#include "cache.h"
#include "commit.h"
#include "refs.h"
#include "builtin.h"
#include "color.h"
#include "parse-options.h"

static const char* show_branch_usage[] = {
    N_("git show-branch [-a|--all] [-r|--remotes] [--topo-order | --date-order] [--current] [--color[=<when>] | --no-color] [--sparse] [--more=<n> | --list | --independent | --merge-base] [--no-name | --sha1-name] [--topics] [(<rev> | <glob>)...]"),
    N_("git show-branch (-g|--reflog)[=<n>[,<base>]] [--list] [<ref>]"),
    NULL
};

static int showbranch_use_color = -1;

static int default_num;
static int default_alloc;
static const char **default_arg;

#define UNINTERESTING   01

#define REV_SHIFT        2
#define MAX_REVS        (FLAG_BITS - REV_SHIFT) /* should not exceed bits_per_int - REV_SHIFT */

#define DEFAULT_REFLOG  4

static const char *get_color_code(int idx)
{
        if (want_color(showbranch_use_color))
                return column_colors_ansi[idx % column_colors_ansi_max];
        return "";
}

static const char *get_color_reset_code(void)
{
        if (want_color(showbranch_use_color))
                return GIT_COLOR_RESET;
        return "";
}

static struct commit *interesting(struct commit_list *list)
{
        while (list) {
                struct commit *commit = list->item;
                list = list->next;
                if (commit->object.flags & UNINTERESTING)
                        continue;
                return commit;
        }
        return NULL;
}

static struct commit *pop_one_commit(struct commit_list **list_p)
{
        struct commit *commit;
        struct commit_list *list;
        list = *list_p;
        commit = list->item;
        *list_p = list->next;
        free(list);
        return commit;
}

struct commit_name {
        const char *head_name; /* which head's ancestor? */
        int generation; /* how many parents away from head_name */
};

/* Name the commit as nth generation ancestor of head_name;
 * we count only the first-parent relationship for naming purposes.
 */
static void name_commit(struct commit *commit, const char *head_name, int nth)
{
        struct commit_name *name;
        if (!commit->util)
                commit->util = xmalloc(sizeof(struct commit_name));
        name = commit->util;
        name->head_name = head_name;
        name->generation = nth;
}

/* Parent is the first parent of the commit.  We may name it
 * as (n+1)th generation ancestor of the same head_name as
 * commit is nth generation ancestor of, if that generation
 * number is better than the name it already has.
 */
static void name_parent(struct commit *commit, struct commit *parent)
{
        struct commit_name *commit_name = commit->util;
        struct commit_name *parent_name = parent->util;
        if (!commit_name)
                return;
        if (!parent_name ||
            commit_name->generation + 1 < parent_name->generation)
                name_commit(parent, commit_name->head_name,
                            commit_name->generation + 1);
}

static int name_first_parent_chain(struct commit *c)
{
        int i = 0;
        while (c) {
                struct commit *p;
                if (!c->util)
                        break;
                if (!c->parents)
                        break;
                p = c->parents->item;
                if (!p->util) {
                        name_parent(c, p);
                        i++;
                }
                else
                        break;
                c = p;
        }
        return i;
}

static void name_commits(struct commit_list *list,
                         struct commit **rev,
                         char **ref_name,
                         int num_rev)
{
        struct commit_list *cl;
        struct commit *c;
        int i;

        /* First give names to the given heads */
        for (cl = list; cl; cl = cl->next) {
                c = cl->item;
                if (c->util)
                        continue;
                for (i = 0; i < num_rev; i++) {
                        if (rev[i] == c) {
                                name_commit(c, ref_name[i], 0);
                                break;
                        }
                }
        }

        /* Then commits on the first parent ancestry chain */
        do {
                i = 0;
                for (cl = list; cl; cl = cl->next) {
                        i += name_first_parent_chain(cl->item);
                }
        } while (i);

