refs / files-backend.con commit Merge branch 'bw/oidmap-autoinit' into maint (6ef449e)
   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
  13/*
  14 * This backend uses the following flags in `ref_update::flags` for
  15 * internal bookkeeping purposes. Their numerical values must not
  16 * conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
  17 * REF_HAVE_OLD, or REF_IS_PRUNING, which are also stored in
  18 * `ref_update::flags`.
  19 */
  20
  21/*
  22 * Used as a flag in ref_update::flags when a loose ref is being
  23 * pruned. This flag must only be used when REF_NO_DEREF is set.
  24 */
  25#define REF_IS_PRUNING (1 << 4)
  26
  27/*
  28 * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
  29 * refs (i.e., because the reference is about to be deleted anyway).
  30 */
  31#define REF_DELETING (1 << 5)
  32
  33/*
  34 * Used as a flag in ref_update::flags when the lockfile needs to be
  35 * committed.
  36 */
  37#define REF_NEEDS_COMMIT (1 << 6)
  38
  39/*
  40 * Used as a flag in ref_update::flags when we want to log a ref
  41 * update but not actually perform it.  This is used when a symbolic
  42 * ref update is split up.
  43 */
  44#define REF_LOG_ONLY (1 << 7)
  45
  46/*
  47 * Used as a flag in ref_update::flags when the ref_update was via an
  48 * update to HEAD.
  49 */
  50#define REF_UPDATE_VIA_HEAD (1 << 8)
  51
  52/*
  53 * Used as a flag in ref_update::flags when the loose reference has
  54 * been deleted.
  55 */
  56#define REF_DELETED_LOOSE (1 << 9)
  57
  58struct ref_lock {
  59        char *ref_name;
  60        struct lock_file lk;
  61        struct object_id old_oid;
  62};
  63
  64/*
  65 * Future: need to be in "struct repository"
  66 * when doing a full libification.
  67 */
  68struct files_ref_store {
  69        struct ref_store base;
  70        unsigned int store_flags;
  71
  72        char *gitdir;
  73        char *gitcommondir;
  74
  75        struct ref_cache *loose;
  76
  77        struct ref_store *packed_ref_store;
  78};
  79
  80static void clear_loose_ref_cache(struct files_ref_store *refs)
  81{
  82        if (refs->loose) {
  83                free_ref_cache(refs->loose);
  84                refs->loose = NULL;
  85        }
  86}
  87
  88/*
  89 * Create a new submodule ref cache and add it to the internal
  90 * set of caches.
  91 */
  92static struct ref_store *files_ref_store_create(const char *gitdir,
  93                                                unsigned int flags)
  94{
  95        struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  96        struct ref_store *ref_store = (struct ref_store *)refs;
  97        struct strbuf sb = STRBUF_INIT;
  98
  99        base_ref_store_init(ref_store, &refs_be_files);
 100        refs->store_flags = flags;
 101
 102        refs->gitdir = xstrdup(gitdir);
 103        get_common_dir_noenv(&sb, gitdir);
 104        refs->gitcommondir = strbuf_detach(&sb, NULL);
 105        strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
 106        refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
 107        strbuf_release(&sb);
 108
 109        return ref_store;
 110}
 111
 112/*
 113 * Die if refs is not the main ref store. caller is used in any
 114 * necessary error messages.
 115 */
 116static void files_assert_main_repository(struct files_ref_store *refs,
 117                                         const char *caller)
 118{
 119        if (refs->store_flags & REF_STORE_MAIN)
 120                return;
 121
 122        die("BUG: operation %s only allowed for main ref store", caller);
 123}
 124
 125/*
 126 * Downcast ref_store to files_ref_store. Die if ref_store is not a
 127 * files_ref_store. required_flags is compared with ref_store's
 128 * store_flags to ensure the ref_store has all required capabilities.
 129 * "caller" is used in any necessary error messages.
 130 */
 131static struct files_ref_store *files_downcast(struct ref_store *ref_store,
 132                                              unsigned int required_flags,
 133                                              const char *caller)
 134{
 135        struct files_ref_store *refs;
 136
 137        if (ref_store->be != &refs_be_files)
 138                die("BUG: ref_store is type \"%s\" not \"files\" in %s",
 139                    ref_store->be->name, caller);
 140
 141        refs = (struct files_ref_store *)ref_store;
 142
 143        if ((refs->store_flags & required_flags) != required_flags)
 144                die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
 145                    caller, required_flags, refs->store_flags);
 146
 147        return refs;
 148}
 149
 150static void files_reflog_path(struct files_ref_store *refs,
 151                              struct strbuf *sb,
 152                              const char *refname)
 153{
 154        switch (ref_type(refname)) {
 155        case REF_TYPE_PER_WORKTREE:
 156        case REF_TYPE_PSEUDOREF:
 157                strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 158                break;
 159        case REF_TYPE_NORMAL:
 160                strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 161                break;
 162        default:
 163                die("BUG: unknown ref type %d of ref %s",
 164                    ref_type(refname), refname);
 165        }
 166}
 167
 168static void files_ref_path(struct files_ref_store *refs,
 169                           struct strbuf *sb,
 170                           const char *refname)
 171{
 172        switch (ref_type(refname)) {
 173        case REF_TYPE_PER_WORKTREE:
 174        case REF_TYPE_PSEUDOREF:
 175                strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 176                break;
 177        case REF_TYPE_NORMAL:
 178                strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 179                break;
 180        default:
 181                die("BUG: unknown ref type %d of ref %s",
 182                    ref_type(refname), refname);
 183        }
 184}
 185
 186/*
 187 * Read the loose references from the namespace dirname into dir
 188 * (without recursing).  dirname must end with '/'.  dir must be the
 189 * directory entry corresponding to dirname.
 190 */
 191static void loose_fill_ref_dir(struct ref_store *ref_store,
 192                               struct ref_dir *dir, const char *dirname)
 193{
 194        struct files_ref_store *refs =
 195                files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 196        DIR *d;
 197        struct dirent *de;
 198        int dirnamelen = strlen(dirname);
 199        struct strbuf refname;
 200        struct strbuf path = STRBUF_INIT;
 201        size_t path_baselen;
 202
 203        files_ref_path(refs, &path, dirname);
 204        path_baselen = path.len;
 205
 206        d = opendir(path.buf);
 207        if (!d) {
 208                strbuf_release(&path);
 209                return;
 210        }
 211
 212        strbuf_init(&refname, dirnamelen + 257);
 213        strbuf_add(&refname, dirname, dirnamelen);
 214
 215        while ((de = readdir(d)) != NULL) {
 216                struct object_id oid;
 217                struct stat st;
 218                int flag;
 219
 220                if (de->d_name[0] == '.')
 221                        continue;
 222                if (ends_with(de->d_name, ".lock"))
 223                        continue;
 224                strbuf_addstr(&refname, de->d_name);
 225                strbuf_addstr(&path, de->d_name);
 226                if (stat(path.buf, &st) < 0) {
 227                        ; /* silently ignore */
 228                } else if (S_ISDIR(st.st_mode)) {
 229                        strbuf_addch(&refname, '/');
 230                        add_entry_to_dir(dir,
 231                                         create_dir_entry(dir->cache, refname.buf,
 232                                                          refname.len, 1));
 233                } else {
 234                        if (!refs_resolve_ref_unsafe(&refs->base,
 235                                                     refname.buf,
 236                                                     RESOLVE_REF_READING,
 237                                                     &oid, &flag)) {
 238                                oidclr(&oid);
 239                                flag |= REF_ISBROKEN;
 240                        } else if (is_null_oid(&oid)) {
 241                                /*
 242                                 * It is so astronomically unlikely
 243                                 * that null_oid is the OID of an
 244                                 * actual object that we consider its
 245                                 * appearance in a loose reference
 246                                 * file to be repo corruption
 247                                 * (probably due to a software bug).
 248                                 */
 249                                flag |= REF_ISBROKEN;
 250                        }
 251
 252                        if (check_refname_format(refname.buf,
 253                                                 REFNAME_ALLOW_ONELEVEL)) {
 254                                if (!refname_is_safe(refname.buf))
 255                                        die("loose refname is dangerous: %s", refname.buf);
 256                                oidclr(&oid);
 257                                flag |= REF_BAD_NAME | REF_ISBROKEN;
 258                        }
 259                        add_entry_to_dir(dir,
 260                                         create_ref_entry(refname.buf, &oid, flag));
 261                }
 262                strbuf_setlen(&refname, dirnamelen);
 263                strbuf_setlen(&path, path_baselen);
 264        }
 265        strbuf_release(&refname);
 266        strbuf_release(&path);
 267        closedir(d);
 268
 269        /*
 270         * Manually add refs/bisect, which, being per-worktree, might
 271         * not appear in the directory listing for refs/ in the main
 272         * repo.
 273         */
 274        if (!strcmp(dirname, "refs/")) {
 275                int pos = search_ref_dir(dir, "refs/bisect/", 12);
 276
 277                if (pos < 0) {
 278                        struct ref_entry *child_entry = create_dir_entry(
 279                                        dir->cache, "refs/bisect/", 12, 1);
 280                        add_entry_to_dir(dir, child_entry);
 281                }
 282        }
 283}
 284
 285static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 286{
 287        if (!refs->loose) {
 288                /*
 289                 * Mark the top-level directory complete because we
 290                 * are about to read the only subdirectory that can
 291                 * hold references:
 292                 */
 293                refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 294
 295                /* We're going to fill the top level ourselves: */
 296                refs->loose->root->flag &= ~REF_INCOMPLETE;
 297
 298                /*
 299                 * Add an incomplete entry for "refs/" (to be filled
 300                 * lazily):
 301                 */
 302                add_entry_to_dir(get_ref_dir(refs->loose->root),
 303                                 create_dir_entry(refs->loose, "refs/", 5, 1));
 304        }
 305        return refs->loose;
 306}
 307
 308static int files_read_raw_ref(struct ref_store *ref_store,
 309                              const char *refname, struct object_id *oid,
 310                              struct strbuf *referent, unsigned int *type)
 311{
 312        struct files_ref_store *refs =
 313                files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 314        struct strbuf sb_contents = STRBUF_INIT;
 315        struct strbuf sb_path = STRBUF_INIT;
 316        const char *path;
 317        const char *buf;
 318        const char *p;
 319        struct stat st;
 320        int fd;
 321        int ret = -1;
 322        int save_errno;
 323        int remaining_retries = 3;
 324
 325        *type = 0;
 326        strbuf_reset(&sb_path);
 327
 328        files_ref_path(refs, &sb_path, refname);
 329
 330        path = sb_path.buf;
 331
 332stat_ref:
 333        /*
 334         * We might have to loop back here to avoid a race
 335         * condition: first we lstat() the file, then we try
 336         * to read it as a link or as a file.  But if somebody
 337         * changes the type of the file (file <-> directory
 338         * <-> symlink) between the lstat() and reading, then
 339         * we don't want to report that as an error but rather
 340         * try again starting with the lstat().
 341         *
 342         * We'll keep a count of the retries, though, just to avoid
 343         * any confusing situation sending us into an infinite loop.
 344         */
 345
 346        if (remaining_retries-- <= 0)
 347                goto out;
 348
 349        if (lstat(path, &st) < 0) {
 350                if (errno != ENOENT)
 351                        goto out;
 352                if (refs_read_raw_ref(refs->packed_ref_store, refname,
 353                                      oid, referent, type)) {
 354                        errno = ENOENT;
 355                        goto out;
 356                }
 357                ret = 0;
 358                goto out;
 359        }
 360
 361        /* Follow "normalized" - ie "refs/.." symlinks by hand */
 362        if (S_ISLNK(st.st_mode)) {
 363                strbuf_reset(&sb_contents);
 364                if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 365                        if (errno == ENOENT || errno == EINVAL)
 366                                /* inconsistent with lstat; retry */
 367                                goto stat_ref;
 368                        else
 369                                goto out;
 370                }
 371                if (starts_with(sb_contents.buf, "refs/") &&
 372                    !check_refname_format(sb_contents.buf, 0)) {
 373                        strbuf_swap(&sb_contents, referent);
 374                        *type |= REF_ISSYMREF;
 375                        ret = 0;
 376                        goto out;
 377                }
 378                /*
 379                 * It doesn't look like a refname; fall through to just
 380                 * treating it like a non-symlink, and reading whatever it
 381                 * points to.
