Merge branch 'js/msgfmt-on-windows' of ../git-gui into js/git-gui-msgfmt-on-windows
[git] / builtin / fsck.c
1 #include "builtin.h"
2 #include "cache.h"
3 #include "config.h"
4 #include "commit.h"
5 #include "tree.h"
6 #include "blob.h"
7 #include "tag.h"
8 #include "refs.h"
9 #include "pack.h"
10 #include "cache-tree.h"
11 #include "tree-walk.h"
12 #include "fsck.h"
13 #include "parse-options.h"
14 #include "dir.h"
15 #include "progress.h"
16 #include "streaming.h"
17 #include "decorate.h"
18
19 #define REACHABLE 0x0001
20 #define SEEN      0x0002
21 #define HAS_OBJ   0x0004
22
23 static int show_root;
24 static int show_tags;
25 static int show_unreachable;
26 static int include_reflogs = 1;
27 static int check_full = 1;
28 static int connectivity_only;
29 static int check_strict;
30 static int keep_cache_objects;
31 static struct fsck_options fsck_walk_options = FSCK_OPTIONS_DEFAULT;
32 static struct fsck_options fsck_obj_options = FSCK_OPTIONS_DEFAULT;
33 static struct object_id head_oid;
34 static const char *head_points_at;
35 static int errors_found;
36 static int write_lost_and_found;
37 static int verbose;
38 static int show_progress = -1;
39 static int show_dangling = 1;
40 static int name_objects;
41 #define ERROR_OBJECT 01
42 #define ERROR_REACHABLE 02
43 #define ERROR_PACK 04
44 #define ERROR_REFS 010
45
46 static const char *describe_object(struct object *obj)
47 {
48         static struct strbuf buf = STRBUF_INIT;
49         char *name = name_objects ?
50                 lookup_decoration(fsck_walk_options.object_names, obj) : NULL;
51
52         strbuf_reset(&buf);
53         strbuf_addstr(&buf, oid_to_hex(&obj->oid));
54         if (name)
55                 strbuf_addf(&buf, " (%s)", name);
56
57         return buf.buf;
58 }
59
60 static const char *printable_type(struct object *obj)
61 {
62         const char *ret;
63
64         if (obj->type == OBJ_NONE) {
65                 enum object_type type = sha1_object_info(obj->oid.hash, NULL);
66                 if (type > 0)
67                         object_as_type(obj, type, 0);
68         }
69
70         ret = typename(obj->type);
71         if (!ret)
72                 ret = "unknown";
73
74         return ret;
75 }
76
77 static int fsck_config(const char *var, const char *value, void *cb)
78 {
79         if (strcmp(var, "fsck.skiplist") == 0) {
80                 const char *path;
81                 struct strbuf sb = STRBUF_INIT;
82
83                 if (git_config_pathname(&path, var, value))
84                         return 1;
85                 strbuf_addf(&sb, "skiplist=%s", path);
86                 free((char *)path);
87                 fsck_set_msg_types(&fsck_obj_options, sb.buf);
88                 strbuf_release(&sb);
89                 return 0;
90         }
91
92         if (skip_prefix(var, "fsck.", &var)) {
93                 fsck_set_msg_type(&fsck_obj_options, var, value);
94                 return 0;
95         }
96
97         return git_default_config(var, value, cb);
98 }
99
100 static void objreport(struct object *obj, const char *msg_type,
101                         const char *err)
102 {
103         fprintf(stderr, "%s in %s %s: %s\n",
104                 msg_type, printable_type(obj), describe_object(obj), err);
105 }
106
107 static int objerror(struct object *obj, const char *err)
108 {
109         errors_found |= ERROR_OBJECT;
110         objreport(obj, "error", err);
111         return -1;
112 }
113
114 static int fsck_error_func(struct fsck_options *o,
115         struct object *obj, int type, const char *message)
116 {
117         objreport(obj, (type == FSCK_WARN) ? "warning" : "error", message);
118         return (type == FSCK_WARN) ? 0 : 1;
119 }
120
121 static struct object_array pending;
122
123 static int mark_object(struct object *obj, int type, void *data, struct fsck_options *options)
124 {
125         struct object *parent = data;
126
127         /*
128          * The only case data is NULL or type is OBJ_ANY is when
129          * mark_object_reachable() calls us.  All the callers of
130          * that function has non-NULL obj hence ...
