builtin/fsck.c

   1 #include "builtin.h"
   2 #include "cache.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tag.h"
   7 #include "refs.h"
   8 #include "pack.h"
   9 #include "cache-tree.h"
  10 #include "tree-walk.h"
  11 #include "fsck.h"
  12 #include "parse-options.h"
  13 #include "dir.h"
  14 #include "progress.h"
  15 #include "streaming.h"
  16
  17 #define REACHABLE 0x0001
  18 #define SEEN      0x0002
  19 #define HAS_OBJ   0x0004
  20
  21 static int show_root;
  22 static int show_tags;
  23 static int show_unreachable;
  24 static int include_reflogs = 1;
  25 static int check_full = 1;
  26 static int check_strict;
  27 static int keep_cache_objects;
  28 static struct object_id head_oid;
  29 static const char *head_points_at;
  30 static int errors_found;
  31 static int write_lost_and_found;
  32 static int verbose;
  33 static int show_progress = -1;
  34 static int show_dangling = 1;
  35 #define ERROR_OBJECT 01
  36 #define ERROR_REACHABLE 02
  37 #define ERROR_PACK 04
  38 #define ERROR_REFS 010
  39
  40 #ifdef NO_D_INO_IN_DIRENT
  41 #define SORT_DIRENT 0
  42 #define DIRENT_SORT_HINT(de) 0
  43 #else
  44 #define SORT_DIRENT 1
  45 #define DIRENT_SORT_HINT(de) ((de)->d_ino)
  46 #endif
  47
  48 static void objreport(struct object *obj, const char *severity,
  49                       const char *err, va_list params)
  50 {
  51         fprintf(stderr, "%s in %s %s: ",
  52                 severity, typename(obj->type), sha1_to_hex(obj->sha1));
  53         vfprintf(stderr, err, params);
  54         fputs("\n", stderr);
  55 }
  56
  57 __attribute__((format (printf, 2, 3)))
  58 static int objerror(struct object *obj, const char *err, ...)
  59 {
  60         va_list params;
  61         va_start(params, err);
  62         errors_found |= ERROR_OBJECT;
  63         objreport(obj, "error", err, params);
  64         va_end(params);
  65         return -1;
  66 }
  67
  68 __attribute__((format (printf, 3, 4)))
  69 static int fsck_error_func(struct object *obj, int type, const char *err, ...)
  70 {
  71         va_list params;
  72         va_start(params, err);
  73         objreport(obj, (type == FSCK_WARN) ? "warning" : "error", err, params);
  74         va_end(params);
  75         return (type == FSCK_WARN) ? 0 : 1;
  76 }
  77
  78 static struct object_array pending;
  79
  80 static int mark_object(struct object *obj, int type, void *data)
  81 {
  82         struct object *parent = data;
  83
  84         /*
  85          * The only case data is NULL or type is OBJ_ANY is when
  86          * mark_object_reachable() calls us.  All the callers of
  87          * that function has non-NULL obj hence ...
  88          */
  89         if (!obj) {
  90                 /* ... these references to parent->fld are safe here */
  91                 printf("broken link from %7s %s\n",
  92                            typename(parent->type), sha1_to_hex(parent->sha1));
  93                 printf("broken link from %7s %s\n",
  94                            (type == OBJ_ANY ? "unknown" : typename(type)), "unknown");
  95                 errors_found |= ERROR_REACHABLE;
  96                 return 1;
  97         }
  98
  99         if (type != OBJ_ANY && obj->type != type)
 100                 /* ... and the reference to parent is safe here */
 101                 objerror(parent, "wrong object type in link");
 102
 103         if (obj->flags & REACHABLE)
 104                 return 0;
 105         obj->flags |= REACHABLE;
 106         if (!(obj->flags & HAS_OBJ)) {
 107                 if (parent && !has_sha1_file(obj->sha1)) {
 108                         printf("broken link from %7s %s\n",
 109                                  typename(parent->type), sha1_to_hex(parent->sha1));
 110                         printf("              to %7s %s\n",
 111                                  typename(obj->type), sha1_to_hex(obj->sha1));
 112                         errors_found |= ERROR_REACHABLE;
 113                 }
 114                 return 1;
 115         }
 116
 117         add_object_array(obj, NULL, &pending);
 118         return 0;
 119 }
 120
 121 static void mark_object_reachable(struct object *obj)
 122 {
 123         mark_object(obj, OBJ_ANY, NULL);
 124 }
 125
 126 static int traverse_one_object(struct object *obj)
 127 {
 128         int result;
 129         struct tree *tree = NULL;
 130
 131         if (obj->type == OBJ_TREE) {
 132                 tree = (struct tree *)obj;
 133                 if (parse_tree(tree) < 0)
 134                         return 1; /* error already displayed */
 135         }
 136         result = fsck_walk(obj, mark_object, obj);
 137         if (tree)
 138                 free_tree_buffer(tree);
 139         return result;
 140 }
 141