 382                 */
 383        }
 384
 385        /* Is it a directory? */
 386        if (S_ISDIR(st.st_mode)) {
 387                /*
 388                 * Even though there is a directory where the loose
 389                 * ref is supposed to be, there could still be a
 390                 * packed ref:
 391                 */
 392                if (refs_read_raw_ref(refs->packed_ref_store, refname,
 393                                      oid, referent, type)) {
 394                        errno = EISDIR;
 395                        goto out;
 396                }
 397                ret = 0;
 398                goto out;
 399        }
 400
 401        /*
 402         * Anything else, just open it and try to use it as
 403         * a ref
 404         */
 405        fd = open(path, O_RDONLY);
 406        if (fd < 0) {
 407                if (errno == ENOENT && !S_ISLNK(st.st_mode))
 408                        /* inconsistent with lstat; retry */
 409                        goto stat_ref;
 410                else
 411                        goto out;
 412        }
 413        strbuf_reset(&sb_contents);
 414        if (strbuf_read(&sb_contents, fd, 256) < 0) {
 415                int save_errno = errno;
 416                close(fd);
 417                errno = save_errno;
 418                goto out;
 419        }
 420        close(fd);
 421        strbuf_rtrim(&sb_contents);
 422        buf = sb_contents.buf;
 423        if (starts_with(buf, "ref:")) {
 424                buf += 4;
 425                while (isspace(*buf))
 426                        buf++;
 427
 428                strbuf_reset(referent);
 429                strbuf_addstr(referent, buf);
 430                *type |= REF_ISSYMREF;
 431                ret = 0;
 432                goto out;
 433        }
 434
 435        /*
 436         * Please note that FETCH_HEAD has additional
 437         * data after the sha.
 438         */
 439        if (parse_oid_hex(buf, oid, &p) ||
 440            (*p != '\0' && !isspace(*p))) {
 441                *type |= REF_ISBROKEN;
 442                errno = EINVAL;
 443                goto out;
 444        }
 445
 446        ret = 0;
 447
 448out:
 449        save_errno = errno;
 450        strbuf_release(&sb_path);
 451        strbuf_release(&sb_contents);
 452        errno = save_errno;
 453        return ret;
 454}
 455
 456static void unlock_ref(struct ref_lock *lock)
 457{
 458        rollback_lock_file(&lock->lk);
 459        free(lock->ref_name);
 460        free(lock);
 461}
 462
 463/*
 464 * Lock refname, without following symrefs, and set *lock_p to point
 465 * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 466 * and type similarly to read_raw_ref().
 467 *
 468 * The caller must verify that refname is a "safe" reference name (in
 469 * the sense of refname_is_safe()) before calling this function.
 470 *
 471 * If the reference doesn't already exist, verify that refname doesn't
 472 * have a D/F conflict with any existing references. extras and skip
 473 * are passed to refs_verify_refname_available() for this check.
 474 *
 475 * If mustexist is not set and the reference is not found or is
 476 * broken, lock the reference anyway but clear old_oid.
 477 *
 478 * Return 0 on success. On failure, write an error message to err and
 479 * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 480 *
 481 * Implementation note: This function is basically
 482 *
 483 *     lock reference
 484 *     read_raw_ref()
 485 *
 486 * but it includes a lot more code to
 487 * - Deal with possible races with other processes
 488 * - Avoid calling refs_verify_refname_available() when it can be
 489 *   avoided, namely if we were successfully able to read the ref
 490 * - Generate informative error messages in the case of failure
 491 */
 492static int lock_raw_ref(struct files_ref_store *refs,
 493                        const char *refname, int mustexist,
 494                        const struct string_list *extras,
 495                        const struct string_list *skip,
 496                        struct ref_lock **lock_p,
 497                        struct strbuf *referent,
 498                        unsigned int *type,
 499                        struct strbuf *err)
 500{
 501        struct ref_lock *lock;
 502        struct strbuf ref_file = STRBUF_INIT;
 503        int attempts_remaining = 3;
 504        int ret = TRANSACTION_GENERIC_ERROR;
 505
 506        assert(err);
 507        files_assert_main_repository(refs, "lock_raw_ref");
 508
 509        *type = 0;
 510
 511        /* First lock the file so it can't change out from under us. */
 512
 513        *lock_p = lock = xcalloc(1, sizeof(*lock));
 514
 515        lock->ref_name = xstrdup(refname);
 516        files_ref_path(refs, &ref_file, refname);
 517
 518retry:
 519        switch (safe_create_leading_directories(ref_file.buf)) {
 520        case SCLD_OK:
 521                break; /* success */
 522        case SCLD_EXISTS:
 523                /*
 524                 * Suppose refname is "refs/foo/bar". We just failed
 525                 * to create the containing directory, "refs/foo",
 526                 * because there was a non-directory in the way. This
 527                 * indicates a D/F conflict, probably because of
 528                 * another reference such as "refs/foo". There is no
 529                 * reason to expect this error to be transitory.
 530                 */
 531                if (refs_verify_refname_available(&refs->base, refname,
 532                                                  extras, skip, err)) {
 533                        if (mustexist) {
 534                                /*
 535                                 * To the user the relevant error is
 536                                 * that the "mustexist" reference is
 537                                 * missing:
 538                                 */
 539                                strbuf_reset(err);
 540                                strbuf_addf(err, "unable to resolve reference '%s'",
 541                                            refname);
 542                        } else {
 543                                /*
 544                                 * The error message set by
 545                                 * refs_verify_refname_available() is
 546                                 * OK.
 547                                 */
 548                                ret = TRANSACTION_NAME_CONFLICT;
 549                        }
 550                } else {
 551                        /*
 552                         * The file that is in the way isn't a loose
 553                         * reference. Report it as a low-level
 554                         * failure.
 555                         */
 556                        strbuf_addf(err, "unable to create lock file %s.lock; "
 557                                    "non-directory in the way",
 558                                    ref_file.buf);
 559                }
 560                goto error_return;
 561        case SCLD_VANISHED:
 562                /* Maybe another process was tidying up. Try again. */
 563                if (--attempts_remaining > 0)
 564                        goto retry;
 565                /* fall through */
 566        default:
 567                strbuf_addf(err, "unable to create directory for %s",
 568                            ref_file.buf);
 569                goto error_return;
 570        }
 571
 572        if (hold_lock_file_for_update_timeout(
 573                            &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 574                            get_files_ref_lock_timeout_ms()) < 0) {
 575                if (errno == ENOENT && --attempts_remaining > 0) {
 576                        /*
 577                         * Maybe somebody just deleted one of the
 578                         * directories leading to ref_file.  Try
 579                         * again:
 580                         */
 581                        goto retry;
 582                } else {
 583                        unable_to_lock_message(ref_file.buf, errno, err);
 584                        goto error_return;
 585                }
 586        }
 587
 588        /*
 589         * Now we hold the lock and can read the reference without
 590         * fear that its value will change.
 591         */
 592
 593        if (files_read_raw_ref(&refs->base, refname,
 594                               &lock->old_oid, referent, type)) {
 595                if (errno == ENOENT) {
 596                        if (mustexist) {
 597                                /* Garden variety missing reference. */
 598                                strbuf_addf(err, "unable to resolve reference '%s'",
 599                                            refname);
 600                                goto error_return;
 601                        } else {
 602                                /*
 603                                 * Reference is missing, but that's OK. We
 604                                 * know that there is not a conflict with
 605                                 * another loose reference because
 606                                 * (supposing that we are trying to lock
 607                                 * reference "refs/foo/bar"):
 608                                 *
 609                                 * - We were successfully able to create
 610                                 *   the lockfile refs/foo/bar.lock, so we
 611                                 *   know there cannot be a loose reference
 612                                 *   named "refs/foo".
 613                                 *
 614                                 * - We got ENOENT and not EISDIR, so we
 615                                 *   know that there cannot be a loose
 616                                 *   reference named "refs/foo/bar/baz".
 617                                 */
 618                        }
 619                } else if (errno == EISDIR) {
 620                        /*
 621                         * There is a directory in the way. It might have
 622                         * contained references that have been deleted. If
 623                         * we don't require that the reference already
 624                         * exists, try to remove the directory so that it
 625                         * doesn't cause trouble when we want to rename the
 626                         * lockfile into place later.
 627                         */
 628                        if (mustexist) {
 629                                /* Garden variety missing reference. */
 630                                strbuf_addf(err, "unable to resolve reference '%s'",
 631                                            refname);
 632                                goto error_return;
 633                        } else if (remove_dir_recursively(&ref_file,
 634                                                          REMOVE_DIR_EMPTY_ONLY)) {
 635                                if (refs_verify_refname_available(
 636                                                    &refs->base, refname,
 637                                                    extras, skip, err)) {
 638                                        /*
 639                                         * The error message set by
 640                                         * verify_refname_available() is OK.
 641                                         */
 642                                        ret = TRANSACTION_NAME_CONFLICT;
 643                                        goto error_return;
 644                                } else {
 645                                        /*
 646                                         * We can't delete the directory,
 647                                         * but we also don't know of any
 648                                         * references that it should
 649                                         * contain.
 650                                         */
 651                                        strbuf_addf(err, "there is a non-empty directory '%s' "
 652                                                    "blocking reference '%s'",
 653                                                    ref_file.buf, refname);
 654                                        goto error_return;
 655                                }
 656                        }
 657                } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 658                        strbuf_addf(err, "unable to resolve reference '%s': "
 659                                    "reference broken", refname);
 660                        goto error_return;
 661                } else {
 662                        strbuf_addf(err, "unable to resolve reference '%s': %s",
 663                                    refname, strerror(errno));
 664                        goto error_return;
 665                }
 666
 667                /*
 668                 * If the ref did not exist and we are creating it,
 669                 * make sure there is no existing packed ref that
 670                 * conflicts with refname:
 671                 */
 672                if (refs_verify_refname_available(
 673                                    refs->packed_ref_store, refname,
 674                                    extras, skip, err))
 675                        goto error_return;
 676        }
 677
 678        ret = 0;
 679        goto out;
 680
 681error_return:
 682        unlock_ref(lock);
 683        *lock_p = NULL;
 684
 685out:
 686        strbuf_release(&ref_file);
 687        return ret;
 688}
 689
 690struct files_ref_iterator {
 691        struct ref_iterator base;
 692
 693        struct ref_iterator *iter0;
 694        unsigned int flags;
 695};
 696
 697static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 698{
 699        struct files_ref_iterator *iter =
 700                (struct files_ref_iterator *)ref_iterator;
 701        int ok;
 702
 703        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 704                if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 705                    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 706                        continue;
 707
 708                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 709                    !ref_resolves_to_object(iter->iter0->refname,
 710                                            iter->iter0->oid,
 711                                            iter->iter0->flags))
 712                        continue;
 713
 714                iter->base.refname = iter->iter0->refname;
 715                iter->base.oid = iter->iter0->oid;
 716                iter->base.flags = iter->iter0->flags;
 717                return ITER_OK;
 718        }
 719
 720        iter->iter0 = NULL;
 721        if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 722                ok = ITER_ERROR;
 723
 724        return ok;
 725}
 726
 727static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 728                                   struct object_id *peeled)
 729{
 730        struct files_ref_iterator *iter =
 731                (struct files_ref_iterator *)ref_iterator;
 732
 733        return ref_iterator_peel(iter->iter0, peeled);
 734}
 735
 736static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 737{
 738        struct files_ref_iterator *iter =
 739                (struct files_ref_iterator *)ref_iterator;
 740        int ok = ITER_DONE;
 741
 742        if (iter->iter0)
 743                ok = ref_iterator_abort(iter->iter0);
 744
 745        base_ref_iterator_free(ref_iterator);
 746        return ok;
 747}
 748
 749static struct ref_iterator_vtable files_ref_iterator_vtable = {
 750        files_ref_iterator_advance,
 751        files_ref_iterator_peel,
 752        files_ref_iterator_abort
 753};
 754
 755static struct ref_iterator *files_ref_iterator_begin(
 756                struct ref_store *ref_store,
 757                const char *prefix, unsigned int flags)
 758{
 759        struct files_ref_store *refs;
 760        struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 761        struct files_ref_iterator *iter;
 762        struct ref_iterator *ref_iterator;
 763        unsigned int required_flags = REF_STORE_READ;
 764
 765        if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 766                required_flags |= REF_STORE_ODB;
 767
 768        refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 769
 770        /*
 771         * We must make sure that all loose refs are read before
 772         * accessing the packed-refs file; this avoids a race
 773         * condition if loose refs are migrated to the packed-refs
 774         * file by a simultaneous process, but our in-memory view is
 775         * from before the migration. We ensure this as follows:
 776         * First, we call start the loose refs iteration with its
 777         * `prime_ref` argument set to true. This causes the loose
 778         * references in the subtree to be pre-read into the cache.
 779         * (If they've already been read, that's OK; we only need to
 780         * guarantee that they're read before the packed refs, not
 781         * *how much* before.) After that, we call
 782         * packed_ref_iterator_begin(), which internally checks
 783         * whether the packed-ref cache is up to date with what is on
 784         * disk, and re-reads it if not.
 785         */
 786
 787        loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 788                                              prefix, 1);
 789
 790        /*
 791         * The packed-refs file might contain broken references, for
 792         * example an old version of a reference that points at an
 793         * object that has since been garbage-collected. This is OK as
 794         * long as there is a corresponding loose reference that
 795         * overrides it, and we don't want to emit an error message in
 796         * this case. So ask the packed_ref_store for all of its
 797         * references, and (if needed) do our own check for broken
 798         * ones in files_ref_iterator_advance(), after we have merged
 799         * the packed and loose references.
