updated, too.
2642          */
2643         head_ref = refs_resolve_refdup(ref_store, "HEAD",
2644                                        RESOLVE_REF_NO_RECURSE,
2645                                        NULL, &head_type);
2646
2647         if (head_ref && !(head_type & REF_ISSYMREF)) {
2648                 FREE_AND_NULL(head_ref);
2649         }
2650
2651         /*
2652          * Acquire all locks, verify old values if provided, check
2653          * that new values are valid, and write new values to the
2654          * lockfiles, ready to be activated. Only keep one lockfile
2655          * open at a time to avoid running out of file descriptors.
2656          * Note that lock_ref_for_update() might append more updates
2657          * to the transaction.
2658          */
2659         for (i = 0; i < transaction->nr; i++) {
2660                 struct ref_update *update = transaction->updates[i];
2661
2662                 ret = lock_ref_for_update(refs, update, transaction,
2663                                           head_ref, &affected_refnames, err);
2664                 if (ret)
2665                         goto cleanup;
2666
2667                 if (update->flags & REF_DELETING &&
2668                     !(update->flags & REF_LOG_ONLY) &&
2669                     !(update->flags & REF_IS_PRUNING)) {
2670                         /*
2671                          * This reference has to be deleted from
2672                          * packed-refs if it exists there.
2673                          */
2674                         if (!packed_transaction) {
2675                                 packed_transaction = ref_store_transaction_begin(
2676                                                 refs->packed_ref_store, err);
2677                                 if (!packed_transaction) {
2678                                         ret = TRANSACTION_GENERIC_ERROR;
2679                                         goto cleanup;
2680                                 }
2681
2682                                 backend_data->packed_transaction =
2683                                         packed_transaction;
2684                         }
2685
2686                         ref_transaction_add_update(
2687                                         packed_transaction, update->refname,
2688                                         REF_HAVE_NEW | REF_NO_DEREF,
2689                                         &update->new_oid, NULL,
2690                                         NULL);
2691                 }
2692         }
2693
2694         if (packed_transaction) {
2695                 if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2696                         ret = TRANSACTION_GENERIC_ERROR;
2697                         goto cleanup;
2698                 }
2699                 backend_data->packed_refs_locked = 1;
2700
2701                 if (is_packed_transaction_needed(refs->packed_ref_store,
2702                                                  packed_transaction)) {
2703                         ret = ref_transaction_prepare(packed_transaction, err);
2704                 } else {
2705                         /*
2706                          * We can skip rewriting the `packed-refs`
2707                          * file. But we do need to leave it locked, so
2708                          * that somebody else doesn't pack a reference
2709                          * that we are trying to delete.
2710                          */
2711                         if (ref_transaction_abort(packed_transaction, err)) {
2712                                 ret = TRANSACTION_GENERIC_ERROR;
2713                                 goto cleanup;
2714                         }
2715                         backend_data->packed_transaction = NULL;
2716                 }
2717         }
2718
2719 cleanup:
2720         free(head_ref);
2721         string_list_clear(&affected_refnames, 0);
2722
2723         if (ret)
2724                 files_transaction_cleanup(refs, transaction);
2725         else
2726                 transaction->state = REF_TRANSACTION_PREPARED;
2727
2728         return ret;
2729 }
2730
2731 static int files_transaction_finish(struct ref_store *ref_store,
2732                                     struct ref_transaction *transaction,
2733                                     struct strbuf *err)
2734 {
2735         struct files_ref_store *refs =
2736                 files_downcast(ref_store, 0, "ref_transaction_finish");
2737         size_t i;
2738         int ret = 0;
2739         struct strbuf sb = STRBUF_INIT;
2740         struct files_transaction_backend_data *backend_data;
2741         struct ref_transaction *packed_transaction;
2742
2743
2744         assert(err);
2745
2746         if (!transaction->nr) {
2747                 transaction->state = REF_TRANSACTION_CLOSED;
2748                 return 0;
2749         }
2750
2751         backend_data = transaction->backend_data;
2752         packed_transaction = backend_data->packed_transaction;
2753
2754         /* Perform updates first so live commits remain referenced */
2755         for (i = 0; i < transaction->nr; i++) {
2756                 struct ref_update *update = transaction->updates[i];