 142 static int traverse_reachable(void)
 143 {
 144         struct progress *progress = NULL;
 145         unsigned int nr = 0;
 146         int result = 0;
 147         if (show_progress)
 148                 progress = start_progress_delay(_("Checking connectivity"), 0, 0, 2);
 149         while (pending.nr) {
 150                 struct object_array_entry *entry;
 151                 struct object *obj;
 152
 153                 entry = pending.objects + --pending.nr;
 154                 obj = entry->item;
 155                 result |= traverse_one_object(obj);
 156                 display_progress(progress, ++nr);
 157         }
 158         stop_progress(&progress);
 159         return !!result;
 160 }
 161
 162 static int mark_used(struct object *obj, int type, void *data)
 163 {
 164         if (!obj)
 165                 return 1;
 166         obj->used = 1;
 167         return 0;
 168 }
 169
 170 /*
 171  * Check a single reachable object
 172  */
 173 static void check_reachable_object(struct object *obj)
 174 {
 175         /*
 176          * We obviously want the object to be parsed,
 177          * except if it was in a pack-file and we didn't
 178          * do a full fsck
 179          */
 180         if (!(obj->flags & HAS_OBJ)) {
 181                 if (has_sha1_pack(obj->sha1))
 182                         return; /* it is in pack - forget about it */
 183                 printf("missing %s %s\n", typename(obj->type), sha1_to_hex(obj->sha1));
 184                 errors_found |= ERROR_REACHABLE;
 185                 return;
 186         }
 187 }
 188
 189 /*
 190  * Check a single unreachable object
 191  */
 192 static void check_unreachable_object(struct object *obj)
 193 {
 194         /*
 195          * Missing unreachable object? Ignore it. It's not like
 196          * we miss it (since it can't be reached), nor do we want
 197          * to complain about it being unreachable (since it does
 198          * not exist).
 199          */
 200         if (!obj->parsed)
 201                 return;
 202
 203         /*
 204          * Unreachable object that exists? Show it if asked to,
 205          * since this is something that is prunable.
 206          */
 207         if (show_unreachable) {
 208                 printf("unreachable %s %s\n", typename(obj->type), sha1_to_hex(obj->sha1));
 209                 return;
 210         }
 211
 212         /*
 213          * "!used" means that nothing at all points to it, including
 214          * other unreachable objects. In other words, it's the "tip"
 215          * of some set of unreachable objects, usually a commit that
 216          * got dropped.
 217          *
 218          * Such starting points are more interesting than some random
 219          * set of unreachable objects, so we show them even if the user
 220          * hasn't asked for _all_ unreachable objects. If you have
 221          * deleted a branch by mistake, this is a prime candidate to
 222          * start looking at, for example.
 223          */
 224         if (!obj->used) {
 225                 if (show_dangling)
 226                         printf("dangling %s %s\n", typename(obj->type),
 227                                sha1_to_hex(obj->sha1));
 228                 if (write_lost_and_found) {
 229                         const char *filename = git_path("lost-found/%s/%s",
 230                                 obj->type == OBJ_COMMIT ? "commit" : "other",
 231                                 sha1_to_hex(obj->sha1));
 232                         FILE *f;
 233
 234                         if (safe_create_leading_directories_const(filename)) {
 235                                 error("Could not create lost-found");
 236                                 return;
 237                         }
 238                         if (!(f = fopen(filename, "w")))
 239                                 die_errno("Could not open '%s'", filename);
 240                         if (obj->type == OBJ_BLOB) {
 241                                 if (stream_blob_to_fd(fileno(f), obj->sha1, NULL, 1))
 242                                         die_errno("Could not write '%s'", filename);
 243                         } else
 244                                 fprintf(f, "%s\n", sha1_to_hex(obj->sha1));
 245                         if (fclose(f))
 246                                 die_errno("Could not finish '%s'",
 247                                           filename);
 248                 }
 249                 return;
 250         }
 251
 252         /*
 253          * Otherwise? It's there, it's unreachable, and some other unreachable
 254          * object points to it. Ignore it - it's not interesting, and we showed
 255          * all the interesting cases above.