 800         */
 801        packed_iter = refs_ref_iterator_begin(
 802                        refs->packed_ref_store, prefix, 0,
 803                        DO_FOR_EACH_INCLUDE_BROKEN);
 804
 805        overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 806
 807        iter = xcalloc(1, sizeof(*iter));
 808        ref_iterator = &iter->base;
 809        base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 810                               overlay_iter->ordered);
 811        iter->iter0 = overlay_iter;
 812        iter->flags = flags;
 813
 814        return ref_iterator;
 815}
 816
 817/*
 818 * Verify that the reference locked by lock has the value old_oid
 819 * (unless it is NULL).  Fail if the reference doesn't exist and
 820 * mustexist is set. Return 0 on success. On error, write an error
 821 * message to err, set errno, and return a negative value.
 822 */
 823static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 824                       const struct object_id *old_oid, int mustexist,
 825                       struct strbuf *err)
 826{
 827        assert(err);
 828
 829        if (refs_read_ref_full(ref_store, lock->ref_name,
 830                               mustexist ? RESOLVE_REF_READING : 0,
 831                               &lock->old_oid, NULL)) {
 832                if (old_oid) {
 833                        int save_errno = errno;
 834                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 835                        errno = save_errno;
 836                        return -1;
 837                } else {
 838                        oidclr(&lock->old_oid);
 839                        return 0;
 840                }
 841        }
 842        if (old_oid && oidcmp(&lock->old_oid, old_oid)) {
 843                strbuf_addf(err, "ref '%s' is at %s but expected %s",
 844                            lock->ref_name,
 845                            oid_to_hex(&lock->old_oid),
 846                            oid_to_hex(old_oid));
 847                errno = EBUSY;
 848                return -1;
 849        }
 850        return 0;
 851}
 852
 853static int remove_empty_directories(struct strbuf *path)
 854{
 855        /*
 856         * we want to create a file but there is a directory there;
 857         * if that is an empty directory (or a directory that contains
 858         * only empty directories), remove them.
 859         */
 860        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 861}
 862
 863static int create_reflock(const char *path, void *cb)
 864{
 865        struct lock_file *lk = cb;
 866
 867        return hold_lock_file_for_update_timeout(
 868                        lk, path, LOCK_NO_DEREF,
 869                        get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 870}
 871
 872/*
 873 * Locks a ref returning the lock on success and NULL on failure.
 874 * On failure errno is set to something meaningful.
 875 */
 876static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
 877                                           const char *refname,
 878                                           const struct object_id *old_oid,
 879                                           const struct string_list *extras,
 880                                           const struct string_list *skip,
 881                                           unsigned int flags, int *type,
 882                                           struct strbuf *err)
 883{
 884        struct strbuf ref_file = STRBUF_INIT;
 885        struct ref_lock *lock;
 886        int last_errno = 0;
 887        int mustexist = (old_oid && !is_null_oid(old_oid));
 888        int resolve_flags = RESOLVE_REF_NO_RECURSE;
 889        int resolved;
 890
 891        files_assert_main_repository(refs, "lock_ref_oid_basic");
 892        assert(err);
 893
 894        lock = xcalloc(1, sizeof(struct ref_lock));
 895
 896        if (mustexist)
 897                resolve_flags |= RESOLVE_REF_READING;
 898        if (flags & REF_DELETING)
 899                resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 900
 901        files_ref_path(refs, &ref_file, refname);
 902        resolved = !!refs_resolve_ref_unsafe(&refs->base,
 903                                             refname, resolve_flags,
 904                                             &lock->old_oid, type);
 905        if (!resolved && errno == EISDIR) {
 906                /*
 907                 * we are trying to lock foo but we used to
 908                 * have foo/bar which now does not exist;
 909                 * it is normal for the empty directory 'foo'
 910                 * to remain.
 911                 */
 912                if (remove_empty_directories(&ref_file)) {
 913                        last_errno = errno;
 914                        if (!refs_verify_refname_available(
 915                                            &refs->base,
 916                                            refname, extras, skip, err))
 917                                strbuf_addf(err, "there are still refs under '%s'",
 918                                            refname);
 919                        goto error_return;
 920                }
 921                resolved = !!refs_resolve_ref_unsafe(&refs->base,
 922                                                     refname, resolve_flags,
 923                                                     &lock->old_oid, type);
 924        }
 925        if (!resolved) {
 926                last_errno = errno;
 927                if (last_errno != ENOTDIR ||
 928                    !refs_verify_refname_available(&refs->base, refname,
 929                                                   extras, skip, err))
 930                        strbuf_addf(err, "unable to resolve reference '%s': %s",
 931                                    refname, strerror(last_errno));
 932
 933                goto error_return;
 934        }
 935
 936        /*
 937         * If the ref did not exist and we are creating it, make sure
 938         * there is no existing packed ref whose name begins with our
 939         * refname, nor a packed ref whose name is a proper prefix of
 940         * our refname.
 941         */
 942        if (is_null_oid(&lock->old_oid) &&
 943            refs_verify_refname_available(refs->packed_ref_store, refname,
 944                                          extras, skip, err)) {
 945                last_errno = ENOTDIR;
 946                goto error_return;
 947        }
 948
 949        lock->ref_name = xstrdup(refname);
 950
 951        if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 952                last_errno = errno;
 953                unable_to_lock_message(ref_file.buf, errno, err);
 954                goto error_return;
 955        }
 956
 957        if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
 958                last_errno = errno;
 959                goto error_return;
 960        }
 961        goto out;
 962
 963 error_return:
 964        unlock_ref(lock);
 965        lock = NULL;
 966
 967 out:
 968        strbuf_release(&ref_file);
 969        errno = last_errno;
 970        return lock;
 971}
 972
 973struct ref_to_prune {
 974        struct ref_to_prune *next;
 975        struct object_id oid;
 976        char name[FLEX_ARRAY];
 977};
 978
 979enum {
 980        REMOVE_EMPTY_PARENTS_REF = 0x01,
 981        REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 982};
 983
 984/*
 985 * Remove empty parent directories associated with the specified
 986 * reference and/or its reflog, but spare [logs/]refs/ and immediate
 987 * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 988 * REMOVE_EMPTY_PARENTS_REFLOG.
 989 */
 990static void try_remove_empty_parents(struct files_ref_store *refs,
 991                                     const char *refname,
 992                                     unsigned int flags)
 993{
 994        struct strbuf buf = STRBUF_INIT;
 995        struct strbuf sb = STRBUF_INIT;
 996        char *p, *q;
 997        int i;
 998
 999        strbuf_addstr(&buf, refname);
1000        p = buf.buf;
1001        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1002                while (*p && *p != '/')
1003                        p++;
1004                /* tolerate duplicate slashes; see check_refname_format() */
1005                while (*p == '/')
1006                        p++;
1007        }
1008        q = buf.buf + buf.len;
1009        while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1010                while (q > p && *q != '/')
1011                        q--;
1012                while (q > p && *(q-1) == '/')
1013                        q--;
1014                if (q == p)
1015                        break;
1016                strbuf_setlen(&buf, q - buf.buf);
1017
1018                strbuf_reset(&sb);
1019                files_ref_path(refs, &sb, buf.buf);
1020                if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1021                        flags &= ~REMOVE_EMPTY_PARENTS_REF;
1022
1023                strbuf_reset(&sb);
1024                files_reflog_path(refs, &sb, buf.buf);
1025                if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1026                        flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1027        }
1028        strbuf_release(&buf);
1029        strbuf_release(&sb);
1030}
1031
1032/* make sure nobody touched the ref, and unlink */
1033static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1034{
1035        struct ref_transaction *transaction;
1036        struct strbuf err = STRBUF_INIT;
1037        int ret = -1;
1038
1039        if (check_refname_format(r->name, 0))
1040                return;
1041
1042        transaction = ref_store_transaction_begin(&refs->base, &err);
1043        if (!transaction)
1044                goto cleanup;
1045        ref_transaction_add_update(
1046                        transaction, r->name,
1047                        REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
1048                        &null_oid, &r->oid, NULL);
1049        if (ref_transaction_commit(transaction, &err))
1050                goto cleanup;
1051
1052        ret = 0;
1053
1054cleanup:
1055        if (ret)
1056                error("%s", err.buf);
1057        strbuf_release(&err);
1058        ref_transaction_free(transaction);
1059        return;
1060}
1061
1062/*
1063 * Prune the loose versions of the references in the linked list
1064 * `*refs_to_prune`, freeing the entries in the list as we go.
1065 */
1066static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1067{
1068        while (*refs_to_prune) {
1069                struct ref_to_prune *r = *refs_to_prune;
1070                *refs_to_prune = r->next;
1071                prune_ref(refs, r);
1072                free(r);
1073        }
1074}
1075
1076/*
1077 * Return true if the specified reference should be packed.
1078 */
1079static int should_pack_ref(const char *refname,
1080                           const struct object_id *oid, unsigned int ref_flags,
1081                           unsigned int pack_flags)
1082{
1083        /* Do not pack per-worktree refs: */
1084        if (ref_type(refname) != REF_TYPE_NORMAL)
1085                return 0;
1086
1087        /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1088        if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1089                return 0;
1090
1091        /* Do not pack symbolic refs: */
1092        if (ref_flags & REF_ISSYMREF)
1093                return 0;
1094
1095        /* Do not pack broken refs: */
1096        if (!ref_resolves_to_object(refname, oid, ref_flags))
1097                return 0;
1098
1099        return 1;
1100}
1101
1102static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1103{
1104        struct files_ref_store *refs =
1105                files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1106                               "pack_refs");
1107        struct ref_iterator *iter;
1108        int ok;
1109        struct ref_to_prune *refs_to_prune = NULL;
1110        struct strbuf err = STRBUF_INIT;
1111        struct ref_transaction *transaction;
1112
1113        transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1114        if (!transaction)
1115                return -1;
1116
1117        packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1118
1119        iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1120        while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1121                /*
1122                 * If the loose reference can be packed, add an entry
1123                 * in the packed ref cache. If the reference should be
1124                 * pruned, also add it to refs_to_prune.
1125                 */
1126                if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1127                                     flags))
1128                        continue;
1129
1130                /*
1131                 * Add a reference creation for this reference to the
1132                 * packed-refs transaction:
1133                 */
1134                if (ref_transaction_update(transaction, iter->refname,
1135                                           iter->oid, NULL,
1136                                           REF_NO_DEREF, NULL, &err))
1137                        die("failure preparing to create packed reference %s: %s",
1138                            iter->refname, err.buf);
1139
1140                /* Schedule the loose reference for pruning if requested. */
1141                if ((flags & PACK_REFS_PRUNE)) {
1142                        struct ref_to_prune *n;
1143                        FLEX_ALLOC_STR(n, name, iter->refname);
1144                        oidcpy(&n->oid, iter->oid);
1145                        n->next = refs_to_prune;
1146                        refs_to_prune = n;
1147                }
1148        }
1149        if (ok != ITER_DONE)
1150                die("error while iterating over references");
1151
1152        if (ref_transaction_commit(transaction, &err))
1153                die("unable to write new packed-refs: %s", err.buf);
1154
1155        ref_transaction_free(transaction);
1156
1157        packed_refs_unlock(refs->packed_ref_store);
1158
1159        prune_refs(refs, &refs_to_prune);
1160        strbuf_release(&err);
1161        return 0;
1162}
1163
1164static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1165                             struct string_list *refnames, unsigned int flags)
1166{
1167        struct files_ref_store *refs =
1168                files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1169        struct strbuf err = STRBUF_INIT;
1170        int i, result = 0;
1171
1172        if (!refnames->nr)
1173                return 0;
1174
1175        if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1176                goto error;
1177
1178        if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1179                packed_refs_unlock(refs->packed_ref_store);
1180                goto error;
1181        }
1182
1183        packed_refs_unlock(refs->packed_ref_store);
1184
1185        for (i = 0; i < refnames->nr; i++) {
1186                const char *refname = refnames->items[i].string;
1187
1188                if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1189                        result |= error(_("could not remove reference %s"), refname);
1190        }
1191
1192        strbuf_release(&err);
1193        return result;
1194
1195error:
1196        /*
1197         * If we failed to rewrite the packed-refs file, then it is
1198         * unsafe to try to remove loose refs, because doing so might
1199         * expose an obsolete packed value for a reference that might
1200         * even point at an object that has been garbage collected.
1201         */
1202        if (refnames->nr == 1)
1203                error(_("could not delete reference %s: %s"),
1204                      refnames->items[0].string, err.buf);
1205        else
1206                error(_("could not delete references: %s"), err.buf);
1207
1208        strbuf_release(&err);
1209        return -1;
1210}
1211
1212/*
1213 * People using contrib's git-new-workdir have .git/logs/refs ->
1214 * /some/other/path/.git/logs/refs, and that may live on another device.
