refs / files-backend.con commit Merge branch 'br/mergetools-guiffy' (da36be5)
   1#include "../cache.h"
   2#include "../config.h"
   3#include "../refs.h"
   4#include "refs-internal.h"
   5#include "ref-cache.h"
   6#include "packed-backend.h"
   7#include "../iterator.h"
   8#include "../dir-iterator.h"
   9#include "../lockfile.h"
  10#include "../object.h"
  11#include "../dir.h"
  12#include "../chdir-notify.h"
  13
  14/*
  15 * This backend uses the following flags in `ref_update::flags` for
  16 * internal bookkeeping purposes. Their numerical values must not
  17 * conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
  18 * REF_HAVE_OLD, or REF_IS_PRUNING, which are also stored in
  19 * `ref_update::flags`.
  20 */
  21
  22/*
  23 * Used as a flag in ref_update::flags when a loose ref is being
  24 * pruned. This flag must only be used when REF_NO_DEREF is set.
  25 */
  26#define REF_IS_PRUNING (1 << 4)
  27
  28/*
  29 * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
  30 * refs (i.e., because the reference is about to be deleted anyway).
  31 */
  32#define REF_DELETING (1 << 5)
  33
  34/*
  35 * Used as a flag in ref_update::flags when the lockfile needs to be
  36 * committed.
  37 */
  38#define REF_NEEDS_COMMIT (1 << 6)
  39
  40/*
  41 * Used as a flag in ref_update::flags when we want to log a ref
  42 * update but not actually perform it.  This is used when a symbolic
  43 * ref update is split up.
  44 */
  45#define REF_LOG_ONLY (1 << 7)
  46
  47/*
  48 * Used as a flag in ref_update::flags when the ref_update was via an
  49 * update to HEAD.
  50 */
  51#define REF_UPDATE_VIA_HEAD (1 << 8)
  52
  53/*
  54 * Used as a flag in ref_update::flags when the loose reference has
  55 * been deleted.
  56 */
  57#define REF_DELETED_LOOSE (1 << 9)
  58
  59struct ref_lock {
  60        char *ref_name;
  61        struct lock_file lk;
  62        struct object_id old_oid;
  63};
  64
  65/*
  66 * Future: need to be in "struct repository"
  67 * when doing a full libification.
  68 */
  69struct files_ref_store {
  70        struct ref_store base;
  71        unsigned int store_flags;
  72
  73        char *gitdir;
  74        char *gitcommondir;
  75
  76        struct ref_cache *loose;
  77
  78        struct ref_store *packed_ref_store;
  79};
  80
  81static void clear_loose_ref_cache(struct files_ref_store *refs)
  82{
  83        if (refs->loose) {
  84                free_ref_cache(refs->loose);
  85                refs->loose = NULL;
  86        }
  87}
  88
  89/*
  90 * Create a new submodule ref cache and add it to the internal
  91 * set of caches.
  92 */
  93static struct ref_store *files_ref_store_create(const char *gitdir,
  94                                                unsigned int flags)
  95{
  96        struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
  97        struct ref_store *ref_store = (struct ref_store *)refs;
  98        struct strbuf sb = STRBUF_INIT;
  99
 100        base_ref_store_init(ref_store, &refs_be_files);
 101        refs->store_flags = flags;
 102
 103        refs->gitdir = xstrdup(gitdir);
 104        get_common_dir_noenv(&sb, gitdir);
 105        refs->gitcommondir = strbuf_detach(&sb, NULL);
 106        strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
 107        refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
 108        strbuf_release(&sb);
 109
 110        chdir_notify_reparent("files-backend $GIT_DIR",
 111                              &refs->gitdir);
 112        chdir_notify_reparent("files-backend $GIT_COMMONDIR",
 113                              &refs->gitcommondir);
 114
 115        return ref_store;
 116}
 117
 118/*
 119 * Die if refs is not the main ref store. caller is used in any
 120 * necessary error messages.
 121 */
 122static void files_assert_main_repository(struct files_ref_store *refs,
 123                                         const char *caller)
 124{
 125        if (refs->store_flags & REF_STORE_MAIN)
 126                return;
 127
 128        die("BUG: operation %s only allowed for main ref store", caller);
 129}
 130
 131/*
 132 * Downcast ref_store to files_ref_store. Die if ref_store is not a
 133 * files_ref_store. required_flags is compared with ref_store's
 134 * store_flags to ensure the ref_store has all required capabilities.
 135 * "caller" is used in any necessary error messages.
 136 */
 137static struct files_ref_store *files_downcast(struct ref_store *ref_store,
 138                                              unsigned int required_flags,
 139                                              const char *caller)
 140{
 141        struct files_ref_store *refs;
 142
 143        if (ref_store->be != &refs_be_files)
 144                die("BUG: ref_store is type \"%s\" not \"files\" in %s",
 145                    ref_store->be->name, caller);
 146
 147        refs = (struct files_ref_store *)ref_store;
 148
 149        if ((refs->store_flags & required_flags) != required_flags)
 150                die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
 151                    caller, required_flags, refs->store_flags);
 152
 153        return refs;
 154}
 155
 156static void files_reflog_path(struct files_ref_store *refs,
 157                              struct strbuf *sb,
 158                              const char *refname)
 159{
 160        switch (ref_type(refname)) {
 161        case REF_TYPE_PER_WORKTREE:
 162        case REF_TYPE_PSEUDOREF:
 163                strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
 164                break;
 165        case REF_TYPE_NORMAL:
 166                strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
 167                break;
 168        default:
 169                die("BUG: unknown ref type %d of ref %s",
 170                    ref_type(refname), refname);
 171        }
 172}
 173
 174static void files_ref_path(struct files_ref_store *refs,
 175                           struct strbuf *sb,
 176                           const char *refname)
 177{
 178        switch (ref_type(refname)) {
 179        case REF_TYPE_PER_WORKTREE:
 180        case REF_TYPE_PSEUDOREF:
 181                strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
 182                break;
 183        case REF_TYPE_NORMAL:
 184                strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
 185                break;
 186        default:
 187                die("BUG: unknown ref type %d of ref %s",
 188                    ref_type(refname), refname);
 189        }
 190}
 191
 192/*
 193 * Read the loose references from the namespace dirname into dir
 194 * (without recursing).  dirname must end with '/'.  dir must be the
 195 * directory entry corresponding to dirname.
 196 */
 197static void loose_fill_ref_dir(struct ref_store *ref_store,
 198                               struct ref_dir *dir, const char *dirname)
 199{
 200        struct files_ref_store *refs =
 201                files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
 202        DIR *d;
 203        struct dirent *de;
 204        int dirnamelen = strlen(dirname);
 205        struct strbuf refname;
 206        struct strbuf path = STRBUF_INIT;
 207        size_t path_baselen;
 208
 209        files_ref_path(refs, &path, dirname);
 210        path_baselen = path.len;
 211
 212        d = opendir(path.buf);
 213        if (!d) {
 214                strbuf_release(&path);
 215                return;
 216        }
 217
 218        strbuf_init(&refname, dirnamelen + 257);
 219        strbuf_add(&refname, dirname, dirnamelen);
 220
 221        while ((de = readdir(d)) != NULL) {
 222                struct object_id oid;
 223                struct stat st;
 224                int flag;
 225
 226                if (de->d_name[0] == '.')
 227                        continue;
 228                if (ends_with(de->d_name, ".lock"))
 229                        continue;
 230                strbuf_addstr(&refname, de->d_name);
 231                strbuf_addstr(&path, de->d_name);
 232                if (stat(path.buf, &st) < 0) {
 233                        ; /* silently ignore */
 234                } else if (S_ISDIR(st.st_mode)) {
 235                        strbuf_addch(&refname, '/');
 236                        add_entry_to_dir(dir,
 237                                         create_dir_entry(dir->cache, refname.buf,
 238                                                          refname.len, 1));
 239                } else {
 240                        if (!refs_resolve_ref_unsafe(&refs->base,
 241                                                     refname.buf,
 242                                                     RESOLVE_REF_READING,
 243                                                     &oid, &flag)) {
 244                                oidclr(&oid);
 245                                flag |= REF_ISBROKEN;
 246                        } else if (is_null_oid(&oid)) {
 247                                /*
 248                                 * It is so astronomically unlikely
 249                                 * that null_oid is the OID of an
 250                                 * actual object that we consider its
 251                                 * appearance in a loose reference
 252                                 * file to be repo corruption
 253                                 * (probably due to a software bug).
 254                                 */
 255                                flag |= REF_ISBROKEN;
 256                        }
 257
 258                        if (check_refname_format(refname.buf,
 259                                                 REFNAME_ALLOW_ONELEVEL)) {
 260                                if (!refname_is_safe(refname.buf))
 261                                        die("loose refname is dangerous: %s", refname.buf);
 262                                oidclr(&oid);
 263                                flag |= REF_BAD_NAME | REF_ISBROKEN;
 264                        }
 265                        add_entry_to_dir(dir,
 266                                         create_ref_entry(refname.buf, &oid, flag));
 267                }
 268                strbuf_setlen(&refname, dirnamelen);
 269                strbuf_setlen(&path, path_baselen);
 270        }
 271        strbuf_release(&refname);
 272        strbuf_release(&path);
 273        closedir(d);
 274
 275        /*
 276         * Manually add refs/bisect, which, being per-worktree, might
 277         * not appear in the directory listing for refs/ in the main
 278         * repo.
 279         */
 280        if (!strcmp(dirname, "refs/")) {
 281                int pos = search_ref_dir(dir, "refs/bisect/", 12);
 282
 283                if (pos < 0) {
 284                        struct ref_entry *child_entry = create_dir_entry(
 285                                        dir->cache, "refs/bisect/", 12, 1);
 286                        add_entry_to_dir(dir, child_entry);
 287                }
 288        }
 289}
 290
 291static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
 292{
 293        if (!refs->loose) {
 294                /*
 295                 * Mark the top-level directory complete because we
 296                 * are about to read the only subdirectory that can
 297                 * hold references:
 298                 */
 299                refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
 300
 301                /* We're going to fill the top level ourselves: */
 302                refs->loose->root->flag &= ~REF_INCOMPLETE;
 303
 304                /*
 305                 * Add an incomplete entry for "refs/" (to be filled
 306                 * lazily):
 307                 */
 308                add_entry_to_dir(get_ref_dir(refs->loose->root),
 309                                 create_dir_entry(refs->loose, "refs/", 5, 1));
 310        }
 311        return refs->loose;
 312}
 313
 314static int files_read_raw_ref(struct ref_store *ref_store,
 315                              const char *refname, struct object_id *oid,
 316                              struct strbuf *referent, unsigned int *type)
 317{
 318        struct files_ref_store *refs =
 319                files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
 320        struct strbuf sb_contents = STRBUF_INIT;
 321        struct strbuf sb_path = STRBUF_INIT;
 322        const char *path;
 323        const char *buf;
 324        const char *p;
 325        struct stat st;
 326        int fd;
 327        int ret = -1;
 328        int save_errno;
 329        int remaining_retries = 3;
 330
 331        *type = 0;
 332        strbuf_reset(&sb_path);
 333
 334        files_ref_path(refs, &sb_path, refname);
 335
 336        path = sb_path.buf;
 337
 338stat_ref:
 339        /*
 340         * We might have to loop back here to avoid a race
 341         * condition: first we lstat() the file, then we try
 342         * to read it as a link or as a file.  But if somebody
 343         * changes the type of the file (file <-> directory
 344         * <-> symlink) between the lstat() and reading, then
 345         * we don't want to report that as an error but rather
 346         * try again starting with the lstat().
 347         *
 348         * We'll keep a count of the retries, though, just to avoid
 349         * any confusing situation sending us into an infinite loop.
 350         */
 351
 352        if (remaining_retries-- <= 0)
 353                goto out;
 354
 355        if (lstat(path, &st) < 0) {
 356                if (errno != ENOENT)
 357                        goto out;
 358                if (refs_read_raw_ref(refs->packed_ref_store, refname,
 359                                      oid, referent, type)) {
 360                        errno = ENOENT;
 361                        goto out;
 362                }
 363                ret = 0;
 364                goto out;
 365        }
 366
 367        /* Follow "normalized" - ie "refs/.." symlinks by hand */
 368        if (S_ISLNK(st.st_mode)) {
 369                strbuf_reset(&sb_contents);
 370                if (strbuf_readlink(&sb_contents, path, 0) < 0) {
 371                        if (errno == ENOENT || errno == EINVAL)
 372                                /* inconsistent with lstat; retry */
 373                                goto stat_ref;
 374                        else
 375                                goto out;
 376                }
 377                if (starts_with(sb_contents.buf, "refs/") &&
 378                    !check_refname_format(sb_contents.buf, 0)) {
 379                        strbuf_swap(&sb_contents, referent);
 380                        *type |= REF_ISSYMREF;
 381                        ret = 0;
 382                        goto out;
 383                }
 384                /*
 385                 * It doesn't look like a refname; fall through to just
 386                 * treating it like a non-symlink, and reading whatever it
 387                 * points to.
