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

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