        /* Finally, any unnamed commits */
        do {
                i = 0;
                for (cl = list; cl; cl = cl->next) {
                        struct commit_list *parents;
                        struct commit_name *n;
                        int nth;
                        c = cl->item;
                        if (!c->util)
                                continue;
                        n = c->util;
                        parents = c->parents;
                        nth = 0;
                        while (parents) {
                                struct commit *p = parents->item;
                                struct strbuf newname = STRBUF_INIT;
                                parents = parents->next;
                                nth++;
                                if (p->util)
                                        continue;
                                switch (n->generation) {
                                case 0:
                                        strbuf_addstr(&newname, n->head_name);
                                        break;
                                case 1:
                                        strbuf_addf(&newname, "%s^", n->head_name);
                                        break;
                                default:
                                        strbuf_addf(&newname, "%s~%d",
                                                    n->head_name, n->generation);
                                        break;
                                }
                                if (nth == 1)
                                        strbuf_addch(&newname, '^');
                                else
                                        strbuf_addf(&newname, "^%d", nth);
                                name_commit(p, strbuf_detach(&newname, NULL), 0);
                                i++;
                                name_first_parent_chain(p);
                        }
                }
        } while (i);
}

static int mark_seen(struct commit *commit, struct commit_list **seen_p)
{
        if (!commit->object.flags) {
                commit_list_insert(commit, seen_p);
                return 1;
        }
        return 0;
}

static void join_revs(struct commit_list **list_p,
                      struct commit_list **seen_p,
                      int num_rev, int extra)
{
        int all_mask = ((1u << (REV_SHIFT + num_rev)) - 1);
        int all_revs = all_mask & ~((1u << REV_SHIFT) - 1);

        while (*list_p) {
                struct commit_list *parents;
                int still_interesting = !!interesting(*list_p);
                struct commit *commit = pop_one_commit(list_p);
                int flags = commit->object.flags & all_mask;

                if (!still_interesting && extra <= 0)
                        break;

                mark_seen(commit, seen_p);
                if ((flags & all_revs) == all_revs)
                        flags |= UNINTERESTING;
                parents = commit->parents;

                while (parents) {
                        struct commit *p = parents->item;
                        int this_flag = p->object.flags;
                        parents = parents->next;
                        if ((this_flag & flags) == flags)
                                continue;
                        if (!p->object.parsed)
                                parse_commit(p);
                        if (mark_seen(p, seen_p) && !still_interesting)
                                extra--;
                        p->object.flags |= flags;
                        commit_list_insert_by_date(p, list_p);
                }
        }

        /*
         * Postprocess to complete well-poisoning.
         *
         * At this point we have all the commits we have seen in
         * seen_p list.  Mark anything that can be reached from
         * uninteresting commits not interesting.
         */
        for (;;) {
                int changed = 0;
                struct commit_list *s;
                for (s = *seen_p; s; s = s->next) {
                        struct commit *c = s->item;
                        struct commit_list *parents;

                        if (((c->object.flags & all_revs) != all_revs) &&
                            !(c->object.flags & UNINTERESTING))
                                continue;

                        /* The current commit is either a merge base or
                         * already uninteresting one.  Mark its parents
                         * as uninteresting commits _only_ if they are
                         * already parsed.  No reason to find new ones
                         * here.
                         */
                        parents = c->parents;
                        while (parents) {
                                struct commit *p = parents->item;
                                parents = parents->next;
                                if (!(p->object.flags & UNINTERESTING)) {
                                        p->object.flags |= UNINTERESTING;
                                        changed = 1;
                                }
                        }
                }
                if (!changed)
                        break;
        }
}

static void show_one_commit(struct commit *commit, int no_name)
{
        struct strbuf pretty = STRBUF_INIT;
        const char *pretty_str = "(unavailable)";
        struct commit_name *name = commit->util;

        if (commit->object.parsed) {
                pp_commit_easy(CMIT_FMT_ONELINE, commit, &pretty);
                pretty_str = pretty.buf;
        }
        if (!prefixcmp(pretty_str, "[PATCH] "))
                pretty_str += 8;