1215 *
1216 * IOW, to avoid cross device rename errors, the temporary renamed log must
1217 * live into logs/refs.
1218 */
1219#define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1220
1221struct rename_cb {
1222        const char *tmp_renamed_log;
1223        int true_errno;
1224};
1225
1226static int rename_tmp_log_callback(const char *path, void *cb_data)
1227{
1228        struct rename_cb *cb = cb_data;
1229
1230        if (rename(cb->tmp_renamed_log, path)) {
1231                /*
1232                 * rename(a, b) when b is an existing directory ought
1233                 * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1234                 * Sheesh. Record the true errno for error reporting,
1235                 * but report EISDIR to raceproof_create_file() so
1236                 * that it knows to retry.
1237                 */
1238                cb->true_errno = errno;
1239                if (errno == ENOTDIR)
1240                        errno = EISDIR;
1241                return -1;
1242        } else {
1243                return 0;
1244        }
1245}
1246
1247static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1248{
1249        struct strbuf path = STRBUF_INIT;
1250        struct strbuf tmp = STRBUF_INIT;
1251        struct rename_cb cb;
1252        int ret;
1253
1254        files_reflog_path(refs, &path, newrefname);
1255        files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1256        cb.tmp_renamed_log = tmp.buf;
1257        ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1258        if (ret) {
1259                if (errno == EISDIR)
1260                        error("directory not empty: %s", path.buf);
1261                else
1262                        error("unable to move logfile %s to %s: %s",
1263                              tmp.buf, path.buf,
1264                              strerror(cb.true_errno));
1265        }
1266
1267        strbuf_release(&path);
1268        strbuf_release(&tmp);
1269        return ret;
1270}
1271
1272static int write_ref_to_lockfile(struct ref_lock *lock,
1273                                 const struct object_id *oid, struct strbuf *err);
1274static int commit_ref_update(struct files_ref_store *refs,
1275                             struct ref_lock *lock,
1276                             const struct object_id *oid, const char *logmsg,
1277                             struct strbuf *err);
1278
1279static int files_copy_or_rename_ref(struct ref_store *ref_store,
1280                            const char *oldrefname, const char *newrefname,
1281                            const char *logmsg, int copy)
1282{
1283        struct files_ref_store *refs =
1284                files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1285        struct object_id oid, orig_oid;
1286        int flag = 0, logmoved = 0;
1287        struct ref_lock *lock;
1288        struct stat loginfo;
1289        struct strbuf sb_oldref = STRBUF_INIT;
1290        struct strbuf sb_newref = STRBUF_INIT;
1291        struct strbuf tmp_renamed_log = STRBUF_INIT;
1292        int log, ret;
1293        struct strbuf err = STRBUF_INIT;
1294
1295        files_reflog_path(refs, &sb_oldref, oldrefname);
1296        files_reflog_path(refs, &sb_newref, newrefname);
1297        files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1298
1299        log = !lstat(sb_oldref.buf, &loginfo);
1300        if (log && S_ISLNK(loginfo.st_mode)) {
1301                ret = error("reflog for %s is a symlink", oldrefname);
1302                goto out;
1303        }
1304
1305        if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1306                                     RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1307                                &orig_oid, &flag)) {
1308                ret = error("refname %s not found", oldrefname);
1309                goto out;
1310        }
1311
1312        if (flag & REF_ISSYMREF) {
1313                if (copy)
1314                        ret = error("refname %s is a symbolic ref, copying it is not supported",
1315                                    oldrefname);
1316                else
1317                        ret = error("refname %s is a symbolic ref, renaming it is not supported",
1318                                    oldrefname);
1319                goto out;
1320        }
1321        if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1322                ret = 1;
1323                goto out;
1324        }
1325
1326        if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1327                ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1328                            oldrefname, strerror(errno));
1329                goto out;
1330        }
1331
1332        if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1333                ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1334                            oldrefname, strerror(errno));
1335                goto out;
1336        }
1337
1338        if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1339                            &orig_oid, REF_NO_DEREF)) {
1340                error("unable to delete old %s", oldrefname);
1341                goto rollback;
1342        }
1343
1344        /*
1345         * Since we are doing a shallow lookup, oid is not the
1346         * correct value to pass to delete_ref as old_oid. But that
1347         * doesn't matter, because an old_oid check wouldn't add to
1348         * the safety anyway; we want to delete the reference whatever
1349         * its current value.
1350         */
1351        if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1352                                RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1353                                &oid, NULL) &&
1354            refs_delete_ref(&refs->base, NULL, newrefname,
1355                            NULL, REF_NO_DEREF)) {
1356                if (errno == EISDIR) {
1357                        struct strbuf path = STRBUF_INIT;
1358                        int result;
1359
1360                        files_ref_path(refs, &path, newrefname);
1361                        result = remove_empty_directories(&path);
1362                        strbuf_release(&path);
1363
1364                        if (result) {
1365                                error("Directory not empty: %s", newrefname);
1366                                goto rollback;
1367                        }
1368                } else {
1369                        error("unable to delete existing %s", newrefname);
1370                        goto rollback;
1371                }
1372        }
1373
1374        if (log && rename_tmp_log(refs, newrefname))
1375                goto rollback;
1376
1377        logmoved = log;
1378
1379        lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1380                                  REF_NO_DEREF, NULL, &err);
1381        if (!lock) {
1382                if (copy)
1383                        error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1384                else
1385                        error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1386                strbuf_release(&err);
1387                goto rollback;
1388        }
1389        oidcpy(&lock->old_oid, &orig_oid);
1390
1391        if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1392            commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1393                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1394                strbuf_release(&err);
1395                goto rollback;
1396        }
1397
1398        ret = 0;
1399        goto out;
1400
1401 rollback:
1402        lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1403                                  REF_NO_DEREF, NULL, &err);
1404        if (!lock) {
1405                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1406                strbuf_release(&err);
1407                goto rollbacklog;
1408        }
1409
1410        flag = log_all_ref_updates;
1411        log_all_ref_updates = LOG_REFS_NONE;
1412        if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1413            commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1414                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1415                strbuf_release(&err);
1416        }
1417        log_all_ref_updates = flag;
1418
1419 rollbacklog:
1420        if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1421                error("unable to restore logfile %s from %s: %s",
1422                        oldrefname, newrefname, strerror(errno));
1423        if (!logmoved && log &&
1424            rename(tmp_renamed_log.buf, sb_oldref.buf))
1425                error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1426                        oldrefname, strerror(errno));
1427        ret = 1;
1428 out:
1429        strbuf_release(&sb_newref);
1430        strbuf_release(&sb_oldref);
1431        strbuf_release(&tmp_renamed_log);
1432
1433        return ret;
1434}
1435
1436static int files_rename_ref(struct ref_store *ref_store,
1437                            const char *oldrefname, const char *newrefname,
1438                            const char *logmsg)
1439{
1440        return files_copy_or_rename_ref(ref_store, oldrefname,
1441                                 newrefname, logmsg, 0);
1442}
1443
1444static int files_copy_ref(struct ref_store *ref_store,
1445                            const char *oldrefname, const char *newrefname,
1446                            const char *logmsg)
1447{
1448        return files_copy_or_rename_ref(ref_store, oldrefname,
1449                                 newrefname, logmsg, 1);
1450}
1451
1452static int close_ref_gently(struct ref_lock *lock)
1453{
1454        if (close_lock_file_gently(&lock->lk))
1455                return -1;
1456        return 0;
1457}
1458
1459static int commit_ref(struct ref_lock *lock)
1460{
1461        char *path = get_locked_file_path(&lock->lk);
1462        struct stat st;
1463
1464        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1465                /*
1466                 * There is a directory at the path we want to rename
1467                 * the lockfile to. Hopefully it is empty; try to
1468                 * delete it.
1469                 */
1470                size_t len = strlen(path);
1471                struct strbuf sb_path = STRBUF_INIT;
1472
1473                strbuf_attach(&sb_path, path, len, len);
1474
1475                /*
1476                 * If this fails, commit_lock_file() will also fail
1477                 * and will report the problem.
1478                 */
1479                remove_empty_directories(&sb_path);
1480                strbuf_release(&sb_path);
1481        } else {
1482                free(path);
1483        }
1484
1485        if (commit_lock_file(&lock->lk))
1486                return -1;
1487        return 0;
1488}
1489
1490static int open_or_create_logfile(const char *path, void *cb)
1491{
1492        int *fd = cb;
1493
1494        *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1495        return (*fd < 0) ? -1 : 0;
1496}
1497
1498/*
1499 * Create a reflog for a ref. If force_create = 0, only create the
1500 * reflog for certain refs (those for which should_autocreate_reflog
1501 * returns non-zero). Otherwise, create it regardless of the reference
1502 * name. If the logfile already existed or was created, return 0 and
1503 * set *logfd to the file descriptor opened for appending to the file.
1504 * If no logfile exists and we decided not to create one, return 0 and
1505 * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1506 * return -1.
1507 */
1508static int log_ref_setup(struct files_ref_store *refs,
1509                         const char *refname, int force_create,
1510                         int *logfd, struct strbuf *err)
1511{
1512        struct strbuf logfile_sb = STRBUF_INIT;
1513        char *logfile;
1514
1515        files_reflog_path(refs, &logfile_sb, refname);
1516        logfile = strbuf_detach(&logfile_sb, NULL);
1517
1518        if (force_create || should_autocreate_reflog(refname)) {
1519                if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1520                        if (errno == ENOENT)
1521                                strbuf_addf(err, "unable to create directory for '%s': "
1522                                            "%s", logfile, strerror(errno));
1523                        else if (errno == EISDIR)
1524                                strbuf_addf(err, "there are still logs under '%s'",
1525                                            logfile);
1526                        else
1527                                strbuf_addf(err, "unable to append to '%s': %s",
1528                                            logfile, strerror(errno));
1529
1530                        goto error;
1531                }
1532        } else {
1533                *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1534                if (*logfd < 0) {
1535                        if (errno == ENOENT || errno == EISDIR) {
1536                                /*
1537                                 * The logfile doesn't already exist,
1538                                 * but that is not an error; it only
1539                                 * means that we won't write log
1540                                 * entries to it.
1541                                 */
1542                                ;
1543                        } else {
1544                                strbuf_addf(err, "unable to append to '%s': %s",
1545                                            logfile, strerror(errno));
1546                                goto error;
1547                        }
1548                }
1549        }
1550
1551        if (*logfd >= 0)
1552                adjust_shared_perm(logfile);
1553
1554        free(logfile);
1555        return 0;
1556
1557error:
1558        free(logfile);
1559        return -1;
1560}
1561
1562static int files_create_reflog(struct ref_store *ref_store,
1563                               const char *refname, int force_create,
1564                               struct strbuf *err)
1565{
1566        struct files_ref_store *refs =
1567                files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1568        int fd;
1569
1570        if (log_ref_setup(refs, refname, force_create, &fd, err))
1571                return -1;
1572
1573        if (fd >= 0)
1574                close(fd);
1575
1576        return 0;
1577}
1578
1579static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1580                            const struct object_id *new_oid,
1581                            const char *committer, const char *msg)
1582{
1583        int msglen, written;
1584        unsigned maxlen, len;
1585        char *logrec;
1586
1587        msglen = msg ? strlen(msg) : 0;
1588        maxlen = strlen(committer) + msglen + 100;
1589        logrec = xmalloc(maxlen);
1590        len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1591                        oid_to_hex(old_oid),
1592                        oid_to_hex(new_oid),
1593                        committer);
1594        if (msglen)
1595                len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1596
1597        written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1598        free(logrec);
1599        if (written < 0)
1600                return -1;
1601
1602        return 0;
1603}
1604
1605static int files_log_ref_write(struct files_ref_store *refs,
1606                               const char *refname, const struct object_id *old_oid,
1607                               const struct object_id *new_oid, const char *msg,
1608                               int flags, struct strbuf *err)
1609{
1610        int logfd, result;
1611
1612        if (log_all_ref_updates == LOG_REFS_UNSET)
1613                log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1614
1615        result = log_ref_setup(refs, refname,
1616                               flags & REF_FORCE_CREATE_REFLOG,
1617                               &logfd, err);
1618
1619        if (result)
1620                return result;
1621
1622        if (logfd < 0)
1623                return 0;
1624        result = log_ref_write_fd(logfd, old_oid, new_oid,
1625                                  git_committer_info(0), msg);
1626        if (result) {
1627                struct strbuf sb = STRBUF_INIT;
1628                int save_errno = errno;
1629
1630                files_reflog_path(refs, &sb, refname);
1631                strbuf_addf(err, "unable to append to '%s': %s",
1632                            sb.buf, strerror(save_errno));
1633                strbuf_release(&sb);
1634                close(logfd);
1635                return -1;
1636        }
1637        if (close(logfd)) {
1638                struct strbuf sb = STRBUF_INIT;
1639                int save_errno = errno;
1640
1641                files_reflog_path(refs, &sb, refname);
1642                strbuf_addf(err, "unable to append to '%s': %s",
1643                            sb.buf, strerror(save_errno));
1644                strbuf_release(&sb);
1645                return -1;
1646        }
1647        return 0;
1648}
1649
1650/*
1651 * Write oid into the open lockfile, then close the lockfile. On
1652 * errors, rollback the lockfile, fill in *err and return -1.
