#include "builtin.h"
#include "cache.h"
#include "parse-options.h"
#include "refs.h"
#include "wildmatch.h"
#include "commit.h"
#include "remote.h"
#include "color.h"
#include "tag.h"
#include "quote.h"
#include "ref-filter.h"
#include "revision.h"
#include "utf8.h"
#include "git-compat-util.h"
#include "version.h"
#include "trailer.h"
#include "wt-status.h"
#include "commit-slab.h"

static struct ref_msg {
        const char *gone;
        const char *ahead;
        const char *behind;
        const char *ahead_behind;
} msgs = {
         /* Untranslated plumbing messages: */
        "gone",
        "ahead %d",
        "behind %d",
        "ahead %d, behind %d"
};

void setup_ref_filter_porcelain_msg(void)
{
        msgs.gone = _("gone");
        msgs.ahead = _("ahead %d");
        msgs.behind = _("behind %d");
        msgs.ahead_behind = _("ahead %d, behind %d");
}

typedef enum { FIELD_STR, FIELD_ULONG, FIELD_TIME } cmp_type;
typedef enum { COMPARE_EQUAL, COMPARE_UNEQUAL, COMPARE_NONE } cmp_status;

struct align {
        align_type position;
        unsigned int width;
};

struct if_then_else {
        cmp_status cmp_status;
        const char *str;
        unsigned int then_atom_seen : 1,
                else_atom_seen : 1,
                condition_satisfied : 1;
};

struct refname_atom {
        enum { R_NORMAL, R_SHORT, R_LSTRIP, R_RSTRIP } option;
        int lstrip, rstrip;
};

/*
 * An atom is a valid field atom listed below, possibly prefixed with
 * a "*" to denote deref_tag().
 *
 * We parse given format string and sort specifiers, and make a list
 * of properties that we need to extract out of objects.  ref_array_item
 * structure will hold an array of values extracted that can be
 * indexed with the "atom number", which is an index into this
 * array.
 */
static struct used_atom {
        const char *name;
        cmp_type type;
        union {
                char color[COLOR_MAXLEN];
                struct align align;
                struct {
                        enum {
                                RR_REF, RR_TRACK, RR_TRACKSHORT, RR_REMOTE_NAME, RR_REMOTE_REF
                        } option;
                        struct refname_atom refname;
                        unsigned int nobracket : 1, push : 1, push_remote : 1;
                } remote_ref;
                struct {
                        enum { C_BARE, C_BODY, C_BODY_DEP, C_LINES, C_SIG, C_SUB, C_TRAILERS } option;
                        struct process_trailer_options trailer_opts;
                        unsigned int nlines;
                } contents;
                struct {
                        cmp_status cmp_status;
                        const char *str;
                } if_then_else;
                struct {
                        enum { O_FULL, O_LENGTH, O_SHORT } option;
                        unsigned int length;
                } objectname;
                struct refname_atom refname;
                char *head;
        } u;
} *used_atom;
static int used_atom_cnt, need_tagged, need_symref;

/*
 * Expand string, append it to strbuf *sb, then return error code ret.
 * Allow to save few lines of code.
 */
static int strbuf_addf_ret(struct strbuf *sb, int ret, const char *fmt, ...)
{
        va_list ap;
        va_start(ap, fmt);
        strbuf_vaddf(sb, fmt, ap);
        va_end(ap);
        return ret;
}

static int color_atom_parser(const struct ref_format *format, struct used_atom *atom,
                             const char *color_value, struct strbuf *err)
{
        if (!color_value)
                return strbuf_addf_ret(err, -1, _("expected format: %%(color:<color>)"));
        if (color_parse(color_value, atom->u.color) < 0)
                return strbuf_addf_ret(err, -1, _("unrecognized color: %%(color:%s)"),
                                       color_value);
        /*
         * We check this after we've parsed the color, which lets us complain
         * about syntactically bogus color names even if they won't be used.
         */
        if (!want_color(format->use_color))
                color_parse("", atom->u.color);
        return 0;
}

static int refname_atom_parser_internal(struct refname_atom *atom, const char *arg,
                                         const char *name, struct strbuf *err)
{
        if (!arg)
                atom->option = R_NORMAL;
        else if (!strcmp(arg, "short"))
                atom->option = R_SHORT;
        else if (skip_prefix(arg, "lstrip=", &arg) ||
                 skip_prefix(arg, "strip=", &arg)) {
                atom->option = R_LSTRIP;
                if (strtol_i(arg, 10, &atom->lstrip))
                        return strbuf_addf_ret(err, -1, _("Integer value expected refname:lstrip=%s"), arg);
        } else if (skip_prefix(arg, "rstrip=", &arg)) {
                atom->option = R_RSTRIP;
                if (strtol_i(arg, 10, &atom->rstrip))
                        return strbuf_addf_ret(err, -1, _("Integer value expected refname:rstrip=%s"), arg);
        } else
                return strbuf_addf_ret(err, -1, _("unrecognized %%(%s) argument: %s"), name, arg);
        return 0;
}

