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