1653 */
1654static int write_ref_to_lockfile(struct ref_lock *lock,
1655                                 const struct object_id *oid, struct strbuf *err)
1656{
1657        static char term = '\n';
1658        struct object *o;
1659        int fd;
1660
1661        o = parse_object(oid);
1662        if (!o) {
1663                strbuf_addf(err,
1664                            "trying to write ref '%s' with nonexistent object %s",
1665                            lock->ref_name, oid_to_hex(oid));
1666                unlock_ref(lock);
1667                return -1;
1668        }
1669        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1670                strbuf_addf(err,
1671                            "trying to write non-commit object %s to branch '%s'",
1672                            oid_to_hex(oid), lock->ref_name);
1673                unlock_ref(lock);
1674                return -1;
1675        }
1676        fd = get_lock_file_fd(&lock->lk);
1677        if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1678            write_in_full(fd, &term, 1) < 0 ||
1679            close_ref_gently(lock) < 0) {
1680                strbuf_addf(err,
1681                            "couldn't write '%s'", get_lock_file_path(&lock->lk));
1682                unlock_ref(lock);
1683                return -1;
1684        }
1685        return 0;
1686}
1687
1688/*
1689 * Commit a change to a loose reference that has already been written
1690 * to the loose reference lockfile. Also update the reflogs if
1691 * necessary, using the specified lockmsg (which can be NULL).
1692 */
1693static int commit_ref_update(struct files_ref_store *refs,
1694                             struct ref_lock *lock,
1695                             const struct object_id *oid, const char *logmsg,
1696                             struct strbuf *err)
1697{
1698        files_assert_main_repository(refs, "commit_ref_update");
1699
1700        clear_loose_ref_cache(refs);
1701        if (files_log_ref_write(refs, lock->ref_name,
1702                                &lock->old_oid, oid,
1703                                logmsg, 0, err)) {
1704                char *old_msg = strbuf_detach(err, NULL);
1705                strbuf_addf(err, "cannot update the ref '%s': %s",
1706                            lock->ref_name, old_msg);
1707                free(old_msg);
1708                unlock_ref(lock);
1709                return -1;
1710        }
1711
1712        if (strcmp(lock->ref_name, "HEAD") != 0) {
1713                /*
1714                 * Special hack: If a branch is updated directly and HEAD
1715                 * points to it (may happen on the remote side of a push
1716                 * for example) then logically the HEAD reflog should be
1717                 * updated too.
1718                 * A generic solution implies reverse symref information,
1719                 * but finding all symrefs pointing to the given branch
1720                 * would be rather costly for this rare event (the direct
1721                 * update of a branch) to be worth it.  So let's cheat and
1722                 * check with HEAD only which should cover 99% of all usage
1723                 * scenarios (even 100% of the default ones).
1724                 */
1725                int head_flag;
1726                const char *head_ref;
1727
1728                head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1729                                                   RESOLVE_REF_READING,
1730                                                   NULL, &head_flag);
1731                if (head_ref && (head_flag & REF_ISSYMREF) &&
1732                    !strcmp(head_ref, lock->ref_name)) {
1733                        struct strbuf log_err = STRBUF_INIT;
1734                        if (files_log_ref_write(refs, "HEAD",
1735                                                &lock->old_oid, oid,
1736                                                logmsg, 0, &log_err)) {
1737                                error("%s", log_err.buf);
1738                                strbuf_release(&log_err);
1739                        }
1740                }
1741        }
1742
1743        if (commit_ref(lock)) {
1744                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1745                unlock_ref(lock);
1746                return -1;
1747        }
1748
1749        unlock_ref(lock);
1750        return 0;
1751}
1752
1753static int create_ref_symlink(struct ref_lock *lock, const char *target)
1754{
1755        int ret = -1;
1756#ifndef NO_SYMLINK_HEAD
1757        char *ref_path = get_locked_file_path(&lock->lk);
1758        unlink(ref_path);
1759        ret = symlink(target, ref_path);
1760        free(ref_path);
1761
1762        if (ret)
1763                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1764#endif
1765        return ret;
1766}
1767
1768static void update_symref_reflog(struct files_ref_store *refs,
1769                                 struct ref_lock *lock, const char *refname,
1770                                 const char *target, const char *logmsg)
1771{
1772        struct strbuf err = STRBUF_INIT;
1773        struct object_id new_oid;
1774        if (logmsg &&
1775            !refs_read_ref_full(&refs->base, target,
1776                                RESOLVE_REF_READING, &new_oid, NULL) &&
1777            files_log_ref_write(refs, refname, &lock->old_oid,
1778                                &new_oid, logmsg, 0, &err)) {
1779                error("%s", err.buf);
1780                strbuf_release(&err);
1781        }
1782}
1783
1784static int create_symref_locked(struct files_ref_store *refs,
1785                                struct ref_lock *lock, const char *refname,
1786                                const char *target, const char *logmsg)
1787{
1788        if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1789                update_symref_reflog(refs, lock, refname, target, logmsg);
1790                return 0;
1791        }
1792
1793        if (!fdopen_lock_file(&lock->lk, "w"))
1794                return error("unable to fdopen %s: %s",
1795                             lock->lk.tempfile->filename.buf, strerror(errno));
1796
1797        update_symref_reflog(refs, lock, refname, target, logmsg);
1798
1799        /* no error check; commit_ref will check ferror */
1800        fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1801        if (commit_ref(lock) < 0)
1802                return error("unable to write symref for %s: %s", refname,
1803                             strerror(errno));
1804        return 0;
1805}
1806
1807static int files_create_symref(struct ref_store *ref_store,
1808                               const char *refname, const char *target,
1809                               const char *logmsg)
1810{
1811        struct files_ref_store *refs =
1812                files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1813        struct strbuf err = STRBUF_INIT;
1814        struct ref_lock *lock;
1815        int ret;
1816
1817        lock = lock_ref_oid_basic(refs, refname, NULL,
1818                                  NULL, NULL, REF_NO_DEREF, NULL,
1819                                  &err);
1820        if (!lock) {
1821                error("%s", err.buf);
1822                strbuf_release(&err);
1823                return -1;
1824        }
1825
1826        ret = create_symref_locked(refs, lock, refname, target, logmsg);
1827        unlock_ref(lock);
1828        return ret;
1829}
1830
1831static int files_reflog_exists(struct ref_store *ref_store,
1832                               const char *refname)
1833{
1834        struct files_ref_store *refs =
1835                files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1836        struct strbuf sb = STRBUF_INIT;
1837        struct stat st;
1838        int ret;
1839
1840        files_reflog_path(refs, &sb, refname);
1841        ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1842        strbuf_release(&sb);
1843        return ret;
1844}
1845
1846static int files_delete_reflog(struct ref_store *ref_store,
1847                               const char *refname)
1848{
1849        struct files_ref_store *refs =
1850                files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1851        struct strbuf sb = STRBUF_INIT;
1852        int ret;
1853
1854        files_reflog_path(refs, &sb, refname);
1855        ret = remove_path(sb.buf);
1856        strbuf_release(&sb);
1857        return ret;
1858}
1859
1860static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1861{
1862        struct object_id ooid, noid;
1863        char *email_end, *message;
1864        timestamp_t timestamp;
1865        int tz;
1866        const char *p = sb->buf;
1867
1868        /* old SP new SP name <email> SP time TAB msg LF */
1869        if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1870            parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1871            parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1872            !(email_end = strchr(p, '>')) ||
1873            email_end[1] != ' ' ||
1874            !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1875            !message || message[0] != ' ' ||
1876            (message[1] != '+' && message[1] != '-') ||
1877            !isdigit(message[2]) || !isdigit(message[3]) ||
1878            !isdigit(message[4]) || !isdigit(message[5]))
1879                return 0; /* corrupt? */
1880        email_end[1] = '\0';
1881        tz = strtol(message + 1, NULL, 10);
1882        if (message[6] != '\t')
1883                message += 6;
1884        else
1885                message += 7;
1886        return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1887}
1888
1889static char *find_beginning_of_line(char *bob, char *scan)
1890{
1891        while (bob < scan && *(--scan) != '\n')
1892                ; /* keep scanning backwards */
1893        /*
1894         * Return either beginning of the buffer, or LF at the end of
1895         * the previous line.
1896         */
1897        return scan;
1898}
1899
1900static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1901                                             const char *refname,
1902                                             each_reflog_ent_fn fn,
1903                                             void *cb_data)
1904{
1905        struct files_ref_store *refs =
1906                files_downcast(ref_store, REF_STORE_READ,
1907                               "for_each_reflog_ent_reverse");
1908        struct strbuf sb = STRBUF_INIT;
1909        FILE *logfp;
1910        long pos;
1911        int ret = 0, at_tail = 1;
1912
1913        files_reflog_path(refs, &sb, refname);
1914        logfp = fopen(sb.buf, "r");
1915        strbuf_release(&sb);
1916        if (!logfp)
1917                return -1;
1918
1919        /* Jump to the end */
1920        if (fseek(logfp, 0, SEEK_END) < 0)
1921                ret = error("cannot seek back reflog for %s: %s",
1922                            refname, strerror(errno));
1923        pos = ftell(logfp);
1924        while (!ret && 0 < pos) {
1925                int cnt;
1926                size_t nread;
1927                char buf[BUFSIZ];
1928                char *endp, *scanp;
1929
1930                /* Fill next block from the end */
1931                cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1932                if (fseek(logfp, pos - cnt, SEEK_SET)) {
1933                        ret = error("cannot seek back reflog for %s: %s",
1934                                    refname, strerror(errno));
1935                        break;
1936                }
1937                nread = fread(buf, cnt, 1, logfp);
1938                if (nread != 1) {
1939                        ret = error("cannot read %d bytes from reflog for %s: %s",
1940                                    cnt, refname, strerror(errno));
1941                        break;
1942                }
1943                pos -= cnt;
1944
1945                scanp = endp = buf + cnt;
1946                if (at_tail && scanp[-1] == '\n')
1947                        /* Looking at the final LF at the end of the file */
1948                        scanp--;
1949                at_tail = 0;
1950
1951                while (buf < scanp) {
1952                        /*
1953                         * terminating LF of the previous line, or the beginning
1954                         * of the buffer.
1955                         */
1956                        char *bp;
1957
1958                        bp = find_beginning_of_line(buf, scanp);
1959
1960                        if (*bp == '\n') {
1961                                /*
1962                                 * The newline is the end of the previous line,
1963                                 * so we know we have complete line starting
1964                                 * at (bp + 1). Prefix it onto any prior data
1965                                 * we collected for the line and process it.
1966                                 */
1967                                strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1968                                scanp = bp;
1969                                endp = bp + 1;
1970                                ret = show_one_reflog_ent(&sb, fn, cb_data);
1971                                strbuf_reset(&sb);
1972                                if (ret)
1973                                        break;
1974                        } else if (!pos) {
1975                                /*
1976                                 * We are at the start of the buffer, and the
1977                                 * start of the file; there is no previous
1978                                 * line, and we have everything for this one.
1979                                 * Process it, and we can end the loop.
1980                                 */
1981                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
1982                                ret = show_one_reflog_ent(&sb, fn, cb_data);
1983                                strbuf_reset(&sb);
1984                                break;
1985                        }
1986
1987                        if (bp == buf) {
1988                                /*
1989                                 * We are at the start of the buffer, and there
1990                                 * is more file to read backwards. Which means
1991                                 * we are in the middle of a line. Note that we
1992                                 * may get here even if *bp was a newline; that
1993                                 * just means we are at the exact end of the
1994                                 * previous line, rather than some spot in the
1995                                 * middle.
1996                                 *
1997                                 * Save away what we have to be combined with
1998                                 * the data from the next read.
