#include "builtin.h"
#include "cache.h"
#include "repository.h"
#include "config.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"
#include "tag.h"
#include "refs.h"
#include "pack.h"
#include "cache-tree.h"
#include "tree-walk.h"
#include "fsck.h"
#include "parse-options.h"
#include "dir.h"
#include "progress.h"
#include "streaming.h"
#include "decorate.h"
#include "packfile.h"
#include "object-store.h"
#include "run-command.h"
#include "worktree.h"

#define REACHABLE 0x0001
#define SEEN      0x0002
#define HAS_OBJ   0x0004
/* This flag is set if something points to this object. */
#define USED      0x0008

static int show_root;
static int show_tags;
static int show_unreachable;
static int include_reflogs = 1;
static int check_full = 1;
static int connectivity_only;
static int check_strict;
static int keep_cache_objects;
static struct fsck_options fsck_walk_options = FSCK_OPTIONS_DEFAULT;
static struct fsck_options fsck_obj_options = FSCK_OPTIONS_DEFAULT;
static int errors_found;
static int write_lost_and_found;
static int verbose;
static int show_progress = -1;
static int show_dangling = 1;
static int name_objects;
#define ERROR_OBJECT 01
#define ERROR_REACHABLE 02
#define ERROR_PACK 04
#define ERROR_REFS 010
#define ERROR_COMMIT_GRAPH 020

static const char *describe_object(struct object *obj)
{
        static struct strbuf bufs[] = {
                STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
        };
        static int b = 0;
        struct strbuf *buf;
        char *name = NULL;

        if (name_objects)
                name = lookup_decoration(fsck_walk_options.object_names, obj);

        buf = bufs + b;
        b = (b + 1) % ARRAY_SIZE(bufs);
        strbuf_reset(buf);
        strbuf_addstr(buf, oid_to_hex(&obj->oid));
        if (name)
                strbuf_addf(buf, " (%s)", name);

        return buf->buf;
}

static const char *printable_type(struct object *obj)
{
        const char *ret;

        if (obj->type == OBJ_NONE) {
                enum object_type type = oid_object_info(the_repository,
                                                        &obj->oid, NULL);
                if (type > 0)
                        object_as_type(the_repository, obj, type, 0);
        }

        ret = type_name(obj->type);
        if (!ret)
                ret = _("unknown");

        return ret;
}

static int fsck_config(const char *var, const char *value, void *cb)
{
        if (strcmp(var, "fsck.skiplist") == 0) {
                const char *path;
                struct strbuf sb = STRBUF_INIT;

                if (git_config_pathname(&path, var, value))
                        return 1;
                strbuf_addf(&sb, "skiplist=%s", path);
                free((char *)path);
                fsck_set_msg_types(&fsck_obj_options, sb.buf);
                strbuf_release(&sb);
                return 0;
        }

        if (skip_prefix(var, "fsck.", &var)) {
                fsck_set_msg_type(&fsck_obj_options, var, value);
                return 0;
        }

        return git_default_config(var, value, cb);
}

static int objerror(struct object *obj, const char *err)
{
        errors_found |= ERROR_OBJECT;
        /* TRANSLATORS: e.g. error in tree 01bfda: <more explanation> */
        fprintf_ln(stderr, _("error in %s %s: %s"),
                   printable_type(obj), describe_object(obj), err);
        return -1;
}

static int fsck_error_func(struct fsck_options *o,
        struct object *obj, int type, const char *message)
{
        switch (type) {
        case FSCK_WARN:
                /* TRANSLATORS: e.g. warning in tree 01bfda: <more explanation> */
                fprintf_ln(stderr, _("warning in %s %s: %s"),
                           printable_type(obj), describe_object(obj), message);
                return 0;
        case FSCK_ERROR:
                /* TRANSLATORS: e.g. error in tree 01bfda: <more explanation> */
                fprintf_ln(stderr, _("error in %s %s: %s"),
                           printable_type(obj), describe_object(obj), message);
                return 1;
        default:
                BUG("%d (FSCK_IGNORE?) should never trigger this callback", type);
        }
}

static struct object_array pending;

static int mark_object(struct object *obj, int type, void *data, struct fsck_options *options)
{
        struct object *parent = data;

