Merge branch 'cc/subprocess-handshake-missing-capabilities'
[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 #include "packfile.h"
19
20 #define REACHABLE 0x0001
21 #define SEEN      0x0002
22 #define HAS_OBJ   0x0004
23 /* This flag is set if something points to this object. */
24 #define USED      0x0008
25
26 static int show_root;
27 static int show_tags;
28 static int show_unreachable;
29 static int include_reflogs = 1;
30 static int check_full = 1;
31 static int connectivity_only;
32 static int check_strict;
33 static int keep_cache_objects;
34 static struct fsck_options fsck_walk_options = FSCK_OPTIONS_DEFAULT;
35 static struct fsck_options fsck_obj_options = FSCK_OPTIONS_DEFAULT;
36 static struct object_id head_oid;
37 static const char *head_points_at;
38 static int errors_found;
39 static int write_lost_and_found;
40 static int verbose;
41 static int show_progress = -1;
42 static int show_dangling = 1;
43 static int name_objects;
44 #define ERROR_OBJECT 01
45 #define ERROR_REACHABLE 02
46 #define ERROR_PACK 04
47 #define ERROR_REFS 010
48
49 static const char *describe_object(struct object *obj)
50 {
51         static struct strbuf buf = STRBUF_INIT;
52         char *name = name_objects ?
53                 lookup_decoration(fsck_walk_options.object_names, obj) : NULL;
54
55         strbuf_reset(&buf);
56         strbuf_addstr(&buf, oid_to_hex(&obj->oid));
57         if (name)
58                 strbuf_addf(&buf, " (%s)", name);
59
60         return buf.buf;
61 }
62
63 static const char *printable_type(struct object *obj)
64 {
65         const char *ret;
66
67         if (obj->type == OBJ_NONE) {
68                 enum object_type type = sha1_object_info(obj->oid.hash, NULL);
69                 if (type > 0)
70                         object_as_type(obj, type, 0);
71         }
72
73         ret = typename(obj->type);
74         if (!ret)
75                 ret = "unknown";
76
77         return ret;
78 }
79
80 static int fsck_config(const char *var, const char *value, void *cb)
81 {
82         if (strcmp(var, "fsck.skiplist") == 0) {
83                 const char *path;
84                 struct strbuf sb = STRBUF_INIT;
85
86                 if (git_config_pathname(&path, var, value))
87                         return 1;
88                 strbuf_addf(&sb, "skiplist=%s", path);
89                 free((char *)path);
90                 fsck_set_msg_types(&fsck_obj_options, sb.buf);
91                 strbuf_release(&sb);
92                 return 0;
93         }
94
95         if (skip_prefix(var, "fsck.", &var)) {
96                 fsck_set_msg_type(&fsck_obj_options, var, value);
97                 return 0;
98         }
99
100         return git_default_config(var, value, cb);
101 }
102
103 static void objreport(struct object *obj, const char *msg_type,
104                         const char *err)
105 {
106         fprintf(stderr, "%s in %s %s: %s\n",
107                 msg_type, printable_type(obj), describe_object(obj), err);
108 }
109
110 static int objerror(struct object *obj, const char *err)
111 {
112         errors_found |= ERROR_OBJECT;
113         objreport(obj, "error", err);
114         return -1;
115 }
116
117 static int fsck_error_func(struct fsck_options *o,
118         struct object *obj, int type, const char *message)
119 {
120         objreport(obj, (type == FSCK_WARN) ? "warning" : "error", message);
121         return (type == FSCK_WARN) ? 0 : 1;
122 }
123
124 static struct object_array pending;
125
126 static int mark_object(struct object *obj, int type, void *data, struct fsck_options *options)
127 {
128         struct object *parent = data;
129
130         /*
131          * The only case data is NULL or type is OBJ_ANY is when
132          * mark_object_reachable() calls us.  All the callers of
133          * that function has non-NULL obj hence ...