131          */
132         if (!obj) {
133                 /* ... these references to parent->fld are safe here */
134                 printf("broken link from %7s %s\n",
135                            printable_type(parent), describe_object(parent));
136                 printf("broken link from %7s %s\n",
137                            (type == OBJ_ANY ? "unknown" : typename(type)), "unknown");
138                 errors_found |= ERROR_REACHABLE;
139                 return 1;
140         }
141
142         if (type != OBJ_ANY && obj->type != type)
143                 /* ... and the reference to parent is safe here */
144                 objerror(parent, "wrong object type in link");
145
146         if (obj->flags & REACHABLE)
147                 return 0;
148         obj->flags |= REACHABLE;
149         if (!(obj->flags & HAS_OBJ)) {
150                 if (parent && !has_object_file(&obj->oid)) {
151                         printf("broken link from %7s %s\n",
152                                  printable_type(parent), describe_object(parent));
153                         printf("              to %7s %s\n",
154                                  printable_type(obj), describe_object(obj));
155                         errors_found |= ERROR_REACHABLE;
156                 }
157                 return 1;
158         }
159
160         add_object_array(obj, NULL, &pending);
161         return 0;
162 }
163
164 static void mark_object_reachable(struct object *obj)
165 {
166         mark_object(obj, OBJ_ANY, NULL, NULL);
167 }
168
169 static int traverse_one_object(struct object *obj)
170 {
171         int result;
172         struct tree *tree = NULL;
173
174         if (obj->type == OBJ_TREE) {
175                 tree = (struct tree *)obj;
176                 if (parse_tree(tree) < 0)
177                         return 1; /* error already displayed */
178         }
179         result = fsck_walk(obj, obj, &fsck_walk_options);
180         if (tree)
181                 free_tree_buffer(tree);
182         return result;
183 }
184
185 static int traverse_reachable(void)
186 {
187         struct progress *progress = NULL;
188         unsigned int nr = 0;
189         int result = 0;
190         if (show_progress)
191                 progress = start_progress_delay(_("Checking connectivity"), 0, 0, 2);
192         while (pending.nr) {
193                 struct object_array_entry *entry;
194                 struct object *obj;
195
196                 entry = pending.objects + --pending.nr;
197                 obj = entry->item;
198                 result |= traverse_one_object(obj);
199                 display_progress(progress, ++nr);
200         }
201         stop_progress(&progress);
202         return !!result;
203 }
204
205 static int mark_used(struct object *obj, int type, void *data, struct fsck_options *options)
206 {
207         if (!obj)
208                 return 1;
209         obj->used = 1;
210         return 0;
211 }
212
213 /*
214  * Check a single reachable object
215  */
216 static void check_reachable_object(struct object *obj)
217 {
218         /*
219          * We obviously want the object to be parsed,
220          * except if it was in a pack-file and we didn't
221          * do a full fsck
222          */
223         if (!(obj->flags & HAS_OBJ)) {
224                 if (has_sha1_pack(obj->oid.hash))
225                         return; /* it is in pack - forget about it */
226                 printf("missing %s %s\n", printable_type(obj),
227                         describe_object(obj));
228                 errors_found |= ERROR_REACHABLE;
229                 return;
230         }
231 }
232
233 /*
234  * Check a single unreachable object
235  */
236 static void check_unreachable_object(struct object *obj)
237 {
238         /*
239          * Missing unreachable object? Ignore it. It's not like
240          * we miss it (since it can't be reached), nor do we want
241          * to complain about it being unreachable (since it does
242          * not exist).
243          */
244         if (!(obj->flags & HAS_OBJ))
245                 return;
246
247         /*
248          * Unreachable object that exists? Show it if asked to,
249          * since this is something that is prunable.
250          */
251         if (show_unreachable) {
252                 printf("unreachable %s %s\n", printable_type(obj),
253                         describe_object(obj));
254                 return;
255         }
256
257         /*
258          * "!used" means that nothing at all points to it, including
259          * other unreachable objects. In other words, it's the "tip"
260          * of some set of unreachable objects, usually a commit that
261          * got dropped.
262          *
263          * Such starting points are more interesting than some random
264          * set of unreachable objects, so we show them even if the user
265          * hasn't asked for _all_ unreachable objects. If you have
266          * deleted a branch by mistake, this is a prime candidate to
267          * start looking at, for example.