static int remote_ref_atom_parser(const struct ref_format *format, struct used_atom *atom,
                                  const char *arg, struct strbuf *err)
{
        struct string_list params = STRING_LIST_INIT_DUP;
        int i;

        if (!strcmp(atom->name, "push") || starts_with(atom->name, "push:"))
                atom->u.remote_ref.push = 1;

        if (!arg) {
                atom->u.remote_ref.option = RR_REF;
                return refname_atom_parser_internal(&atom->u.remote_ref.refname,
                                                    arg, atom->name, err);
        }

        atom->u.remote_ref.nobracket = 0;
        string_list_split(&params, arg, ',', -1);

        for (i = 0; i < params.nr; i++) {
                const char *s = params.items[i].string;

                if (!strcmp(s, "track"))
                        atom->u.remote_ref.option = RR_TRACK;
                else if (!strcmp(s, "trackshort"))
                        atom->u.remote_ref.option = RR_TRACKSHORT;
                else if (!strcmp(s, "nobracket"))
                        atom->u.remote_ref.nobracket = 1;
                else if (!strcmp(s, "remotename")) {
                        atom->u.remote_ref.option = RR_REMOTE_NAME;
                        atom->u.remote_ref.push_remote = 1;
                } else if (!strcmp(s, "remoteref")) {
                        atom->u.remote_ref.option = RR_REMOTE_REF;
                        atom->u.remote_ref.push_remote = 1;
                } else {
                        atom->u.remote_ref.option = RR_REF;
                        if (refname_atom_parser_internal(&atom->u.remote_ref.refname,
                                                         arg, atom->name, err)) {
                                string_list_clear(&params, 0);
                                return -1;
                        }
                }
        }

        string_list_clear(&params, 0);
        return 0;
}

static int body_atom_parser(const struct ref_format *format, struct used_atom *atom,
                            const char *arg, struct strbuf *err)
{
        if (arg)
                return strbuf_addf_ret(err, -1, _("%%(body) does not take arguments"));
        atom->u.contents.option = C_BODY_DEP;
        return 0;
}

static int subject_atom_parser(const struct ref_format *format, struct used_atom *atom,
                               const char *arg, struct strbuf *err)
{
        if (arg)
                return strbuf_addf_ret(err, -1, _("%%(subject) does not take arguments"));
        atom->u.contents.option = C_SUB;
        return 0;
}

static int trailers_atom_parser(const struct ref_format *format, struct used_atom *atom,
                                const char *arg, struct strbuf *err)
{
        struct string_list params = STRING_LIST_INIT_DUP;
        int i;

        if (arg) {
                string_list_split(&params, arg, ',', -1);
                for (i = 0; i < params.nr; i++) {
                        const char *s = params.items[i].string;
                        if (!strcmp(s, "unfold"))
                                atom->u.contents.trailer_opts.unfold = 1;
                        else if (!strcmp(s, "only"))
                                atom->u.contents.trailer_opts.only_trailers = 1;
                        else {
                                strbuf_addf(err, _("unknown %%(trailers) argument: %s"), s);
                                string_list_clear(&params, 0);
                                return -1;
                        }
                }
        }
        atom->u.contents.option = C_TRAILERS;
        string_list_clear(&params, 0);
        return 0;
}

static int contents_atom_parser(const struct ref_format *format, struct used_atom *atom,
                                const char *arg, struct strbuf *err)
{
        if (!arg)
                atom->u.contents.option = C_BARE;
        else if (!strcmp(arg, "body"))
                atom->u.contents.option = C_BODY;
        else if (!strcmp(arg, "signature"))
                atom->u.contents.option = C_SIG;
        else if (!strcmp(arg, "subject"))
                atom->u.contents.option = C_SUB;
        else if (skip_prefix(arg, "trailers", &arg)) {
                skip_prefix(arg, ":", &arg);
                if (trailers_atom_parser(format, atom, *arg ? arg : NULL, err))
                        return -1;
        } else if (skip_prefix(arg, "lines=", &arg)) {
                atom->u.contents.option = C_LINES;
                if (strtoul_ui(arg, 10, &atom->u.contents.nlines))
                        return strbuf_addf_ret(err, -1, _("positive value expected contents:lines=%s"), arg);
        } else
                return strbuf_addf_ret(err, -1, _("unrecognized %%(contents) argument: %s"), arg);
        return 0;
}

static int objectname_atom_parser(const struct ref_format *format, struct used_atom *atom,
                                  const char *arg, struct strbuf *err)
{
        if (!arg)
                atom->u.objectname.option = O_FULL;
        else if (!strcmp(arg, "short"))
                atom->u.objectname.option = O_SHORT;
        else if (skip_prefix(arg, "short=", &arg)) {
                atom->u.objectname.option = O_LENGTH;
                if (strtoul_ui(arg, 10, &atom->u.objectname.length) ||
                    atom->u.objectname.length == 0)
                        return strbuf_addf_ret(err, -1, _("positive value expected objectname:short=%s"), arg);
                if (atom->u.objectname.length < MINIMUM_ABBREV)
                        atom->u.objectname.length = MINIMUM_ABBREV;
        } else
                return strbuf_addf_ret(err, -1, _("unrecognized %%(objectname) argument: %s"), arg);
        return 0;
}