2757                 struct ref_lock *lock = update->backend_data;
2758
2759                 if (update->flags & REF_NEEDS_COMMIT ||
2760                     update->flags & REF_LOG_ONLY) {
2761                         if (files_log_ref_write(refs,
2762                                                 lock->ref_name,
2763                                                 &lock->old_oid,
2764                                                 &update->new_oid,
2765                                                 update->msg, update->flags,
2766                                                 err)) {
2767                                 char *old_msg = strbuf_detach(err, NULL);
2768
2769                                 strbuf_addf(err, "cannot update the ref '%s': %s",
2770                                             lock->ref_name, old_msg);
2771                                 free(old_msg);
2772                                 unlock_ref(lock);
2773                                 update->backend_data = NULL;
2774                                 ret = TRANSACTION_GENERIC_ERROR;
2775                                 goto cleanup;
2776                         }
2777                 }
2778                 if (update->flags & REF_NEEDS_COMMIT) {
2779                         clear_loose_ref_cache(refs);
2780                         if (commit_ref(lock)) {
2781                                 strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2782                                 unlock_ref(lock);
2783                                 update->backend_data = NULL;
2784                                 ret = TRANSACTION_GENERIC_ERROR;
2785                                 goto cleanup;
2786                         }
2787                 }
2788         }
2789
2790         /*
2791          * Now that updates are safely completed, we can perform
2792          * deletes. First delete the reflogs of any references that
2793          * will be deleted, since (in the unexpected event of an
2794          * error) leaving a reference without a reflog is less bad
2795          * than leaving a reflog without a reference (the latter is a
2796          * mildly invalid repository state):
2797          */
2798         for (i = 0; i < transaction->nr; i++) {
2799                 struct ref_update *update = transaction->updates[i];
2800                 if (update->flags & REF_DELETING &&
2801                     !(update->flags & REF_LOG_ONLY) &&
2802                     !(update->flags & REF_IS_PRUNING)) {
2803                         strbuf_reset(&sb);
2804                         files_reflog_path(refs, &sb, update->refname);
2805                         if (!unlink_or_warn(sb.buf))
2806                                 try_remove_empty_parents(refs, update->refname,
2807                                                          REMOVE_EMPTY_PARENTS_REFLOG);
2808                 }
2809         }
2810
2811         /*
2812          * Perform deletes now that updates are safely completed.
2813          *
2814          * First delete any packed versions of the references, while
2815          * retaining the packed-refs lock:
2816          */
2817         if (packed_transaction) {
2818                 ret = ref_transaction_commit(packed_transaction, err);
2819                 ref_transaction_free(packed_transaction);
2820                 packed_transaction = NULL;
2821                 backend_data->packed_transaction = NULL;
2822                 if (ret)
2823                         goto cleanup;
2824         }
2825
2826         /* Now delete the loose versions of the references: */
2827         for (i = 0; i < transaction->nr; i++) {
2828                 struct ref_update *update = transaction->updates[i];
2829                 struct ref_lock *lock = update->backend_data;
2830
2831                 if (update->flags & REF_DELETING &&
2832                     !(update->flags & REF_LOG_ONLY)) {
2833                         if (!(update->type & REF_ISPACKED) ||
2834                             update->type & REF_ISSYMREF) {
2835                                 /* It is a loose reference. */
2836                                 strbuf_reset(&sb);
2837                                 files_ref_path(refs, &sb, lock->ref_name);
2838                                 if (unlink_or_msg(sb.buf, err)) {
2839                                         ret = TRANSACTION_GENERIC_ERROR;
2840                                         goto cleanup;
2841                                 }
2842                                 update->flags |= REF_DELETED_LOOSE;
2843                         }
2844                 }
2845         }
2846
2847         clear_loose_ref_cache(refs);
2848
2849 cleanup:
2850         files_transaction_cleanup(refs, transaction);
2851
2852         for (i = 0; i < transaction->nr; i++) {
2853                 struct ref_update *update = transaction->updates[i];
2854
2855                 if (update->flags & REF_DELETED_LOOSE) {
2856                         /*
2857                          * The loose reference was deleted. Delete any
2858                          * empty parent directories. (Note that this
2859                          * can only work because we have already
2860                          * removed the lockfile.)