 256          */
 257 }
 258
 259 static void check_object(struct object *obj)
 260 {
 261         if (verbose)
 262                 fprintf(stderr, "Checking %s\n", sha1_to_hex(obj->sha1));
 263
 264         if (obj->flags & REACHABLE)
 265                 check_reachable_object(obj);
 266         else
 267                 check_unreachable_object(obj);
 268 }
 269
 270 static void check_connectivity(void)
 271 {
 272         int i, max;
 273
 274         /* Traverse the pending reachable objects */
 275         traverse_reachable();
 276
 277         /* Look up all the requirements, warn about missing objects.. */
 278         max = get_max_object_index();
 279         if (verbose)
 280                 fprintf(stderr, "Checking connectivity (%d objects)\n", max);
 281
 282         for (i = 0; i < max; i++) {
 283                 struct object *obj = get_indexed_object(i);
 284
 285                 if (obj)
 286                         check_object(obj);
 287         }
 288 }
 289
 290 static int fsck_obj(struct object *obj)
 291 {
 292         if (obj->flags & SEEN)
 293                 return 0;
 294         obj->flags |= SEEN;
 295
 296         if (verbose)
 297                 fprintf(stderr, "Checking %s %s\n",
 298                         typename(obj->type), sha1_to_hex(obj->sha1));
 299
 300         if (fsck_walk(obj, mark_used, NULL))
 301                 objerror(obj, "broken links");
 302         if (fsck_object(obj, NULL, 0, check_strict, fsck_error_func))
 303                 return -1;
 304
 305         if (obj->type == OBJ_TREE) {
 306                 struct tree *item = (struct tree *) obj;
 307
 308                 free_tree_buffer(item);
 309         }
 310
 311         if (obj->type == OBJ_COMMIT) {
 312                 struct commit *commit = (struct commit *) obj;
 313
 314                 free_commit_buffer(commit);
 315
 316                 if (!commit->parents && show_root)
 317                         printf("root %s\n", sha1_to_hex(commit->object.sha1));
 318         }
 319
 320         if (obj->type == OBJ_TAG) {
 321                 struct tag *tag = (struct tag *) obj;
 322
 323                 if (show_tags && tag->tagged) {
 324                         printf("tagged %s %s", typename(tag->tagged->type), sha1_to_hex(tag->tagged->sha1));
 325                         printf(" (%s) in %s\n", tag->tag, sha1_to_hex(tag->object.sha1));
 326                 }
 327         }
 328
 329         return 0;
 330 }
 331
 332 static int fsck_sha1(const unsigned char *sha1)
 333 {
 334         struct object *obj = parse_object(sha1);
 335         if (!obj) {
 336                 errors_found |= ERROR_OBJECT;
 337                 return error("%s: object corrupt or missing",
 338                              sha1_to_hex(sha1));
 339         }
 340         obj->flags |= HAS_OBJ;
 341         return fsck_obj(obj);
 342 }
 343
 344 static int fsck_obj_buffer(const unsigned char *sha1, enum object_type type,
 345                            unsigned long size, void *buffer, int *eaten)
 346 {
 347         struct object *obj;
 348         obj = parse_object_buffer(sha1, type, size, buffer, eaten);
 349         if (!obj) {
 350                 errors_found |= ERROR_OBJECT;
 351                 return error("%s: object corrupt or missing", sha1_to_hex(sha1));
 352         }
 353         obj->flags = HAS_OBJ;
 354         return fsck_obj(obj);
 355 }
 356
 357 /*
 358  * This is the sorting chunk size: make it reasonably
 359  * big so that we can sort well..