static int refname_atom_parser(const struct ref_format *format, struct used_atom *atom,
                               const char *arg, struct strbuf *err)
{
        return refname_atom_parser_internal(&atom->u.refname, arg, atom->name, err);
}

static align_type parse_align_position(const char *s)
{
        if (!strcmp(s, "right"))
                return ALIGN_RIGHT;
        else if (!strcmp(s, "middle"))
                return ALIGN_MIDDLE;
        else if (!strcmp(s, "left"))
                return ALIGN_LEFT;
        return -1;
}

static int align_atom_parser(const struct ref_format *format, struct used_atom *atom,
                             const char *arg, struct strbuf *err)
{
        struct align *align = &atom->u.align;
        struct string_list params = STRING_LIST_INIT_DUP;
        int i;
        unsigned int width = ~0U;

        if (!arg)
                return strbuf_addf_ret(err, -1, _("expected format: %%(align:<width>,<position>)"));

        align->position = ALIGN_LEFT;

        string_list_split(&params, arg, ',', -1);
        for (i = 0; i < params.nr; i++) {
                const char *s = params.items[i].string;
                int position;

                if (skip_prefix(s, "position=", &s)) {
                        position = parse_align_position(s);
                        if (position < 0) {
                                strbuf_addf(err, _("unrecognized position:%s"), s);
                                string_list_clear(&params, 0);
                                return -1;
                        }
                        align->position = position;
                } else if (skip_prefix(s, "width=", &s)) {
                        if (strtoul_ui(s, 10, &width)) {
                                strbuf_addf(err, _("unrecognized width:%s"), s);
                                string_list_clear(&params, 0);
                                return -1;
                        }
                } else if (!strtoul_ui(s, 10, &width))
                        ;
                else if ((position = parse_align_position(s)) >= 0)
                        align->position = position;
                else {
                        strbuf_addf(err, _("unrecognized %%(align) argument: %s"), s);
                        string_list_clear(&params, 0);
                        return -1;
                }
        }

        if (width == ~0U) {
                string_list_clear(&params, 0);
                return strbuf_addf_ret(err, -1, _("positive width expected with the %%(align) atom"));
        }
        align->width = width;
        string_list_clear(&params, 0);
        return 0;
}

static int if_atom_parser(const struct ref_format *format, struct used_atom *atom,
                          const char *arg, struct strbuf *err)
{
        if (!arg) {
                atom->u.if_then_else.cmp_status = COMPARE_NONE;
                return 0;
        } else if (skip_prefix(arg, "equals=", &atom->u.if_then_else.str)) {
                atom->u.if_then_else.cmp_status = COMPARE_EQUAL;
        } else if (skip_prefix(arg, "notequals=", &atom->u.if_then_else.str)) {
                atom->u.if_then_else.cmp_status = COMPARE_UNEQUAL;
        } else
                return strbuf_addf_ret(err, -1, _("unrecognized %%(if) argument: %s"), arg);
        return 0;
}

static int head_atom_parser(const struct ref_format *format, struct used_atom *atom,
                            const char *arg, struct strbuf *unused_err)
{
        atom->u.head = resolve_refdup("HEAD", RESOLVE_REF_READING, NULL, NULL);
        return 0;
}

static struct {
        const char *name;
        cmp_type cmp_type;
        int (*parser)(const struct ref_format *format, struct used_atom *atom,
                      const char *arg, struct strbuf *err);
} valid_atom[] = {
        { "refname" , FIELD_STR, refname_atom_parser },
        { "objecttype" },
        { "objectsize", FIELD_ULONG },
        { "objectname", FIELD_STR, objectname_atom_parser },
        { "tree" },
        { "parent" },
        { "numparent", FIELD_ULONG },
        { "object" },
        { "type" },
        { "tag" },
        { "author" },
        { "authorname" },
        { "authoremail" },
        { "authordate", FIELD_TIME },
        { "committer" },
        { "committername" },
        { "committeremail" },
        { "committerdate", FIELD_TIME },
        { "tagger" },
        { "taggername" },
        { "taggeremail" },
        { "taggerdate", FIELD_TIME },
        { "creator" },
        { "creatordate", FIELD_TIME },
        { "subject", FIELD_STR, subject_atom_parser },
        { "body", FIELD_STR, body_atom_parser },
        { "trailers", FIELD_STR, trailers_atom_parser },
        { "contents", FIELD_STR, contents_atom_parser },
        { "upstream", FIELD_STR, remote_ref_atom_parser },
        { "push", FIELD_STR, remote_ref_atom_parser },
        { "symref", FIELD_STR, refname_atom_parser },
        { "flag" },
        { "HEAD", FIELD_STR, head_atom_parser },
        { "color", FIELD_STR, color_atom_parser },
        { "align", FIELD_STR, align_atom_parser },
        { "end" },
        { "if", FIELD_STR, if_atom_parser },
        { "then" },
        { "else" },
};