134          */
135         if (!obj) {
136                 /* ... these references to parent->fld are safe here */
137                 printf("broken link from %7s %s\n",
138                            printable_type(parent), describe_object(parent));
139                 printf("broken link from %7s %s\n",
140                            (type == OBJ_ANY ? "unknown" : typename(type)), "unknown");
141                 errors_found |= ERROR_REACHABLE;
142                 return 1;
143         }
144
145         if (type != OBJ_ANY && obj->type != type)
146                 /* ... and the reference to parent is safe here */
147                 objerror(parent, "wrong object type in link");
148
149         if (obj->flags & REACHABLE)
150                 return 0;
151         obj->flags |= REACHABLE;
152         if (!(obj->flags & HAS_OBJ)) {
153                 if (parent && !has_object_file(&obj->oid)) {
154                         printf("broken link from %7s %s\n",
155                                  printable_type(parent), describe_object(parent));
156                         printf("              to %7s %s\n",
157                                  printable_type(obj), describe_object(obj));
158                         errors_found |= ERROR_REACHABLE;
159                 }
160                 return 1;
161         }
162
163         add_object_array(obj, NULL, &pending);
164         return 0;
165 }
166
167 static void mark_object_reachable(struct object *obj)
168 {
169         mark_object(obj, OBJ_ANY, NULL, NULL);
170 }
171
172 static int traverse_one_object(struct object *obj)
173 {
174         return fsck_walk(obj, obj, &fsck_walk_options);
175 }
176
177 static int traverse_reachable(void)
178 {
179         struct progress *progress = NULL;
180         unsigned int nr = 0;
181         int result = 0;
182         if (show_progress)
183                 progress = start_delayed_progress(_("Checking connectivity"), 0);
184         while (pending.nr) {
185                 struct object_array_entry *entry;
186                 struct object *obj;
187
188                 entry = pending.objects + --pending.nr;
189                 obj = entry->item;
190                 result |= traverse_one_object(obj);
191                 display_progress(progress, ++nr);
192         }
193         stop_progress(&progress);
194         return !!result;
195 }
196
197 static int mark_used(struct object *obj, int type, void *data, struct fsck_options *options)
198 {
199         if (!obj)
200                 return 1;
201         obj->flags |= USED;
202         return 0;
203 }
204
205 /*
206  * Check a single reachable object
207  */
208 static void check_reachable_object(struct object *obj)
209 {
210         /*
211          * We obviously want the object to be parsed,
212          * except if it was in a pack-file and we didn't
213          * do a full fsck
214          */
215         if (!(obj->flags & HAS_OBJ)) {
216                 if (has_sha1_pack(obj->oid.hash))
217                         return; /* it is in pack - forget about it */
218                 printf("missing %s %s\n", printable_type(obj),
219                         describe_object(obj));
220                 errors_found |= ERROR_REACHABLE;
221                 return;
222         }
223 }
224
225 /*
226  * Check a single unreachable object
227  */
228 static void check_unreachable_object(struct object *obj)
229 {
230         /*
231          * Missing unreachable object? Ignore it. It's not like
232          * we miss it (since it can't be reached), nor do we want
233          * to complain about it being unreachable (since it does
234          * not exist).
235          */
236         if (!(obj->flags & HAS_OBJ))
237                 return;
238
239         /*
240          * Unreachable object that exists? Show it if asked to,
241          * since this is something that is prunable.
242          */
243         if (show_unreachable) {
244                 printf("unreachable %s %s\n", printable_type(obj),
245                         describe_object(obj));
246                 return;
247         }
248
249         /*
250          * "!USED" means that nothing at all points to it, including
251          * other unreachable objects. In other words, it's the "tip"
252          * of some set of unreachable objects, usually a commit that
253          * got dropped.
254          *
255          * Such starting points are more interesting than some random
256          * set of unreachable objects, so we show them even if the user
257          * hasn't asked for _all_ unreachable objects. If you have
258          * deleted a branch by mistake, this is a prime candidate to
259          * start looking at, for example.
260          */
261         if (!(obj->flags & USED)) {
262                 if (show_dangling)
263                         printf("dangling %s %s\n", printable_type(obj),
264                                describe_object(obj));
265                 if (write_lost_and_found) {
266                         char *filename = git_pathdup("lost-found/%s/%s",
267                                 obj->type == OBJ_COMMIT ? "commit" : "other",
268                                 describe_object(obj));
269                         FILE *f;
270
271                         if (safe_create_leading_directories_const(filename)) {
272                                 error("Could not create lost-found");
273                                 free(filename);
274                                 return;
275                         }
276                         f = xfopen(filename, "w");
277                         if (obj->type == OBJ_BLOB) {
278                                 if (stream_blob_to_fd(fileno(f), &obj->oid, NULL, 1))
279                                         die_errno("Could not write '%s'", filename);
280                         } else
281                                 fprintf(f, "%s\n", describe_object(obj));
282                         if (fclose(f))
283                                 die_errno("Could not finish '%s'",
284                                           filename);
285                         free(filename);
286                 }
287                 return;
288         }
289
290         /*
291          * Otherwise? It's there, it's unreachable, and some other unreachable
292          * object points to it. Ignore it - it's not interesting, and we showed
293          * all the interesting cases above.