268          */
269         if (!obj->used) {
270                 if (show_dangling)
271                         printf("dangling %s %s\n", printable_type(obj),
272                                describe_object(obj));
273                 if (write_lost_and_found) {
274                         char *filename = git_pathdup("lost-found/%s/%s",
275                                 obj->type == OBJ_COMMIT ? "commit" : "other",
276                                 describe_object(obj));
277                         FILE *f;
278
279                         if (safe_create_leading_directories_const(filename)) {
280                                 error("Could not create lost-found");
281                                 free(filename);
282                                 return;
283                         }
284                         f = xfopen(filename, "w");
285                         if (obj->type == OBJ_BLOB) {
286                                 if (stream_blob_to_fd(fileno(f), &obj->oid, NULL, 1))
287                                         die_errno("Could not write '%s'", filename);
288                         } else
289                                 fprintf(f, "%s\n", describe_object(obj));
290                         if (fclose(f))
291                                 die_errno("Could not finish '%s'",
292                                           filename);
293                         free(filename);
294                 }
295                 return;
296         }
297
298         /*
299          * Otherwise? It's there, it's unreachable, and some other unreachable
300          * object points to it. Ignore it - it's not interesting, and we showed
301          * all the interesting cases above.
302          */
303 }
304
305 static void check_object(struct object *obj)
306 {
307         if (verbose)
308                 fprintf(stderr, "Checking %s\n", describe_object(obj));
309
310         if (obj->flags & REACHABLE)
311                 check_reachable_object(obj);
312         else
313                 check_unreachable_object(obj);
314 }
315
316 static void check_connectivity(void)
317 {
318         int i, max;
319
320         /* Traverse the pending reachable objects */
321         traverse_reachable();
322
323         /* Look up all the requirements, warn about missing objects.. */
324         max = get_max_object_index();
325         if (verbose)
326                 fprintf(stderr, "Checking connectivity (%d objects)\n", max);
327
328         for (i = 0; i < max; i++) {
329                 struct object *obj = get_indexed_object(i);
330
331                 if (obj)
332                         check_object(obj);
333         }
334 }
335
336 static int fsck_obj(struct object *obj)
337 {
338         if (obj->flags & SEEN)
339                 return 0;
340         obj->flags |= SEEN;
341
342         if (verbose)
343                 fprintf(stderr, "Checking %s %s\n",
344                         printable_type(obj), describe_object(obj));
345
346         if (fsck_walk(obj, NULL, &fsck_obj_options))
347                 objerror(obj, "broken links");
348         if (fsck_object(obj, NULL, 0, &fsck_obj_options))
349                 return -1;
350
351         if (obj->type == OBJ_TREE) {
352                 struct tree *item = (struct tree *) obj;
353
354                 free_tree_buffer(item);
355         }
356
357         if (obj->type == OBJ_COMMIT) {
358                 struct commit *commit = (struct commit *) obj;
359
360                 free_commit_buffer(commit);
361
362                 if (!commit->parents && show_root)
363                         printf("root %s\n", describe_object(&commit->object));
364         }
365
366         if (obj->type == OBJ_TAG) {
367                 struct tag *tag = (struct tag *) obj;
368
369                 if (show_tags && tag->tagged) {
370                         printf("tagged %s %s", printable_type(tag->tagged),
371                                 describe_object(tag->tagged));
372                         printf(" (%s) in %s\n", tag->tag,
373                                 describe_object(&tag->object));
374                 }
375         }
376
377         return 0;
378 }
379
380 static int fsck_obj_buffer(const struct object_id *oid, enum object_type type,
381                            unsigned long size, void *buffer, int *eaten)
382 {
383         /*
384          * Note, buffer may be NULL if type is OBJ_BLOB. See
385          * verify_packfile(), data_valid variable for details.