#define REF_FORMATTING_STATE_INIT  { 0, NULL }

struct ref_formatting_stack {
        struct ref_formatting_stack *prev;
        struct strbuf output;
        void (*at_end)(struct ref_formatting_stack **stack);
        void *at_end_data;
};

struct ref_formatting_state {
        int quote_style;
        struct ref_formatting_stack *stack;
};

struct atom_value {
        const char *s;
        int (*handler)(struct atom_value *atomv, struct ref_formatting_state *state,
                       struct strbuf *err);
        uintmax_t value; /* used for sorting when not FIELD_STR */
        struct used_atom *atom;
};

/*
 * Used to parse format string and sort specifiers
 */
static int parse_ref_filter_atom(const struct ref_format *format,
                                 const char *atom, const char *ep,
                                 struct strbuf *err)
{
        const char *sp;
        const char *arg;
        int i, at, atom_len;

        sp = atom;
        if (*sp == '*' && sp < ep)
                sp++; /* deref */
        if (ep <= sp)
                return strbuf_addf_ret(err, -1, _("malformed field name: %.*s"),
                                       (int)(ep-atom), atom);

        /* Do we have the atom already used elsewhere? */
        for (i = 0; i < used_atom_cnt; i++) {
                int len = strlen(used_atom[i].name);
                if (len == ep - atom && !memcmp(used_atom[i].name, atom, len))
                        return i;
        }

        /*
         * If the atom name has a colon, strip it and everything after
         * it off - it specifies the format for this entry, and
         * shouldn't be used for checking against the valid_atom
         * table.
         */
        arg = memchr(sp, ':', ep - sp);
        atom_len = (arg ? arg : ep) - sp;

        /* Is the atom a valid one? */
        for (i = 0; i < ARRAY_SIZE(valid_atom); i++) {
                int len = strlen(valid_atom[i].name);
                if (len == atom_len && !memcmp(valid_atom[i].name, sp, len))
                        break;
        }

        if (ARRAY_SIZE(valid_atom) <= i)
                return strbuf_addf_ret(err, -1, _("unknown field name: %.*s"),
                                       (int)(ep-atom), atom);

        /* Add it in, including the deref prefix */
        at = used_atom_cnt;
        used_atom_cnt++;
        REALLOC_ARRAY(used_atom, used_atom_cnt);
        used_atom[at].name = xmemdupz(atom, ep - atom);
        used_atom[at].type = valid_atom[i].cmp_type;
        if (arg) {
                arg = used_atom[at].name + (arg - atom) + 1;
                if (!*arg) {
                        /*
                         * Treat empty sub-arguments list as NULL (i.e.,
                         * "%(atom:)" is equivalent to "%(atom)").
                         */
                        arg = NULL;
                }
        }
        memset(&used_atom[at].u, 0, sizeof(used_atom[at].u));
        if (valid_atom[i].parser && valid_atom[i].parser(format, &used_atom[at], arg, err))
                return -1;
        if (*atom == '*')
                need_tagged = 1;
        if (!strcmp(valid_atom[i].name, "symref"))
                need_symref = 1;
        return at;
}

static void quote_formatting(struct strbuf *s, const char *str, int quote_style)
{
        switch (quote_style) {
        case QUOTE_NONE:
                strbuf_addstr(s, str);
                break;
        case QUOTE_SHELL:
                sq_quote_buf(s, str);
                break;
        case QUOTE_PERL:
                perl_quote_buf(s, str);
                break;
        case QUOTE_PYTHON:
                python_quote_buf(s, str);
                break;
        case QUOTE_TCL:
                tcl_quote_buf(s, str);
                break;
        }
}

static int append_atom(struct atom_value *v, struct ref_formatting_state *state,
                       struct strbuf *unused_err)
{
        /*
         * Quote formatting is only done when the stack has a single
         * element. Otherwise quote formatting is done on the
         * element's entire output strbuf when the %(end) atom is
         * encountered.
         */
        if (!state->stack->prev)
                quote_formatting(&state->stack->output, v->s, state->quote_style);
        else
                strbuf_addstr(&state->stack->output, v->s);
        return 0;
}

static void push_stack_element(struct ref_formatting_stack **stack)
{
        struct ref_formatting_stack *s = xcalloc(1, sizeof(struct ref_formatting_stack));

        strbuf_init(&s->output, 0);
        s->prev = *stack;
        *stack = s;
}

static void pop_stack_element(struct ref_formatting_stack **stack)
{
        struct ref_formatting_stack *current = *stack;
        struct ref_formatting_stack *prev = current->prev;

        if (prev)
                strbuf_addbuf(&prev->output, &current->output);
        strbuf_release(&current->output);
        free(current);
        *stack = prev;
}

static void end_align_handler(struct ref_formatting_stack **stack)
{
        struct ref_formatting_stack *cur = *stack;
        struct align *align = (struct align *)cur->at_end_data;
        struct strbuf s = STRBUF_INIT;

        strbuf_utf8_align(&s, align->position, align->width, cur->output.buf);
        strbuf_swap(&cur->output, &s);
        strbuf_release(&s);
}

static int align_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state,
                              struct strbuf *unused_err)
{
        struct ref_formatting_stack *new_stack;