2861                          */
2862                         try_remove_empty_parents(refs, update->refname,
2863                                                  REMOVE_EMPTY_PARENTS_REF);
2864                 }
2865         }
2866
2867         strbuf_release(&sb);
2868         return ret;
2869 }
2870
2871 static int files_transaction_abort(struct ref_store *ref_store,
2872                                    struct ref_transaction *transaction,
2873                                    struct strbuf *err)
2874 {
2875         struct files_ref_store *refs =
2876                 files_downcast(ref_store, 0, "ref_transaction_abort");
2877
2878         files_transaction_cleanup(refs, transaction);
2879         return 0;
2880 }
2881
2882 static int ref_present(const char *refname,
2883                        const struct object_id *oid, int flags, void *cb_data)
2884 {
2885         struct string_list *affected_refnames = cb_data;
2886
2887         return string_list_has_string(affected_refnames, refname);
2888 }
2889
2890 static int files_initial_transaction_commit(struct ref_store *ref_store,
2891                                             struct ref_transaction *transaction,
2892                                             struct strbuf *err)
2893 {
2894         struct files_ref_store *refs =
2895                 files_downcast(ref_store, REF_STORE_WRITE,
2896                                "initial_ref_transaction_commit");
2897         size_t i;
2898         int ret = 0;
2899         struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2900         struct ref_transaction *packed_transaction = NULL;
2901
2902         assert(err);
2903
2904         if (transaction->state != REF_TRANSACTION_OPEN)
2905                 BUG("commit called for transaction that is not open");
2906
2907         /* Fail if a refname appears more than once in the transaction: */
2908         for (i = 0; i < transaction->nr; i++)
2909                 string_list_append(&affected_refnames,
2910                                    transaction->updates[i]->refname);
2911         string_list_sort(&affected_refnames);
2912         if (ref_update_reject_duplicates(&affected_refnames, err)) {
2913                 ret = TRANSACTION_GENERIC_ERROR;
2914                 goto cleanup;
2915         }
2916
2917         /*
2918          * It's really undefined to call this function in an active
2919          * repository or when there are existing references: we are
2920          * only locking and changing packed-refs, so (1) any
2921          * simultaneous processes might try to change a reference at
2922          * the same time we do, and (2) any existing loose versions of
2923          * the references that we are setting would have precedence
2924          * over our values. But some remote helpers create the remote
2925          * "HEAD" and "master" branches before calling this function,
2926          * so here we really only check that none of the references
2927          * that we are creating already exists.