1999                                 */
2000                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
2001                                break;
2002                        }
2003                }
2004
2005        }
2006        if (!ret && sb.len)
2007                die("BUG: reverse reflog parser had leftover data");
2008
2009        fclose(logfp);
2010        strbuf_release(&sb);
2011        return ret;
2012}
2013
2014static int files_for_each_reflog_ent(struct ref_store *ref_store,
2015                                     const char *refname,
2016                                     each_reflog_ent_fn fn, void *cb_data)
2017{
2018        struct files_ref_store *refs =
2019                files_downcast(ref_store, REF_STORE_READ,
2020                               "for_each_reflog_ent");
2021        FILE *logfp;
2022        struct strbuf sb = STRBUF_INIT;
2023        int ret = 0;
2024
2025        files_reflog_path(refs, &sb, refname);
2026        logfp = fopen(sb.buf, "r");
2027        strbuf_release(&sb);
2028        if (!logfp)
2029                return -1;
2030
2031        while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2032                ret = show_one_reflog_ent(&sb, fn, cb_data);
2033        fclose(logfp);
2034        strbuf_release(&sb);
2035        return ret;
2036}
2037
2038struct files_reflog_iterator {
2039        struct ref_iterator base;
2040
2041        struct ref_store *ref_store;
2042        struct dir_iterator *dir_iterator;
2043        struct object_id oid;
2044};
2045
2046static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2047{
2048        struct files_reflog_iterator *iter =
2049                (struct files_reflog_iterator *)ref_iterator;
2050        struct dir_iterator *diter = iter->dir_iterator;
2051        int ok;
2052
2053        while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2054                int flags;
2055
2056                if (!S_ISREG(diter->st.st_mode))
2057                        continue;
2058                if (diter->basename[0] == '.')
2059                        continue;
2060                if (ends_with(diter->basename, ".lock"))
2061                        continue;
2062
2063                if (refs_read_ref_full(iter->ref_store,
2064                                       diter->relative_path, 0,
2065                                       &iter->oid, &flags)) {
2066                        error("bad ref for %s", diter->path.buf);
2067                        continue;
2068                }
2069
2070                iter->base.refname = diter->relative_path;
2071                iter->base.oid = &iter->oid;
2072                iter->base.flags = flags;
2073                return ITER_OK;
2074        }
2075
2076        iter->dir_iterator = NULL;
2077        if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2078                ok = ITER_ERROR;
2079        return ok;
2080}
2081
2082static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2083                                   struct object_id *peeled)
2084{
2085        die("BUG: ref_iterator_peel() called for reflog_iterator");
2086}
2087
2088static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2089{
2090        struct files_reflog_iterator *iter =
2091                (struct files_reflog_iterator *)ref_iterator;
2092        int ok = ITER_DONE;
2093
2094        if (iter->dir_iterator)
2095                ok = dir_iterator_abort(iter->dir_iterator);
2096
2097        base_ref_iterator_free(ref_iterator);
2098        return ok;
2099}
2100
2101static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2102        files_reflog_iterator_advance,
2103        files_reflog_iterator_peel,
2104        files_reflog_iterator_abort
2105};
2106
2107static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2108                                                  const char *gitdir)
2109{
2110        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2111        struct ref_iterator *ref_iterator = &iter->base;
2112        struct strbuf sb = STRBUF_INIT;
2113
2114        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2115        strbuf_addf(&sb, "%s/logs", gitdir);
2116        iter->dir_iterator = dir_iterator_begin(sb.buf);
2117        iter->ref_store = ref_store;
2118        strbuf_release(&sb);
2119
2120        return ref_iterator;
2121}
2122
2123static enum iterator_selection reflog_iterator_select(
2124        struct ref_iterator *iter_worktree,
2125        struct ref_iterator *iter_common,
2126        void *cb_data)
2127{
2128        if (iter_worktree) {
2129                /*
2130                 * We're a bit loose here. We probably should ignore
2131                 * common refs if they are accidentally added as
2132                 * per-worktree refs.
2133                 */
2134                return ITER_SELECT_0;
2135        } else if (iter_common) {
2136                if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2137                        return ITER_SELECT_1;
2138
2139                /*
2140                 * The main ref store may contain main worktree's
2141                 * per-worktree refs, which should be ignored
2142                 */
2143                return ITER_SKIP_1;
2144        } else
2145                return ITER_DONE;
2146}
2147
2148static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2149{
2150        struct files_ref_store *refs =
2151                files_downcast(ref_store, REF_STORE_READ,
2152                               "reflog_iterator_begin");
2153
2154        if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2155                return reflog_iterator_begin(ref_store, refs->gitcommondir);
2156        } else {
2157                return merge_ref_iterator_begin(
2158                        0,
2159                        reflog_iterator_begin(ref_store, refs->gitdir),
2160                        reflog_iterator_begin(ref_store, refs->gitcommondir),
2161                        reflog_iterator_select, refs);
2162        }
2163}
2164
2165/*
2166 * If update is a direct update of head_ref (the reference pointed to
2167 * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2168 */
2169static int split_head_update(struct ref_update *update,
2170                             struct ref_transaction *transaction,
2171                             const char *head_ref,
2172                             struct string_list *affected_refnames,
2173                             struct strbuf *err)
2174{
2175        struct string_list_item *item;
2176        struct ref_update *new_update;
2177
2178        if ((update->flags & REF_LOG_ONLY) ||
2179            (update->flags & REF_IS_PRUNING) ||
2180            (update->flags & REF_UPDATE_VIA_HEAD))
2181                return 0;
2182
2183        if (strcmp(update->refname, head_ref))
2184                return 0;
2185
2186        /*
2187         * First make sure that HEAD is not already in the
2188         * transaction. This check is O(lg N) in the transaction
2189         * size, but it happens at most once per transaction.
2190         */
2191        if (string_list_has_string(affected_refnames, "HEAD")) {
2192                /* An entry already existed */
2193                strbuf_addf(err,
2194                            "multiple updates for 'HEAD' (including one "
2195                            "via its referent '%s') are not allowed",
2196                            update->refname);
2197                return TRANSACTION_NAME_CONFLICT;
2198        }
2199
2200        new_update = ref_transaction_add_update(
2201                        transaction, "HEAD",
2202                        update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2203                        &update->new_oid, &update->old_oid,
2204                        update->msg);
2205
2206        /*
2207         * Add "HEAD". This insertion is O(N) in the transaction
2208         * size, but it happens at most once per transaction.
2209         * Add new_update->refname instead of a literal "HEAD".
2210         */
2211        if (strcmp(new_update->refname, "HEAD"))
2212                BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2213        item = string_list_insert(affected_refnames, new_update->refname);
2214        item->util = new_update;
2215
2216        return 0;
2217}
2218
2219/*
2220 * update is for a symref that points at referent and doesn't have
2221 * REF_NO_DEREF set. Split it into two updates:
2222 * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2223 * - A new, separate update for the referent reference
2224 * Note that the new update will itself be subject to splitting when
2225 * the iteration gets to it.
2226 */
2227static int split_symref_update(struct files_ref_store *refs,
2228                               struct ref_update *update,
2229                               const char *referent,
2230                               struct ref_transaction *transaction,
2231                               struct string_list *affected_refnames,
2232                               struct strbuf *err)
2233{
2234        struct string_list_item *item;
2235        struct ref_update *new_update;
2236        unsigned int new_flags;
2237
2238        /*
2239         * First make sure that referent is not already in the
2240         * transaction. This check is O(lg N) in the transaction
2241         * size, but it happens at most once per symref in a
2242         * transaction.
2243         */
2244        if (string_list_has_string(affected_refnames, referent)) {
2245                /* An entry already exists */
2246                strbuf_addf(err,
2247                            "multiple updates for '%s' (including one "
2248                            "via symref '%s') are not allowed",
2249                            referent, update->refname);
2250                return TRANSACTION_NAME_CONFLICT;
2251        }
2252
2253        new_flags = update->flags;
2254        if (!strcmp(update->refname, "HEAD")) {
2255                /*
2256                 * Record that the new update came via HEAD, so that
2257                 * when we process it, split_head_update() doesn't try
2258                 * to add another reflog update for HEAD. Note that
2259                 * this bit will be propagated if the new_update
2260                 * itself needs to be split.
2261                 */
2262                new_flags |= REF_UPDATE_VIA_HEAD;
2263        }
2264
2265        new_update = ref_transaction_add_update(
2266                        transaction, referent, new_flags,
2267                        &update->new_oid, &update->old_oid,
2268                        update->msg);
2269
2270        new_update->parent_update = update;
2271
2272        /*
2273         * Change the symbolic ref update to log only. Also, it
2274         * doesn't need to check its old OID value, as that will be
2275         * done when new_update is processed.
2276         */
2277        update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2278        update->flags &= ~REF_HAVE_OLD;
2279
2280        /*
2281         * Add the referent. This insertion is O(N) in the transaction
2282         * size, but it happens at most once per symref in a
2283         * transaction. Make sure to add new_update->refname, which will
2284         * be valid as long as affected_refnames is in use, and NOT
2285         * referent, which might soon be freed by our caller.
2286         */
2287        item = string_list_insert(affected_refnames, new_update->refname);
2288        if (item->util)
2289                BUG("%s unexpectedly found in affected_refnames",
2290                    new_update->refname);
2291        item->util = new_update;
2292
2293        return 0;
2294}
2295
2296/*
2297 * Return the refname under which update was originally requested.
2298 */
2299static const char *original_update_refname(struct ref_update *update)
2300{
2301        while (update->parent_update)
2302                update = update->parent_update;
2303
2304        return update->refname;
2305}
2306
2307/*
2308 * Check whether the REF_HAVE_OLD and old_oid values stored in update
2309 * are consistent with oid, which is the reference's current value. If
2310 * everything is OK, return 0; otherwise, write an error message to
2311 * err and return -1.
2312 */
2313static int check_old_oid(struct ref_update *update, struct object_id *oid,
2314                         struct strbuf *err)
2315{
2316        if (!(update->flags & REF_HAVE_OLD) ||
2317                   !oidcmp(oid, &update->old_oid))
2318                return 0;
2319
2320        if (is_null_oid(&update->old_oid))
2321                strbuf_addf(err, "cannot lock ref '%s': "
2322                            "reference already exists",
2323                            original_update_refname(update));
2324        else if (is_null_oid(oid))
2325                strbuf_addf(err, "cannot lock ref '%s': "
2326                            "reference is missing but expected %s",
2327                            original_update_refname(update),
2328                            oid_to_hex(&update->old_oid));
2329        else
2330                strbuf_addf(err, "cannot lock ref '%s': "
2331                            "is at %s but expected %s",
2332                            original_update_refname(update),
2333                            oid_to_hex(oid),
2334                            oid_to_hex(&update->old_oid));
2335
2336        return -1;
2337}
2338
2339/*
2340 * Prepare for carrying out update:
2341 * - Lock the reference referred to by update.
2342 * - Read the reference under lock.
2343 * - Check that its old OID value (if specified) is correct, and in
2344 *   any case record it in update->lock->old_oid for later use when
2345 *   writing the reflog.
2346 * - If it is a symref update without REF_NO_DEREF, split it up into a
2347 *   REF_LOG_ONLY update of the symref and add a separate update for
2348 *   the referent to transaction.
2349 * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2350 *   update of HEAD.
2351 */
2352static int lock_ref_for_update(struct files_ref_store *refs,
2353                               struct ref_update *update,
2354                               struct ref_transaction *transaction,
2355                               const char *head_ref,
2356                               struct string_list *affected_refnames,
2357                               struct strbuf *err)
2358{
2359        struct strbuf referent = STRBUF_INIT;
2360        int mustexist = (update->flags & REF_HAVE_OLD) &&
2361                !is_null_oid(&update->old_oid);
2362        int ret = 0;
2363        struct ref_lock *lock;
2364
2365        files_assert_main_repository(refs, "lock_ref_for_update");
2366
2367        if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2368                update->flags |= REF_DELETING;
2369
2370        if (head_ref) {
2371                ret = split_head_update(update, transaction, head_ref,
2372                                        affected_refnames, err);
2373                if (ret)
2374                        goto out;
2375        }
2376
2377        ret = lock_raw_ref(refs, update->refname, mustexist,
2378                           affected_refnames, NULL,
2379                           &lock, &referent,
2380                           &update->type, err);
2381        if (ret) {
2382                char *reason;
2383
2384                reason = strbuf_detach(err, NULL);
2385                strbuf_addf(err, "cannot lock ref '%s': %s",
2386                            original_update_refname(update), reason);
2387                free(reason);
2388                goto out;
2389        }
2390
2391        update->backend_data = lock;
2392
2393        if (update->type & REF_ISSYMREF) {
2394                if (update->flags & REF_NO_DEREF) {
2395                        /*
2396                         * We won't be reading the referent as part of
2397                         * the transaction, so we have to read it here
2398                         * to record and possibly check old_oid:
2399                         */
2400                        if (refs_read_ref_full(&refs->base,
2401                                               referent.buf, 0,
2402                                               &lock->old_oid, NULL)) {
2403                                if (update->flags & REF_HAVE_OLD) {
2404                                        strbuf_addf(err, "cannot lock ref '%s': "
2405                                                    "error reading reference",
2406                                                    original_update_refname(update));
2407                                        ret = TRANSACTION_GENERIC_ERROR;
2408                                        goto out;
2409                                }
2410                        } else if (check_old_oid(update, &lock->old_oid, err)) {
2411                                ret = TRANSACTION_GENERIC_ERROR;
2412                                goto out;
2413                        }
2414                } else {
2415                        /*
2416                         * Create a new update for the reference this
2417                         * symref is pointing at. Also, we will record
2418                         * and verify old_oid for this update as part
2419                         * of processing the split-off update, so we
2420                         * don't have to do it here.