        push_stack_element(&state->stack);
        new_stack = state->stack;
        new_stack->at_end = end_align_handler;
        new_stack->at_end_data = &atomv->atom->u.align;
        return 0;
}

static void if_then_else_handler(struct ref_formatting_stack **stack)
{
        struct ref_formatting_stack *cur = *stack;
        struct ref_formatting_stack *prev = cur->prev;
        struct if_then_else *if_then_else = (struct if_then_else *)cur->at_end_data;

        if (!if_then_else->then_atom_seen)
                die(_("format: %%(if) atom used without a %%(then) atom"));

        if (if_then_else->else_atom_seen) {
                /*
                 * There is an %(else) atom: we need to drop one state from the
                 * stack, either the %(else) branch if the condition is satisfied, or
                 * the %(then) branch if it isn't.
                 */
                if (if_then_else->condition_satisfied) {
                        strbuf_reset(&cur->output);
                        pop_stack_element(&cur);
                } else {
                        strbuf_swap(&cur->output, &prev->output);
                        strbuf_reset(&cur->output);
                        pop_stack_element(&cur);
                }
        } else if (!if_then_else->condition_satisfied) {
                /*
                 * No %(else) atom: just drop the %(then) branch if the
                 * condition is not satisfied.
                 */
                strbuf_reset(&cur->output);
        }

        *stack = cur;
        free(if_then_else);
}

static int if_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state,
                           struct strbuf *unused_err)
{
        struct ref_formatting_stack *new_stack;
        struct if_then_else *if_then_else = xcalloc(sizeof(struct if_then_else), 1);

        if_then_else->str = atomv->atom->u.if_then_else.str;
        if_then_else->cmp_status = atomv->atom->u.if_then_else.cmp_status;

        push_stack_element(&state->stack);
        new_stack = state->stack;
        new_stack->at_end = if_then_else_handler;
        new_stack->at_end_data = if_then_else;
        return 0;
}

static int is_empty(const char *s)
{
        while (*s != '\0') {
                if (!isspace(*s))
                        return 0;
                s++;
        }
        return 1;
}

static int then_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state,
                             struct strbuf *err)
{
        struct ref_formatting_stack *cur = state->stack;
        struct if_then_else *if_then_else = NULL;

        if (cur->at_end == if_then_else_handler)
                if_then_else = (struct if_then_else *)cur->at_end_data;
        if (!if_then_else)
                return strbuf_addf_ret(err, -1, _("format: %%(then) atom used without an %%(if) atom"));
        if (if_then_else->then_atom_seen)
                return strbuf_addf_ret(err, -1, _("format: %%(then) atom used more than once"));
        if (if_then_else->else_atom_seen)
                return strbuf_addf_ret(err, -1, _("format: %%(then) atom used after %%(else)"));
        if_then_else->then_atom_seen = 1;
        /*
         * If the 'equals' or 'notequals' attribute is used then
         * perform the required comparison. If not, only non-empty
         * strings satisfy the 'if' condition.
         */
        if (if_then_else->cmp_status == COMPARE_EQUAL) {
                if (!strcmp(if_then_else->str, cur->output.buf))
                        if_then_else->condition_satisfied = 1;
        } else if (if_then_else->cmp_status == COMPARE_UNEQUAL) {
                if (strcmp(if_then_else->str, cur->output.buf))
                        if_then_else->condition_satisfied = 1;
        } else if (cur->output.len && !is_empty(cur->output.buf))
                if_then_else->condition_satisfied = 1;
        strbuf_reset(&cur->output);
        return 0;
}

static int else_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state,
                             struct strbuf *err)
{
        struct ref_formatting_stack *prev = state->stack;
        struct if_then_else *if_then_else = NULL;

        if (prev->at_end == if_then_else_handler)
                if_then_else = (struct if_then_else *)prev->at_end_data;
        if (!if_then_else)
                return strbuf_addf_ret(err, -1, _("format: %%(else) atom used without an %%(if) atom"));
        if (!if_then_else->then_atom_seen)
                return strbuf_addf_ret(err, -1, _("format: %%(else) atom used without a %%(then) atom"));
        if (if_then_else->else_atom_seen)
                return strbuf_addf_ret(err, -1, _("format: %%(else) atom used more than once"));
        if_then_else->else_atom_seen = 1;
        push_stack_element(&state->stack);
        state->stack->at_end_data = prev->at_end_data;
        state->stack->at_end = prev->at_end;
        return 0;
}

static int end_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state,
                            struct strbuf *err)
{
        struct ref_formatting_stack *current = state->stack;
        struct strbuf s = STRBUF_INIT;

        if (!current->at_end)
                return strbuf_addf_ret(err, -1, _("format: %%(end) atom used without corresponding atom"));
        current->at_end(&state->stack);

        /*  Stack may have been popped within at_end(), hence reset the current pointer */
        current = state->stack;

        /*
         * Perform quote formatting when the stack element is that of
         * a supporting atom. If nested then perform quote formatting
         * only on the topmost supporting atom.
         */
        if (!current->prev->prev) {
                quote_formatting(&s, current->output.buf, state->quote_style);
                strbuf_swap(&current->output, &s);
        }
        strbuf_release(&s);
        pop_stack_element(&state->stack);
        return 0;
}