        /*
         * The only case data is NULL or type is OBJ_ANY is when
         * mark_object_reachable() calls us.  All the callers of
         * that function has non-NULL obj hence ...
         */
        if (!obj) {
                /* ... these references to parent->fld are safe here */
                printf_ln(_("broken link from %7s %s"),
                          printable_type(parent), describe_object(parent));
                printf_ln(_("broken link from %7s %s"),
                          (type == OBJ_ANY ? _("unknown") : type_name(type)),
                          _("unknown"));
                errors_found |= ERROR_REACHABLE;
                return 1;
        }

        if (type != OBJ_ANY && obj->type != type)
                /* ... and the reference to parent is safe here */
                objerror(parent, _("wrong object type in link"));

        if (obj->flags & REACHABLE)
                return 0;
        obj->flags |= REACHABLE;

        if (is_promisor_object(&obj->oid))
                /*
                 * Further recursion does not need to be performed on this
                 * object since it is a promisor object (so it does not need to
                 * be added to "pending").
                 */
                return 0;

        if (!(obj->flags & HAS_OBJ)) {
                if (parent && !has_object_file(&obj->oid)) {
                        printf_ln(_("broken link from %7s %s\n"
                                    "              to %7s %s"),
                                  printable_type(parent),
                                  describe_object(parent),
                                  printable_type(obj),
                                  describe_object(obj));
                        errors_found |= ERROR_REACHABLE;
                }
                return 1;
        }

        add_object_array(obj, NULL, &pending);
        return 0;
}

static void mark_object_reachable(struct object *obj)
{
        mark_object(obj, OBJ_ANY, NULL, NULL);
}

static int traverse_one_object(struct object *obj)
{
        int result = fsck_walk(obj, obj, &fsck_walk_options);

        if (obj->type == OBJ_TREE) {
                struct tree *tree = (struct tree *)obj;
                free_tree_buffer(tree);
        }
        return result;
}

static int traverse_reachable(void)
{
        struct progress *progress = NULL;
        unsigned int nr = 0;
        int result = 0;
        if (show_progress)
                progress = start_delayed_progress(_("Checking connectivity"), 0);
        while (pending.nr) {
                result |= traverse_one_object(object_array_pop(&pending));
                display_progress(progress, ++nr);
        }
        stop_progress(&progress);
        return !!result;
}

static int mark_used(struct object *obj, int type, void *data, struct fsck_options *options)
{
        if (!obj)
                return 1;
        obj->flags |= USED;
        return 0;
}

/*
 * Check a single reachable object
 */
static void check_reachable_object(struct object *obj)
{
        /*
         * We obviously want the object to be parsed,
         * except if it was in a pack-file and we didn't
         * do a full fsck
         */
        if (!(obj->flags & HAS_OBJ)) {
                if (is_promisor_object(&obj->oid))
                        return;
                if (has_object_pack(&obj->oid))
                        return; /* it is in pack - forget about it */
                printf_ln(_("missing %s %s"), printable_type(obj),
                          describe_object(obj));
                errors_found |= ERROR_REACHABLE;
                return;
        }
}

/*
 * Check a single unreachable object
 */
static void check_unreachable_object(struct object *obj)
{
        /*
         * Missing unreachable object? Ignore it. It's not like
         * we miss it (since it can't be reached), nor do we want
         * to complain about it being unreachable (since it does
         * not exist).
         */
        if (!(obj->flags & HAS_OBJ))
                return;

        /*
         * Unreachable object that exists? Show it if asked to,
         * since this is something that is prunable.
         */
        if (show_unreachable) {
                printf_ln(_("unreachable %s %s"), printable_type(obj),
                          describe_object(obj));
                return;
        }