294          */
295 }
296
297 static void check_object(struct object *obj)
298 {
299         if (verbose)
300                 fprintf(stderr, "Checking %s\n", describe_object(obj));
301
302         if (obj->flags & REACHABLE)
303                 check_reachable_object(obj);
304         else
305                 check_unreachable_object(obj);
306 }
307
308 static void check_connectivity(void)
309 {
310         int i, max;
311
312         /* Traverse the pending reachable objects */
313         traverse_reachable();
314
315         /* Look up all the requirements, warn about missing objects.. */
316         max = get_max_object_index();
317         if (verbose)
318                 fprintf(stderr, "Checking connectivity (%d objects)\n", max);
319
320         for (i = 0; i < max; i++) {
321                 struct object *obj = get_indexed_object(i);
322
323                 if (obj)
324                         check_object(obj);
325         }
326 }
327
328 static int fsck_obj(struct object *obj)
329 {
330         int err;
331
332         if (obj->flags & SEEN)
333                 return 0;
334         obj->flags |= SEEN;
335
336         if (verbose)
337                 fprintf(stderr, "Checking %s %s\n",
338                         printable_type(obj), describe_object(obj));
339
340         if (fsck_walk(obj, NULL, &fsck_obj_options))
341                 objerror(obj, "broken links");
342         err = fsck_object(obj, NULL, 0, &fsck_obj_options);
343         if (err)
344                 goto out;
345
346         if (obj->type == OBJ_COMMIT) {
347                 struct commit *commit = (struct commit *) obj;
348
349                 if (!commit->parents && show_root)
350                         printf("root %s\n", describe_object(&commit->object));
351         }
352
353         if (obj->type == OBJ_TAG) {
354                 struct tag *tag = (struct tag *) obj;
355
356                 if (show_tags && tag->tagged) {
357                         printf("tagged %s %s", printable_type(tag->tagged),
358                                 describe_object(tag->tagged));
359                         printf(" (%s) in %s\n", tag->tag,
360                                 describe_object(&tag->object));
361                 }
362         }
363
364 out:
365         if (obj->type == OBJ_TREE)
366                 free_tree_buffer((struct tree *)obj);
367         if (obj->type == OBJ_COMMIT)
368                 free_commit_buffer((struct commit *)obj);
369         return err;
370 }
371
372 static int fsck_obj_buffer(const struct object_id *oid, enum object_type type,
373                            unsigned long size, void *buffer, int *eaten)
374 {
375         /*
376          * Note, buffer may be NULL if type is OBJ_BLOB. See
377          * verify_packfile(), data_valid variable for details.
378          */
379         struct object *obj;
380         obj = parse_object_buffer(oid, type, size, buffer, eaten);
381         if (!obj) {
382                 errors_found |= ERROR_OBJECT;
383                 return error("%s: object corrupt or missing", oid_to_hex(oid));
384         }
385         obj->flags &= ~(REACHABLE | SEEN);
386         obj->flags |= HAS_OBJ;
387         return fsck_obj(obj);
388 }
389
390 static int default_refs;
391
392 static void fsck_handle_reflog_oid(const char *refname, struct object_id *oid,
393         timestamp_t timestamp)
394 {
395         struct object *obj;
396
397         if (!is_null_oid(oid)) {
398                 obj = lookup_object(oid->hash);
399                 if (obj && (obj->flags & HAS_OBJ)) {
400                         if (timestamp && name_objects)
401                                 add_decoration(fsck_walk_options.object_names,
402                                         obj,
403                                         xstrfmt("%s@{%"PRItime"}", refname, timestamp));
404                         obj->flags |= USED;
405                         mark_object_reachable(obj);
406                 } else {
407                         error("%s: invalid reflog entry %s", refname, oid_to_hex(oid));
408                         errors_found |= ERROR_REACHABLE;
409                 }
410         }
411 }
412
413 static int fsck_handle_reflog_ent(struct object_id *ooid, struct object_id *noid,
414                 const char *email, timestamp_t timestamp, int tz,
415                 const char *message, void *cb_data)
416 {
417         const char *refname = cb_data;
418
419         if (verbose)
420                 fprintf(stderr, "Checking reflog %s->%s\n",
421                         oid_to_hex(ooid), oid_to_hex(noid));
422
423         fsck_handle_reflog_oid(refname, ooid, 0);
424         fsck_handle_reflog_oid(refname, noid, timestamp);
425         return 0;
426 }
427
428 static int fsck_handle_reflog(const char *logname, const struct object_id *oid,