 388                 */
 389        }
 390
 391        /* Is it a directory? */
 392        if (S_ISDIR(st.st_mode)) {
 393                /*
 394                 * Even though there is a directory where the loose
 395                 * ref is supposed to be, there could still be a
 396                 * packed ref:
 397                 */
 398                if (refs_read_raw_ref(refs->packed_ref_store, refname,
 399                                      oid, referent, type)) {
 400                        errno = EISDIR;
 401                        goto out;
 402                }
 403                ret = 0;
 404                goto out;
 405        }
 406
 407        /*
 408         * Anything else, just open it and try to use it as
 409         * a ref
 410         */
 411        fd = open(path, O_RDONLY);
 412        if (fd < 0) {
 413                if (errno == ENOENT && !S_ISLNK(st.st_mode))
 414                        /* inconsistent with lstat; retry */
 415                        goto stat_ref;
 416                else
 417                        goto out;
 418        }
 419        strbuf_reset(&sb_contents);
 420        if (strbuf_read(&sb_contents, fd, 256) < 0) {
 421                int save_errno = errno;
 422                close(fd);
 423                errno = save_errno;
 424                goto out;
 425        }
 426        close(fd);
 427        strbuf_rtrim(&sb_contents);
 428        buf = sb_contents.buf;
 429        if (starts_with(buf, "ref:")) {
 430                buf += 4;
 431                while (isspace(*buf))
 432                        buf++;
 433
 434                strbuf_reset(referent);
 435                strbuf_addstr(referent, buf);
 436                *type |= REF_ISSYMREF;
 437                ret = 0;
 438                goto out;
 439        }
 440
 441        /*
 442         * Please note that FETCH_HEAD has additional
 443         * data after the sha.
 444         */
 445        if (parse_oid_hex(buf, oid, &p) ||
 446            (*p != '\0' && !isspace(*p))) {
 447                *type |= REF_ISBROKEN;
 448                errno = EINVAL;
 449                goto out;
 450        }
 451
 452        ret = 0;
 453
 454out:
 455        save_errno = errno;
 456        strbuf_release(&sb_path);
 457        strbuf_release(&sb_contents);
 458        errno = save_errno;
 459        return ret;
 460}
 461
 462static void unlock_ref(struct ref_lock *lock)
 463{
 464        rollback_lock_file(&lock->lk);
 465        free(lock->ref_name);
 466        free(lock);
 467}
 468
 469/*
 470 * Lock refname, without following symrefs, and set *lock_p to point
 471 * at a newly-allocated lock object. Fill in lock->old_oid, referent,
 472 * and type similarly to read_raw_ref().
 473 *
 474 * The caller must verify that refname is a "safe" reference name (in
 475 * the sense of refname_is_safe()) before calling this function.
 476 *
 477 * If the reference doesn't already exist, verify that refname doesn't
 478 * have a D/F conflict with any existing references. extras and skip
 479 * are passed to refs_verify_refname_available() for this check.
 480 *
 481 * If mustexist is not set and the reference is not found or is
 482 * broken, lock the reference anyway but clear old_oid.
 483 *
 484 * Return 0 on success. On failure, write an error message to err and
 485 * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
 486 *
 487 * Implementation note: This function is basically
 488 *
 489 *     lock reference
 490 *     read_raw_ref()
 491 *
 492 * but it includes a lot more code to
 493 * - Deal with possible races with other processes
 494 * - Avoid calling refs_verify_refname_available() when it can be
 495 *   avoided, namely if we were successfully able to read the ref
 496 * - Generate informative error messages in the case of failure
 497 */
 498static int lock_raw_ref(struct files_ref_store *refs,
 499                        const char *refname, int mustexist,
 500                        const struct string_list *extras,
 501                        const struct string_list *skip,
 502                        struct ref_lock **lock_p,
 503                        struct strbuf *referent,
 504                        unsigned int *type,
 505                        struct strbuf *err)
 506{
 507        struct ref_lock *lock;
 508        struct strbuf ref_file = STRBUF_INIT;
 509        int attempts_remaining = 3;
 510        int ret = TRANSACTION_GENERIC_ERROR;
 511
 512        assert(err);
 513        files_assert_main_repository(refs, "lock_raw_ref");
 514
 515        *type = 0;
 516
 517        /* First lock the file so it can't change out from under us. */
 518
 519        *lock_p = lock = xcalloc(1, sizeof(*lock));
 520
 521        lock->ref_name = xstrdup(refname);
 522        files_ref_path(refs, &ref_file, refname);
 523
 524retry:
 525        switch (safe_create_leading_directories(ref_file.buf)) {
 526        case SCLD_OK:
 527                break; /* success */
 528        case SCLD_EXISTS:
 529                /*
 530                 * Suppose refname is "refs/foo/bar". We just failed
 531                 * to create the containing directory, "refs/foo",
 532                 * because there was a non-directory in the way. This
 533                 * indicates a D/F conflict, probably because of
 534                 * another reference such as "refs/foo". There is no
 535                 * reason to expect this error to be transitory.
 536                 */
 537                if (refs_verify_refname_available(&refs->base, refname,
 538                                                  extras, skip, err)) {
 539                        if (mustexist) {
 540                                /*
 541                                 * To the user the relevant error is
 542                                 * that the "mustexist" reference is
 543                                 * missing:
 544                                 */
 545                                strbuf_reset(err);
 546                                strbuf_addf(err, "unable to resolve reference '%s'",
 547                                            refname);
 548                        } else {
 549                                /*
 550                                 * The error message set by
 551                                 * refs_verify_refname_available() is
 552                                 * OK.
 553                                 */
 554                                ret = TRANSACTION_NAME_CONFLICT;
 555                        }
 556                } else {
 557                        /*
 558                         * The file that is in the way isn't a loose
 559                         * reference. Report it as a low-level
 560                         * failure.
 561                         */
 562                        strbuf_addf(err, "unable to create lock file %s.lock; "
 563                                    "non-directory in the way",
 564                                    ref_file.buf);
 565                }
 566                goto error_return;
 567        case SCLD_VANISHED:
 568                /* Maybe another process was tidying up. Try again. */
 569                if (--attempts_remaining > 0)
 570                        goto retry;
 571                /* fall through */
 572        default:
 573                strbuf_addf(err, "unable to create directory for %s",
 574                            ref_file.buf);
 575                goto error_return;
 576        }
 577
 578        if (hold_lock_file_for_update_timeout(
 579                            &lock->lk, ref_file.buf, LOCK_NO_DEREF,
 580                            get_files_ref_lock_timeout_ms()) < 0) {
 581                if (errno == ENOENT && --attempts_remaining > 0) {
 582                        /*
 583                         * Maybe somebody just deleted one of the
 584                         * directories leading to ref_file.  Try
 585                         * again:
 586                         */
 587                        goto retry;
 588                } else {
 589                        unable_to_lock_message(ref_file.buf, errno, err);
 590                        goto error_return;
 591                }
 592        }
 593
 594        /*
 595         * Now we hold the lock and can read the reference without
 596         * fear that its value will change.
 597         */
 598
 599        if (files_read_raw_ref(&refs->base, refname,
 600                               &lock->old_oid, referent, type)) {
 601                if (errno == ENOENT) {
 602                        if (mustexist) {
 603                                /* Garden variety missing reference. */
 604                                strbuf_addf(err, "unable to resolve reference '%s'",
 605                                            refname);
 606                                goto error_return;
 607                        } else {
 608                                /*
 609                                 * Reference is missing, but that's OK. We
 610                                 * know that there is not a conflict with
 611                                 * another loose reference because
 612                                 * (supposing that we are trying to lock
 613                                 * reference "refs/foo/bar"):
 614                                 *
 615                                 * - We were successfully able to create
 616                                 *   the lockfile refs/foo/bar.lock, so we
 617                                 *   know there cannot be a loose reference
 618                                 *   named "refs/foo".
 619                                 *
 620                                 * - We got ENOENT and not EISDIR, so we
 621                                 *   know that there cannot be a loose
 622                                 *   reference named "refs/foo/bar/baz".
 623                                 */
 624                        }
 625                } else if (errno == EISDIR) {
 626                        /*
 627                         * There is a directory in the way. It might have
 628                         * contained references that have been deleted. If
 629                         * we don't require that the reference already
 630                         * exists, try to remove the directory so that it
 631                         * doesn't cause trouble when we want to rename the
 632                         * lockfile into place later.
 633                         */
 634                        if (mustexist) {
 635                                /* Garden variety missing reference. */
 636                                strbuf_addf(err, "unable to resolve reference '%s'",
 637                                            refname);
 638                                goto error_return;
 639                        } else if (remove_dir_recursively(&ref_file,
 640                                                          REMOVE_DIR_EMPTY_ONLY)) {
 641                                if (refs_verify_refname_available(
 642                                                    &refs->base, refname,
 643                                                    extras, skip, err)) {
 644                                        /*
 645                                         * The error message set by
 646                                         * verify_refname_available() is OK.
 647                                         */
 648                                        ret = TRANSACTION_NAME_CONFLICT;
 649                                        goto error_return;
 650                                } else {
 651                                        /*
 652                                         * We can't delete the directory,
 653                                         * but we also don't know of any
 654                                         * references that it should
 655                                         * contain.
 656                                         */
 657                                        strbuf_addf(err, "there is a non-empty directory '%s' "
 658                                                    "blocking reference '%s'",
 659                                                    ref_file.buf, refname);
 660                                        goto error_return;
 661                                }
 662                        }
 663                } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
 664                        strbuf_addf(err, "unable to resolve reference '%s': "
 665                                    "reference broken", refname);
 666                        goto error_return;
 667                } else {
 668                        strbuf_addf(err, "unable to resolve reference '%s': %s",
 669                                    refname, strerror(errno));
 670                        goto error_return;
 671                }
 672
 673                /*
 674                 * If the ref did not exist and we are creating it,
 675                 * make sure there is no existing packed ref that
 676                 * conflicts with refname:
 677                 */
 678                if (refs_verify_refname_available(
 679                                    refs->packed_ref_store, refname,
 680                                    extras, skip, err))
 681                        goto error_return;
 682        }
 683
 684        ret = 0;
 685        goto out;
 686
 687error_return:
 688        unlock_ref(lock);
 689        *lock_p = NULL;
 690
 691out:
 692        strbuf_release(&ref_file);
 693        return ret;
 694}
 695
 696struct files_ref_iterator {
 697        struct ref_iterator base;
 698
 699        struct ref_iterator *iter0;
 700        unsigned int flags;
 701};
 702
 703static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 704{
 705        struct files_ref_iterator *iter =
 706                (struct files_ref_iterator *)ref_iterator;
 707        int ok;
 708
 709        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 710                if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
 711                    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
 712                        continue;
 713
 714                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
 715                    !ref_resolves_to_object(iter->iter0->refname,
 716                                            iter->iter0->oid,
 717                                            iter->iter0->flags))
 718                        continue;
 719
 720                iter->base.refname = iter->iter0->refname;
 721                iter->base.oid = iter->iter0->oid;
 722                iter->base.flags = iter->iter0->flags;
 723                return ITER_OK;
 724        }
 725
 726        iter->iter0 = NULL;
 727        if (ref_iterator_abort(ref_iterator) != ITER_DONE)
 728                ok = ITER_ERROR;
 729
 730        return ok;
 731}
 732
 733static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
 734                                   struct object_id *peeled)
 735{
 736        struct files_ref_iterator *iter =
 737                (struct files_ref_iterator *)ref_iterator;
 738
 739        return ref_iterator_peel(iter->iter0, peeled);
 740}
 741
 742static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
 743{
 744        struct files_ref_iterator *iter =
 745                (struct files_ref_iterator *)ref_iterator;
 746        int ok = ITER_DONE;
 747
 748        if (iter->iter0)
 749                ok = ref_iterator_abort(iter->iter0);
 750
 751        base_ref_iterator_free(ref_iterator);
 752        return ok;
 753}
 754
 755static struct ref_iterator_vtable files_ref_iterator_vtable = {
 756        files_ref_iterator_advance,
 757        files_ref_iterator_peel,
 758        files_ref_iterator_abort
 759};
 760
 761static struct ref_iterator *files_ref_iterator_begin(
 762                struct ref_store *ref_store,
 763                const char *prefix, unsigned int flags)
 764{
 765        struct files_ref_store *refs;
 766        struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
 767        struct files_ref_iterator *iter;
 768        struct ref_iterator *ref_iterator;
 769        unsigned int required_flags = REF_STORE_READ;
 770
 771        if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
 772                required_flags |= REF_STORE_ODB;
 773
 774        refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 775
 776        /*
 777         * We must make sure that all loose refs are read before
 778         * accessing the packed-refs file; this avoids a race
 779         * condition if loose refs are migrated to the packed-refs
 780         * file by a simultaneous process, but our in-memory view is
 781         * from before the migration. We ensure this as follows:
 782         * First, we call start the loose refs iteration with its
 783         * `prime_ref` argument set to true. This causes the loose
 784         * references in the subtree to be pre-read into the cache.
 785         * (If they've already been read, that's OK; we only need to
 786         * guarantee that they're read before the packed refs, not
 787         * *how much* before.) After that, we call
 788         * packed_ref_iterator_begin(), which internally checks
 789         * whether the packed-ref cache is up to date with what is on
 790         * disk, and re-reads it if not.