        if (!no_name) {
                if (name && name->head_name) {
                        printf("[%s", name->head_name);
                        if (name->generation) {
                                if (name->generation == 1)
                                        printf("^");
                                else
                                        printf("~%d", name->generation);
                        }
                        printf("] ");
                }
                else
                        printf("[%s] ",
                               find_unique_abbrev(commit->object.sha1,
                                                  DEFAULT_ABBREV));
        }
        puts(pretty_str);
        strbuf_release(&pretty);
}

static char *ref_name[MAX_REVS + 1];
static int ref_name_cnt;

static const char *find_digit_prefix(const char *s, int *v)
{
        const char *p;
        int ver;
        char ch;

        for (p = s, ver = 0;
             '0' <= (ch = *p) && ch <= '9';
             p++)
                ver = ver * 10 + ch - '0';
        *v = ver;
        return p;
}


static int version_cmp(const char *a, const char *b)
{
        while (1) {
                int va, vb;

                a = find_digit_prefix(a, &va);
                b = find_digit_prefix(b, &vb);
                if (va != vb)
                        return va - vb;

                while (1) {
                        int ca = *a;
                        int cb = *b;
                        if ('0' <= ca && ca <= '9')
                                ca = 0;
                        if ('0' <= cb && cb <= '9')
                                cb = 0;
                        if (ca != cb)
                                return ca - cb;
                        if (!ca)
                                break;
                        a++;
                        b++;
                }
                if (!*a && !*b)
                        return 0;
        }
}

static int compare_ref_name(const void *a_, const void *b_)
{
        const char * const*a = a_, * const*b = b_;
        return version_cmp(*a, *b);
}

static void sort_ref_range(int bottom, int top)
{
        qsort(ref_name + bottom, top - bottom, sizeof(ref_name[0]),
              compare_ref_name);
}

static int append_ref(const char *refname, const unsigned char *sha1,
                      int allow_dups)
{
        struct commit *commit = lookup_commit_reference_gently(sha1, 1);
        int i;

        if (!commit)
                return 0;

        if (!allow_dups) {
                /* Avoid adding the same thing twice */
                for (i = 0; i < ref_name_cnt; i++)
                        if (!strcmp(refname, ref_name[i]))
                                return 0;
        }
        if (MAX_REVS <= ref_name_cnt) {
                warning("ignoring %s; cannot handle more than %d refs",
                        refname, MAX_REVS);
                return 0;
        }
        ref_name[ref_name_cnt++] = xstrdup(refname);
        ref_name[ref_name_cnt] = NULL;
        return 0;
}

static int append_head_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
{
        unsigned char tmp[20];
        int ofs = 11;
        if (prefixcmp(refname, "refs/heads/"))
                return 0;
        /* If both heads/foo and tags/foo exists, get_sha1 would
         * get confused.
         */
        if (get_sha1(refname + ofs, tmp) || hashcmp(tmp, sha1))
                ofs = 5;
        return append_ref(refname + ofs, sha1, 0);
}

static int append_remote_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
{
        unsigned char tmp[20];
        int ofs = 13;
        if (prefixcmp(refname, "refs/remotes/"))
                return 0;
        /* If both heads/foo and tags/foo exists, get_sha1 would
         * get confused.
         */
        if (get_sha1(refname + ofs, tmp) || hashcmp(tmp, sha1))
                ofs = 5;
        return append_ref(refname + ofs, sha1, 0);
}

static int append_tag_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
{
        if (prefixcmp(refname, "refs/tags/"))
                return 0;
        return append_ref(refname + 5, sha1, 0);
}

static const char *match_ref_pattern = NULL;
static int match_ref_slash = 0;
static int count_slash(const char *s)
{
        int cnt = 0;
        while (*s)
                if (*s++ == '/')
                        cnt++;
        return cnt;
}

static int append_matching_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
{
        /* we want to allow pattern hold/<asterisk> to show all
         * branches under refs/heads/hold/, and v0.99.9? to show
         * refs/tags/v0.99.9a and friends.
         */
        const char *tail;
        int slash = count_slash(refname);
        for (tail = refname; *tail && match_ref_slash < slash; )
                if (*tail++ == '/')
                        slash--;
        if (!*tail)
                return 0;
        if (fnmatch(match_ref_pattern, tail, 0))
                return 0;
        if (!prefixcmp(refname, "refs/heads/"))
                return append_head_ref(refname, sha1, flag, cb_data);
        if (!prefixcmp(refname, "refs/tags/"))
                return append_tag_ref(refname, sha1, flag, cb_data);
        return append_ref(refname, sha1, 0);
}