        /*
         * "!USED" means that nothing at all points to it, including
         * other unreachable objects. In other words, it's the "tip"
         * of some set of unreachable objects, usually a commit that
         * got dropped.
         *
         * Such starting points are more interesting than some random
         * set of unreachable objects, so we show them even if the user
         * hasn't asked for _all_ unreachable objects. If you have
         * deleted a branch by mistake, this is a prime candidate to
         * start looking at, for example.
         */
        if (!(obj->flags & USED)) {
                if (show_dangling)
                        printf_ln(_("dangling %s %s"), printable_type(obj),
                                  describe_object(obj));
                if (write_lost_and_found) {
                        char *filename = git_pathdup("lost-found/%s/%s",
                                obj->type == OBJ_COMMIT ? "commit" : "other",
                                describe_object(obj));
                        FILE *f;

                        if (safe_create_leading_directories_const(filename)) {
                                error(_("could not create lost-found"));
                                free(filename);
                                return;
                        }
                        f = xfopen(filename, "w");
                        if (obj->type == OBJ_BLOB) {
                                if (stream_blob_to_fd(fileno(f), &obj->oid, NULL, 1))
                                        die_errno(_("could not write '%s'"), filename);
                        } else
                                fprintf(f, "%s\n", describe_object(obj));
                        if (fclose(f))
                                die_errno(_("could not finish '%s'"),
                                          filename);
                        free(filename);
                }
                return;
        }

        /*
         * Otherwise? It's there, it's unreachable, and some other unreachable
         * object points to it. Ignore it - it's not interesting, and we showed
         * all the interesting cases above.
         */
}

static void check_object(struct object *obj)
{
        if (verbose)
                fprintf_ln(stderr, _("Checking %s"), describe_object(obj));

        if (obj->flags & REACHABLE)
                check_reachable_object(obj);
        else
                check_unreachable_object(obj);
}

static void check_connectivity(void)
{
        int i, max;

        /* Traverse the pending reachable objects */
        traverse_reachable();

        /* Look up all the requirements, warn about missing objects.. */
        max = get_max_object_index();
        if (verbose)
                fprintf_ln(stderr, _("Checking connectivity (%d objects)"), max);

        for (i = 0; i < max; i++) {
                struct object *obj = get_indexed_object(i);

                if (obj)
                        check_object(obj);
        }
}

static int fsck_obj(struct object *obj, void *buffer, unsigned long size)
{
        int err;

        if (obj->flags & SEEN)
                return 0;
        obj->flags |= SEEN;

        if (verbose)
                fprintf_ln(stderr, _("Checking %s %s"),
                           printable_type(obj), describe_object(obj));

        if (fsck_walk(obj, NULL, &fsck_obj_options))
                objerror(obj, _("broken links"));
        err = fsck_object(obj, buffer, size, &fsck_obj_options);
        if (err)
                goto out;

        if (obj->type == OBJ_COMMIT) {
                struct commit *commit = (struct commit *) obj;

                if (!commit->parents && show_root)
                        printf_ln(_("root %s"),
                                  describe_object(&commit->object));
        }

        if (obj->type == OBJ_TAG) {
                struct tag *tag = (struct tag *) obj;

                if (show_tags && tag->tagged) {
                        printf_ln(_("tagged %s %s (%s) in %s"),
                                  printable_type(tag->tagged),
                                  describe_object(tag->tagged),
                                  tag->tag,
                                  describe_object(&tag->object));
                }
        }

out:
        if (obj->type == OBJ_TREE)
                free_tree_buffer((struct tree *)obj);
        if (obj->type == OBJ_COMMIT)
                free_commit_buffer((struct commit *)obj);
        return err;
}

static int fsck_obj_buffer(const struct object_id *oid, enum object_type type,
                           unsigned long size, void *buffer, int *eaten)
{
        /*
         * Note, buffer may be NULL if type is OBJ_BLOB. See
         * verify_packfile(), data_valid variable for details.
         */
        struct object *obj;
        obj = parse_object_buffer(the_repository, oid, type, size, buffer,
                                  eaten);
        if (!obj) {
                errors_found |= ERROR_OBJECT;
                return error(_("%s: object corrupt or missing"),
                             oid_to_hex(oid));
        }
        obj->flags &= ~(REACHABLE | SEEN);
        obj->flags |= HAS_OBJ;
        return fsck_obj(obj, buffer, size);
}