 791         */
 792
 793        loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
 794                                              prefix, 1);
 795
 796        /*
 797         * The packed-refs file might contain broken references, for
 798         * example an old version of a reference that points at an
 799         * object that has since been garbage-collected. This is OK as
 800         * long as there is a corresponding loose reference that
 801         * overrides it, and we don't want to emit an error message in
 802         * this case. So ask the packed_ref_store for all of its
 803         * references, and (if needed) do our own check for broken
 804         * ones in files_ref_iterator_advance(), after we have merged
 805         * the packed and loose references.
 806         */
 807        packed_iter = refs_ref_iterator_begin(
 808                        refs->packed_ref_store, prefix, 0,
 809                        DO_FOR_EACH_INCLUDE_BROKEN);
 810
 811        overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
 812
 813        iter = xcalloc(1, sizeof(*iter));
 814        ref_iterator = &iter->base;
 815        base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
 816                               overlay_iter->ordered);
 817        iter->iter0 = overlay_iter;
 818        iter->flags = flags;
 819
 820        return ref_iterator;
 821}
 822
 823/*
 824 * Verify that the reference locked by lock has the value old_oid
 825 * (unless it is NULL).  Fail if the reference doesn't exist and
 826 * mustexist is set. Return 0 on success. On error, write an error
 827 * message to err, set errno, and return a negative value.
 828 */
 829static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
 830                       const struct object_id *old_oid, int mustexist,
 831                       struct strbuf *err)
 832{
 833        assert(err);
 834
 835        if (refs_read_ref_full(ref_store, lock->ref_name,
 836                               mustexist ? RESOLVE_REF_READING : 0,
 837                               &lock->old_oid, NULL)) {
 838                if (old_oid) {
 839                        int save_errno = errno;
 840                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
 841                        errno = save_errno;
 842                        return -1;
 843                } else {
 844                        oidclr(&lock->old_oid);
 845                        return 0;
 846                }
 847        }
 848        if (old_oid && oidcmp(&lock->old_oid, old_oid)) {
 849                strbuf_addf(err, "ref '%s' is at %s but expected %s",
 850                            lock->ref_name,
 851                            oid_to_hex(&lock->old_oid),
 852                            oid_to_hex(old_oid));
 853                errno = EBUSY;
 854                return -1;
 855        }
 856        return 0;
 857}
 858
 859static int remove_empty_directories(struct strbuf *path)
 860{
 861        /*
 862         * we want to create a file but there is a directory there;
 863         * if that is an empty directory (or a directory that contains
 864         * only empty directories), remove them.
 865         */
 866        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 867}
 868
 869static int create_reflock(const char *path, void *cb)
 870{
 871        struct lock_file *lk = cb;
 872
 873        return hold_lock_file_for_update_timeout(
 874                        lk, path, LOCK_NO_DEREF,
 875                        get_files_ref_lock_timeout_ms()) < 0 ? -1 : 0;
 876}
 877
 878/*
 879 * Locks a ref returning the lock on success and NULL on failure.
 880 * On failure errno is set to something meaningful.
 881 */
 882static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
 883                                           const char *refname,
 884                                           const struct object_id *old_oid,
 885                                           const struct string_list *extras,
 886                                           const struct string_list *skip,
 887                                           unsigned int flags, int *type,
 888                                           struct strbuf *err)
 889{
 890        struct strbuf ref_file = STRBUF_INIT;
 891        struct ref_lock *lock;
 892        int last_errno = 0;
 893        int mustexist = (old_oid && !is_null_oid(old_oid));
 894        int resolve_flags = RESOLVE_REF_NO_RECURSE;
 895        int resolved;
 896
 897        files_assert_main_repository(refs, "lock_ref_oid_basic");
 898        assert(err);
 899
 900        lock = xcalloc(1, sizeof(struct ref_lock));
 901
 902        if (mustexist)
 903                resolve_flags |= RESOLVE_REF_READING;
 904        if (flags & REF_DELETING)
 905                resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
 906
 907        files_ref_path(refs, &ref_file, refname);
 908        resolved = !!refs_resolve_ref_unsafe(&refs->base,
 909                                             refname, resolve_flags,
 910                                             &lock->old_oid, type);
 911        if (!resolved && errno == EISDIR) {
 912                /*
 913                 * we are trying to lock foo but we used to
 914                 * have foo/bar which now does not exist;
 915                 * it is normal for the empty directory 'foo'
 916                 * to remain.
 917                 */
 918                if (remove_empty_directories(&ref_file)) {
 919                        last_errno = errno;
 920                        if (!refs_verify_refname_available(
 921                                            &refs->base,
 922                                            refname, extras, skip, err))
 923                                strbuf_addf(err, "there are still refs under '%s'",
 924                                            refname);
 925                        goto error_return;
 926                }
 927                resolved = !!refs_resolve_ref_unsafe(&refs->base,
 928                                                     refname, resolve_flags,
 929                                                     &lock->old_oid, type);
 930        }
 931        if (!resolved) {
 932                last_errno = errno;
 933                if (last_errno != ENOTDIR ||
 934                    !refs_verify_refname_available(&refs->base, refname,
 935                                                   extras, skip, err))
 936                        strbuf_addf(err, "unable to resolve reference '%s': %s",
 937                                    refname, strerror(last_errno));
 938
 939                goto error_return;
 940        }
 941
 942        /*
 943         * If the ref did not exist and we are creating it, make sure
 944         * there is no existing packed ref whose name begins with our
 945         * refname, nor a packed ref whose name is a proper prefix of
 946         * our refname.
 947         */
 948        if (is_null_oid(&lock->old_oid) &&
 949            refs_verify_refname_available(refs->packed_ref_store, refname,
 950                                          extras, skip, err)) {
 951                last_errno = ENOTDIR;
 952                goto error_return;
 953        }
 954
 955        lock->ref_name = xstrdup(refname);
 956
 957        if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
 958                last_errno = errno;
 959                unable_to_lock_message(ref_file.buf, errno, err);
 960                goto error_return;
 961        }
 962
 963        if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
 964                last_errno = errno;
 965                goto error_return;
 966        }
 967        goto out;
 968
 969 error_return:
 970        unlock_ref(lock);
 971        lock = NULL;
 972
 973 out:
 974        strbuf_release(&ref_file);
 975        errno = last_errno;
 976        return lock;
 977}
 978
 979struct ref_to_prune {
 980        struct ref_to_prune *next;
 981        struct object_id oid;
 982        char name[FLEX_ARRAY];
 983};
 984
 985enum {
 986        REMOVE_EMPTY_PARENTS_REF = 0x01,
 987        REMOVE_EMPTY_PARENTS_REFLOG = 0x02
 988};
 989
 990/*
 991 * Remove empty parent directories associated with the specified
 992 * reference and/or its reflog, but spare [logs/]refs/ and immediate
 993 * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
 994 * REMOVE_EMPTY_PARENTS_REFLOG.
 995 */
 996static void try_remove_empty_parents(struct files_ref_store *refs,
 997                                     const char *refname,
 998                                     unsigned int flags)
 999{
1000        struct strbuf buf = STRBUF_INIT;
1001        struct strbuf sb = STRBUF_INIT;
1002        char *p, *q;
1003        int i;
1004
1005        strbuf_addstr(&buf, refname);
1006        p = buf.buf;
1007        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
1008                while (*p && *p != '/')
1009                        p++;
1010                /* tolerate duplicate slashes; see check_refname_format() */
1011                while (*p == '/')
1012                        p++;
1013        }
1014        q = buf.buf + buf.len;
1015        while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
1016                while (q > p && *q != '/')
1017                        q--;
1018                while (q > p && *(q-1) == '/')
1019                        q--;
1020                if (q == p)
1021                        break;
1022                strbuf_setlen(&buf, q - buf.buf);
1023
1024                strbuf_reset(&sb);
1025                files_ref_path(refs, &sb, buf.buf);
1026                if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
1027                        flags &= ~REMOVE_EMPTY_PARENTS_REF;
1028
1029                strbuf_reset(&sb);
1030                files_reflog_path(refs, &sb, buf.buf);
1031                if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
1032                        flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
1033        }
1034        strbuf_release(&buf);
1035        strbuf_release(&sb);
1036}
1037
1038/* make sure nobody touched the ref, and unlink */
1039static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
1040{
1041        struct ref_transaction *transaction;
1042        struct strbuf err = STRBUF_INIT;
1043        int ret = -1;
1044
1045        if (check_refname_format(r->name, 0))
1046                return;
1047
1048        transaction = ref_store_transaction_begin(&refs->base, &err);
1049        if (!transaction)
1050                goto cleanup;
1051        ref_transaction_add_update(
1052                        transaction, r->name,
1053                        REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
1054                        &null_oid, &r->oid, NULL);
1055        if (ref_transaction_commit(transaction, &err))
1056                goto cleanup;
1057
1058        ret = 0;
1059
1060cleanup:
1061        if (ret)
1062                error("%s", err.buf);
1063        strbuf_release(&err);
1064        ref_transaction_free(transaction);
1065        return;
1066}
1067
1068/*
1069 * Prune the loose versions of the references in the linked list
1070 * `*refs_to_prune`, freeing the entries in the list as we go.
1071 */
1072static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
1073{
1074        while (*refs_to_prune) {
1075                struct ref_to_prune *r = *refs_to_prune;
1076                *refs_to_prune = r->next;
1077                prune_ref(refs, r);
1078                free(r);
1079        }
1080}
1081
1082/*
1083 * Return true if the specified reference should be packed.
1084 */
1085static int should_pack_ref(const char *refname,
1086                           const struct object_id *oid, unsigned int ref_flags,
1087                           unsigned int pack_flags)
1088{
1089        /* Do not pack per-worktree refs: */
1090        if (ref_type(refname) != REF_TYPE_NORMAL)
1091                return 0;
1092
1093        /* Do not pack non-tags unless PACK_REFS_ALL is set: */
1094        if (!(pack_flags & PACK_REFS_ALL) && !starts_with(refname, "refs/tags/"))
1095                return 0;
1096
1097        /* Do not pack symbolic refs: */
1098        if (ref_flags & REF_ISSYMREF)
1099                return 0;
1100
1101        /* Do not pack broken refs: */
1102        if (!ref_resolves_to_object(refname, oid, ref_flags))
1103                return 0;
1104
1105        return 1;
1106}
1107
1108static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
1109{
1110        struct files_ref_store *refs =
1111                files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
1112                               "pack_refs");
1113        struct ref_iterator *iter;
1114        int ok;
1115        struct ref_to_prune *refs_to_prune = NULL;
1116        struct strbuf err = STRBUF_INIT;
1117        struct ref_transaction *transaction;
1118
1119        transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
1120        if (!transaction)
1121                return -1;
1122
1123        packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
1124
1125        iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
1126        while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
1127                /*
1128                 * If the loose reference can be packed, add an entry
1129                 * in the packed ref cache. If the reference should be
1130                 * pruned, also add it to refs_to_prune.
1131                 */
1132                if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
1133                                     flags))
1134                        continue;
1135
1136                /*
1137                 * Add a reference creation for this reference to the
1138                 * packed-refs transaction:
1139                 */
1140                if (ref_transaction_update(transaction, iter->refname,
1141                                           iter->oid, NULL,
1142                                           REF_NO_DEREF, NULL, &err))
1143                        die("failure preparing to create packed reference %s: %s",
1144                            iter->refname, err.buf);
1145
1146                /* Schedule the loose reference for pruning if requested. */
1147                if ((flags & PACK_REFS_PRUNE)) {
1148                        struct ref_to_prune *n;
1149                        FLEX_ALLOC_STR(n, name, iter->refname);
1150                        oidcpy(&n->oid, iter->oid);
1151                        n->next = refs_to_prune;
1152                        refs_to_prune = n;
1153                }
1154        }
1155        if (ok != ITER_DONE)
1156                die("error while iterating over references");
1157
1158        if (ref_transaction_commit(transaction, &err))
1159                die("unable to write new packed-refs: %s", err.buf);
1160
1161        ref_transaction_free(transaction);
1162
1163        packed_refs_unlock(refs->packed_ref_store);
1164
1165        prune_refs(refs, &refs_to_prune);
1166        strbuf_release(&err);
1167        return 0;
1168}
1169
1170static int files_delete_refs(struct ref_store *ref_store, const char *msg,
1171                             struct string_list *refnames, unsigned int flags)
1172{
1173        struct files_ref_store *refs =
1174                files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1175        struct strbuf err = STRBUF_INIT;
1176        int i, result = 0;
1177
1178        if (!refnames->nr)
1179                return 0;
1180
1181        if (packed_refs_lock(refs->packed_ref_store, 0, &err))
1182                goto error;
1183
1184        if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
1185                packed_refs_unlock(refs->packed_ref_store);
1186                goto error;
1187        }
1188
1189        packed_refs_unlock(refs->packed_ref_store);
1190
1191        for (i = 0; i < refnames->nr; i++) {
1192                const char *refname = refnames->items[i].string;
1193
1194                if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
1195                        result |= error(_("could not remove reference %s"), refname);
1196        }
1197
1198        strbuf_release(&err);
1199        return result;
1200
1201error:
1202        /*
1203         * If we failed to rewrite the packed-refs file, then it is
1204         * unsafe to try to remove loose refs, because doing so might
1205         * expose an obsolete packed value for a reference that might
1206         * even point at an object that has been garbage collected.