/*
 * In a format string, find the next occurrence of %(atom).
 */
static const char *find_next(const char *cp)
{
        while (*cp) {
                if (*cp == '%') {
                        /*
                         * %( is the start of an atom;
                         * %% is a quoted per-cent.
                         */
                        if (cp[1] == '(')
                                return cp;
                        else if (cp[1] == '%')
                                cp++; /* skip over two % */
                        /* otherwise this is a singleton, literal % */
                }
                cp++;
        }
        return NULL;
}

/*
 * Make sure the format string is well formed, and parse out
 * the used atoms.
 */
int verify_ref_format(struct ref_format *format)
{
        const char *cp, *sp;

        format->need_color_reset_at_eol = 0;
        for (cp = format->format; *cp && (sp = find_next(cp)); ) {
                struct strbuf err = STRBUF_INIT;
                const char *color, *ep = strchr(sp, ')');
                int at;

                if (!ep)
                        return error(_("malformed format string %s"), sp);
                /* sp points at "%(" and ep points at the closing ")" */
                at = parse_ref_filter_atom(format, sp + 2, ep, &err);
                if (at < 0)
                        die("%s", err.buf);
                cp = ep + 1;

                if (skip_prefix(used_atom[at].name, "color:", &color))
                        format->need_color_reset_at_eol = !!strcmp(color, "reset");
                strbuf_release(&err);
        }
        if (format->need_color_reset_at_eol && !want_color(format->use_color))
                format->need_color_reset_at_eol = 0;
        return 0;
}

/*
 * Given an object name, read the object data and size, and return a
 * "struct object".  If the object data we are returning is also borrowed
 * by the "struct object" representation, set *eaten as well---it is a
 * signal from parse_object_buffer to us not to free the buffer.
 */
static void *get_obj(const struct object_id *oid, struct object **obj, unsigned long *sz, int *eaten)
{
        enum object_type type;
        void *buf = read_sha1_file(oid->hash, &type, sz);

        if (buf)
                *obj = parse_object_buffer(oid, type, *sz, buf, eaten);
        else
                *obj = NULL;
        return buf;
}

static int grab_objectname(const char *name, const unsigned char *sha1,
                           struct atom_value *v, struct used_atom *atom)
{
        if (starts_with(name, "objectname")) {
                if (atom->u.objectname.option == O_SHORT) {
                        v->s = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
                        return 1;
                } else if (atom->u.objectname.option == O_FULL) {
                        v->s = xstrdup(sha1_to_hex(sha1));
                        return 1;
                } else if (atom->u.objectname.option == O_LENGTH) {
                        v->s = xstrdup(find_unique_abbrev(sha1, atom->u.objectname.length));
                        return 1;
                } else
                        die("BUG: unknown %%(objectname) option");
        }
        return 0;
}

/* See grab_values */
static void grab_common_values(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        int i;

        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i].name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (!strcmp(name, "objecttype"))
                        v->s = type_name(obj->type);
                else if (!strcmp(name, "objectsize")) {
                        v->value = sz;
                        v->s = xstrfmt("%lu", sz);
                }
                else if (deref)
                        grab_objectname(name, obj->oid.hash, v, &used_atom[i]);
        }
}

/* See grab_values */
static void grab_tag_values(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        int i;
        struct tag *tag = (struct tag *) obj;

        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i].name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (!strcmp(name, "tag"))
                        v->s = tag->tag;
                else if (!strcmp(name, "type") && tag->tagged)
                        v->s = type_name(tag->tagged->type);
                else if (!strcmp(name, "object") && tag->tagged)
                        v->s = xstrdup(oid_to_hex(&tag->tagged->oid));
        }
}

/* See grab_values */
static void grab_commit_values(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        int i;
        struct commit *commit = (struct commit *) obj;

        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i].name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (!strcmp(name, "tree")) {
                        v->s = xstrdup(oid_to_hex(&commit->tree->object.oid));
                }
                else if (!strcmp(name, "numparent")) {
                        v->value = commit_list_count(commit->parents);
                        v->s = xstrfmt("%lu", (unsigned long)v->value);
                }
                else if (!strcmp(name, "parent")) {
                        struct commit_list *parents;
                        struct strbuf s = STRBUF_INIT;
                        for (parents = commit->parents; parents; parents = parents->next) {
                                struct commit *parent = parents->item;
                                if (parents != commit->parents)
                                        strbuf_addch(&s, ' ');
                                strbuf_addstr(&s, oid_to_hex(&parent->object.oid));
                        }
                        v->s = strbuf_detach(&s, NULL);
                }
        }
}

static const char *find_wholine(const char *who, int wholen, const char *buf, unsigned long sz)
{
        const char *eol;
        while (*buf) {
                if (!strncmp(buf, who, wholen) &&
                    buf[wholen] == ' ')
                        return buf + wholen + 1;
                eol = strchr(buf, '\n');
                if (!eol)
                        return "";
                eol++;
                if (*eol == '\n')
                        return ""; /* end of header */
                buf = eol;
        }
        return "";
}