static int default_refs;

static void fsck_handle_reflog_oid(const char *refname, struct object_id *oid,
        timestamp_t timestamp)
{
        struct object *obj;

        if (!is_null_oid(oid)) {
                obj = lookup_object(the_repository, oid->hash);
                if (obj && (obj->flags & HAS_OBJ)) {
                        if (timestamp && name_objects)
                                add_decoration(fsck_walk_options.object_names,
                                        obj,
                                        xstrfmt("%s@{%"PRItime"}", refname, timestamp));
                        obj->flags |= USED;
                        mark_object_reachable(obj);
                } else if (!is_promisor_object(oid)) {
                        error(_("%s: invalid reflog entry %s"),
                              refname, oid_to_hex(oid));
                        errors_found |= ERROR_REACHABLE;
                }
        }
}

static int fsck_handle_reflog_ent(struct object_id *ooid, struct object_id *noid,
                const char *email, timestamp_t timestamp, int tz,
                const char *message, void *cb_data)
{
        const char *refname = cb_data;

        if (verbose)
                fprintf_ln(stderr, _("Checking reflog %s->%s"),
                           oid_to_hex(ooid), oid_to_hex(noid));

        fsck_handle_reflog_oid(refname, ooid, 0);
        fsck_handle_reflog_oid(refname, noid, timestamp);
        return 0;
}

static int fsck_handle_reflog(const char *logname, const struct object_id *oid,
                              int flag, void *cb_data)
{
        struct strbuf refname = STRBUF_INIT;

        strbuf_worktree_ref(cb_data, &refname, logname);
        for_each_reflog_ent(refname.buf, fsck_handle_reflog_ent, refname.buf);
        strbuf_release(&refname);
        return 0;
}

static int fsck_handle_ref(const char *refname, const struct object_id *oid,
                           int flag, void *cb_data)
{
        struct object *obj;

        obj = parse_object(the_repository, oid);
        if (!obj) {
                if (is_promisor_object(oid)) {
                        /*
                         * Increment default_refs anyway, because this is a
                         * valid ref.
                         */
                         default_refs++;
                         return 0;
                }
                error(_("%s: invalid sha1 pointer %s"),
                      refname, oid_to_hex(oid));
                errors_found |= ERROR_REACHABLE;
                /* We'll continue with the rest despite the error.. */
                return 0;
        }
        if (obj->type != OBJ_COMMIT && is_branch(refname)) {
                error(_("%s: not a commit"), refname);
                errors_found |= ERROR_REFS;
        }
        default_refs++;
        obj->flags |= USED;
        if (name_objects)
                add_decoration(fsck_walk_options.object_names,
                        obj, xstrdup(refname));
        mark_object_reachable(obj);

        return 0;
}

static int fsck_head_link(const char *head_ref_name,
                          const char **head_points_at,
                          struct object_id *head_oid);

static void get_default_heads(void)
{
        struct worktree **worktrees, **p;
        const char *head_points_at;
        struct object_id head_oid;

        for_each_rawref(fsck_handle_ref, NULL);

        worktrees = get_worktrees(0);
        for (p = worktrees; *p; p++) {
                struct worktree *wt = *p;
                struct strbuf ref = STRBUF_INIT;

                strbuf_worktree_ref(wt, &ref, "HEAD");
                fsck_head_link(ref.buf, &head_points_at, &head_oid);
                if (head_points_at && !is_null_oid(&head_oid))
                        fsck_handle_ref(ref.buf, &head_oid, 0, NULL);
                strbuf_release(&ref);

                if (include_reflogs)
                        refs_for_each_reflog(get_worktree_ref_store(wt),
                                             fsck_handle_reflog, wt);
        }
        free_worktrees(worktrees);