429                               int flag, void *cb_data)
430 {
431         for_each_reflog_ent(logname, fsck_handle_reflog_ent, (void *)logname);
432         return 0;
433 }
434
435 static int fsck_handle_ref(const char *refname, const struct object_id *oid,
436                            int flag, void *cb_data)
437 {
438         struct object *obj;
439
440         obj = parse_object(oid);
441         if (!obj) {
442                 error("%s: invalid sha1 pointer %s", refname, oid_to_hex(oid));
443                 errors_found |= ERROR_REACHABLE;
444                 /* We'll continue with the rest despite the error.. */
445                 return 0;
446         }
447         if (obj->type != OBJ_COMMIT && is_branch(refname)) {
448                 error("%s: not a commit", refname);
449                 errors_found |= ERROR_REFS;
450         }
451         default_refs++;
452         obj->flags |= USED;
453         if (name_objects)
454                 add_decoration(fsck_walk_options.object_names,
455                         obj, xstrdup(refname));
456         mark_object_reachable(obj);
457
458         return 0;
459 }
460
461 static void get_default_heads(void)
462 {
463         if (head_points_at && !is_null_oid(&head_oid))
464                 fsck_handle_ref("HEAD", &head_oid, 0, NULL);
465         for_each_rawref(fsck_handle_ref, NULL);
466         if (include_reflogs)
467                 for_each_reflog(fsck_handle_reflog, NULL);
468
469         /*
470          * Not having any default heads isn't really fatal, but
471          * it does mean that "--unreachable" no longer makes any
472          * sense (since in this case everything will obviously
473          * be unreachable by definition.
474          *
475          * Showing dangling objects is valid, though (as those
476          * dangling objects are likely lost heads).
477          *
478          * So we just print a warning about it, and clear the
479          * "show_unreachable" flag.
480          */
481         if (!default_refs) {
482                 fprintf(stderr, "notice: No default references\n");
483                 show_unreachable = 0;
484         }
485 }
486
487 static struct object *parse_loose_object(const struct object_id *oid,
488                                          const char *path)
489 {
490         struct object *obj;
491         void *contents;
492         enum object_type type;
493         unsigned long size;
494         int eaten;
495
496         if (read_loose_object(path, oid->hash, &type, &size, &contents) < 0)
497                 return NULL;
498
499         if (!contents && type != OBJ_BLOB)
500                 die("BUG: read_loose_object streamed a non-blob");
501
502         obj = parse_object_buffer(oid, type, size, contents, &eaten);
503
504         if (!eaten)
505                 free(contents);
506         return obj;
507 }
508
509 static int fsck_loose(const struct object_id *oid, const char *path, void *data)
510 {
511         struct object *obj = parse_loose_object(oid, path);
512
513         if (!obj) {
514                 errors_found |= ERROR_OBJECT;
515                 error("%s: object corrupt or missing: %s",
516                       oid_to_hex(oid), path);
517                 return 0; /* keep checking other objects */
518         }
519
520         obj->flags &= ~(REACHABLE | SEEN);
521         obj->flags |= HAS_OBJ;
522         if (fsck_obj(obj))
523                 errors_found |= ERROR_OBJECT;
524         return 0;
525 }
526
527 static int fsck_cruft(const char *basename, const char *path, void *data)
528 {
529         if (!starts_with(basename, "tmp_obj_"))
530                 fprintf(stderr, "bad sha1 file: %s\n", path);
531         return 0;
532 }
533
534 static int fsck_subdir(unsigned int nr, const char *path, void *progress)
535 {
536         display_progress(progress, nr + 1);
537         return 0;
538 }
539
540 static void fsck_object_dir(const char *path)
541 {
542         struct progress *progress = NULL;
543
544         if (verbose)
545                 fprintf(stderr, "Checking object directory\n");
546
547         if (show_progress)
548                 progress = start_progress(_("Checking object directories"), 256);
549
550         for_each_loose_file_in_objdir(path, fsck_loose, fsck_cruft, fsck_subdir,
551                                       progress);
552         display_progress(progress, 256);
553         stop_progress(&progress);
554 }
555
556 static int fsck_head_link(void)
557 {
558         int null_is_error = 0;
559
560         if (verbose)
561                 fprintf(stderr, "Checking HEAD link\n");
562
563         head_points_at = resolve_ref_unsafe("HEAD", 0, head_oid.hash, NULL);
564         if (!head_points_at) {
565                 errors_found |= ERROR_REFS;