1207         */
1208        if (refnames->nr == 1)
1209                error(_("could not delete reference %s: %s"),
1210                      refnames->items[0].string, err.buf);
1211        else
1212                error(_("could not delete references: %s"), err.buf);
1213
1214        strbuf_release(&err);
1215        return -1;
1216}
1217
1218/*
1219 * People using contrib's git-new-workdir have .git/logs/refs ->
1220 * /some/other/path/.git/logs/refs, and that may live on another device.
1221 *
1222 * IOW, to avoid cross device rename errors, the temporary renamed log must
1223 * live into logs/refs.
1224 */
1225#define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
1226
1227struct rename_cb {
1228        const char *tmp_renamed_log;
1229        int true_errno;
1230};
1231
1232static int rename_tmp_log_callback(const char *path, void *cb_data)
1233{
1234        struct rename_cb *cb = cb_data;
1235
1236        if (rename(cb->tmp_renamed_log, path)) {
1237                /*
1238                 * rename(a, b) when b is an existing directory ought
1239                 * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
1240                 * Sheesh. Record the true errno for error reporting,
1241                 * but report EISDIR to raceproof_create_file() so
1242                 * that it knows to retry.
1243                 */
1244                cb->true_errno = errno;
1245                if (errno == ENOTDIR)
1246                        errno = EISDIR;
1247                return -1;
1248        } else {
1249                return 0;
1250        }
1251}
1252
1253static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
1254{
1255        struct strbuf path = STRBUF_INIT;
1256        struct strbuf tmp = STRBUF_INIT;
1257        struct rename_cb cb;
1258        int ret;
1259
1260        files_reflog_path(refs, &path, newrefname);
1261        files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
1262        cb.tmp_renamed_log = tmp.buf;
1263        ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
1264        if (ret) {
1265                if (errno == EISDIR)
1266                        error("directory not empty: %s", path.buf);
1267                else
1268                        error("unable to move logfile %s to %s: %s",
1269                              tmp.buf, path.buf,
1270                              strerror(cb.true_errno));
1271        }
1272
1273        strbuf_release(&path);
1274        strbuf_release(&tmp);
1275        return ret;
1276}
1277
1278static int write_ref_to_lockfile(struct ref_lock *lock,
1279                                 const struct object_id *oid, struct strbuf *err);
1280static int commit_ref_update(struct files_ref_store *refs,
1281                             struct ref_lock *lock,
1282                             const struct object_id *oid, const char *logmsg,
1283                             struct strbuf *err);
1284
1285static int files_copy_or_rename_ref(struct ref_store *ref_store,
1286                            const char *oldrefname, const char *newrefname,
1287                            const char *logmsg, int copy)
1288{
1289        struct files_ref_store *refs =
1290                files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1291        struct object_id oid, orig_oid;
1292        int flag = 0, logmoved = 0;
1293        struct ref_lock *lock;
1294        struct stat loginfo;
1295        struct strbuf sb_oldref = STRBUF_INIT;
1296        struct strbuf sb_newref = STRBUF_INIT;
1297        struct strbuf tmp_renamed_log = STRBUF_INIT;
1298        int log, ret;
1299        struct strbuf err = STRBUF_INIT;
1300
1301        files_reflog_path(refs, &sb_oldref, oldrefname);
1302        files_reflog_path(refs, &sb_newref, newrefname);
1303        files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
1304
1305        log = !lstat(sb_oldref.buf, &loginfo);
1306        if (log && S_ISLNK(loginfo.st_mode)) {
1307                ret = error("reflog for %s is a symlink", oldrefname);
1308                goto out;
1309        }
1310
1311        if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
1312                                     RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1313                                &orig_oid, &flag)) {
1314                ret = error("refname %s not found", oldrefname);
1315                goto out;
1316        }
1317
1318        if (flag & REF_ISSYMREF) {
1319                if (copy)
1320                        ret = error("refname %s is a symbolic ref, copying it is not supported",
1321                                    oldrefname);
1322                else
1323                        ret = error("refname %s is a symbolic ref, renaming it is not supported",
1324                                    oldrefname);
1325                goto out;
1326        }
1327        if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
1328                ret = 1;
1329                goto out;
1330        }
1331
1332        if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
1333                ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1334                            oldrefname, strerror(errno));
1335                goto out;
1336        }
1337
1338        if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
1339                ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
1340                            oldrefname, strerror(errno));
1341                goto out;
1342        }
1343
1344        if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
1345                            &orig_oid, REF_NO_DEREF)) {
1346                error("unable to delete old %s", oldrefname);
1347                goto rollback;
1348        }
1349
1350        /*
1351         * Since we are doing a shallow lookup, oid is not the
1352         * correct value to pass to delete_ref as old_oid. But that
1353         * doesn't matter, because an old_oid check wouldn't add to
1354         * the safety anyway; we want to delete the reference whatever
1355         * its current value.
1356         */
1357        if (!copy && !refs_read_ref_full(&refs->base, newrefname,
1358                                RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
1359                                &oid, NULL) &&
1360            refs_delete_ref(&refs->base, NULL, newrefname,
1361                            NULL, REF_NO_DEREF)) {
1362                if (errno == EISDIR) {
1363                        struct strbuf path = STRBUF_INIT;
1364                        int result;
1365
1366                        files_ref_path(refs, &path, newrefname);
1367                        result = remove_empty_directories(&path);
1368                        strbuf_release(&path);
1369
1370                        if (result) {
1371                                error("Directory not empty: %s", newrefname);
1372                                goto rollback;
1373                        }
1374                } else {
1375                        error("unable to delete existing %s", newrefname);
1376                        goto rollback;
1377                }
1378        }
1379
1380        if (log && rename_tmp_log(refs, newrefname))
1381                goto rollback;
1382
1383        logmoved = log;
1384
1385        lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
1386                                  REF_NO_DEREF, NULL, &err);
1387        if (!lock) {
1388                if (copy)
1389                        error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1390                else
1391                        error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
1392                strbuf_release(&err);
1393                goto rollback;
1394        }
1395        oidcpy(&lock->old_oid, &orig_oid);
1396
1397        if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1398            commit_ref_update(refs, lock, &orig_oid, logmsg, &err)) {
1399                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
1400                strbuf_release(&err);
1401                goto rollback;
1402        }
1403
1404        ret = 0;
1405        goto out;
1406
1407 rollback:
1408        lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
1409                                  REF_NO_DEREF, NULL, &err);
1410        if (!lock) {
1411                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
1412                strbuf_release(&err);
1413                goto rollbacklog;
1414        }
1415
1416        flag = log_all_ref_updates;
1417        log_all_ref_updates = LOG_REFS_NONE;
1418        if (write_ref_to_lockfile(lock, &orig_oid, &err) ||
1419            commit_ref_update(refs, lock, &orig_oid, NULL, &err)) {
1420                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
1421                strbuf_release(&err);
1422        }
1423        log_all_ref_updates = flag;
1424
1425 rollbacklog:
1426        if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
1427                error("unable to restore logfile %s from %s: %s",
1428                        oldrefname, newrefname, strerror(errno));
1429        if (!logmoved && log &&
1430            rename(tmp_renamed_log.buf, sb_oldref.buf))
1431                error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
1432                        oldrefname, strerror(errno));
1433        ret = 1;
1434 out:
1435        strbuf_release(&sb_newref);
1436        strbuf_release(&sb_oldref);
1437        strbuf_release(&tmp_renamed_log);
1438
1439        return ret;
1440}
1441
1442static int files_rename_ref(struct ref_store *ref_store,
1443                            const char *oldrefname, const char *newrefname,
1444                            const char *logmsg)
1445{
1446        return files_copy_or_rename_ref(ref_store, oldrefname,
1447                                 newrefname, logmsg, 0);
1448}
1449
1450static int files_copy_ref(struct ref_store *ref_store,
1451                            const char *oldrefname, const char *newrefname,
1452                            const char *logmsg)
1453{
1454        return files_copy_or_rename_ref(ref_store, oldrefname,
1455                                 newrefname, logmsg, 1);
1456}
1457
1458static int close_ref_gently(struct ref_lock *lock)
1459{
1460        if (close_lock_file_gently(&lock->lk))
1461                return -1;
1462        return 0;
1463}
1464
1465static int commit_ref(struct ref_lock *lock)
1466{
1467        char *path = get_locked_file_path(&lock->lk);
1468        struct stat st;
1469
1470        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
1471                /*
1472                 * There is a directory at the path we want to rename
1473                 * the lockfile to. Hopefully it is empty; try to
1474                 * delete it.
1475                 */
1476                size_t len = strlen(path);
1477                struct strbuf sb_path = STRBUF_INIT;
1478
1479                strbuf_attach(&sb_path, path, len, len);
1480
1481                /*
1482                 * If this fails, commit_lock_file() will also fail
1483                 * and will report the problem.
1484                 */
1485                remove_empty_directories(&sb_path);
1486                strbuf_release(&sb_path);
1487        } else {
1488                free(path);
1489        }
1490
1491        if (commit_lock_file(&lock->lk))
1492                return -1;
1493        return 0;
1494}
1495
1496static int open_or_create_logfile(const char *path, void *cb)
1497{
1498        int *fd = cb;
1499
1500        *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
1501        return (*fd < 0) ? -1 : 0;
1502}
1503
1504/*
1505 * Create a reflog for a ref. If force_create = 0, only create the
1506 * reflog for certain refs (those for which should_autocreate_reflog
1507 * returns non-zero). Otherwise, create it regardless of the reference
1508 * name. If the logfile already existed or was created, return 0 and
1509 * set *logfd to the file descriptor opened for appending to the file.
1510 * If no logfile exists and we decided not to create one, return 0 and
1511 * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
1512 * return -1.
1513 */
1514static int log_ref_setup(struct files_ref_store *refs,
1515                         const char *refname, int force_create,
1516                         int *logfd, struct strbuf *err)
1517{
1518        struct strbuf logfile_sb = STRBUF_INIT;
1519        char *logfile;
1520
1521        files_reflog_path(refs, &logfile_sb, refname);
1522        logfile = strbuf_detach(&logfile_sb, NULL);
1523
1524        if (force_create || should_autocreate_reflog(refname)) {
1525                if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
1526                        if (errno == ENOENT)
1527                                strbuf_addf(err, "unable to create directory for '%s': "
1528                                            "%s", logfile, strerror(errno));
1529                        else if (errno == EISDIR)
1530                                strbuf_addf(err, "there are still logs under '%s'",
1531                                            logfile);
1532                        else
1533                                strbuf_addf(err, "unable to append to '%s': %s",
1534                                            logfile, strerror(errno));
1535
1536                        goto error;
1537                }
1538        } else {
1539                *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
1540                if (*logfd < 0) {
1541                        if (errno == ENOENT || errno == EISDIR) {
1542                                /*
1543                                 * The logfile doesn't already exist,
1544                                 * but that is not an error; it only
1545                                 * means that we won't write log
1546                                 * entries to it.
1547                                 */
1548                                ;
1549                        } else {
1550                                strbuf_addf(err, "unable to append to '%s': %s",
1551                                            logfile, strerror(errno));
1552                                goto error;
1553                        }
1554                }
1555        }
1556
1557        if (*logfd >= 0)
1558                adjust_shared_perm(logfile);
1559
1560        free(logfile);
1561        return 0;
1562
1563error:
1564        free(logfile);
1565        return -1;
1566}
1567
1568static int files_create_reflog(struct ref_store *ref_store,
1569                               const char *refname, int force_create,
1570                               struct strbuf *err)
1571{
1572        struct files_ref_store *refs =
1573                files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
1574        int fd;
1575
1576        if (log_ref_setup(refs, refname, force_create, &fd, err))
1577                return -1;
1578
1579        if (fd >= 0)
1580                close(fd);
1581
1582        return 0;
1583}
1584
1585static int log_ref_write_fd(int fd, const struct object_id *old_oid,
1586                            const struct object_id *new_oid,
1587                            const char *committer, const char *msg)
1588{
1589        int msglen, written;
1590        unsigned maxlen, len;
1591        char *logrec;
1592
1593        msglen = msg ? strlen(msg) : 0;
1594        maxlen = strlen(committer) + msglen + 100;
1595        logrec = xmalloc(maxlen);
1596        len = xsnprintf(logrec, maxlen, "%s %s %s\n",
1597                        oid_to_hex(old_oid),
1598                        oid_to_hex(new_oid),
1599                        committer);
1600        if (msglen)
1601                len += copy_reflog_msg(logrec + len - 1, msg) - 1;
1602
1603        written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
1604        free(logrec);
1605        if (written < 0)
1606                return -1;
1607
1608        return 0;
1609}
1610
1611static int files_log_ref_write(struct files_ref_store *refs,
1612                               const char *refname, const struct object_id *old_oid,
1613                               const struct object_id *new_oid, const char *msg,
1614                               int flags, struct strbuf *err)
1615{
1616        int logfd, result;
1617
1618        if (log_all_ref_updates == LOG_REFS_UNSET)
1619                log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1620
1621        result = log_ref_setup(refs, refname,
1622                               flags & REF_FORCE_CREATE_REFLOG,
1623                               &logfd, err);
1624
1625        if (result)
1626                return result;
1627
1628        if (logfd < 0)
1629                return 0;
1630        result = log_ref_write_fd(logfd, old_oid, new_oid,
1631                                  git_committer_info(0), msg);
1632        if (result) {
1633                struct strbuf sb = STRBUF_INIT;
1634                int save_errno = errno;
1635
1636                files_reflog_path(refs, &sb, refname);
1637                strbuf_addf(err, "unable to append to '%s': %s",
1638                            sb.buf, strerror(save_errno));
1639                strbuf_release(&sb);
1640                close(logfd);
1641                return -1;
1642        }
1643        if (close(logfd)) {
1644                struct strbuf sb = STRBUF_INIT;
1645                int save_errno = errno;
1646
1647                files_reflog_path(refs, &sb, refname);
1648                strbuf_addf(err, "unable to append to '%s': %s",
1649                            sb.buf, strerror(save_errno));
1650                strbuf_release(&sb);
1651                return -1;
1652        }
1653        return 0;
1654}
1655
1656/*
1657 * Write oid into the open lockfile, then close the lockfile. On
1658 * errors, rollback the lockfile, fill in *err and return -1.