        /*
         * Not having any default heads isn't really fatal, but
         * it does mean that "--unreachable" no longer makes any
         * sense (since in this case everything will obviously
         * be unreachable by definition.
         *
         * Showing dangling objects is valid, though (as those
         * dangling objects are likely lost heads).
         *
         * So we just print a warning about it, and clear the
         * "show_unreachable" flag.
         */
        if (!default_refs) {
                fprintf_ln(stderr, _("notice: No default references"));
                show_unreachable = 0;
        }
}

static int fsck_loose(const struct object_id *oid, const char *path, void *data)
{
        struct object *obj;
        enum object_type type;
        unsigned long size;
        void *contents;
        int eaten;

        if (read_loose_object(path, oid, &type, &size, &contents) < 0) {
                errors_found |= ERROR_OBJECT;
                error(_("%s: object corrupt or missing: %s"),
                      oid_to_hex(oid), path);
                return 0; /* keep checking other objects */
        }

        if (!contents && type != OBJ_BLOB)
                BUG("read_loose_object streamed a non-blob");

        obj = parse_object_buffer(the_repository, oid, type, size,
                                  contents, &eaten);

        if (!obj) {
                errors_found |= ERROR_OBJECT;
                error(_("%s: object could not be parsed: %s"),
                      oid_to_hex(oid), path);
                if (!eaten)
                        free(contents);
                return 0; /* keep checking other objects */
        }

        obj->flags &= ~(REACHABLE | SEEN);
        obj->flags |= HAS_OBJ;
        if (fsck_obj(obj, contents, size))
                errors_found |= ERROR_OBJECT;

        if (!eaten)
                free(contents);
        return 0; /* keep checking other objects, even if we saw an error */
}

static int fsck_cruft(const char *basename, const char *path, void *data)
{
        if (!starts_with(basename, "tmp_obj_"))
                fprintf_ln(stderr, _("bad sha1 file: %s"), path);
        return 0;
}

static int fsck_subdir(unsigned int nr, const char *path, void *progress)
{
        display_progress(progress, nr + 1);
        return 0;
}

static void fsck_object_dir(const char *path)
{
        struct progress *progress = NULL;

        if (verbose)
                fprintf_ln(stderr, _("Checking object directory"));

        if (show_progress)
                progress = start_progress(_("Checking object directories"), 256);

        for_each_loose_file_in_objdir(path, fsck_loose, fsck_cruft, fsck_subdir,
                                      progress);
        display_progress(progress, 256);
        stop_progress(&progress);
}

static int fsck_head_link(const char *head_ref_name,
                          const char **head_points_at,
                          struct object_id *head_oid)
{
        int null_is_error = 0;

        if (verbose)
                fprintf_ln(stderr, _("Checking %s link"), head_ref_name);

        *head_points_at = resolve_ref_unsafe(head_ref_name, 0, head_oid, NULL);
        if (!*head_points_at) {
                errors_found |= ERROR_REFS;
                return error(_("invalid %s"), head_ref_name);
        }
        if (!strcmp(*head_points_at, head_ref_name))
                /* detached HEAD */
                null_is_error = 1;
        else if (!starts_with(*head_points_at, "refs/heads/")) {
                errors_found |= ERROR_REFS;
                return error(_("%s points to something strange (%s)"),
                             head_ref_name, *head_points_at);
        }
        if (is_null_oid(head_oid)) {
                if (null_is_error) {
                        errors_found |= ERROR_REFS;
                        return error(_("%s: detached HEAD points at nothing"),
                                     head_ref_name);
                }
                fprintf_ln(stderr,
                           _("notice: %s points to an unborn branch (%s)"),
                           head_ref_name, *head_points_at + 11);
        }
        return 0;
}

static int fsck_cache_tree(struct cache_tree *it)
{
        int i;
        int err = 0;

        if (verbose)
                fprintf_ln(stderr, _("Checking cache tree"));