static const char *copy_line(const char *buf)
{
        const char *eol = strchrnul(buf, '\n');
        return xmemdupz(buf, eol - buf);
}

static const char *copy_name(const char *buf)
{
        const char *cp;
        for (cp = buf; *cp && *cp != '\n'; cp++) {
                if (!strncmp(cp, " <", 2))
                        return xmemdupz(buf, cp - buf);
        }
        return "";
}

static const char *copy_email(const char *buf)
{
        const char *email = strchr(buf, '<');
        const char *eoemail;
        if (!email)
                return "";
        eoemail = strchr(email, '>');
        if (!eoemail)
                return "";
        return xmemdupz(email, eoemail + 1 - email);
}

static char *copy_subject(const char *buf, unsigned long len)
{
        char *r = xmemdupz(buf, len);
        int i;

        for (i = 0; i < len; i++)
                if (r[i] == '\n')
                        r[i] = ' ';

        return r;
}

static void grab_date(const char *buf, struct atom_value *v, const char *atomname)
{
        const char *eoemail = strstr(buf, "> ");
        char *zone;
        timestamp_t timestamp;
        long tz;
        struct date_mode date_mode = { DATE_NORMAL };
        const char *formatp;

        /*
         * We got here because atomname ends in "date" or "date<something>";
         * it's not possible that <something> is not ":<format>" because
         * parse_ref_filter_atom() wouldn't have allowed it, so we can assume that no
         * ":" means no format is specified, and use the default.
         */
        formatp = strchr(atomname, ':');
        if (formatp != NULL) {
                formatp++;
                parse_date_format(formatp, &date_mode);
        }

        if (!eoemail)
                goto bad;
        timestamp = parse_timestamp(eoemail + 2, &zone, 10);
        if (timestamp == TIME_MAX)
                goto bad;
        tz = strtol(zone, NULL, 10);
        if ((tz == LONG_MIN || tz == LONG_MAX) && errno == ERANGE)
                goto bad;
        v->s = xstrdup(show_date(timestamp, tz, &date_mode));
        v->value = timestamp;
        return;
 bad:
        v->s = "";
        v->value = 0;
}

/* See grab_values */
static void grab_person(const char *who, struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        int i;
        int wholen = strlen(who);
        const char *wholine = NULL;

        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i].name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (strncmp(who, name, wholen))
                        continue;
                if (name[wholen] != 0 &&
                    strcmp(name + wholen, "name") &&
                    strcmp(name + wholen, "email") &&
                    !starts_with(name + wholen, "date"))
                        continue;
                if (!wholine)
                        wholine = find_wholine(who, wholen, buf, sz);
                if (!wholine)
                        return; /* no point looking for it */
                if (name[wholen] == 0)
                        v->s = copy_line(wholine);
                else if (!strcmp(name + wholen, "name"))
                        v->s = copy_name(wholine);
                else if (!strcmp(name + wholen, "email"))
                        v->s = copy_email(wholine);
                else if (starts_with(name + wholen, "date"))
                        grab_date(wholine, v, name);
        }

        /*
         * For a tag or a commit object, if "creator" or "creatordate" is
         * requested, do something special.
         */
        if (strcmp(who, "tagger") && strcmp(who, "committer"))
                return; /* "author" for commit object is not wanted */
        if (!wholine)
                wholine = find_wholine(who, wholen, buf, sz);
        if (!wholine)
                return;
        for (i = 0; i < used_atom_cnt; i++) {
                const char *name = used_atom[i].name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;

                if (starts_with(name, "creatordate"))
                        grab_date(wholine, v, name);
                else if (!strcmp(name, "creator"))
                        v->s = copy_line(wholine);
        }
}

static void find_subpos(const char *buf, unsigned long sz,
                        const char **sub, unsigned long *sublen,
                        const char **body, unsigned long *bodylen,
                        unsigned long *nonsiglen,
                        const char **sig, unsigned long *siglen)
{
        const char *eol;
        /* skip past header until we hit empty line */
        while (*buf && *buf != '\n') {
                eol = strchrnul(buf, '\n');
                if (*eol)
                        eol++;
                buf = eol;
        }
        /* skip any empty lines */
        while (*buf == '\n')
                buf++;

        /* parse signature first; we might not even have a subject line */
        *sig = buf + parse_signature(buf, strlen(buf));
        *siglen = strlen(*sig);

        /* subject is first non-empty line */
        *sub = buf;
        /* subject goes to first empty line */
        while (buf < *sig && *buf && *buf != '\n') {
                eol = strchrnul(buf, '\n');
                if (*eol)
                        eol++;
                buf = eol;
        }
        *sublen = buf - *sub;
        /* drop trailing newline, if present */
        if (*sublen && (*sub)[*sublen - 1] == '\n')
                *sublen -= 1;

        /* skip any empty lines */
        while (*buf == '\n')
                buf++;
        *body = buf;
        *bodylen = strlen(buf);
        *nonsiglen = *sig - buf;
}