1659 */
1660static int write_ref_to_lockfile(struct ref_lock *lock,
1661                                 const struct object_id *oid, struct strbuf *err)
1662{
1663        static char term = '\n';
1664        struct object *o;
1665        int fd;
1666
1667        o = parse_object(oid);
1668        if (!o) {
1669                strbuf_addf(err,
1670                            "trying to write ref '%s' with nonexistent object %s",
1671                            lock->ref_name, oid_to_hex(oid));
1672                unlock_ref(lock);
1673                return -1;
1674        }
1675        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1676                strbuf_addf(err,
1677                            "trying to write non-commit object %s to branch '%s'",
1678                            oid_to_hex(oid), lock->ref_name);
1679                unlock_ref(lock);
1680                return -1;
1681        }
1682        fd = get_lock_file_fd(&lock->lk);
1683        if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
1684            write_in_full(fd, &term, 1) < 0 ||
1685            close_ref_gently(lock) < 0) {
1686                strbuf_addf(err,
1687                            "couldn't write '%s'", get_lock_file_path(&lock->lk));
1688                unlock_ref(lock);
1689                return -1;
1690        }
1691        return 0;
1692}
1693
1694/*
1695 * Commit a change to a loose reference that has already been written
1696 * to the loose reference lockfile. Also update the reflogs if
1697 * necessary, using the specified lockmsg (which can be NULL).
1698 */
1699static int commit_ref_update(struct files_ref_store *refs,
1700                             struct ref_lock *lock,
1701                             const struct object_id *oid, const char *logmsg,
1702                             struct strbuf *err)
1703{
1704        files_assert_main_repository(refs, "commit_ref_update");
1705
1706        clear_loose_ref_cache(refs);
1707        if (files_log_ref_write(refs, lock->ref_name,
1708                                &lock->old_oid, oid,
1709                                logmsg, 0, err)) {
1710                char *old_msg = strbuf_detach(err, NULL);
1711                strbuf_addf(err, "cannot update the ref '%s': %s",
1712                            lock->ref_name, old_msg);
1713                free(old_msg);
1714                unlock_ref(lock);
1715                return -1;
1716        }
1717
1718        if (strcmp(lock->ref_name, "HEAD") != 0) {
1719                /*
1720                 * Special hack: If a branch is updated directly and HEAD
1721                 * points to it (may happen on the remote side of a push
1722                 * for example) then logically the HEAD reflog should be
1723                 * updated too.
1724                 * A generic solution implies reverse symref information,
1725                 * but finding all symrefs pointing to the given branch
1726                 * would be rather costly for this rare event (the direct
1727                 * update of a branch) to be worth it.  So let's cheat and
1728                 * check with HEAD only which should cover 99% of all usage
1729                 * scenarios (even 100% of the default ones).
1730                 */
1731                int head_flag;
1732                const char *head_ref;
1733
1734                head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
1735                                                   RESOLVE_REF_READING,
1736                                                   NULL, &head_flag);
1737                if (head_ref && (head_flag & REF_ISSYMREF) &&
1738                    !strcmp(head_ref, lock->ref_name)) {
1739                        struct strbuf log_err = STRBUF_INIT;
1740                        if (files_log_ref_write(refs, "HEAD",
1741                                                &lock->old_oid, oid,
1742                                                logmsg, 0, &log_err)) {
1743                                error("%s", log_err.buf);
1744                                strbuf_release(&log_err);
1745                        }
1746                }
1747        }
1748
1749        if (commit_ref(lock)) {
1750                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
1751                unlock_ref(lock);
1752                return -1;
1753        }
1754
1755        unlock_ref(lock);
1756        return 0;
1757}
1758
1759static int create_ref_symlink(struct ref_lock *lock, const char *target)
1760{
1761        int ret = -1;
1762#ifndef NO_SYMLINK_HEAD
1763        char *ref_path = get_locked_file_path(&lock->lk);
1764        unlink(ref_path);
1765        ret = symlink(target, ref_path);
1766        free(ref_path);
1767
1768        if (ret)
1769                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1770#endif
1771        return ret;
1772}
1773
1774static void update_symref_reflog(struct files_ref_store *refs,
1775                                 struct ref_lock *lock, const char *refname,
1776                                 const char *target, const char *logmsg)
1777{
1778        struct strbuf err = STRBUF_INIT;
1779        struct object_id new_oid;
1780        if (logmsg &&
1781            !refs_read_ref_full(&refs->base, target,
1782                                RESOLVE_REF_READING, &new_oid, NULL) &&
1783            files_log_ref_write(refs, refname, &lock->old_oid,
1784                                &new_oid, logmsg, 0, &err)) {
1785                error("%s", err.buf);
1786                strbuf_release(&err);
1787        }
1788}
1789
1790static int create_symref_locked(struct files_ref_store *refs,
1791                                struct ref_lock *lock, const char *refname,
1792                                const char *target, const char *logmsg)
1793{
1794        if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
1795                update_symref_reflog(refs, lock, refname, target, logmsg);
1796                return 0;
1797        }
1798
1799        if (!fdopen_lock_file(&lock->lk, "w"))
1800                return error("unable to fdopen %s: %s",
1801                             lock->lk.tempfile->filename.buf, strerror(errno));
1802
1803        update_symref_reflog(refs, lock, refname, target, logmsg);
1804
1805        /* no error check; commit_ref will check ferror */
1806        fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
1807        if (commit_ref(lock) < 0)
1808                return error("unable to write symref for %s: %s", refname,
1809                             strerror(errno));
1810        return 0;
1811}
1812
1813static int files_create_symref(struct ref_store *ref_store,
1814                               const char *refname, const char *target,
1815                               const char *logmsg)
1816{
1817        struct files_ref_store *refs =
1818                files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
1819        struct strbuf err = STRBUF_INIT;
1820        struct ref_lock *lock;
1821        int ret;
1822
1823        lock = lock_ref_oid_basic(refs, refname, NULL,
1824                                  NULL, NULL, REF_NO_DEREF, NULL,
1825                                  &err);
1826        if (!lock) {
1827                error("%s", err.buf);
1828                strbuf_release(&err);
1829                return -1;
1830        }
1831
1832        ret = create_symref_locked(refs, lock, refname, target, logmsg);
1833        unlock_ref(lock);
1834        return ret;
1835}
1836
1837static int files_reflog_exists(struct ref_store *ref_store,
1838                               const char *refname)
1839{
1840        struct files_ref_store *refs =
1841                files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
1842        struct strbuf sb = STRBUF_INIT;
1843        struct stat st;
1844        int ret;
1845
1846        files_reflog_path(refs, &sb, refname);
1847        ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
1848        strbuf_release(&sb);
1849        return ret;
1850}
1851
1852static int files_delete_reflog(struct ref_store *ref_store,
1853                               const char *refname)
1854{
1855        struct files_ref_store *refs =
1856                files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
1857        struct strbuf sb = STRBUF_INIT;
1858        int ret;
1859
1860        files_reflog_path(refs, &sb, refname);
1861        ret = remove_path(sb.buf);
1862        strbuf_release(&sb);
1863        return ret;
1864}
1865
1866static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
1867{
1868        struct object_id ooid, noid;
1869        char *email_end, *message;
1870        timestamp_t timestamp;
1871        int tz;
1872        const char *p = sb->buf;
1873
1874        /* old SP new SP name <email> SP time TAB msg LF */
1875        if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
1876            parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
1877            parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
1878            !(email_end = strchr(p, '>')) ||
1879            email_end[1] != ' ' ||
1880            !(timestamp = parse_timestamp(email_end + 2, &message, 10)) ||
1881            !message || message[0] != ' ' ||
1882            (message[1] != '+' && message[1] != '-') ||
1883            !isdigit(message[2]) || !isdigit(message[3]) ||
1884            !isdigit(message[4]) || !isdigit(message[5]))
1885                return 0; /* corrupt? */
1886        email_end[1] = '\0';
1887        tz = strtol(message + 1, NULL, 10);
1888        if (message[6] != '\t')
1889                message += 6;
1890        else
1891                message += 7;
1892        return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
1893}
1894
1895static char *find_beginning_of_line(char *bob, char *scan)
1896{
1897        while (bob < scan && *(--scan) != '\n')
1898                ; /* keep scanning backwards */
1899        /*
1900         * Return either beginning of the buffer, or LF at the end of
1901         * the previous line.
1902         */
1903        return scan;
1904}
1905
1906static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1907                                             const char *refname,
1908                                             each_reflog_ent_fn fn,
1909                                             void *cb_data)
1910{
1911        struct files_ref_store *refs =
1912                files_downcast(ref_store, REF_STORE_READ,
1913                               "for_each_reflog_ent_reverse");
1914        struct strbuf sb = STRBUF_INIT;
1915        FILE *logfp;
1916        long pos;
1917        int ret = 0, at_tail = 1;
1918
1919        files_reflog_path(refs, &sb, refname);
1920        logfp = fopen(sb.buf, "r");
1921        strbuf_release(&sb);
1922        if (!logfp)
1923                return -1;
1924
1925        /* Jump to the end */
1926        if (fseek(logfp, 0, SEEK_END) < 0)
1927                ret = error("cannot seek back reflog for %s: %s",
1928                            refname, strerror(errno));
1929        pos = ftell(logfp);
1930        while (!ret && 0 < pos) {
1931                int cnt;
1932                size_t nread;
1933                char buf[BUFSIZ];
1934                char *endp, *scanp;
1935
1936                /* Fill next block from the end */
1937                cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
1938                if (fseek(logfp, pos - cnt, SEEK_SET)) {
1939                        ret = error("cannot seek back reflog for %s: %s",
1940                                    refname, strerror(errno));
1941                        break;
1942                }
1943                nread = fread(buf, cnt, 1, logfp);
1944                if (nread != 1) {
1945                        ret = error("cannot read %d bytes from reflog for %s: %s",
1946                                    cnt, refname, strerror(errno));
1947                        break;
1948                }
1949                pos -= cnt;
1950
1951                scanp = endp = buf + cnt;
1952                if (at_tail && scanp[-1] == '\n')
1953                        /* Looking at the final LF at the end of the file */
1954                        scanp--;
1955                at_tail = 0;
1956
1957                while (buf < scanp) {
1958                        /*
1959                         * terminating LF of the previous line, or the beginning
1960                         * of the buffer.
1961                         */
1962                        char *bp;
1963
1964                        bp = find_beginning_of_line(buf, scanp);
1965
1966                        if (*bp == '\n') {
1967                                /*
1968                                 * The newline is the end of the previous line,
1969                                 * so we know we have complete line starting
1970                                 * at (bp + 1). Prefix it onto any prior data
1971                                 * we collected for the line and process it.
1972                                 */
1973                                strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
1974                                scanp = bp;
1975                                endp = bp + 1;
1976                                ret = show_one_reflog_ent(&sb, fn, cb_data);
1977                                strbuf_reset(&sb);
1978                                if (ret)
1979                                        break;
1980                        } else if (!pos) {
1981                                /*
1982                                 * We are at the start of the buffer, and the
1983                                 * start of the file; there is no previous
1984                                 * line, and we have everything for this one.
1985                                 * Process it, and we can end the loop.
1986                                 */
1987                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
1988                                ret = show_one_reflog_ent(&sb, fn, cb_data);
1989                                strbuf_reset(&sb);
1990                                break;
1991                        }
1992
1993                        if (bp == buf) {
1994                                /*
1995                                 * We are at the start of the buffer, and there
1996                                 * is more file to read backwards. Which means
1997                                 * we are in the middle of a line. Note that we
1998                                 * may get here even if *bp was a newline; that
1999                                 * just means we are at the exact end of the
2000                                 * previous line, rather than some spot in the
2001                                 * middle.
2002                                 *
2003                                 * Save away what we have to be combined with
2004                                 * the data from the next read.