566                 return error("Invalid HEAD");
567         }
568         if (!strcmp(head_points_at, "HEAD"))
569                 /* detached HEAD */
570                 null_is_error = 1;
571         else if (!starts_with(head_points_at, "refs/heads/")) {
572                 errors_found |= ERROR_REFS;
573                 return error("HEAD points to something strange (%s)",
574                              head_points_at);
575         }
576         if (is_null_oid(&head_oid)) {
577                 if (null_is_error) {
578                         errors_found |= ERROR_REFS;
579                         return error("HEAD: detached HEAD points at nothing");
580                 }
581                 fprintf(stderr, "notice: HEAD points to an unborn branch (%s)\n",
582                         head_points_at + 11);
583         }
584         return 0;
585 }
586
587 static int fsck_cache_tree(struct cache_tree *it)
588 {
589         int i;
590         int err = 0;
591
592         if (verbose)
593                 fprintf(stderr, "Checking cache tree\n");
594
595         if (0 <= it->entry_count) {
596                 struct object *obj = parse_object(&it->oid);
597                 if (!obj) {
598                         error("%s: invalid sha1 pointer in cache-tree",
599                               oid_to_hex(&it->oid));
600                         errors_found |= ERROR_REFS;
601                         return 1;
602                 }
603                 obj->flags |= USED;
604                 if (name_objects)
605                         add_decoration(fsck_walk_options.object_names,
606                                 obj, xstrdup(":"));
607                 mark_object_reachable(obj);
608                 if (obj->type != OBJ_TREE)
609                         err |= objerror(obj, "non-tree in cache-tree");
610         }
611         for (i = 0; i < it->subtree_nr; i++)
612                 err |= fsck_cache_tree(it->down[i]->cache_tree);
613         return err;
614 }
615
616 static void mark_object_for_connectivity(const struct object_id *oid)
617 {
618         struct object *obj = lookup_unknown_object(oid->hash);
619         obj->flags |= HAS_OBJ;
620 }
621
622 static int mark_loose_for_connectivity(const struct object_id *oid,
623                                        const char *path,
624                                        void *data)
625 {
626         mark_object_for_connectivity(oid);
627         return 0;
628 }
629
630 static int mark_packed_for_connectivity(const struct object_id *oid,
631                                         struct packed_git *pack,
632                                         uint32_t pos,
633                                         void *data)
634 {
635         mark_object_for_connectivity(oid);
636         return 0;
637 }
638
639 static char const * const fsck_usage[] = {
640         N_("git fsck [<options>] [<object>...]"),
641         NULL
642 };
643
644 static struct option fsck_opts[] = {
645         OPT__VERBOSE(&verbose, N_("be verbose")),
646         OPT_BOOL(0, "unreachable", &show_unreachable, N_("show unreachable objects")),
647         OPT_BOOL(0, "dangling", &show_dangling, N_("show dangling objects")),
648         OPT_BOOL(0, "tags", &show_tags, N_("report tags")),
649         OPT_BOOL(0, "root", &show_root, N_("report root nodes")),
650         OPT_BOOL(0, "cache", &keep_cache_objects, N_("make index objects head nodes")),
651         OPT_BOOL(0, "reflogs", &include_reflogs, N_("make reflogs head nodes (default)")),
652         OPT_BOOL(0, "full", &check_full, N_("also consider packs and alternate objects")),
653         OPT_BOOL(0, "connectivity-only", &connectivity_only, N_("check only connectivity")),
654         OPT_BOOL(0, "strict", &check_strict, N_("enable more strict checking")),
655         OPT_BOOL(0, "lost-found", &write_lost_and_found,
656                                 N_("write dangling objects in .git/lost-found")),
657         OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
658         OPT_BOOL(0, "name-objects", &name_objects, N_("show verbose names for reachable objects")),
659         OPT_END(),
660 };
661
662 int cmd_fsck(int argc, const char **argv, const char *prefix)
663 {
664         int i;
665         struct alternate_object_database *alt;
666
667         errors_found = 0;
668         check_replace_refs = 0;
669
670         argc = parse_options(argc, argv, prefix, fsck_opts, fsck_usage, 0);
671
672         fsck_walk_options.walk = mark_object;
673         fsck_obj_options.walk = mark_used;
674         fsck_obj_options.error_func = fsck_error_func;
675         if (check_strict)
676                 fsck_obj_options.strict = 1;
677
678         if (show_progress == -1)
679                 show_progress = isatty(2);
680         if (verbose)
681                 show_progress = 0;