        if (0 <= it->entry_count) {
                struct object *obj = parse_object(the_repository, &it->oid);
                if (!obj) {
                        error(_("%s: invalid sha1 pointer in cache-tree"),
                              oid_to_hex(&it->oid));
                        errors_found |= ERROR_REFS;
                        return 1;
                }
                obj->flags |= USED;
                if (name_objects)
                        add_decoration(fsck_walk_options.object_names,
                                obj, xstrdup(":"));
                mark_object_reachable(obj);
                if (obj->type != OBJ_TREE)
                        err |= objerror(obj, _("non-tree in cache-tree"));
        }
        for (i = 0; i < it->subtree_nr; i++)
                err |= fsck_cache_tree(it->down[i]->cache_tree);
        return err;
}

static void mark_object_for_connectivity(const struct object_id *oid)
{
        struct object *obj = lookup_unknown_object(oid->hash);
        obj->flags |= HAS_OBJ;
}

static int mark_loose_for_connectivity(const struct object_id *oid,
                                       const char *path,
                                       void *data)
{
        mark_object_for_connectivity(oid);
        return 0;
}

static int mark_packed_for_connectivity(const struct object_id *oid,
                                        struct packed_git *pack,
                                        uint32_t pos,
                                        void *data)
{
        mark_object_for_connectivity(oid);
        return 0;
}

static char const * const fsck_usage[] = {
        N_("git fsck [<options>] [<object>...]"),
        NULL
};

static struct option fsck_opts[] = {
        OPT__VERBOSE(&verbose, N_("be verbose")),
        OPT_BOOL(0, "unreachable", &show_unreachable, N_("show unreachable objects")),
        OPT_BOOL(0, "dangling", &show_dangling, N_("show dangling objects")),
        OPT_BOOL(0, "tags", &show_tags, N_("report tags")),
        OPT_BOOL(0, "root", &show_root, N_("report root nodes")),
        OPT_BOOL(0, "cache", &keep_cache_objects, N_("make index objects head nodes")),
        OPT_BOOL(0, "reflogs", &include_reflogs, N_("make reflogs head nodes (default)")),
        OPT_BOOL(0, "full", &check_full, N_("also consider packs and alternate objects")),
        OPT_BOOL(0, "connectivity-only", &connectivity_only, N_("check only connectivity")),
        OPT_BOOL(0, "strict", &check_strict, N_("enable more strict checking")),
        OPT_BOOL(0, "lost-found", &write_lost_and_found,
                                N_("write dangling objects in .git/lost-found")),
        OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
        OPT_BOOL(0, "name-objects", &name_objects, N_("show verbose names for reachable objects")),
        OPT_END(),
};

int cmd_fsck(int argc, const char **argv, const char *prefix)
{
        int i;
        struct object_directory *odb;

        /* fsck knows how to handle missing promisor objects */
        fetch_if_missing = 0;

        errors_found = 0;
        read_replace_refs = 0;

        argc = parse_options(argc, argv, prefix, fsck_opts, fsck_usage, 0);

        fsck_walk_options.walk = mark_object;
        fsck_obj_options.walk = mark_used;
        fsck_obj_options.error_func = fsck_error_func;
        if (check_strict)
                fsck_obj_options.strict = 1;

        if (show_progress == -1)
                show_progress = isatty(2);
        if (verbose)
                show_progress = 0;

        if (write_lost_and_found) {
                check_full = 1;
                include_reflogs = 0;
        }

        if (name_objects)
                fsck_walk_options.object_names =
                        xcalloc(1, sizeof(struct decoration));

        git_config(fsck_config, NULL);

        if (connectivity_only) {
                for_each_loose_object(mark_loose_for_connectivity, NULL, 0);
                for_each_packed_object(mark_packed_for_connectivity, NULL, 0);
        } else {
                prepare_alt_odb(the_repository);
                for (odb = the_repository->objects->odb; odb; odb = odb->next)
                        fsck_object_dir(odb->path);

                if (check_full) {
                        struct packed_git *p;
                        uint32_t total = 0, count = 0;
                        struct progress *progress = NULL;

                        if (show_progress) {
                                for (p = get_all_packs(the_repository); p;
                                     p = p->next) {
                                        if (open_pack_index(p))
                                                continue;
                                        total += p->num_objects;
                                }