2928          */
2929         if (refs_for_each_rawref(&refs->base, ref_present,
2930                                  &affected_refnames))
2931                 BUG("initial ref transaction called with existing refs");
2932
2933         packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2934         if (!packed_transaction) {
2935                 ret = TRANSACTION_GENERIC_ERROR;
2936                 goto cleanup;
2937         }
2938
2939         for (i = 0; i < transaction->nr; i++) {
2940                 struct ref_update *update = transaction->updates[i];
2941
2942                 if ((update->flags & REF_HAVE_OLD) &&
2943                     !is_null_oid(&update->old_oid))
2944                         BUG("initial ref transaction with old_sha1 set");
2945                 if (refs_verify_refname_available(&refs->base, update->refname,
2946                                                   &affected_refnames, NULL,
2947                                                   err)) {
2948                         ret = TRANSACTION_NAME_CONFLICT;
2949                         goto cleanup;
2950                 }
2951
2952                 /*
2953                  * Add a reference creation for this reference to the
2954                  * packed-refs transaction:
2955                  */
2956                 ref_transaction_add_update(packed_transaction, update->refname,
2957                                            update->flags & ~REF_HAVE_OLD,
2958                                            &update->new_oid, &update->old_oid,
2959                                            NULL);
2960         }
2961
2962         if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2963                 ret = TRANSACTION_GENERIC_ERROR;
2964                 goto cleanup;
2965         }
2966
2967         if (initial_ref_transaction_commit(packed_transaction, err)) {
2968                 ret = TRANSACTION_GENERIC_ERROR;
2969         }
2970
2971         packed_refs_unlock(refs->packed_ref_store);
2972 cleanup:
2973         if (packed_transaction)
2974                 ref_transaction_free(packed_transaction);
2975         transaction->state = REF_TRANSACTION_CLOSED;
2976         string_list_clear(&affected_refnames, 0);
2977         return ret;
2978 }
2979
2980 struct expire_reflog_cb {
2981         unsigned int flags;
2982         reflog_expiry_should_prune_fn *should_prune_fn;
2983         void *policy_cb;
2984         FILE *newlog;
2985         struct object_id last_kept_oid;
2986 };
2987
2988 static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2989                              const char *email, timestamp_t timestamp, int tz,
2990                              const char *message, void *cb_data)
2991 {
2992         struct expire_reflog_cb *cb = cb_data;
2993         struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2994
2995         if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2996                 ooid = &cb->last_kept_oid;
2997
2998         if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2999                                    message, policy_cb)) {
3000                 if (!cb->newlog)
3001                         printf("would prune %s", message);
3002                 else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3003                         printf("prune %s", message);
3004         } else {
3005                 if (cb->newlog) {
3006                         fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
3007                                 oid_to_hex(ooid), oid_to_hex(noid),
3008                                 email, timestamp, tz, message);
3009                         oidcpy(&cb->last_kept_oid, noid);
3010                 }
3011                 if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3012                         printf("keep %s", message);
3013         }
3014         return 0;
3015 }
3016
3017 static int files_reflog_expire(struct ref_store *ref_store,
3018                                const char *refname, const struct object_id *oid,
3019                                unsigned int flags,
3020                                reflog_expiry_prepare_fn prepare_fn,
3021                                reflog_expiry_should_prune_fn should_prune_fn,
3022                                reflog_expiry_cleanup_fn cleanup_fn,
3023                                void *policy_cb_data)
3024 {
3025         struct files_ref_store *refs =
3026                 files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
3027         struct lock_file reflog_lock = LOCK_INIT;
3028         struct expire_reflog_cb cb;
3029         struct ref_lock *lock;
3030         struct strbuf log_file_sb = STRBUF_INIT;
3031         char *log_file;
3032         int status = 0;
3033         int type;
3034         struct strbuf err = STRBUF_INIT;
3035
3036         memset(&cb, 0, sizeof(cb));
3037         cb.flags = flags;
3038         cb.policy_cb = policy_cb_data;
3039         cb.should_prune_fn = should_prune_fn;
3040
3041         /*
3042          * The reflog file is locked by holding the lock on the
3043          * reference itself, plus we might need to update the
3044          * reference if --updateref was specified:
3045          */
3046         lock = lock_ref_oid_basic(refs, refname, oid,
3047                                   NULL, NULL, REF_NO_DEREF,
3048                                   &type, &err);
3049         if (!lock) {
3050                 error("cannot lock ref '%s': %s", refname, err.buf);
3051                 strbuf_release(&err);
3052                 return -1;
3053         }
3054         if (!refs_reflog_exists(ref_store, refname)) {
3055                 unlock_ref(lock);
3056                 return 0;
3057         }
3058
3059         files_reflog_path(refs, &log_file_sb, refname);
3060         log_file = strbuf_detach(&log_file_sb, NULL);
3061         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3062                 /*
3063                  * Even though holding $GIT_DIR/logs/$reflog.lock has
3064                  * no locking implications, we use the lock_file
3065                  * machinery here anyway because it does a lot of the
3066                  * work we need, including cleaning up if the program
3067                  * exits unexpectedly.