2005                                 */
2006                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
2007                                break;
2008                        }
2009                }
2010
2011        }
2012        if (!ret && sb.len)
2013                die("BUG: reverse reflog parser had leftover data");
2014
2015        fclose(logfp);
2016        strbuf_release(&sb);
2017        return ret;
2018}
2019
2020static int files_for_each_reflog_ent(struct ref_store *ref_store,
2021                                     const char *refname,
2022                                     each_reflog_ent_fn fn, void *cb_data)
2023{
2024        struct files_ref_store *refs =
2025                files_downcast(ref_store, REF_STORE_READ,
2026                               "for_each_reflog_ent");
2027        FILE *logfp;
2028        struct strbuf sb = STRBUF_INIT;
2029        int ret = 0;
2030
2031        files_reflog_path(refs, &sb, refname);
2032        logfp = fopen(sb.buf, "r");
2033        strbuf_release(&sb);
2034        if (!logfp)
2035                return -1;
2036
2037        while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
2038                ret = show_one_reflog_ent(&sb, fn, cb_data);
2039        fclose(logfp);
2040        strbuf_release(&sb);
2041        return ret;
2042}
2043
2044struct files_reflog_iterator {
2045        struct ref_iterator base;
2046
2047        struct ref_store *ref_store;
2048        struct dir_iterator *dir_iterator;
2049        struct object_id oid;
2050};
2051
2052static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2053{
2054        struct files_reflog_iterator *iter =
2055                (struct files_reflog_iterator *)ref_iterator;
2056        struct dir_iterator *diter = iter->dir_iterator;
2057        int ok;
2058
2059        while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
2060                int flags;
2061
2062                if (!S_ISREG(diter->st.st_mode))
2063                        continue;
2064                if (diter->basename[0] == '.')
2065                        continue;
2066                if (ends_with(diter->basename, ".lock"))
2067                        continue;
2068
2069                if (refs_read_ref_full(iter->ref_store,
2070                                       diter->relative_path, 0,
2071                                       &iter->oid, &flags)) {
2072                        error("bad ref for %s", diter->path.buf);
2073                        continue;
2074                }
2075
2076                iter->base.refname = diter->relative_path;
2077                iter->base.oid = &iter->oid;
2078                iter->base.flags = flags;
2079                return ITER_OK;
2080        }
2081
2082        iter->dir_iterator = NULL;
2083        if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
2084                ok = ITER_ERROR;
2085        return ok;
2086}
2087
2088static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
2089                                   struct object_id *peeled)
2090{
2091        die("BUG: ref_iterator_peel() called for reflog_iterator");
2092}
2093
2094static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
2095{
2096        struct files_reflog_iterator *iter =
2097                (struct files_reflog_iterator *)ref_iterator;
2098        int ok = ITER_DONE;
2099
2100        if (iter->dir_iterator)
2101                ok = dir_iterator_abort(iter->dir_iterator);
2102
2103        base_ref_iterator_free(ref_iterator);
2104        return ok;
2105}
2106
2107static struct ref_iterator_vtable files_reflog_iterator_vtable = {
2108        files_reflog_iterator_advance,
2109        files_reflog_iterator_peel,
2110        files_reflog_iterator_abort
2111};
2112
2113static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
2114                                                  const char *gitdir)
2115{
2116        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
2117        struct ref_iterator *ref_iterator = &iter->base;
2118        struct strbuf sb = STRBUF_INIT;
2119
2120        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
2121        strbuf_addf(&sb, "%s/logs", gitdir);
2122        iter->dir_iterator = dir_iterator_begin(sb.buf);
2123        iter->ref_store = ref_store;
2124        strbuf_release(&sb);
2125
2126        return ref_iterator;
2127}
2128
2129static enum iterator_selection reflog_iterator_select(
2130        struct ref_iterator *iter_worktree,
2131        struct ref_iterator *iter_common,
2132        void *cb_data)
2133{
2134        if (iter_worktree) {
2135                /*
2136                 * We're a bit loose here. We probably should ignore
2137                 * common refs if they are accidentally added as
2138                 * per-worktree refs.
2139                 */
2140                return ITER_SELECT_0;
2141        } else if (iter_common) {
2142                if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
2143                        return ITER_SELECT_1;
2144
2145                /*
2146                 * The main ref store may contain main worktree's
2147                 * per-worktree refs, which should be ignored
2148                 */
2149                return ITER_SKIP_1;
2150        } else
2151                return ITER_DONE;
2152}
2153
2154static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
2155{
2156        struct files_ref_store *refs =
2157                files_downcast(ref_store, REF_STORE_READ,
2158                               "reflog_iterator_begin");
2159
2160        if (!strcmp(refs->gitdir, refs->gitcommondir)) {
2161                return reflog_iterator_begin(ref_store, refs->gitcommondir);
2162        } else {
2163                return merge_ref_iterator_begin(
2164                        0,
2165                        reflog_iterator_begin(ref_store, refs->gitdir),
2166                        reflog_iterator_begin(ref_store, refs->gitcommondir),
2167                        reflog_iterator_select, refs);
2168        }
2169}
2170
2171/*
2172 * If update is a direct update of head_ref (the reference pointed to
2173 * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
2174 */
2175static int split_head_update(struct ref_update *update,
2176                             struct ref_transaction *transaction,
2177                             const char *head_ref,
2178                             struct string_list *affected_refnames,
2179                             struct strbuf *err)
2180{
2181        struct string_list_item *item;
2182        struct ref_update *new_update;
2183
2184        if ((update->flags & REF_LOG_ONLY) ||
2185            (update->flags & REF_IS_PRUNING) ||
2186            (update->flags & REF_UPDATE_VIA_HEAD))
2187                return 0;
2188
2189        if (strcmp(update->refname, head_ref))
2190                return 0;
2191
2192        /*
2193         * First make sure that HEAD is not already in the
2194         * transaction. This check is O(lg N) in the transaction
2195         * size, but it happens at most once per transaction.
2196         */
2197        if (string_list_has_string(affected_refnames, "HEAD")) {
2198                /* An entry already existed */
2199                strbuf_addf(err,
2200                            "multiple updates for 'HEAD' (including one "
2201                            "via its referent '%s') are not allowed",
2202                            update->refname);
2203                return TRANSACTION_NAME_CONFLICT;
2204        }
2205
2206        new_update = ref_transaction_add_update(
2207                        transaction, "HEAD",
2208                        update->flags | REF_LOG_ONLY | REF_NO_DEREF,
2209                        &update->new_oid, &update->old_oid,
2210                        update->msg);
2211
2212        /*
2213         * Add "HEAD". This insertion is O(N) in the transaction
2214         * size, but it happens at most once per transaction.
2215         * Add new_update->refname instead of a literal "HEAD".
2216         */
2217        if (strcmp(new_update->refname, "HEAD"))
2218                BUG("%s unexpectedly not 'HEAD'", new_update->refname);
2219        item = string_list_insert(affected_refnames, new_update->refname);
2220        item->util = new_update;
2221
2222        return 0;
2223}
2224
2225/*
2226 * update is for a symref that points at referent and doesn't have
2227 * REF_NO_DEREF set. Split it into two updates:
2228 * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
2229 * - A new, separate update for the referent reference
2230 * Note that the new update will itself be subject to splitting when
2231 * the iteration gets to it.
2232 */
2233static int split_symref_update(struct files_ref_store *refs,
2234                               struct ref_update *update,
2235                               const char *referent,
2236                               struct ref_transaction *transaction,
2237                               struct string_list *affected_refnames,
2238                               struct strbuf *err)
2239{
2240        struct string_list_item *item;
2241        struct ref_update *new_update;
2242        unsigned int new_flags;
2243
2244        /*
2245         * First make sure that referent is not already in the
2246         * transaction. This check is O(lg N) in the transaction
2247         * size, but it happens at most once per symref in a
2248         * transaction.
2249         */
2250        if (string_list_has_string(affected_refnames, referent)) {
2251                /* An entry already exists */
2252                strbuf_addf(err,
2253                            "multiple updates for '%s' (including one "
2254                            "via symref '%s') are not allowed",
2255                            referent, update->refname);
2256                return TRANSACTION_NAME_CONFLICT;
2257        }
2258
2259        new_flags = update->flags;
2260        if (!strcmp(update->refname, "HEAD")) {
2261                /*
2262                 * Record that the new update came via HEAD, so that
2263                 * when we process it, split_head_update() doesn't try
2264                 * to add another reflog update for HEAD. Note that
2265                 * this bit will be propagated if the new_update
2266                 * itself needs to be split.
2267                 */
2268                new_flags |= REF_UPDATE_VIA_HEAD;
2269        }
2270
2271        new_update = ref_transaction_add_update(
2272                        transaction, referent, new_flags,
2273                        &update->new_oid, &update->old_oid,
2274                        update->msg);
2275
2276        new_update->parent_update = update;
2277
2278        /*
2279         * Change the symbolic ref update to log only. Also, it
2280         * doesn't need to check its old OID value, as that will be
2281         * done when new_update is processed.
2282         */
2283        update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
2284        update->flags &= ~REF_HAVE_OLD;
2285
2286        /*
2287         * Add the referent. This insertion is O(N) in the transaction
2288         * size, but it happens at most once per symref in a
2289         * transaction. Make sure to add new_update->refname, which will
2290         * be valid as long as affected_refnames is in use, and NOT
2291         * referent, which might soon be freed by our caller.
2292         */
2293        item = string_list_insert(affected_refnames, new_update->refname);
2294        if (item->util)
2295                BUG("%s unexpectedly found in affected_refnames",
2296                    new_update->refname);
2297        item->util = new_update;
2298
2299        return 0;
2300}
2301
2302/*
2303 * Return the refname under which update was originally requested.
2304 */
2305static const char *original_update_refname(struct ref_update *update)
2306{
2307        while (update->parent_update)
2308                update = update->parent_update;
2309
2310        return update->refname;
2311}
2312
2313/*
2314 * Check whether the REF_HAVE_OLD and old_oid values stored in update
2315 * are consistent with oid, which is the reference's current value. If
2316 * everything is OK, return 0; otherwise, write an error message to
2317 * err and return -1.
2318 */
2319static int check_old_oid(struct ref_update *update, struct object_id *oid,
2320                         struct strbuf *err)
2321{
2322        if (!(update->flags & REF_HAVE_OLD) ||
2323                   !oidcmp(oid, &update->old_oid))
2324                return 0;
2325
2326        if (is_null_oid(&update->old_oid))
2327                strbuf_addf(err, "cannot lock ref '%s': "
2328                            "reference already exists",
2329                            original_update_refname(update));
2330        else if (is_null_oid(oid))
2331                strbuf_addf(err, "cannot lock ref '%s': "
2332                            "reference is missing but expected %s",
2333                            original_update_refname(update),
2334                            oid_to_hex(&update->old_oid));
2335        else
2336                strbuf_addf(err, "cannot lock ref '%s': "
2337                            "is at %s but expected %s",
2338                            original_update_refname(update),
2339                            oid_to_hex(oid),
2340                            oid_to_hex(&update->old_oid));
2341
2342        return -1;
2343}
2344
2345/*
2346 * Prepare for carrying out update:
2347 * - Lock the reference referred to by update.
2348 * - Read the reference under lock.
2349 * - Check that its old OID value (if specified) is correct, and in
2350 *   any case record it in update->lock->old_oid for later use when
2351 *   writing the reflog.
2352 * - If it is a symref update without REF_NO_DEREF, split it up into a
2353 *   REF_LOG_ONLY update of the symref and add a separate update for
2354 *   the referent to transaction.
2355 * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
2356 *   update of HEAD.
2357 */
2358static int lock_ref_for_update(struct files_ref_store *refs,
2359                               struct ref_update *update,
2360                               struct ref_transaction *transaction,
2361                               const char *head_ref,
2362                               struct string_list *affected_refnames,
2363                               struct strbuf *err)
2364{
2365        struct strbuf referent = STRBUF_INIT;
2366        int mustexist = (update->flags & REF_HAVE_OLD) &&
2367                !is_null_oid(&update->old_oid);
2368        int ret = 0;
2369        struct ref_lock *lock;
2370
2371        files_assert_main_repository(refs, "lock_ref_for_update");
2372
2373        if ((update->flags & REF_HAVE_NEW) && is_null_oid(&update->new_oid))
2374                update->flags |= REF_DELETING;
2375
2376        if (head_ref) {
2377                ret = split_head_update(update, transaction, head_ref,
2378                                        affected_refnames, err);
2379                if (ret)
2380                        goto out;
2381        }
2382
2383        ret = lock_raw_ref(refs, update->refname, mustexist,
2384                           affected_refnames, NULL,
2385                           &lock, &referent,
2386                           &update->type, err);
2387        if (ret) {
2388                char *reason;
2389
2390                reason = strbuf_detach(err, NULL);
2391                strbuf_addf(err, "cannot lock ref '%s': %s",
2392                            original_update_refname(update), reason);
2393                free(reason);
2394                goto out;
2395        }
2396
2397        update->backend_data = lock;
2398
2399        if (update->type & REF_ISSYMREF) {
2400                if (update->flags & REF_NO_DEREF) {
2401                        /*
2402                         * We won't be reading the referent as part of
2403                         * the transaction, so we have to read it here
2404                         * to record and possibly check old_oid:
2405                         */
2406                        if (refs_read_ref_full(&refs->base,
2407                                               referent.buf, 0,
2408                                               &lock->old_oid, NULL)) {
2409                                if (update->flags & REF_HAVE_OLD) {
2410                                        strbuf_addf(err, "cannot lock ref '%s': "
2411                                                    "error reading reference",
2412                                                    original_update_refname(update));
2413                                        ret = TRANSACTION_GENERIC_ERROR;
2414                                        goto out;
2415                                }
2416                        } else if (check_old_oid(update, &lock->old_oid, err)) {
2417                                ret = TRANSACTION_GENERIC_ERROR;
2418                                goto out;
2419                        }
2420                } else {
2421                        /*
2422                         * Create a new update for the reference this
2423                         * symref is pointing at. Also, we will record
2424                         * and verify old_oid for this update as part
2425                         * of processing the split-off update, so we
2426                         * don't have to do it here.