                                progress = start_progress(_("Checking objects"), total);
                        }
                        for (p = get_all_packs(the_repository); p;
                             p = p->next) {
                                /* verify gives error messages itself */
                                if (verify_pack(the_repository,
                                                p, fsck_obj_buffer,
                                                progress, count))
                                        errors_found |= ERROR_PACK;
                                count += p->num_objects;
                        }
                        stop_progress(&progress);
                }

                if (fsck_finish(&fsck_obj_options))
                        errors_found |= ERROR_OBJECT;
        }

        for (i = 0; i < argc; i++) {
                const char *arg = argv[i];
                struct object_id oid;
                if (!get_oid(arg, &oid)) {
                        struct object *obj = lookup_object(the_repository,
                                                           oid.hash);

                        if (!obj || !(obj->flags & HAS_OBJ)) {
                                if (is_promisor_object(&oid))
                                        continue;
                                error(_("%s: object missing"), oid_to_hex(&oid));
                                errors_found |= ERROR_OBJECT;
                                continue;
                        }

                        obj->flags |= USED;
                        if (name_objects)
                                add_decoration(fsck_walk_options.object_names,
                                        obj, xstrdup(arg));
                        mark_object_reachable(obj);
                        continue;
                }
                error(_("invalid parameter: expected sha1, got '%s'"), arg);
                errors_found |= ERROR_OBJECT;
        }

        /*
         * If we've not been given any explicit head information, do the
         * default ones from .git/refs. We also consider the index file
         * in this case (ie this implies --cache).
         */
        if (!argc) {
                get_default_heads();
                keep_cache_objects = 1;
        }

        if (keep_cache_objects) {
                verify_index_checksum = 1;
                verify_ce_order = 1;
                read_cache();
                for (i = 0; i < active_nr; i++) {
                        unsigned int mode;
                        struct blob *blob;
                        struct object *obj;

                        mode = active_cache[i]->ce_mode;
                        if (S_ISGITLINK(mode))
                                continue;
                        blob = lookup_blob(the_repository,
                                           &active_cache[i]->oid);
                        if (!blob)
                                continue;
                        obj = &blob->object;
                        obj->flags |= USED;
                        if (name_objects)
                                add_decoration(fsck_walk_options.object_names,
                                        obj,
                                        xstrfmt(":%s", active_cache[i]->name));
                        mark_object_reachable(obj);
                }
                if (active_cache_tree)
                        fsck_cache_tree(active_cache_tree);
        }

        check_connectivity();

        if (!git_config_get_bool("core.commitgraph", &i) && i) {
                struct child_process commit_graph_verify = CHILD_PROCESS_INIT;
                const char *verify_argv[] = { "commit-graph", "verify", NULL, NULL, NULL };

                prepare_alt_odb(the_repository);
                for (odb = the_repository->objects->odb; odb; odb = odb->next) {
                        child_process_init(&commit_graph_verify);
                        commit_graph_verify.argv = verify_argv;
                        commit_graph_verify.git_cmd = 1;
                        verify_argv[2] = "--object-dir";
                        verify_argv[3] = odb->path;
                        if (run_command(&commit_graph_verify))
                                errors_found |= ERROR_COMMIT_GRAPH;
                }
        }

        if (!git_config_get_bool("core.multipackindex", &i) && i) {
                struct child_process midx_verify = CHILD_PROCESS_INIT;
                const char *midx_argv[] = { "multi-pack-index", "verify", NULL, NULL, NULL };

                prepare_alt_odb(the_repository);
                for (odb = the_repository->objects->odb; odb; odb = odb->next) {
                        child_process_init(&midx_verify);
                        midx_verify.argv = midx_argv;
                        midx_verify.git_cmd = 1;
                        midx_argv[2] = "--object-dir";
                        midx_argv[3] = odb->path;
                        if (run_command(&midx_verify))
                                errors_found |= ERROR_COMMIT_GRAPH;
                }
        }

        return errors_found;
}