2421                         */
2422                        ret = split_symref_update(refs, update,
2423                                                  referent.buf, transaction,
2424                                                  affected_refnames, err);
2425                        if (ret)
2426                                goto out;
2427                }
2428        } else {
2429                struct ref_update *parent_update;
2430
2431                if (check_old_oid(update, &lock->old_oid, err)) {
2432                        ret = TRANSACTION_GENERIC_ERROR;
2433                        goto out;
2434                }
2435
2436                /*
2437                 * If this update is happening indirectly because of a
2438                 * symref update, record the old OID in the parent
2439                 * update:
2440                 */
2441                for (parent_update = update->parent_update;
2442                     parent_update;
2443                     parent_update = parent_update->parent_update) {
2444                        struct ref_lock *parent_lock = parent_update->backend_data;
2445                        oidcpy(&parent_lock->old_oid, &lock->old_oid);
2446                }
2447        }
2448
2449        if ((update->flags & REF_HAVE_NEW) &&
2450            !(update->flags & REF_DELETING) &&
2451            !(update->flags & REF_LOG_ONLY)) {
2452                if (!(update->type & REF_ISSYMREF) &&
2453                    !oidcmp(&lock->old_oid, &update->new_oid)) {
2454                        /*
2455                         * The reference already has the desired
2456                         * value, so we don't need to write it.
2457                         */
2458                } else if (write_ref_to_lockfile(lock, &update->new_oid,
2459                                                 err)) {
2460                        char *write_err = strbuf_detach(err, NULL);
2461
2462                        /*
2463                         * The lock was freed upon failure of
2464                         * write_ref_to_lockfile():
2465                         */
2466                        update->backend_data = NULL;
2467                        strbuf_addf(err,
2468                                    "cannot update ref '%s': %s",
2469                                    update->refname, write_err);
2470                        free(write_err);
2471                        ret = TRANSACTION_GENERIC_ERROR;
2472                        goto out;
2473                } else {
2474                        update->flags |= REF_NEEDS_COMMIT;
2475                }
2476        }
2477        if (!(update->flags & REF_NEEDS_COMMIT)) {
2478                /*
2479                 * We didn't call write_ref_to_lockfile(), so
2480                 * the lockfile is still open. Close it to
2481                 * free up the file descriptor:
2482                 */
2483                if (close_ref_gently(lock)) {
2484                        strbuf_addf(err, "couldn't close '%s.lock'",
2485                                    update->refname);
2486                        ret = TRANSACTION_GENERIC_ERROR;
2487                        goto out;
2488                }
2489        }
2490
2491out:
2492        strbuf_release(&referent);
2493        return ret;
2494}
2495
2496struct files_transaction_backend_data {
2497        struct ref_transaction *packed_transaction;
2498        int packed_refs_locked;
2499};
2500
2501/*
2502 * Unlock any references in `transaction` that are still locked, and
2503 * mark the transaction closed.
2504 */
2505static void files_transaction_cleanup(struct files_ref_store *refs,
2506                                      struct ref_transaction *transaction)
2507{
2508        size_t i;
2509        struct files_transaction_backend_data *backend_data =
2510                transaction->backend_data;
2511        struct strbuf err = STRBUF_INIT;
2512
2513        for (i = 0; i < transaction->nr; i++) {
2514                struct ref_update *update = transaction->updates[i];
2515                struct ref_lock *lock = update->backend_data;
2516
2517                if (lock) {
2518                        unlock_ref(lock);
2519                        update->backend_data = NULL;
2520                }
2521        }
2522
2523        if (backend_data->packed_transaction &&
2524            ref_transaction_abort(backend_data->packed_transaction, &err)) {
2525                error("error aborting transaction: %s", err.buf);
2526                strbuf_release(&err);
2527        }
2528
2529        if (backend_data->packed_refs_locked)
2530                packed_refs_unlock(refs->packed_ref_store);
2531
2532        free(backend_data);
2533
2534        transaction->state = REF_TRANSACTION_CLOSED;
2535}
2536
2537static int files_transaction_prepare(struct ref_store *ref_store,
2538                                     struct ref_transaction *transaction,
2539                                     struct strbuf *err)
2540{
2541        struct files_ref_store *refs =
2542                files_downcast(ref_store, REF_STORE_WRITE,
2543                               "ref_transaction_prepare");
2544        size_t i;
2545        int ret = 0;
2546        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2547        char *head_ref = NULL;
2548        int head_type;
2549        struct files_transaction_backend_data *backend_data;
2550        struct ref_transaction *packed_transaction = NULL;
2551
2552        assert(err);
2553
2554        if (!transaction->nr)
2555                goto cleanup;
2556
2557        backend_data = xcalloc(1, sizeof(*backend_data));
2558        transaction->backend_data = backend_data;
2559
2560        /*
2561         * Fail if a refname appears more than once in the
2562         * transaction. (If we end up splitting up any updates using
2563         * split_symref_update() or split_head_update(), those
2564         * functions will check that the new updates don't have the
2565         * same refname as any existing ones.) Also fail if any of the
2566         * updates use REF_IS_PRUNING without REF_NO_DEREF.
2567         */
2568        for (i = 0; i < transaction->nr; i++) {
2569                struct ref_update *update = transaction->updates[i];
2570                struct string_list_item *item =
2571                        string_list_append(&affected_refnames, update->refname);
2572
2573                if ((update->flags & REF_IS_PRUNING) &&
2574                    !(update->flags & REF_NO_DEREF))
2575                        BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2576
2577                /*
2578                 * We store a pointer to update in item->util, but at
2579                 * the moment we never use the value of this field
2580                 * except to check whether it is non-NULL.
2581                 */
2582                item->util = update;
2583        }
2584        string_list_sort(&affected_refnames);
2585        if (ref_update_reject_duplicates(&affected_refnames, err)) {
2586                ret = TRANSACTION_GENERIC_ERROR;
2587                goto cleanup;
2588        }
2589
2590        /*
2591         * Special hack: If a branch is updated directly and HEAD
2592         * points to it (may happen on the remote side of a push
2593         * for example) then logically the HEAD reflog should be
2594         * updated too.
2595         *
2596         * A generic solution would require reverse symref lookups,
2597         * but finding all symrefs pointing to a given branch would be
2598         * rather costly for this rare event (the direct update of a
2599         * branch) to be worth it. So let's cheat and check with HEAD
2600         * only, which should cover 99% of all usage scenarios (even
2601         * 100% of the default ones).
2602         *
2603         * So if HEAD is a symbolic reference, then record the name of
2604         * the reference that it points to. If we see an update of
2605         * head_ref within the transaction, then split_head_update()
2606         * arranges for the reflog of HEAD to be updated, too.
2607         */
2608        head_ref = refs_resolve_refdup(ref_store, "HEAD",
2609                                       RESOLVE_REF_NO_RECURSE,
2610                                       NULL, &head_type);
2611
2612        if (head_ref && !(head_type & REF_ISSYMREF)) {
2613                FREE_AND_NULL(head_ref);
2614        }
2615
2616        /*
2617         * Acquire all locks, verify old values if provided, check
2618         * that new values are valid, and write new values to the
2619         * lockfiles, ready to be activated. Only keep one lockfile
2620         * open at a time to avoid running out of file descriptors.
2621         * Note that lock_ref_for_update() might append more updates
2622         * to the transaction.
2623         */
2624        for (i = 0; i < transaction->nr; i++) {
2625                struct ref_update *update = transaction->updates[i];
2626
2627                ret = lock_ref_for_update(refs, update, transaction,
2628                                          head_ref, &affected_refnames, err);
2629                if (ret)
2630                        goto cleanup;
2631
2632                if (update->flags & REF_DELETING &&
2633                    !(update->flags & REF_LOG_ONLY) &&
2634                    !(update->flags & REF_IS_PRUNING)) {
2635                        /*
2636                         * This reference has to be deleted from
2637                         * packed-refs if it exists there.
2638                         */
2639                        if (!packed_transaction) {
2640                                packed_transaction = ref_store_transaction_begin(
2641                                                refs->packed_ref_store, err);
2642                                if (!packed_transaction) {
2643                                        ret = TRANSACTION_GENERIC_ERROR;
2644                                        goto cleanup;
2645                                }
2646
2647                                backend_data->packed_transaction =
2648                                        packed_transaction;
2649                        }
2650
2651                        ref_transaction_add_update(
2652                                        packed_transaction, update->refname,
2653                                        REF_HAVE_NEW | REF_NO_DEREF,
2654                                        &update->new_oid, NULL,
2655                                        NULL);
2656                }
2657        }
2658
2659        if (packed_transaction) {
2660                if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2661                        ret = TRANSACTION_GENERIC_ERROR;
2662                        goto cleanup;
2663                }
2664                backend_data->packed_refs_locked = 1;
2665
2666                if (is_packed_transaction_needed(refs->packed_ref_store,
2667                                                 packed_transaction)) {
2668                        ret = ref_transaction_prepare(packed_transaction, err);
2669                } else {
2670                        /*
2671                         * We can skip rewriting the `packed-refs`
2672                         * file. But we do need to leave it locked, so
2673                         * that somebody else doesn't pack a reference
2674                         * that we are trying to delete.
2675                         */
2676                        if (ref_transaction_abort(packed_transaction, err)) {
2677                                ret = TRANSACTION_GENERIC_ERROR;
2678                                goto cleanup;
2679                        }
2680                        backend_data->packed_transaction = NULL;
2681                }
2682        }
2683
2684cleanup:
2685        free(head_ref);
2686        string_list_clear(&affected_refnames, 0);
2687
2688        if (ret)
2689                files_transaction_cleanup(refs, transaction);
2690        else
2691                transaction->state = REF_TRANSACTION_PREPARED;
2692
2693        return ret;
2694}
2695
2696static int files_transaction_finish(struct ref_store *ref_store,
2697                                    struct ref_transaction *transaction,
2698                                    struct strbuf *err)
2699{
2700        struct files_ref_store *refs =
2701                files_downcast(ref_store, 0, "ref_transaction_finish");
2702        size_t i;
2703        int ret = 0;
2704        struct strbuf sb = STRBUF_INIT;
2705        struct files_transaction_backend_data *backend_data;
2706        struct ref_transaction *packed_transaction;
2707
2708
2709        assert(err);
2710
2711        if (!transaction->nr) {
2712                transaction->state = REF_TRANSACTION_CLOSED;
2713                return 0;
2714        }
2715
2716        backend_data = transaction->backend_data;
2717        packed_transaction = backend_data->packed_transaction;
2718
2719        /* Perform updates first so live commits remain referenced */
2720        for (i = 0; i < transaction->nr; i++) {
2721                struct ref_update *update = transaction->updates[i];
2722                struct ref_lock *lock = update->backend_data;
2723
2724                if (update->flags & REF_NEEDS_COMMIT ||
2725                    update->flags & REF_LOG_ONLY) {
2726                        if (files_log_ref_write(refs,
2727                                                lock->ref_name,
2728                                                &lock->old_oid,
2729                                                &update->new_oid,
2730                                                update->msg, update->flags,
2731                                                err)) {
2732                                char *old_msg = strbuf_detach(err, NULL);
2733
2734                                strbuf_addf(err, "cannot update the ref '%s': %s",
2735                                            lock->ref_name, old_msg);
2736                                free(old_msg);
2737                                unlock_ref(lock);
2738                                update->backend_data = NULL;
2739                                ret = TRANSACTION_GENERIC_ERROR;
2740                                goto cleanup;
2741                        }
2742                }
2743                if (update->flags & REF_NEEDS_COMMIT) {
2744                        clear_loose_ref_cache(refs);
2745                        if (commit_ref(lock)) {
2746                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2747                                unlock_ref(lock);
2748                                update->backend_data = NULL;
2749                                ret = TRANSACTION_GENERIC_ERROR;
2750                                goto cleanup;
2751                        }
2752                }
2753        }
2754
2755        /*
2756         * Now that updates are safely completed, we can perform
2757         * deletes. First delete the reflogs of any references that
2758         * will be deleted, since (in the unexpected event of an
2759         * error) leaving a reference without a reflog is less bad
2760         * than leaving a reflog without a reference (the latter is a
2761         * mildly invalid repository state):
2762         */
2763        for (i = 0; i < transaction->nr; i++) {
2764                struct ref_update *update = transaction->updates[i];
2765                if (update->flags & REF_DELETING &&
2766                    !(update->flags & REF_LOG_ONLY) &&
2767                    !(update->flags & REF_IS_PRUNING)) {
2768                        strbuf_reset(&sb);
2769                        files_reflog_path(refs, &sb, update->refname);
2770                        if (!unlink_or_warn(sb.buf))
2771                                try_remove_empty_parents(refs, update->refname,
2772                                                         REMOVE_EMPTY_PARENTS_REFLOG);
2773                }
2774        }
2775
2776        /*
2777         * Perform deletes now that updates are safely completed.