386          */
387         struct object *obj;
388         obj = parse_object_buffer(oid, type, size, buffer, eaten);
389         if (!obj) {
390                 errors_found |= ERROR_OBJECT;
391                 return error("%s: object corrupt or missing", oid_to_hex(oid));
392         }
393         obj->flags = HAS_OBJ;
394         return fsck_obj(obj);
395 }
396
397 static int default_refs;
398
399 static void fsck_handle_reflog_oid(const char *refname, struct object_id *oid,
400         timestamp_t timestamp)
401 {
402         struct object *obj;
403
404         if (!is_null_oid(oid)) {
405                 obj = lookup_object(oid->hash);
406                 if (obj && (obj->flags & HAS_OBJ)) {
407                         if (timestamp && name_objects)
408                                 add_decoration(fsck_walk_options.object_names,
409                                         obj,
410                                         xstrfmt("%s@{%"PRItime"}", refname, timestamp));
411                         obj->used = 1;
412                         mark_object_reachable(obj);
413                 } else {
414                         error("%s: invalid reflog entry %s", refname, oid_to_hex(oid));
415                         errors_found |= ERROR_REACHABLE;
416                 }
417         }
418 }
419
420 static int fsck_handle_reflog_ent(struct object_id *ooid, struct object_id *noid,
421                 const char *email, timestamp_t timestamp, int tz,
422                 const char *message, void *cb_data)
423 {
424         const char *refname = cb_data;
425
426         if (verbose)
427                 fprintf(stderr, "Checking reflog %s->%s\n",
428                         oid_to_hex(ooid), oid_to_hex(noid));
429
430         fsck_handle_reflog_oid(refname, ooid, 0);
431         fsck_handle_reflog_oid(refname, noid, timestamp);
432         return 0;
433 }
434
435 static int fsck_handle_reflog(const char *logname, const struct object_id *oid,
436                               int flag, void *cb_data)
437 {
438         for_each_reflog_ent(logname, fsck_handle_reflog_ent, (void *)logname);
439         return 0;
440 }
441
442 static int fsck_handle_ref(const char *refname, const struct object_id *oid,
443                            int flag, void *cb_data)
444 {
445         struct object *obj;
446
447         obj = parse_object(oid);
448         if (!obj) {
449                 error("%s: invalid sha1 pointer %s", refname, oid_to_hex(oid));
450                 errors_found |= ERROR_REACHABLE;
451                 /* We'll continue with the rest despite the error.. */
452                 return 0;
453         }
454         if (obj->type != OBJ_COMMIT && is_branch(refname)) {
455                 error("%s: not a commit", refname);
456                 errors_found |= ERROR_REFS;
457         }
458         default_refs++;
459         obj->used = 1;
460         if (name_objects)
461                 add_decoration(fsck_walk_options.object_names,
462                         obj, xstrdup(refname));
463         mark_object_reachable(obj);
464
465         return 0;
466 }
467
468 static void get_default_heads(void)
469 {
470         if (head_points_at && !is_null_oid(&head_oid))
471                 fsck_handle_ref("HEAD", &head_oid, 0, NULL);
472         for_each_rawref(fsck_handle_ref, NULL);
473         if (include_reflogs)
474                 for_each_reflog(fsck_handle_reflog, NULL);
475
476         /*
477          * Not having any default heads isn't really fatal, but
478          * it does mean that "--unreachable" no longer makes any
479          * sense (since in this case everything will obviously
480          * be unreachable by definition.
481          *
482          * Showing dangling objects is valid, though (as those
483          * dangling objects are likely lost heads).
484          *
485          * So we just print a warning about it, and clear the
486          * "show_unreachable" flag.
487          */
488         if (!default_refs) {
489                 fprintf(stderr, "notice: No default references\n");
490                 show_unreachable = 0;
491         }
492 }
493
494 static struct object *parse_loose_object(const struct object_id *oid,
495                                          const char *path)
496 {
497         struct object *obj;
498         void *contents;
499         enum object_type type;
500         unsigned long size;
501         int eaten;
502
503         if (read_loose_object(path, oid->hash, &type, &size, &contents) < 0)
504                 return NULL;
505
506         if (!contents && type != OBJ_BLOB)
507                 die("BUG: read_loose_object streamed a non-blob");
508
509         obj = parse_object_buffer(oid, type, size, contents, &eaten);
510
511         if (!eaten)
512                 free(contents);
513         return obj;
514 }
515
516 static int fsck_loose(const struct object_id *oid, const char *path, void *data)
517 {
518         struct object *obj = parse_loose_object(oid, path);
519
520         if (!obj) {
521                 errors_found |= ERROR_OBJECT;
522                 error("%s: object corrupt or missing: %s",
523                       oid_to_hex(oid), path);
524                 return 0; /* keep checking other objects */
525         }
526
527         obj->flags = HAS_OBJ;
528         if (fsck_obj(obj))
529                 errors_found |= ERROR_OBJECT;
530         return 0;
531 }
532
533 static int fsck_cruft(const char *basename, const char *path, void *data)