2427                         */
2428                        ret = split_symref_update(refs, update,
2429                                                  referent.buf, transaction,
2430                                                  affected_refnames, err);
2431                        if (ret)
2432                                goto out;
2433                }
2434        } else {
2435                struct ref_update *parent_update;
2436
2437                if (check_old_oid(update, &lock->old_oid, err)) {
2438                        ret = TRANSACTION_GENERIC_ERROR;
2439                        goto out;
2440                }
2441
2442                /*
2443                 * If this update is happening indirectly because of a
2444                 * symref update, record the old OID in the parent
2445                 * update:
2446                 */
2447                for (parent_update = update->parent_update;
2448                     parent_update;
2449                     parent_update = parent_update->parent_update) {
2450                        struct ref_lock *parent_lock = parent_update->backend_data;
2451                        oidcpy(&parent_lock->old_oid, &lock->old_oid);
2452                }
2453        }
2454
2455        if ((update->flags & REF_HAVE_NEW) &&
2456            !(update->flags & REF_DELETING) &&
2457            !(update->flags & REF_LOG_ONLY)) {
2458                if (!(update->type & REF_ISSYMREF) &&
2459                    !oidcmp(&lock->old_oid, &update->new_oid)) {
2460                        /*
2461                         * The reference already has the desired
2462                         * value, so we don't need to write it.
2463                         */
2464                } else if (write_ref_to_lockfile(lock, &update->new_oid,
2465                                                 err)) {
2466                        char *write_err = strbuf_detach(err, NULL);
2467
2468                        /*
2469                         * The lock was freed upon failure of
2470                         * write_ref_to_lockfile():
2471                         */
2472                        update->backend_data = NULL;
2473                        strbuf_addf(err,
2474                                    "cannot update ref '%s': %s",
2475                                    update->refname, write_err);
2476                        free(write_err);
2477                        ret = TRANSACTION_GENERIC_ERROR;
2478                        goto out;
2479                } else {
2480                        update->flags |= REF_NEEDS_COMMIT;
2481                }
2482        }
2483        if (!(update->flags & REF_NEEDS_COMMIT)) {
2484                /*
2485                 * We didn't call write_ref_to_lockfile(), so
2486                 * the lockfile is still open. Close it to
2487                 * free up the file descriptor:
2488                 */
2489                if (close_ref_gently(lock)) {
2490                        strbuf_addf(err, "couldn't close '%s.lock'",
2491                                    update->refname);
2492                        ret = TRANSACTION_GENERIC_ERROR;
2493                        goto out;
2494                }
2495        }
2496
2497out:
2498        strbuf_release(&referent);
2499        return ret;
2500}
2501
2502struct files_transaction_backend_data {
2503        struct ref_transaction *packed_transaction;
2504        int packed_refs_locked;
2505};
2506
2507/*
2508 * Unlock any references in `transaction` that are still locked, and
2509 * mark the transaction closed.
2510 */
2511static void files_transaction_cleanup(struct files_ref_store *refs,
2512                                      struct ref_transaction *transaction)
2513{
2514        size_t i;
2515        struct files_transaction_backend_data *backend_data =
2516                transaction->backend_data;
2517        struct strbuf err = STRBUF_INIT;
2518
2519        for (i = 0; i < transaction->nr; i++) {
2520                struct ref_update *update = transaction->updates[i];
2521                struct ref_lock *lock = update->backend_data;
2522
2523                if (lock) {
2524                        unlock_ref(lock);
2525                        update->backend_data = NULL;
2526                }
2527        }
2528
2529        if (backend_data->packed_transaction &&
2530            ref_transaction_abort(backend_data->packed_transaction, &err)) {
2531                error("error aborting transaction: %s", err.buf);
2532                strbuf_release(&err);
2533        }
2534
2535        if (backend_data->packed_refs_locked)
2536                packed_refs_unlock(refs->packed_ref_store);
2537
2538        free(backend_data);
2539
2540        transaction->state = REF_TRANSACTION_CLOSED;
2541}
2542
2543static int files_transaction_prepare(struct ref_store *ref_store,
2544                                     struct ref_transaction *transaction,
2545                                     struct strbuf *err)
2546{
2547        struct files_ref_store *refs =
2548                files_downcast(ref_store, REF_STORE_WRITE,
2549                               "ref_transaction_prepare");
2550        size_t i;
2551        int ret = 0;
2552        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2553        char *head_ref = NULL;
2554        int head_type;
2555        struct files_transaction_backend_data *backend_data;
2556        struct ref_transaction *packed_transaction = NULL;
2557
2558        assert(err);
2559
2560        if (!transaction->nr)
2561                goto cleanup;
2562
2563        backend_data = xcalloc(1, sizeof(*backend_data));
2564        transaction->backend_data = backend_data;
2565
2566        /*
2567         * Fail if a refname appears more than once in the
2568         * transaction. (If we end up splitting up any updates using
2569         * split_symref_update() or split_head_update(), those
2570         * functions will check that the new updates don't have the
2571         * same refname as any existing ones.) Also fail if any of the
2572         * updates use REF_IS_PRUNING without REF_NO_DEREF.
2573         */
2574        for (i = 0; i < transaction->nr; i++) {
2575                struct ref_update *update = transaction->updates[i];
2576                struct string_list_item *item =
2577                        string_list_append(&affected_refnames, update->refname);
2578
2579                if ((update->flags & REF_IS_PRUNING) &&
2580                    !(update->flags & REF_NO_DEREF))
2581                        BUG("REF_IS_PRUNING set without REF_NO_DEREF");
2582
2583                /*
2584                 * We store a pointer to update in item->util, but at
2585                 * the moment we never use the value of this field
2586                 * except to check whether it is non-NULL.
2587                 */
2588                item->util = update;
2589        }
2590        string_list_sort(&affected_refnames);
2591        if (ref_update_reject_duplicates(&affected_refnames, err)) {
2592                ret = TRANSACTION_GENERIC_ERROR;
2593                goto cleanup;
2594        }
2595
2596        /*
2597         * Special hack: If a branch is updated directly and HEAD
2598         * points to it (may happen on the remote side of a push
2599         * for example) then logically the HEAD reflog should be
2600         * updated too.
2601         *
2602         * A generic solution would require reverse symref lookups,
2603         * but finding all symrefs pointing to a given branch would be
2604         * rather costly for this rare event (the direct update of a
2605         * branch) to be worth it. So let's cheat and check with HEAD
2606         * only, which should cover 99% of all usage scenarios (even
2607         * 100% of the default ones).
2608         *
2609         * So if HEAD is a symbolic reference, then record the name of
2610         * the reference that it points to. If we see an update of
2611         * head_ref within the transaction, then split_head_update()
2612         * arranges for the reflog of HEAD to be updated, too.
2613         */
2614        head_ref = refs_resolve_refdup(ref_store, "HEAD",
2615                                       RESOLVE_REF_NO_RECURSE,
2616                                       NULL, &head_type);
2617
2618        if (head_ref && !(head_type & REF_ISSYMREF)) {
2619                FREE_AND_NULL(head_ref);
2620        }
2621
2622        /*
2623         * Acquire all locks, verify old values if provided, check
2624         * that new values are valid, and write new values to the
2625         * lockfiles, ready to be activated. Only keep one lockfile
2626         * open at a time to avoid running out of file descriptors.
2627         * Note that lock_ref_for_update() might append more updates
2628         * to the transaction.
2629         */
2630        for (i = 0; i < transaction->nr; i++) {
2631                struct ref_update *update = transaction->updates[i];
2632
2633                ret = lock_ref_for_update(refs, update, transaction,
2634                                          head_ref, &affected_refnames, err);
2635                if (ret)
2636                        goto cleanup;
2637
2638                if (update->flags & REF_DELETING &&
2639                    !(update->flags & REF_LOG_ONLY) &&
2640                    !(update->flags & REF_IS_PRUNING)) {
2641                        /*
2642                         * This reference has to be deleted from
2643                         * packed-refs if it exists there.
2644                         */
2645                        if (!packed_transaction) {
2646                                packed_transaction = ref_store_transaction_begin(
2647                                                refs->packed_ref_store, err);
2648                                if (!packed_transaction) {
2649                                        ret = TRANSACTION_GENERIC_ERROR;
2650                                        goto cleanup;
2651                                }
2652
2653                                backend_data->packed_transaction =
2654                                        packed_transaction;
2655                        }
2656
2657                        ref_transaction_add_update(
2658                                        packed_transaction, update->refname,
2659                                        REF_HAVE_NEW | REF_NO_DEREF,
2660                                        &update->new_oid, NULL,
2661                                        NULL);
2662                }
2663        }
2664
2665        if (packed_transaction) {
2666                if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2667                        ret = TRANSACTION_GENERIC_ERROR;
2668                        goto cleanup;
2669                }
2670                backend_data->packed_refs_locked = 1;
2671
2672                if (is_packed_transaction_needed(refs->packed_ref_store,
2673                                                 packed_transaction)) {
2674                        ret = ref_transaction_prepare(packed_transaction, err);
2675                } else {
2676                        /*
2677                         * We can skip rewriting the `packed-refs`
2678                         * file. But we do need to leave it locked, so
2679                         * that somebody else doesn't pack a reference
2680                         * that we are trying to delete.
2681                         */
2682                        if (ref_transaction_abort(packed_transaction, err)) {
2683                                ret = TRANSACTION_GENERIC_ERROR;
2684                                goto cleanup;
2685                        }
2686                        backend_data->packed_transaction = NULL;
2687                }
2688        }
2689
2690cleanup:
2691        free(head_ref);
2692        string_list_clear(&affected_refnames, 0);
2693
2694        if (ret)
2695                files_transaction_cleanup(refs, transaction);
2696        else
2697                transaction->state = REF_TRANSACTION_PREPARED;
2698
2699        return ret;
2700}
2701
2702static int files_transaction_finish(struct ref_store *ref_store,
2703                                    struct ref_transaction *transaction,
2704                                    struct strbuf *err)
2705{
2706        struct files_ref_store *refs =
2707                files_downcast(ref_store, 0, "ref_transaction_finish");
2708        size_t i;
2709        int ret = 0;
2710        struct strbuf sb = STRBUF_INIT;
2711        struct files_transaction_backend_data *backend_data;
2712        struct ref_transaction *packed_transaction;
2713
2714
2715        assert(err);
2716
2717        if (!transaction->nr) {
2718                transaction->state = REF_TRANSACTION_CLOSED;
2719                return 0;
2720        }
2721
2722        backend_data = transaction->backend_data;
2723        packed_transaction = backend_data->packed_transaction;
2724
2725        /* Perform updates first so live commits remain referenced */
2726        for (i = 0; i < transaction->nr; i++) {
2727                struct ref_update *update = transaction->updates[i];
2728                struct ref_lock *lock = update->backend_data;
2729
2730                if (update->flags & REF_NEEDS_COMMIT ||
2731                    update->flags & REF_LOG_ONLY) {
2732                        if (files_log_ref_write(refs,
2733                                                lock->ref_name,
2734                                                &lock->old_oid,
2735                                                &update->new_oid,
2736                                                update->msg, update->flags,
2737                                                err)) {
2738                                char *old_msg = strbuf_detach(err, NULL);
2739
2740                                strbuf_addf(err, "cannot update the ref '%s': %s",
2741                                            lock->ref_name, old_msg);
2742                                free(old_msg);
2743                                unlock_ref(lock);
2744                                update->backend_data = NULL;
2745                                ret = TRANSACTION_GENERIC_ERROR;
2746                                goto cleanup;
2747                        }
2748                }
2749                if (update->flags & REF_NEEDS_COMMIT) {
2750                        clear_loose_ref_cache(refs);
2751                        if (commit_ref(lock)) {
2752                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2753                                unlock_ref(lock);
2754                                update->backend_data = NULL;
2755                                ret = TRANSACTION_GENERIC_ERROR;
2756                                goto cleanup;
2757                        }
2758                }
2759        }
2760
2761        /*
2762         * Now that updates are safely completed, we can perform
2763         * deletes. First delete the reflogs of any references that
2764         * will be deleted, since (in the unexpected event of an
2765         * error) leaving a reference without a reflog is less bad
2766         * than leaving a reflog without a reference (the latter is a
2767         * mildly invalid repository state):
2768         */
2769        for (i = 0; i < transaction->nr; i++) {
2770                struct ref_update *update = transaction->updates[i];
2771                if (update->flags & REF_DELETING &&
2772                    !(update->flags & REF_LOG_ONLY) &&
2773                    !(update->flags & REF_IS_PRUNING)) {
2774                        strbuf_reset(&sb);
2775                        files_reflog_path(refs, &sb, update->refname);
2776                        if (!unlink_or_warn(sb.buf))
2777                                try_remove_empty_parents(refs, update->refname,
2778                                                         REMOVE_EMPTY_PARENTS_REFLOG);
2779                }
2780        }
2781
2782        /*
2783         * Perform deletes now that updates are safely completed.