 360  */
 361 #define MAX_SHA1_ENTRIES (1024)
 362
 363 struct sha1_entry {
 364         unsigned long ino;
 365         unsigned char sha1[20];
 366 };
 367
 368 static struct {
 369         unsigned long nr;
 370         struct sha1_entry *entry[MAX_SHA1_ENTRIES];
 371 } sha1_list;
 372
 373 static int ino_compare(const void *_a, const void *_b)
 374 {
 375         const struct sha1_entry *a = _a, *b = _b;
 376         unsigned long ino1 = a->ino, ino2 = b->ino;
 377         return ino1 < ino2 ? -1 : ino1 > ino2 ? 1 : 0;
 378 }
 379
 380 static void fsck_sha1_list(void)
 381 {
 382         int i, nr = sha1_list.nr;
 383
 384         if (SORT_DIRENT)
 385                 qsort(sha1_list.entry, nr,
 386                       sizeof(struct sha1_entry *), ino_compare);
 387         for (i = 0; i < nr; i++) {
 388                 struct sha1_entry *entry = sha1_list.entry[i];
 389                 unsigned char *sha1 = entry->sha1;
 390
 391                 sha1_list.entry[i] = NULL;
 392                 if (fsck_sha1(sha1))
 393                         errors_found |= ERROR_OBJECT;
 394                 free(entry);
 395         }
 396         sha1_list.nr = 0;
 397 }
 398
 399 static void add_sha1_list(unsigned char *sha1, unsigned long ino)
 400 {
 401         struct sha1_entry *entry = xmalloc(sizeof(*entry));
 402         int nr;
 403
 404         entry->ino = ino;
 405         hashcpy(entry->sha1, sha1);
 406         nr = sha1_list.nr;
 407         if (nr == MAX_SHA1_ENTRIES) {
 408                 fsck_sha1_list();
 409                 nr = 0;
 410         }
 411         sha1_list.entry[nr] = entry;
 412         sha1_list.nr = ++nr;
 413 }
 414
 415 static inline int is_loose_object_file(struct dirent *de,
 416                                        char *name, unsigned char *sha1)
 417 {
 418         if (strlen(de->d_name) != 38)
 419                 return 0;
 420         memcpy(name + 2, de->d_name, 39);
 421         return !get_sha1_hex(name, sha1);
 422 }
 423
 424 static void fsck_dir(int i, char *path)
 425 {
 426         DIR *dir = opendir(path);
 427         struct dirent *de;
 428         char name[100];
 429
 430         if (!dir)
 431                 return;
 432
 433         if (verbose)
 434                 fprintf(stderr, "Checking directory %s\n", path);
 435
 436         sprintf(name, "%02x", i);
 437         while ((de = readdir(dir)) != NULL) {
 438                 unsigned char sha1[20];
 439
 440                 if (is_dot_or_dotdot(de->d_name))
 441                         continue;
 442                 if (is_loose_object_file(de, name, sha1)) {
 443                         add_sha1_list(sha1, DIRENT_SORT_HINT(de));
 444                         continue;
 445                 }
 446                 if (starts_with(de->d_name, "tmp_obj_"))
 447                         continue;
 448                 fprintf(stderr, "bad sha1 file: %s/%s\n", path, de->d_name);
 449         }
 450         closedir(dir);
 451 }
 452
 453 static int default_refs;
 454
 455 static int fsck_handle_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
 456                 const char *email, unsigned long timestamp, int tz,
 457                 const char *message, void *cb_data)
 458 {
 459         struct object *obj;
 460
 461         if (verbose)
 462                 fprintf(stderr, "Checking reflog %s->%s\n",
 463                         sha1_to_hex(osha1), sha1_to_hex(nsha1));
 464
 465         if (!is_null_sha1(osha1)) {
 466                 obj = lookup_object(osha1);
 467                 if (obj) {
 468                         obj->used = 1;
 469                         mark_object_reachable(obj);
 470                 }
 471         }
 472         obj = lookup_object(nsha1);
 473         if (obj) {
 474                 obj->used = 1;
 475                 mark_object_reachable(obj);
 476         }
 477         return 0;
 478 }
 479
 480 static int fsck_handle_reflog(const char *logname, const struct object_id *oid,
 481                               int flag, void *cb_data)
 482 {
 483         for_each_reflog_ent(logname, fsck_handle_reflog_ent, NULL);
 484         return 0;
 485 }
 486
 487 static int fsck_handle_ref(const char *refname, const struct object_id *oid,
 488                            int flag, void *cb_data)
 489 {
 490         struct object *obj;
 491
 492         obj = parse_object(oid->hash);
 493         if (!obj) {
 494                 error("%s: invalid sha1 pointer %s", refname, oid_to_hex(oid));
 495                 errors_found |= ERROR_REACHABLE;
 496                 /* We'll continue with the rest despite the error.. */
 497                 return 0;
 498         }
 499         if (obj->type != OBJ_COMMIT && is_branch(refname)) {
 500                 error("%s: not a commit", refname);
 501                 errors_found |= ERROR_REFS;
 502         }
 503         default_refs++;
 504         obj->used = 1;
 505         mark_object_reachable(obj);
 506
 507         return 0;
 508 }
 509
 510 static void get_default_heads(void)
 511 {
 512         if (head_points_at && !is_null_oid(&head_oid))
 513                 fsck_handle_ref("HEAD", &head_oid, 0, NULL);
 514         for_each_rawref(fsck_handle_ref, NULL);
 515         if (include_reflogs)
 516                 for_each_reflog(fsck_handle_reflog, NULL);
 517
 518         /*
 519          * Not having any default heads isn't really fatal, but
 520          * it does mean that "--unreachable" no longer makes any
 521          * sense (since in this case everything will obviously
 522          * be unreachable by definition.