534 {
535         if (!starts_with(basename, "tmp_obj_"))
536                 fprintf(stderr, "bad sha1 file: %s\n", path);
537         return 0;
538 }
539
540 static int fsck_subdir(unsigned int nr, const char *path, void *progress)
541 {
542         display_progress(progress, nr + 1);
543         return 0;
544 }
545
546 static void fsck_object_dir(const char *path)
547 {
548         struct progress *progress = NULL;
549
550         if (verbose)
551                 fprintf(stderr, "Checking object directory\n");
552
553         if (show_progress)
554                 progress = start_progress(_("Checking object directories"), 256);
555
556         for_each_loose_file_in_objdir(path, fsck_loose, fsck_cruft, fsck_subdir,
557                                       progress);
558         display_progress(progress, 256);
559         stop_progress(&progress);
560 }
561
562 static int fsck_head_link(void)
563 {
564         int null_is_error = 0;
565
566         if (verbose)
567                 fprintf(stderr, "Checking HEAD link\n");
568
569         head_points_at = resolve_ref_unsafe("HEAD", 0, head_oid.hash, NULL);
570         if (!head_points_at) {
571                 errors_found |= ERROR_REFS;
572                 return error("Invalid HEAD");
573         }
574         if (!strcmp(head_points_at, "HEAD"))
575                 /* detached HEAD */
576                 null_is_error = 1;
577         else if (!starts_with(head_points_at, "refs/heads/")) {
578                 errors_found |= ERROR_REFS;
579                 return error("HEAD points to something strange (%s)",
580                              head_points_at);
581         }
582         if (is_null_oid(&head_oid)) {
583                 if (null_is_error) {
584                         errors_found |= ERROR_REFS;
585                         return error("HEAD: detached HEAD points at nothing");
586                 }
587                 fprintf(stderr, "notice: HEAD points to an unborn branch (%s)\n",
588                         head_points_at + 11);
589         }
590         return 0;
591 }
592
593 static int fsck_cache_tree(struct cache_tree *it)
594 {
595         int i;
596         int err = 0;
597
598         if (verbose)
599                 fprintf(stderr, "Checking cache tree\n");
600
601         if (0 <= it->entry_count) {
602                 struct object *obj = parse_object(&it->oid);
603                 if (!obj) {
604                         error("%s: invalid sha1 pointer in cache-tree",
605                               oid_to_hex(&it->oid));
606                         errors_found |= ERROR_REFS;
607                         return 1;
608                 }
609                 obj->used = 1;
610                 if (name_objects)
611                         add_decoration(fsck_walk_options.object_names,
612                                 obj, xstrdup(":"));
613                 mark_object_reachable(obj);
614                 if (obj->type != OBJ_TREE)
615                         err |= objerror(obj, "non-tree in cache-tree");
616         }
617         for (i = 0; i < it->subtree_nr; i++)
618                 err |= fsck_cache_tree(it->down[i]->cache_tree);
619         return err;
620 }
621
622 static void mark_object_for_connectivity(const struct object_id *oid)
623 {
624         struct object *obj = lookup_unknown_object(oid->hash);
625         obj->flags |= HAS_OBJ;
626 }
627
628 static int mark_loose_for_connectivity(const struct object_id *oid,
629                                        const char *path,
630                                        void *data)
631 {
632         mark_object_for_connectivity(oid);
633         return 0;
634 }
635
636 static int mark_packed_for_connectivity(const struct object_id *oid,
637                                         struct packed_git *pack,
638                                         uint32_t pos,
639                                         void *data)
640 {
641         mark_object_for_connectivity(oid);
642         return 0;
643 }
644
645 static char const * const fsck_usage[] = {
646         N_("git fsck [<options>] [<object>...]"),
647         NULL
648 };
649
650 static struct option fsck_opts[] = {
651         OPT__VERBOSE(&verbose, N_("be verbose")),
652         OPT_BOOL(0, "unreachable", &show_unreachable, N_("show unreachable objects")),
653         OPT_BOOL(0, "dangling", &show_dangling, N_("show dangling objects")),
654         OPT_BOOL(0, "tags", &show_tags, N_("report tags")),
655         OPT_BOOL(0, "root", &show_root, N_("report root nodes")),
656         OPT_BOOL(0, "cache", &keep_cache_objects, N_("make index objects head nodes")),
657         OPT_BOOL(0, "reflogs", &include_reflogs, N_("make reflogs head nodes (default)")),
658         OPT_BOOL(0, "full", &check_full, N_("also consider packs and alternate objects")),
659         OPT_BOOL(0, "connectivity-only", &connectivity_only, N_("check only connectivity")),
660         OPT_BOOL(0, "strict", &check_strict, N_("enable more strict checking")),
661         OPT_BOOL(0, "lost-found", &write_lost_and_found,
662                                 N_("write dangling objects in .git/lost-found")),
663         OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
664         OPT_BOOL(0, "name-objects", &name_objects, N_("show verbose names for reachable objects")),
665         OPT_END(),
666 };
667
668 int cmd_fsck(int argc, const char **argv, const char *prefix)
669 {