682
683         if (write_lost_and_found) {
684                 check_full = 1;
685                 include_reflogs = 0;
686         }
687
688         if (name_objects)
689                 fsck_walk_options.object_names =
690                         xcalloc(1, sizeof(struct decoration));
691
692         git_config(fsck_config, NULL);
693
694         fsck_head_link();
695         if (connectivity_only) {
696                 for_each_loose_object(mark_loose_for_connectivity, NULL, 0);
697                 for_each_packed_object(mark_packed_for_connectivity, NULL, 0);
698         } else {
699                 fsck_object_dir(get_object_directory());
700
701                 prepare_alt_odb();
702                 for (alt = alt_odb_list; alt; alt = alt->next)
703                         fsck_object_dir(alt->path);
704
705                 if (check_full) {
706                         struct packed_git *p;
707                         uint32_t total = 0, count = 0;
708                         struct progress *progress = NULL;
709
710                         prepare_packed_git();
711
712                         if (show_progress) {
713                                 for (p = packed_git; p; p = p->next) {
714                                         if (open_pack_index(p))
715                                                 continue;
716                                         total += p->num_objects;
717                                 }
718
719                                 progress = start_progress(_("Checking objects"), total);
720                         }
721                         for (p = packed_git; p; p = p->next) {
722                                 /* verify gives error messages itself */
723                                 if (verify_pack(p, fsck_obj_buffer,
724                                                 progress, count))
725                                         errors_found |= ERROR_PACK;
726                                 count += p->num_objects;
727                         }
728                         stop_progress(&progress);
729                 }
730         }
731
732         for (i = 0; i < argc; i++) {
733                 const char *arg = argv[i];
734                 struct object_id oid;
735                 if (!get_oid(arg, &oid)) {
736                         struct object *obj = lookup_object(oid.hash);
737
738                         if (!obj || !(obj->flags & HAS_OBJ)) {
739                                 error("%s: object missing", oid_to_hex(&oid));
740                                 errors_found |= ERROR_OBJECT;
741                                 continue;
742                         }
743
744                         obj->flags |= USED;
745                         if (name_objects)
746                                 add_decoration(fsck_walk_options.object_names,
747                                         obj, xstrdup(arg));
748                         mark_object_reachable(obj);
749                         continue;
750                 }
751                 error("invalid parameter: expected sha1, got '%s'", arg);
752                 errors_found |= ERROR_OBJECT;
753         }
754
755         /*
756          * If we've not been given any explicit head information, do the
757          * default ones from .git/refs. We also consider the index file
758          * in this case (ie this implies --cache).
759          */
760         if (!argc) {
761                 get_default_heads();
762                 keep_cache_objects = 1;
763         }
764
765         if (keep_cache_objects) {
766                 verify_index_checksum = 1;
767                 read_cache();
768                 for (i = 0; i < active_nr; i++) {
769                         unsigned int mode;
770                         struct blob *blob;
771                         struct object *obj;
772
773                         mode = active_cache[i]->ce_mode;
774                         if (S_ISGITLINK(mode))
775                                 continue;
776                         blob = lookup_blob(&active_cache[i]->oid);
777                         if (!blob)
778                                 continue;
779                         obj = &blob->object;
780                         obj->flags |= USED;
781                         if (name_objects)
782                                 add_decoration(fsck_walk_options.object_names,
783                                         obj,
784                                         xstrfmt(":%s", active_cache[i]->name));
785                         mark_object_reachable(obj);
786                 }
787                 if (active_cache_tree)
788                         fsck_cache_tree(active_cache_tree);
789         }
790
791         check_connectivity();
792         return errors_found;
793 }