static void snarf_refs(int head, int remotes)
{
        if (head) {
                int orig_cnt = ref_name_cnt;
                for_each_ref(append_head_ref, NULL);
                sort_ref_range(orig_cnt, ref_name_cnt);
        }
        if (remotes) {
                int orig_cnt = ref_name_cnt;
                for_each_ref(append_remote_ref, NULL);
                sort_ref_range(orig_cnt, ref_name_cnt);
        }
}

static int rev_is_head(char *head, int headlen, char *name,
                       unsigned char *head_sha1, unsigned char *sha1)
{
        if ((!head[0]) ||
            (head_sha1 && sha1 && hashcmp(head_sha1, sha1)))
                return 0;
        if (!prefixcmp(head, "refs/heads/"))
                head += 11;
        if (!prefixcmp(name, "refs/heads/"))
                name += 11;
        else if (!prefixcmp(name, "heads/"))
                name += 6;
        return !strcmp(head, name);
}

static int show_merge_base(struct commit_list *seen, int num_rev)
{
        int all_mask = ((1u << (REV_SHIFT + num_rev)) - 1);
        int all_revs = all_mask & ~((1u << REV_SHIFT) - 1);
        int exit_status = 1;

        while (seen) {
                struct commit *commit = pop_one_commit(&seen);
                int flags = commit->object.flags & all_mask;
                if (!(flags & UNINTERESTING) &&
                    ((flags & all_revs) == all_revs)) {
                        puts(sha1_to_hex(commit->object.sha1));
                        exit_status = 0;
                        commit->object.flags |= UNINTERESTING;
                }
        }
        return exit_status;
}

static int show_independent(struct commit **rev,
                            int num_rev,
                            char **ref_name,
                            unsigned int *rev_mask)
{
        int i;

        for (i = 0; i < num_rev; i++) {
                struct commit *commit = rev[i];
                unsigned int flag = rev_mask[i];

                if (commit->object.flags == flag)
                        puts(sha1_to_hex(commit->object.sha1));
                commit->object.flags |= UNINTERESTING;
        }
        return 0;
}

static void append_one_rev(const char *av)
{
        unsigned char revkey[20];
        if (!get_sha1(av, revkey)) {
                append_ref(av, revkey, 0);
                return;
        }
        if (strchr(av, '*') || strchr(av, '?') || strchr(av, '[')) {
                /* glob style match */
                int saved_matches = ref_name_cnt;
                match_ref_pattern = av;
                match_ref_slash = count_slash(av);
                for_each_ref(append_matching_ref, NULL);
                if (saved_matches == ref_name_cnt &&
                    ref_name_cnt < MAX_REVS)
                        error("no matching refs with %s", av);
                if (saved_matches + 1 < ref_name_cnt)
                        sort_ref_range(saved_matches, ref_name_cnt);
                return;
        }
        die("bad sha1 reference %s", av);
}

static int git_show_branch_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "showbranch.default")) {
                if (!value)
                        return config_error_nonbool(var);
                /*
                 * default_arg is now passed to parse_options(), so we need to
                 * mimic the real argv a bit better.
                 */
                if (!default_num) {
                        default_alloc = 20;
                        default_arg = xcalloc(default_alloc, sizeof(*default_arg));
                        default_arg[default_num++] = "show-branch";
                } else if (default_alloc <= default_num + 1) {
                        default_alloc = default_alloc * 3 / 2 + 20;
                        default_arg = xrealloc(default_arg, sizeof *default_arg * default_alloc);
                }
                default_arg[default_num++] = xstrdup(value);
                default_arg[default_num] = NULL;
                return 0;
        }

        if (!strcmp(var, "color.showbranch")) {
                showbranch_use_color = git_config_colorbool(var, value);
                return 0;
        }