670         int i, heads;
671         struct alternate_object_database *alt;
672
673         errors_found = 0;
674         check_replace_refs = 0;
675
676         argc = parse_options(argc, argv, prefix, fsck_opts, fsck_usage, 0);
677
678         fsck_walk_options.walk = mark_object;
679         fsck_obj_options.walk = mark_used;
680         fsck_obj_options.error_func = fsck_error_func;
681         if (check_strict)
682                 fsck_obj_options.strict = 1;
683
684         if (show_progress == -1)
685                 show_progress = isatty(2);
686         if (verbose)
687                 show_progress = 0;
688
689         if (write_lost_and_found) {
690                 check_full = 1;
691                 include_reflogs = 0;
692         }
693
694         if (name_objects)
695                 fsck_walk_options.object_names =
696                         xcalloc(1, sizeof(struct decoration));
697
698         git_config(fsck_config, NULL);
699
700         fsck_head_link();
701         if (connectivity_only) {
702                 for_each_loose_object(mark_loose_for_connectivity, NULL, 0);
703                 for_each_packed_object(mark_packed_for_connectivity, NULL, 0);
704         } else {
705                 fsck_object_dir(get_object_directory());
706
707                 prepare_alt_odb();
708                 for (alt = alt_odb_list; alt; alt = alt->next)
709                         fsck_object_dir(alt->path);
710
711                 if (check_full) {
712                         struct packed_git *p;
713                         uint32_t total = 0, count = 0;
714                         struct progress *progress = NULL;
715
716                         prepare_packed_git();
717
718                         if (show_progress) {
719                                 for (p = packed_git; p; p = p->next) {
720                                         if (open_pack_index(p))
721                                                 continue;
722                                         total += p->num_objects;
723                                 }
724
725                                 progress = start_progress(_("Checking objects"), total);
726                         }
727                         for (p = packed_git; p; p = p->next) {
728                                 /* verify gives error messages itself */
729                                 if (verify_pack(p, fsck_obj_buffer,
730                                                 progress, count))
731                                         errors_found |= ERROR_PACK;
732                                 count += p->num_objects;
733                         }
734                         stop_progress(&progress);
735                 }
736         }
737
738         heads = 0;
739         for (i = 0; i < argc; i++) {
740                 const char *arg = argv[i];
741                 unsigned char sha1[20];
742                 if (!get_sha1(arg, sha1)) {
743                         struct object *obj = lookup_object(sha1);
744
745                         if (!obj || !(obj->flags & HAS_OBJ)) {
746                                 error("%s: object missing", sha1_to_hex(sha1));
747                                 errors_found |= ERROR_OBJECT;
748                                 continue;
749                         }
750
751                         obj->used = 1;
752                         if (name_objects)
753                                 add_decoration(fsck_walk_options.object_names,
754                                         obj, xstrdup(arg));
755                         mark_object_reachable(obj);
756                         heads++;
757                         continue;
758                 }
759                 error("invalid parameter: expected sha1, got '%s'", arg);
760                 errors_found |= ERROR_OBJECT;
761         }
762
763         /*
764          * If we've not been given any explicit head information, do the
765          * default ones from .git/refs. We also consider the index file
766          * in this case (ie this implies --cache).
767          */
768         if (!argc) {
769                 get_default_heads();
770                 keep_cache_objects = 1;
771         }
772
773         if (keep_cache_objects) {
774                 verify_index_checksum = 1;
775                 read_cache();
776                 for (i = 0; i < active_nr; i++) {
777                         unsigned int mode;
778                         struct blob *blob;
779                         struct object *obj;
780
781                         mode = active_cache[i]->ce_mode;
782                         if (S_ISGITLINK(mode))
783                                 continue;
784                         blob = lookup_blob(&active_cache[i]->oid);
785                         if (!blob)
786                                 continue;
787                         obj = &blob->object;
788                         obj->used = 1;
789                         if (name_objects)
790                                 add_decoration(fsck_walk_options.object_names,
791                                         obj,
792                                         xstrfmt(":%s", active_cache[i]->name));
793                         mark_object_reachable(obj);
794                 }
795                 if (active_cache_tree)
796                         fsck_cache_tree(active_cache_tree);
797         }
798
799         check_connectivity();
800         return errors_found;
801 }