 523          *
 524          * Showing dangling objects is valid, though (as those
 525          * dangling objects are likely lost heads).
 526          *
 527          * So we just print a warning about it, and clear the
 528          * "show_unreachable" flag.
 529          */
 530         if (!default_refs) {
 531                 fprintf(stderr, "notice: No default references\n");
 532                 show_unreachable = 0;
 533         }
 534 }
 535
 536 static void fsck_object_dir(const char *path)
 537 {
 538         int i;
 539         struct progress *progress = NULL;
 540
 541         if (verbose)
 542                 fprintf(stderr, "Checking object directory\n");
 543
 544         if (show_progress)
 545                 progress = start_progress(_("Checking object directories"), 256);
 546         for (i = 0; i < 256; i++) {
 547                 static char dir[4096];
 548                 sprintf(dir, "%s/%02x", path, i);
 549                 fsck_dir(i, dir);
 550                 display_progress(progress, i+1);
 551         }
 552         stop_progress(&progress);
 553         fsck_sha1_list();
 554 }
 555
 556 static int fsck_head_link(void)
 557 {
 558         int flag;
 559         int null_is_error = 0;
 560
 561         if (verbose)
 562                 fprintf(stderr, "Checking HEAD link\n");
 563
 564         head_points_at = resolve_ref_unsafe("HEAD", 0, head_oid.hash, &flag);
 565         if (!head_points_at) {
 566                 errors_found |= ERROR_REFS;
 567                 return error("Invalid HEAD");
 568         }
 569         if (!strcmp(head_points_at, "HEAD"))
 570                 /* detached HEAD */
 571                 null_is_error = 1;
 572         else if (!starts_with(head_points_at, "refs/heads/")) {
 573                 errors_found |= ERROR_REFS;
 574                 return error("HEAD points to something strange (%s)",
 575                              head_points_at);
 576         }
 577         if (is_null_oid(&head_oid)) {
 578                 if (null_is_error) {
 579                         errors_found |= ERROR_REFS;
 580                         return error("HEAD: detached HEAD points at nothing");
 581                 }
 582                 fprintf(stderr, "notice: HEAD points to an unborn branch (%s)\n",
 583                         head_points_at + 11);
 584         }
 585         return 0;
 586 }
 587
 588 static int fsck_cache_tree(struct cache_tree *it)
 589 {
 590         int i;
 591         int err = 0;
 592
 593         if (verbose)
 594                 fprintf(stderr, "Checking cache tree\n");
 595
 596         if (0 <= it->entry_count) {
 597                 struct object *obj = parse_object(it->sha1);
 598                 if (!obj) {
 599                         error("%s: invalid sha1 pointer in cache-tree",
 600                               sha1_to_hex(it->sha1));
 601                         errors_found |= ERROR_REFS;
 602                         return 1;
 603                 }
 604                 obj->used = 1;
 605                 mark_object_reachable(obj);
 606                 if (obj->type != OBJ_TREE)
 607                         err |= objerror(obj, "non-tree in cache-tree");
 608         }
 609         for (i = 0; i < it->subtree_nr; i++)
 610                 err |= fsck_cache_tree(it->down[i]->cache_tree);
 611         return err;
 612 }
 613
 614 static char const * const fsck_usage[] = {
 615         N_("git fsck [<options>] [<object>...]"),
 616         NULL
 617 };
 618
 619 static struct option fsck_opts[] = {
 620         OPT__VERBOSE(&verbose, N_("be verbose")),
 621         OPT_BOOL(0, "unreachable", &show_unreachable, N_("show unreachable objects")),
 622         OPT_BOOL(0, "dangling", &show_dangling, N_("show dangling objects")),
 623         OPT_BOOL(0, "tags", &show_tags, N_("report tags")),
 624         OPT_BOOL(0, "root", &show_root, N_("report root nodes")),
 625         OPT_BOOL(0, "cache", &keep_cache_objects, N_("make index objects head nodes")),
 626         OPT_BOOL(0, "reflogs", &include_reflogs, N_("make reflogs head nodes (default)")),
 627         OPT_BOOL(0, "full", &check_full, N_("also consider packs and alternate objects")),
 628         OPT_BOOL(0, "strict", &check_strict, N_("enable more strict checking")),
 629         OPT_BOOL(0, "lost-found", &write_lost_and_found,
 630                                 N_("write dangling objects in .git/lost-found")),