2778         *
2779         * First delete any packed versions of the references, while
2780         * retaining the packed-refs lock:
2781         */
2782        if (packed_transaction) {
2783                ret = ref_transaction_commit(packed_transaction, err);
2784                ref_transaction_free(packed_transaction);
2785                packed_transaction = NULL;
2786                backend_data->packed_transaction = NULL;
2787                if (ret)
2788                        goto cleanup;
2789        }
2790
2791        /* Now delete the loose versions of the references: */
2792        for (i = 0; i < transaction->nr; i++) {
2793                struct ref_update *update = transaction->updates[i];
2794                struct ref_lock *lock = update->backend_data;
2795
2796                if (update->flags & REF_DELETING &&
2797                    !(update->flags & REF_LOG_ONLY)) {
2798                        if (!(update->type & REF_ISPACKED) ||
2799                            update->type & REF_ISSYMREF) {
2800                                /* It is a loose reference. */
2801                                strbuf_reset(&sb);
2802                                files_ref_path(refs, &sb, lock->ref_name);
2803                                if (unlink_or_msg(sb.buf, err)) {
2804                                        ret = TRANSACTION_GENERIC_ERROR;
2805                                        goto cleanup;
2806                                }
2807                                update->flags |= REF_DELETED_LOOSE;
2808                        }
2809                }
2810        }
2811
2812        clear_loose_ref_cache(refs);
2813
2814cleanup:
2815        files_transaction_cleanup(refs, transaction);
2816
2817        for (i = 0; i < transaction->nr; i++) {
2818                struct ref_update *update = transaction->updates[i];
2819
2820                if (update->flags & REF_DELETED_LOOSE) {
2821                        /*
2822                         * The loose reference was deleted. Delete any
2823                         * empty parent directories. (Note that this
2824                         * can only work because we have already
2825                         * removed the lockfile.)
2826                         */
2827                        try_remove_empty_parents(refs, update->refname,
2828                                                 REMOVE_EMPTY_PARENTS_REF);
2829                }
2830        }
2831
2832        strbuf_release(&sb);
2833        return ret;
2834}
2835
2836static int files_transaction_abort(struct ref_store *ref_store,
2837                                   struct ref_transaction *transaction,
2838                                   struct strbuf *err)
2839{
2840        struct files_ref_store *refs =
2841                files_downcast(ref_store, 0, "ref_transaction_abort");
2842
2843        files_transaction_cleanup(refs, transaction);
2844        return 0;
2845}
2846
2847static int ref_present(const char *refname,
2848                       const struct object_id *oid, int flags, void *cb_data)
2849{
2850        struct string_list *affected_refnames = cb_data;
2851
2852        return string_list_has_string(affected_refnames, refname);
2853}
2854
2855static int files_initial_transaction_commit(struct ref_store *ref_store,
2856                                            struct ref_transaction *transaction,
2857                                            struct strbuf *err)
2858{
2859        struct files_ref_store *refs =
2860                files_downcast(ref_store, REF_STORE_WRITE,
2861                               "initial_ref_transaction_commit");
2862        size_t i;
2863        int ret = 0;
2864        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2865        struct ref_transaction *packed_transaction = NULL;
2866
2867        assert(err);
2868
2869        if (transaction->state != REF_TRANSACTION_OPEN)
2870                die("BUG: commit called for transaction that is not open");
2871
2872        /* Fail if a refname appears more than once in the transaction: */
2873        for (i = 0; i < transaction->nr; i++)
2874                string_list_append(&affected_refnames,
2875                                   transaction->updates[i]->refname);
2876        string_list_sort(&affected_refnames);
2877        if (ref_update_reject_duplicates(&affected_refnames, err)) {
2878                ret = TRANSACTION_GENERIC_ERROR;
2879                goto cleanup;
2880        }
2881
2882        /*
2883         * It's really undefined to call this function in an active
2884         * repository or when there are existing references: we are
2885         * only locking and changing packed-refs, so (1) any
2886         * simultaneous processes might try to change a reference at
2887         * the same time we do, and (2) any existing loose versions of
2888         * the references that we are setting would have precedence
2889         * over our values. But some remote helpers create the remote
2890         * "HEAD" and "master" branches before calling this function,
2891         * so here we really only check that none of the references
2892         * that we are creating already exists.
2893         */
2894        if (refs_for_each_rawref(&refs->base, ref_present,
2895                                 &affected_refnames))
2896                die("BUG: initial ref transaction called with existing refs");
2897
2898        packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2899        if (!packed_transaction) {
2900                ret = TRANSACTION_GENERIC_ERROR;
2901                goto cleanup;
2902        }
2903
2904        for (i = 0; i < transaction->nr; i++) {
2905                struct ref_update *update = transaction->updates[i];
2906
2907                if ((update->flags & REF_HAVE_OLD) &&
2908                    !is_null_oid(&update->old_oid))
2909                        die("BUG: initial ref transaction with old_sha1 set");
2910                if (refs_verify_refname_available(&refs->base, update->refname,
2911                                                  &affected_refnames, NULL,
2912                                                  err)) {
2913                        ret = TRANSACTION_NAME_CONFLICT;
2914                        goto cleanup;
2915                }
2916
2917                /*
2918                 * Add a reference creation for this reference to the
2919                 * packed-refs transaction:
2920                 */
2921                ref_transaction_add_update(packed_transaction, update->refname,
2922                                           update->flags & ~REF_HAVE_OLD,
2923                                           &update->new_oid, &update->old_oid,
2924                                           NULL);
2925        }
2926
2927        if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2928                ret = TRANSACTION_GENERIC_ERROR;
2929                goto cleanup;
2930        }
2931
2932        if (initial_ref_transaction_commit(packed_transaction, err)) {
2933                ret = TRANSACTION_GENERIC_ERROR;
2934        }
2935
2936        packed_refs_unlock(refs->packed_ref_store);
2937cleanup:
2938        if (packed_transaction)
2939                ref_transaction_free(packed_transaction);
2940        transaction->state = REF_TRANSACTION_CLOSED;
2941        string_list_clear(&affected_refnames, 0);
2942        return ret;
2943}
2944
2945struct expire_reflog_cb {
2946        unsigned int flags;
2947        reflog_expiry_should_prune_fn *should_prune_fn;
2948        void *policy_cb;
2949        FILE *newlog;
2950        struct object_id last_kept_oid;
2951};
2952
2953static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2954                             const char *email, timestamp_t timestamp, int tz,
2955                             const char *message, void *cb_data)
2956{
2957        struct expire_reflog_cb *cb = cb_data;
2958        struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2959
2960        if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2961                ooid = &cb->last_kept_oid;
2962
2963        if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2964                                   message, policy_cb)) {
2965                if (!cb->newlog)
2966                        printf("would prune %s", message);
2967                else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2968                        printf("prune %s", message);
2969        } else {
2970                if (cb->newlog) {
2971                        fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2972                                oid_to_hex(ooid), oid_to_hex(noid),
2973                                email, timestamp, tz, message);
2974                        oidcpy(&cb->last_kept_oid, noid);
2975                }
2976                if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2977                        printf("keep %s", message);
2978        }
2979        return 0;
2980}
2981
2982static int files_reflog_expire(struct ref_store *ref_store,
2983                               const char *refname, const struct object_id *oid,
2984                               unsigned int flags,
2985                               reflog_expiry_prepare_fn prepare_fn,
2986                               reflog_expiry_should_prune_fn should_prune_fn,
2987                               reflog_expiry_cleanup_fn cleanup_fn,
2988                               void *policy_cb_data)
2989{
2990        struct files_ref_store *refs =
2991                files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2992        static struct lock_file reflog_lock;
2993        struct expire_reflog_cb cb;
2994        struct ref_lock *lock;
2995        struct strbuf log_file_sb = STRBUF_INIT;
2996        char *log_file;
2997        int status = 0;
2998        int type;
2999        struct strbuf err = STRBUF_INIT;
3000
3001        memset(&cb, 0, sizeof(cb));
3002        cb.flags = flags;
3003        cb.policy_cb = policy_cb_data;
3004        cb.should_prune_fn = should_prune_fn;
3005
3006        /*
3007         * The reflog file is locked by holding the lock on the
3008         * reference itself, plus we might need to update the
3009         * reference if --updateref was specified:
3010         */
3011        lock = lock_ref_oid_basic(refs, refname, oid,
3012                                  NULL, NULL, REF_NO_DEREF,
3013                                  &type, &err);
3014        if (!lock) {
3015                error("cannot lock ref '%s': %s", refname, err.buf);
3016                strbuf_release(&err);
3017                return -1;
3018        }
3019        if (!refs_reflog_exists(ref_store, refname)) {
3020                unlock_ref(lock);
3021                return 0;
3022        }
3023
3024        files_reflog_path(refs, &log_file_sb, refname);
3025        log_file = strbuf_detach(&log_file_sb, NULL);
3026        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3027                /*
3028                 * Even though holding $GIT_DIR/logs/$reflog.lock has
3029                 * no locking implications, we use the lock_file
3030                 * machinery here anyway because it does a lot of the
3031                 * work we need, including cleaning up if the program
3032                 * exits unexpectedly.
3033                 */
3034                if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3035                        struct strbuf err = STRBUF_INIT;
3036                        unable_to_lock_message(log_file, errno, &err);
3037                        error("%s", err.buf);
3038                        strbuf_release(&err);
3039                        goto failure;
3040                }
3041                cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3042                if (!cb.newlog) {
3043                        error("cannot fdopen %s (%s)",
3044                              get_lock_file_path(&reflog_lock), strerror(errno));
3045                        goto failure;
3046                }
3047        }
3048
3049        (*prepare_fn)(refname, oid, cb.policy_cb);
3050        refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3051        (*cleanup_fn)(cb.policy_cb);
3052
3053        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3054                /*
3055                 * It doesn't make sense to adjust a reference pointed
3056                 * to by a symbolic ref based on expiring entries in
3057                 * the symbolic reference's reflog. Nor can we update
3058                 * a reference if there are no remaining reflog
3059                 * entries.
3060                 */
3061                int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3062                        !(type & REF_ISSYMREF) &&
3063                        !is_null_oid(&cb.last_kept_oid);
3064
3065                if (close_lock_file_gently(&reflog_lock)) {
3066                        status |= error("couldn't write %s: %s", log_file,
3067                                        strerror(errno));
3068                        rollback_lock_file(&reflog_lock);
3069                } else if (update &&
3070                           (write_in_full(get_lock_file_fd(&lock->lk),
3071                                oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3072                            write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3073                            close_ref_gently(lock) < 0)) {
3074                        status |= error("couldn't write %s",
3075                                        get_lock_file_path(&lock->lk));
3076                        rollback_lock_file(&reflog_lock);
3077                } else if (commit_lock_file(&reflog_lock)) {
3078                        status |= error("unable to write reflog '%s' (%s)",
3079                                        log_file, strerror(errno));
3080                } else if (update && commit_ref(lock)) {
3081                        status |= error("couldn't set %s", lock->ref_name);
3082                }
3083        }
3084        free(log_file);
3085        unlock_ref(lock);
3086        return status;
3087
3088 failure:
3089        rollback_lock_file(&reflog_lock);
3090        free(log_file);
3091        unlock_ref(lock);
3092        return -1;
3093}
3094
3095static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3096{
3097        struct files_ref_store *refs =
3098                files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3099        struct strbuf sb = STRBUF_INIT;
3100
3101        /*
3102         * Create .git/refs/{heads,tags}
3103         */
3104        files_ref_path(refs, &sb, "refs/heads");
3105        safe_create_dir(sb.buf, 1);
3106
3107        strbuf_reset(&sb);
3108        files_ref_path(refs, &sb, "refs/tags");
3109        safe_create_dir(sb.buf, 1);
3110
3111        strbuf_release(&sb);
3112        return 0;
3113}
3114
3115struct ref_storage_be refs_be_files = {
3116        NULL,
3117        "files",
3118        files_ref_store_create,
3119        files_init_db,
3120        files_transaction_prepare,
3121        files_transaction_finish,
3122        files_transaction_abort,
3123        files_initial_transaction_commit,
3124
3125        files_pack_refs,
3126        files_create_symref,
3127        files_delete_refs,
3128        files_rename_ref,
3129        files_copy_ref,
3130
3131        files_ref_iterator_begin,
3132        files_read_raw_ref,
3133
3134        files_reflog_iterator_begin,
3135        files_for_each_reflog_ent,
3136        files_for_each_reflog_ent_reverse,
3137        files_reflog_exists,
3138        files_create_reflog,
3139        files_delete_reflog,
3140        files_reflog_expire
3141};