3068                  */
3069                 if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3070                         struct strbuf err = STRBUF_INIT;
3071                         unable_to_lock_message(log_file, errno, &err);
3072                         error("%s", err.buf);
3073                         strbuf_release(&err);
3074                         goto failure;
3075                 }
3076                 cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3077                 if (!cb.newlog) {
3078                         error("cannot fdopen %s (%s)",
3079                               get_lock_file_path(&reflog_lock), strerror(errno));
3080                         goto failure;
3081                 }
3082         }
3083
3084         (*prepare_fn)(refname, oid, cb.policy_cb);
3085         refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3086         (*cleanup_fn)(cb.policy_cb);
3087
3088         if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3089                 /*
3090                  * It doesn't make sense to adjust a reference pointed
3091                  * to by a symbolic ref based on expiring entries in
3092                  * the symbolic reference's reflog. Nor can we update
3093                  * a reference if there are no remaining reflog
3094                  * entries.
3095                  */
3096                 int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3097                         !(type & REF_ISSYMREF) &&
3098                         !is_null_oid(&cb.last_kept_oid);
3099
3100                 if (close_lock_file_gently(&reflog_lock)) {
3101                         status |= error("couldn't write %s: %s", log_file,
3102                                         strerror(errno));
3103                         rollback_lock_file(&reflog_lock);
3104                 } else if (update &&
3105                            (write_in_full(get_lock_file_fd(&lock->lk),
3106                                 oid_to_hex(&cb.last_kept_oid), the_hash_algo->hexsz) < 0 ||
3107                             write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3108                             close_ref_gently(lock) < 0)) {
3109                         status |= error("couldn't write %s",
3110                                         get_lock_file_path(&lock->lk));
3111                         rollback_lock_file(&reflog_lock);
3112                 } else if (commit_lock_file(&reflog_lock)) {
3113                         status |= error("unable to write reflog '%s' (%s)",
3114                                         log_file, strerror(errno));
3115                 } else if (update && commit_ref(lock)) {
3116                         status |= error("couldn't set %s", lock->ref_name);
3117                 }
3118         }
3119         free(log_file);
3120         unlock_ref(lock);
3121         return status;
3122
3123  failure:
3124         rollback_lock_file(&reflog_lock);
3125         free(log_file);
3126         unlock_ref(lock);
3127         return -1;
3128 }
3129
3130 static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3131 {
3132         struct files_ref_store *refs =
3133                 files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3134         struct strbuf sb = STRBUF_INIT;
3135
3136         /*
3137          * Create .git/refs/{heads,tags}
3138          */
3139         files_ref_path(refs, &sb, "refs/heads");
3140         safe_create_dir(sb.buf, 1);
3141
3142         strbuf_reset(&sb);
3143         files_ref_path(refs, &sb, "refs/tags");
3144         safe_create_dir(sb.buf, 1);
3145
3146         strbuf_release(&sb);
3147         return 0;
3148 }
3149
3150 struct ref_storage_be refs_be_files = {
3151         NULL,
3152         "files",
3153         files_ref_store_create,
3154         files_init_db,
3155         files_transaction_prepare,
3156         files_transaction_finish,
3157         files_transaction_abort,
3158         files_initial_transaction_commit,
3159
3160         files_pack_refs,
3161         files_create_symref,
3162         files_delete_refs,
3163         files_rename_ref,
3164         files_copy_ref,
3165
3166         files_ref_iterator_begin,
3167         files_read_raw_ref,
3168
3169         files_reflog_iterator_begin,
3170         files_for_each_reflog_ent,
3171         files_for_each_reflog_ent_reverse,
3172         files_reflog_exists,
3173         files_create_reflog,
3174         files_delete_reflog,
3175         files_reflog_expire
3176 };