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