        return git_color_default_config(var, value, cb);
}

static int omit_in_dense(struct commit *commit, struct commit **rev, int n)
{
        /* If the commit is tip of the named branches, do not
         * omit it.
         * Otherwise, if it is a merge that is reachable from only one
         * tip, it is not that interesting.
         */
        int i, flag, count;
        for (i = 0; i < n; i++)
                if (rev[i] == commit)
                        return 0;
        flag = commit->object.flags;
        for (i = count = 0; i < n; i++) {
                if (flag & (1u << (i + REV_SHIFT)))
                        count++;
        }
        if (count == 1)
                return 1;
        return 0;
}

static int reflog = 0;

static int parse_reflog_param(const struct option *opt, const char *arg,
                              int unset)
{
        char *ep;
        const char **base = (const char **)opt->value;
        if (!arg)
                arg = "";
        reflog = strtoul(arg, &ep, 10);
        if (*ep == ',')
                *base = ep + 1;
        else if (*ep)
                return error("unrecognized reflog param '%s'", arg);
        else
                *base = NULL;
        if (reflog <= 0)
                reflog = DEFAULT_REFLOG;
        return 0;
}

int cmd_show_branch(int ac, const char **av, const char *prefix)
{
        struct commit *rev[MAX_REVS], *commit;
        char *reflog_msg[MAX_REVS];
        struct commit_list *list = NULL, *seen = NULL;
        unsigned int rev_mask[MAX_REVS];
        int num_rev, i, extra = 0;
        int all_heads = 0, all_remotes = 0;
        int all_mask, all_revs;
        enum rev_sort_order sort_order = REV_SORT_IN_GRAPH_ORDER;
        char head[128];
        const char *head_p;
        int head_len;
        unsigned char head_sha1[20];
        int merge_base = 0;
        int independent = 0;
        int no_name = 0;
        int sha1_name = 0;
        int shown_merge_point = 0;
        int with_current_branch = 0;
        int head_at = -1;
        int topics = 0;
        int dense = 1;
        const char *reflog_base = NULL;
        struct option builtin_show_branch_options[] = {
                OPT_BOOLEAN('a', "all", &all_heads,
                            N_("show remote-tracking and local branches")),
                OPT_BOOLEAN('r', "remotes", &all_remotes,
                            N_("show remote-tracking branches")),
                OPT__COLOR(&showbranch_use_color,
                            N_("color '*!+-' corresponding to the branch")),
                { OPTION_INTEGER, 0, "more", &extra, N_("n"),
                            N_("show <n> more commits after the common ancestor"),
                            PARSE_OPT_OPTARG, NULL, (intptr_t)1 },
                OPT_SET_INT(0, "list", &extra, N_("synonym to more=-1"), -1),
                OPT_BOOLEAN(0, "no-name", &no_name, N_("suppress naming strings")),
                OPT_BOOLEAN(0, "current", &with_current_branch,
                            N_("include the current branch")),
                OPT_BOOLEAN(0, "sha1-name", &sha1_name,
                            N_("name commits with their object names")),
                OPT_BOOLEAN(0, "merge-base", &merge_base,
                            N_("show possible merge bases")),
                OPT_BOOLEAN(0, "independent", &independent,
                            N_("show refs unreachable from any other ref")),
                OPT_SET_INT(0, "topo-order", &sort_order,
                            N_("show commits in topological order"),
                            REV_SORT_IN_GRAPH_ORDER),
                OPT_BOOLEAN(0, "topics", &topics,
                            N_("show only commits not on the first branch")),
                OPT_SET_INT(0, "sparse", &dense,
                            N_("show merges reachable from only one tip"), 0),
                OPT_SET_INT(0, "date-order", &sort_order,
                            N_("show commits where no parent comes before its "
                               "children"),
                            REV_SORT_BY_COMMIT_DATE),
                { OPTION_CALLBACK, 'g', "reflog", &reflog_base, N_("<n>[,<base>]"),
                            N_("show <n> most recent ref-log entries starting at "
                               "base"),
                            PARSE_OPT_OPTARG | PARSE_OPT_LITERAL_ARGHELP,
                            parse_reflog_param },
                OPT_END()
        };

        git_config(git_show_branch_config, NULL);