 631         OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
 632         OPT_END(),
 633 };
 634
 635 int cmd_fsck(int argc, const char **argv, const char *prefix)
 636 {
 637         int i, heads;
 638         struct alternate_object_database *alt;
 639
 640         errors_found = 0;
 641         check_replace_refs = 0;
 642
 643         argc = parse_options(argc, argv, prefix, fsck_opts, fsck_usage, 0);
 644
 645         if (show_progress == -1)
 646                 show_progress = isatty(2);
 647         if (verbose)
 648                 show_progress = 0;
 649
 650         if (write_lost_and_found) {
 651                 check_full = 1;
 652                 include_reflogs = 0;
 653         }
 654
 655         fsck_head_link();
 656         fsck_object_dir(get_object_directory());
 657
 658         prepare_alt_odb();
 659         for (alt = alt_odb_list; alt; alt = alt->next) {
 660                 char namebuf[PATH_MAX];
 661                 int namelen = alt->name - alt->base;
 662                 memcpy(namebuf, alt->base, namelen);
 663                 namebuf[namelen - 1] = 0;
 664                 fsck_object_dir(namebuf);
 665         }
 666
 667         if (check_full) {
 668                 struct packed_git *p;
 669                 uint32_t total = 0, count = 0;
 670                 struct progress *progress = NULL;
 671
 672                 prepare_packed_git();
 673
 674                 if (show_progress) {
 675                         for (p = packed_git; p; p = p->next) {
 676                                 if (open_pack_index(p))
 677                                         continue;
 678                                 total += p->num_objects;
 679                         }
 680
 681                         progress = start_progress(_("Checking objects"), total);
 682                 }
 683                 for (p = packed_git; p; p = p->next) {
 684                         /* verify gives error messages itself */
 685                         if (verify_pack(p, fsck_obj_buffer,
 686                                         progress, count))
 687                                 errors_found |= ERROR_PACK;
 688                         count += p->num_objects;
 689                 }
 690                 stop_progress(&progress);
 691         }
 692
 693         heads = 0;
 694         for (i = 0; i < argc; i++) {
 695                 const char *arg = argv[i];
 696                 unsigned char sha1[20];
 697                 if (!get_sha1(arg, sha1)) {
 698                         struct object *obj = lookup_object(sha1);
 699
 700                         /* Error is printed by lookup_object(). */
 701                         if (!obj)
 702                                 continue;
 703
 704                         obj->used = 1;
 705                         mark_object_reachable(obj);
 706                         heads++;
 707                         continue;
 708                 }
 709                 error("invalid parameter: expected sha1, got '%s'", arg);
 710         }
 711
 712         /*
 713          * If we've not been given any explicit head information, do the
 714          * default ones from .git/refs. We also consider the index file
 715          * in this case (ie this implies --cache).
 716          */
 717         if (!heads) {
 718                 get_default_heads();
 719                 keep_cache_objects = 1;
 720         }
 721
 722         if (keep_cache_objects) {
 723                 read_cache();
 724                 for (i = 0; i < active_nr; i++) {
 725                         unsigned int mode;
 726                         struct blob *blob;
 727                         struct object *obj;
 728
 729                         mode = active_cache[i]->ce_mode;
 730                         if (S_ISGITLINK(mode))
 731                                 continue;
 732                         blob = lookup_blob(active_cache[i]->sha1);
 733                         if (!blob)
 734                                 continue;
 735                         obj = &blob->object;
 736                         obj->used = 1;
 737                         mark_object_reachable(obj);
 738                 }
 739                 if (active_cache_tree)
 740                         fsck_cache_tree(active_cache_tree);
 741         }
 742
 743         check_connectivity();
 744         return errors_found;
 745 }