2784         *
2785         * First delete any packed versions of the references, while
2786         * retaining the packed-refs lock:
2787         */
2788        if (packed_transaction) {
2789                ret = ref_transaction_commit(packed_transaction, err);
2790                ref_transaction_free(packed_transaction);
2791                packed_transaction = NULL;
2792                backend_data->packed_transaction = NULL;
2793                if (ret)
2794                        goto cleanup;
2795        }
2796
2797        /* Now delete the loose versions of the references: */
2798        for (i = 0; i < transaction->nr; i++) {
2799                struct ref_update *update = transaction->updates[i];
2800                struct ref_lock *lock = update->backend_data;
2801
2802                if (update->flags & REF_DELETING &&
2803                    !(update->flags & REF_LOG_ONLY)) {
2804                        if (!(update->type & REF_ISPACKED) ||
2805                            update->type & REF_ISSYMREF) {
2806                                /* It is a loose reference. */
2807                                strbuf_reset(&sb);
2808                                files_ref_path(refs, &sb, lock->ref_name);
2809                                if (unlink_or_msg(sb.buf, err)) {
2810                                        ret = TRANSACTION_GENERIC_ERROR;
2811                                        goto cleanup;
2812                                }
2813                                update->flags |= REF_DELETED_LOOSE;
2814                        }
2815                }
2816        }
2817
2818        clear_loose_ref_cache(refs);
2819
2820cleanup:
2821        files_transaction_cleanup(refs, transaction);
2822
2823        for (i = 0; i < transaction->nr; i++) {
2824                struct ref_update *update = transaction->updates[i];
2825
2826                if (update->flags & REF_DELETED_LOOSE) {
2827                        /*
2828                         * The loose reference was deleted. Delete any
2829                         * empty parent directories. (Note that this
2830                         * can only work because we have already
2831                         * removed the lockfile.)
2832                         */
2833                        try_remove_empty_parents(refs, update->refname,
2834                                                 REMOVE_EMPTY_PARENTS_REF);
2835                }
2836        }
2837
2838        strbuf_release(&sb);
2839        return ret;
2840}
2841
2842static int files_transaction_abort(struct ref_store *ref_store,
2843                                   struct ref_transaction *transaction,
2844                                   struct strbuf *err)
2845{
2846        struct files_ref_store *refs =
2847                files_downcast(ref_store, 0, "ref_transaction_abort");
2848
2849        files_transaction_cleanup(refs, transaction);
2850        return 0;
2851}
2852
2853static int ref_present(const char *refname,
2854                       const struct object_id *oid, int flags, void *cb_data)
2855{
2856        struct string_list *affected_refnames = cb_data;
2857
2858        return string_list_has_string(affected_refnames, refname);
2859}
2860
2861static int files_initial_transaction_commit(struct ref_store *ref_store,
2862                                            struct ref_transaction *transaction,
2863                                            struct strbuf *err)
2864{
2865        struct files_ref_store *refs =
2866                files_downcast(ref_store, REF_STORE_WRITE,
2867                               "initial_ref_transaction_commit");
2868        size_t i;
2869        int ret = 0;
2870        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
2871        struct ref_transaction *packed_transaction = NULL;
2872
2873        assert(err);
2874
2875        if (transaction->state != REF_TRANSACTION_OPEN)
2876                die("BUG: commit called for transaction that is not open");
2877
2878        /* Fail if a refname appears more than once in the transaction: */
2879        for (i = 0; i < transaction->nr; i++)
2880                string_list_append(&affected_refnames,
2881                                   transaction->updates[i]->refname);
2882        string_list_sort(&affected_refnames);
2883        if (ref_update_reject_duplicates(&affected_refnames, err)) {
2884                ret = TRANSACTION_GENERIC_ERROR;
2885                goto cleanup;
2886        }
2887
2888        /*
2889         * It's really undefined to call this function in an active
2890         * repository or when there are existing references: we are
2891         * only locking and changing packed-refs, so (1) any
2892         * simultaneous processes might try to change a reference at
2893         * the same time we do, and (2) any existing loose versions of
2894         * the references that we are setting would have precedence
2895         * over our values. But some remote helpers create the remote
2896         * "HEAD" and "master" branches before calling this function,
2897         * so here we really only check that none of the references
2898         * that we are creating already exists.
2899         */
2900        if (refs_for_each_rawref(&refs->base, ref_present,
2901                                 &affected_refnames))
2902                die("BUG: initial ref transaction called with existing refs");
2903
2904        packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
2905        if (!packed_transaction) {
2906                ret = TRANSACTION_GENERIC_ERROR;
2907                goto cleanup;
2908        }
2909
2910        for (i = 0; i < transaction->nr; i++) {
2911                struct ref_update *update = transaction->updates[i];
2912
2913                if ((update->flags & REF_HAVE_OLD) &&
2914                    !is_null_oid(&update->old_oid))
2915                        die("BUG: initial ref transaction with old_sha1 set");
2916                if (refs_verify_refname_available(&refs->base, update->refname,
2917                                                  &affected_refnames, NULL,
2918                                                  err)) {
2919                        ret = TRANSACTION_NAME_CONFLICT;
2920                        goto cleanup;
2921                }
2922
2923                /*
2924                 * Add a reference creation for this reference to the
2925                 * packed-refs transaction:
2926                 */
2927                ref_transaction_add_update(packed_transaction, update->refname,
2928                                           update->flags & ~REF_HAVE_OLD,
2929                                           &update->new_oid, &update->old_oid,
2930                                           NULL);
2931        }
2932
2933        if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
2934                ret = TRANSACTION_GENERIC_ERROR;
2935                goto cleanup;
2936        }
2937
2938        if (initial_ref_transaction_commit(packed_transaction, err)) {
2939                ret = TRANSACTION_GENERIC_ERROR;
2940        }
2941
2942        packed_refs_unlock(refs->packed_ref_store);
2943cleanup:
2944        if (packed_transaction)
2945                ref_transaction_free(packed_transaction);
2946        transaction->state = REF_TRANSACTION_CLOSED;
2947        string_list_clear(&affected_refnames, 0);
2948        return ret;
2949}
2950
2951struct expire_reflog_cb {
2952        unsigned int flags;
2953        reflog_expiry_should_prune_fn *should_prune_fn;
2954        void *policy_cb;
2955        FILE *newlog;
2956        struct object_id last_kept_oid;
2957};
2958
2959static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
2960                             const char *email, timestamp_t timestamp, int tz,
2961                             const char *message, void *cb_data)
2962{
2963        struct expire_reflog_cb *cb = cb_data;
2964        struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
2965
2966        if (cb->flags & EXPIRE_REFLOGS_REWRITE)
2967                ooid = &cb->last_kept_oid;
2968
2969        if ((*cb->should_prune_fn)(ooid, noid, email, timestamp, tz,
2970                                   message, policy_cb)) {
2971                if (!cb->newlog)
2972                        printf("would prune %s", message);
2973                else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2974                        printf("prune %s", message);
2975        } else {
2976                if (cb->newlog) {
2977                        fprintf(cb->newlog, "%s %s %s %"PRItime" %+05d\t%s",
2978                                oid_to_hex(ooid), oid_to_hex(noid),
2979                                email, timestamp, tz, message);
2980                        oidcpy(&cb->last_kept_oid, noid);
2981                }
2982                if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
2983                        printf("keep %s", message);
2984        }
2985        return 0;
2986}
2987
2988static int files_reflog_expire(struct ref_store *ref_store,
2989                               const char *refname, const struct object_id *oid,
2990                               unsigned int flags,
2991                               reflog_expiry_prepare_fn prepare_fn,
2992                               reflog_expiry_should_prune_fn should_prune_fn,
2993                               reflog_expiry_cleanup_fn cleanup_fn,
2994                               void *policy_cb_data)
2995{
2996        struct files_ref_store *refs =
2997                files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2998        static struct lock_file reflog_lock;
2999        struct expire_reflog_cb cb;
3000        struct ref_lock *lock;
3001        struct strbuf log_file_sb = STRBUF_INIT;
3002        char *log_file;
3003        int status = 0;
3004        int type;
3005        struct strbuf err = STRBUF_INIT;
3006
3007        memset(&cb, 0, sizeof(cb));
3008        cb.flags = flags;
3009        cb.policy_cb = policy_cb_data;
3010        cb.should_prune_fn = should_prune_fn;
3011
3012        /*
3013         * The reflog file is locked by holding the lock on the
3014         * reference itself, plus we might need to update the
3015         * reference if --updateref was specified:
3016         */
3017        lock = lock_ref_oid_basic(refs, refname, oid,
3018                                  NULL, NULL, REF_NO_DEREF,
3019                                  &type, &err);
3020        if (!lock) {
3021                error("cannot lock ref '%s': %s", refname, err.buf);
3022                strbuf_release(&err);
3023                return -1;
3024        }
3025        if (!refs_reflog_exists(ref_store, refname)) {
3026                unlock_ref(lock);
3027                return 0;
3028        }
3029
3030        files_reflog_path(refs, &log_file_sb, refname);
3031        log_file = strbuf_detach(&log_file_sb, NULL);
3032        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3033                /*
3034                 * Even though holding $GIT_DIR/logs/$reflog.lock has
3035                 * no locking implications, we use the lock_file
3036                 * machinery here anyway because it does a lot of the
3037                 * work we need, including cleaning up if the program
3038                 * exits unexpectedly.
3039                 */
3040                if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
3041                        struct strbuf err = STRBUF_INIT;
3042                        unable_to_lock_message(log_file, errno, &err);
3043                        error("%s", err.buf);
3044                        strbuf_release(&err);
3045                        goto failure;
3046                }
3047                cb.newlog = fdopen_lock_file(&reflog_lock, "w");
3048                if (!cb.newlog) {
3049                        error("cannot fdopen %s (%s)",
3050                              get_lock_file_path(&reflog_lock), strerror(errno));
3051                        goto failure;
3052                }
3053        }
3054
3055        (*prepare_fn)(refname, oid, cb.policy_cb);
3056        refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
3057        (*cleanup_fn)(cb.policy_cb);
3058
3059        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
3060                /*
3061                 * It doesn't make sense to adjust a reference pointed
3062                 * to by a symbolic ref based on expiring entries in
3063                 * the symbolic reference's reflog. Nor can we update
3064                 * a reference if there are no remaining reflog
3065                 * entries.
3066                 */
3067                int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
3068                        !(type & REF_ISSYMREF) &&
3069                        !is_null_oid(&cb.last_kept_oid);
3070
3071                if (close_lock_file_gently(&reflog_lock)) {
3072                        status |= error("couldn't write %s: %s", log_file,
3073                                        strerror(errno));
3074                        rollback_lock_file(&reflog_lock);
3075                } else if (update &&
3076                           (write_in_full(get_lock_file_fd(&lock->lk),
3077                                oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
3078                            write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
3079                            close_ref_gently(lock) < 0)) {
3080                        status |= error("couldn't write %s",
3081                                        get_lock_file_path(&lock->lk));
3082                        rollback_lock_file(&reflog_lock);
3083                } else if (commit_lock_file(&reflog_lock)) {
3084                        status |= error("unable to write reflog '%s' (%s)",
3085                                        log_file, strerror(errno));
3086                } else if (update && commit_ref(lock)) {
3087                        status |= error("couldn't set %s", lock->ref_name);
3088                }
3089        }
3090        free(log_file);
3091        unlock_ref(lock);
3092        return status;
3093
3094 failure:
3095        rollback_lock_file(&reflog_lock);
3096        free(log_file);
3097        unlock_ref(lock);
3098        return -1;
3099}
3100
3101static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
3102{
3103        struct files_ref_store *refs =
3104                files_downcast(ref_store, REF_STORE_WRITE, "init_db");
3105        struct strbuf sb = STRBUF_INIT;
3106
3107        /*
3108         * Create .git/refs/{heads,tags}
3109         */
3110        files_ref_path(refs, &sb, "refs/heads");
3111        safe_create_dir(sb.buf, 1);
3112
3113        strbuf_reset(&sb);
3114        files_ref_path(refs, &sb, "refs/tags");
3115        safe_create_dir(sb.buf, 1);
3116
3117        strbuf_release(&sb);
3118        return 0;
3119}
3120
3121struct ref_storage_be refs_be_files = {
3122        NULL,
3123        "files",
3124        files_ref_store_create,
3125        files_init_db,
3126        files_transaction_prepare,
3127        files_transaction_finish,
3128        files_transaction_abort,
3129        files_initial_transaction_commit,
3130
3131        files_pack_refs,
3132        files_create_symref,
3133        files_delete_refs,
3134        files_rename_ref,
3135        files_copy_ref,
3136
3137        files_ref_iterator_begin,
3138        files_read_raw_ref,
3139
3140        files_reflog_iterator_begin,
3141        files_for_each_reflog_ent,
3142        files_for_each_reflog_ent_reverse,
3143        files_reflog_exists,
3144        files_create_reflog,
3145        files_delete_reflog,
3146        files_reflog_expire
3147};