        /* If nothing is specified, try the default first */
        if (ac == 1 && default_num) {
                ac = default_num;
                av = default_arg;
        }

        ac = parse_options(ac, av, prefix, builtin_show_branch_options,
                           show_branch_usage, PARSE_OPT_STOP_AT_NON_OPTION);
        if (all_heads)
                all_remotes = 1;

        if (extra || reflog) {
                /* "listing" mode is incompatible with
                 * independent nor merge-base modes.
                 */
                if (independent || merge_base)
                        usage_with_options(show_branch_usage,
                                           builtin_show_branch_options);
                if (reflog && ((0 < extra) || all_heads || all_remotes))
                        /*
                         * Asking for --more in reflog mode does not
                         * make sense.  --list is Ok.
                         *
                         * Also --all and --remotes do not make sense either.
                         */
                        die("--reflog is incompatible with --all, --remotes, "
                            "--independent or --merge-base");
        }

        /* If nothing is specified, show all branches by default */
        if (ac + all_heads + all_remotes == 0)
                all_heads = 1;

        if (reflog) {
                unsigned char sha1[20];
                char nth_desc[256];
                char *ref;
                int base = 0;

                if (ac == 0) {
                        static const char *fake_av[2];

                        fake_av[0] = resolve_refdup("HEAD", sha1, 1, NULL);
                        fake_av[1] = NULL;
                        av = fake_av;
                        ac = 1;
                }
                if (ac != 1)
                        die("--reflog option needs one branch name");

                if (MAX_REVS < reflog)
                        die("Only %d entries can be shown at one time.",
                            MAX_REVS);
                if (!dwim_ref(*av, strlen(*av), sha1, &ref))
                        die("No such ref %s", *av);

                /* Has the base been specified? */
                if (reflog_base) {
                        char *ep;
                        base = strtoul(reflog_base, &ep, 10);
                        if (*ep) {
                                /* Ah, that is a date spec... */
                                unsigned long at;
                                at = approxidate(reflog_base);
                                read_ref_at(ref, at, -1, sha1, NULL,
                                            NULL, NULL, &base);
                        }
                }

                for (i = 0; i < reflog; i++) {
                        char *logmsg, *m;
                        const char *msg;
                        unsigned long timestamp;
                        int tz;

                        if (read_ref_at(ref, 0, base+i, sha1, &logmsg,
                                        &timestamp, &tz, NULL)) {
                                reflog = i;
                                break;
                        }
                        msg = strchr(logmsg, '\t');
                        if (!msg)
                                msg = "(none)";
                        else
                                msg++;
                        m = xmalloc(strlen(msg) + 200);
                        sprintf(m, "(%s) %s",
                                show_date(timestamp, tz, 1),
                                msg);
                        reflog_msg[i] = m;
                        free(logmsg);
                        sprintf(nth_desc, "%s@{%d}", *av, base+i);
                        append_ref(nth_desc, sha1, 1);
                }
        }
        else if (all_heads + all_remotes)
                snarf_refs(all_heads, all_remotes);
        else {
                while (0 < ac) {
                        append_one_rev(*av);
                        ac--; av++;
                }
        }

        head_p = resolve_ref_unsafe("HEAD", head_sha1, 1, NULL);
        if (head_p) {
                head_len = strlen(head_p);
                memcpy(head, head_p, head_len + 1);
        }
        else {
                head_len = 0;
                head[0] = 0;
        }

        if (with_current_branch && head_p) {
                int has_head = 0;
                for (i = 0; !has_head && i < ref_name_cnt; i++) {
                        /* We are only interested in adding the branch
                         * HEAD points at.
                         */
                        if (rev_is_head(head,
                                        head_len,
                                        ref_name[i],
                                        head_sha1, NULL))
                                has_head++;
                }
                if (!has_head) {
                        int offset = !prefixcmp(head, "refs/heads/") ? 11 : 0;
                        append_one_rev(head + offset);
                }
        }

        if (!ref_name_cnt) {
                fprintf(stderr, "No revs to be shown.\n");
                exit(0);
        }

        for (num_rev = 0; ref_name[num_rev]; num_rev++) {
                unsigned char revkey[20];
                unsigned int flag = 1u << (num_rev + REV_SHIFT);

                if (MAX_REVS <= num_rev)
                        die("cannot handle more than %d revs.", MAX_REVS);
                if (get_sha1(ref_name[num_rev], revkey))
                        die("'%s' is not a valid ref.", ref_name[num_rev]);
                commit = lookup_commit_reference(revkey);
                if (!commit)
                        die("cannot find commit %s (%s)",
                            ref_name[num_rev], revkey);
                parse_commit(commit);
                mark_seen(commit, &seen);

                /* rev#0 uses bit REV_SHIFT, rev#1 uses bit REV_SHIFT+1,
                 * and so on.  REV_SHIFT bits from bit 0 are used for
                 * internal bookkeeping.
                 */
                commit->object.flags |= flag;
                if (commit->object.flags == flag)
                        commit_list_insert_by_date(commit, &list);
                rev[num_rev] = commit;
        }
        for (i = 0; i < num_rev; i++)
                rev_mask[i] = rev[i]->object.flags;

        if (0 <= extra)
                join_revs(&list, &seen, num_rev, extra);

        commit_list_sort_by_date(&seen);

        if (merge_base)
                return show_merge_base(seen, num_rev);

        if (independent)
                return show_independent(rev, num_rev, ref_name, rev_mask);

        /* Show list; --more=-1 means list-only */
        if (1 < num_rev || extra < 0) {
                for (i = 0; i < num_rev; i++) {
                        int j;
                        int is_head = rev_is_head(head,
                                                  head_len,
                                                  ref_name[i],
                                                  head_sha1,
                                                  rev[i]->object.sha1);
                        if (extra < 0)
                                printf("%c [%s] ",
                                       is_head ? '*' : ' ', ref_name[i]);
                        else {
                                for (j = 0; j < i; j++)
                                        putchar(' ');
                                printf("%s%c%s [%s] ",
                                       get_color_code(i),
                                       is_head ? '*' : '!',
                                       get_color_reset_code(), ref_name[i]);
                        }

                        if (!reflog) {
                                /* header lines never need name */
                                show_one_commit(rev[i], 1);
                        }
                        else
                                puts(reflog_msg[i]);

                        if (is_head)
                                head_at = i;
                }
                if (0 <= extra) {
                        for (i = 0; i < num_rev; i++)
                                putchar('-');
                        putchar('\n');
                }
        }
        if (extra < 0)
                exit(0);

        /* Sort topologically */
        sort_in_topological_order(&seen, sort_order);

        /* Give names to commits */
        if (!sha1_name && !no_name)
                name_commits(seen, rev, ref_name, num_rev);

        all_mask = ((1u << (REV_SHIFT + num_rev)) - 1);
        all_revs = all_mask & ~((1u << REV_SHIFT) - 1);

        while (seen) {
                struct commit *commit = pop_one_commit(&seen);
                int this_flag = commit->object.flags;
                int is_merge_point = ((this_flag & all_revs) == all_revs);

                shown_merge_point |= is_merge_point;

                if (1 < num_rev) {
                        int is_merge = !!(commit->parents &&
                                          commit->parents->next);
                        if (topics &&
                            !is_merge_point &&
                            (this_flag & (1u << REV_SHIFT)))
                                continue;
                        if (dense && is_merge &&
                            omit_in_dense(commit, rev, num_rev))
                                continue;
                        for (i = 0; i < num_rev; i++) {
                                int mark;
                                if (!(this_flag & (1u << (i + REV_SHIFT))))
                                        mark = ' ';
                                else if (is_merge)
                                        mark = '-';
                                else if (i == head_at)
                                        mark = '*';
                                else
                                        mark = '+';
                                printf("%s%c%s",
                                       get_color_code(i),
                                       mark, get_color_reset_code());
                        }
                        putchar(' ');
                }
                show_one_commit(commit, no_name);

                if (shown_merge_point && --extra < 0)
                        break;
        }
        return 0;
}