/*
 * If 'lines' is greater than 0, append that many lines from the given
 * 'buf' of length 'size' to the given strbuf.
 */
static void append_lines(struct strbuf *out, const char *buf, unsigned long size, int lines)
{
        int i;
        const char *sp, *eol;
        size_t len;

        sp = buf;

        for (i = 0; i < lines && sp < buf + size; i++) {
                if (i)
                        strbuf_addstr(out, "\n    ");
                eol = memchr(sp, '\n', size - (sp - buf));
                len = eol ? eol - sp : size - (sp - buf);
                strbuf_add(out, sp, len);
                if (!eol)
                        break;
                sp = eol + 1;
        }
}

/* See grab_values */
static void grab_sub_body_contents(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        int i;
        const char *subpos = NULL, *bodypos = NULL, *sigpos = NULL;
        unsigned long sublen = 0, bodylen = 0, nonsiglen = 0, siglen = 0;

        for (i = 0; i < used_atom_cnt; i++) {
                struct used_atom *atom = &used_atom[i];
                const char *name = atom->name;
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (strcmp(name, "subject") &&
                    strcmp(name, "body") &&
                    !starts_with(name, "trailers") &&
                    !starts_with(name, "contents"))
                        continue;
                if (!subpos)
                        find_subpos(buf, sz,
                                    &subpos, &sublen,
                                    &bodypos, &bodylen, &nonsiglen,
                                    &sigpos, &siglen);

                if (atom->u.contents.option == C_SUB)
                        v->s = copy_subject(subpos, sublen);
                else if (atom->u.contents.option == C_BODY_DEP)
                        v->s = xmemdupz(bodypos, bodylen);
                else if (atom->u.contents.option == C_BODY)
                        v->s = xmemdupz(bodypos, nonsiglen);
                else if (atom->u.contents.option == C_SIG)
                        v->s = xmemdupz(sigpos, siglen);
                else if (atom->u.contents.option == C_LINES) {
                        struct strbuf s = STRBUF_INIT;
                        const char *contents_end = bodylen + bodypos - siglen;

                        /*  Size is the length of the message after removing the signature */
                        append_lines(&s, subpos, contents_end - subpos, atom->u.contents.nlines);
                        v->s = strbuf_detach(&s, NULL);
                } else if (atom->u.contents.option == C_TRAILERS) {
                        struct strbuf s = STRBUF_INIT;

                        /* Format the trailer info according to the trailer_opts given */
                        format_trailers_from_commit(&s, subpos, &atom->u.contents.trailer_opts);

                        v->s = strbuf_detach(&s, NULL);
                } else if (atom->u.contents.option == C_BARE)
                        v->s = xstrdup(subpos);
        }
}

/*
 * We want to have empty print-string for field requests
 * that do not apply (e.g. "authordate" for a tag object)
 */
static void fill_missing_values(struct atom_value *val)
{
        int i;
        for (i = 0; i < used_atom_cnt; i++) {
                struct atom_value *v = &val[i];
                if (v->s == NULL)
                        v->s = "";
        }
}

/*
 * val is a list of atom_value to hold returned values.  Extract
 * the values for atoms in used_atom array out of (obj, buf, sz).
 * when deref is false, (obj, buf, sz) is the object that is
 * pointed at by the ref itself; otherwise it is the object the
 * ref (which is a tag) refers to.
 */
static void grab_values(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
{
        grab_common_values(val, deref, obj, buf, sz);
        switch (obj->type) {
        case OBJ_TAG:
                grab_tag_values(val, deref, obj, buf, sz);
                grab_sub_body_contents(val, deref, obj, buf, sz);
                grab_person("tagger", val, deref, obj, buf, sz);
                break;
        case OBJ_COMMIT:
                grab_commit_values(val, deref, obj, buf, sz);
                grab_sub_body_contents(val, deref, obj, buf, sz);
                grab_person("author", val, deref, obj, buf, sz);
                grab_person("committer", val, deref, obj, buf, sz);
                break;
        case OBJ_TREE:
                /* grab_tree_values(val, deref, obj, buf, sz); */
                break;
        case OBJ_BLOB:
                /* grab_blob_values(val, deref, obj, buf, sz); */
                break;
        default:
                die("Eh?  Object of type %d?", obj->type);
        }
}

static inline char *copy_advance(char *dst, const char *src)
{
        while (*src)
                *dst++ = *src++;
        return dst;
}

static const char *lstrip_ref_components(const char *refname, int len)
{
        long remaining = len;
        const char *start = refname;

        if (len < 0) {
                int i;
                const char *p = refname;

                /* Find total no of '/' separated path-components */
                for (i = 0; p[i]; p[i] == '/' ? i++ : *p++)
                        ;
                /*
                 * The number of components we need to strip is now
                 * the total minus the components to be left (Plus one
                 * because we count the number of '/', but the number
                 * of components is one more than the no of '/').
                 */
                remaining = i + len + 1;
        }

        while (remaining > 0) {
                switch (*start++) {
                case '\0':
                        return "";
                case '/':
                        remaining--;
                        break;
                }
        }

        return start;
}

static const char *rstrip_ref_components(const char *refname, int len)
{
        long remaining = len;
        char *start = xstrdup(refname);

        if (len < 0) {
                int i;
                const char *p = refname;

                /* Find total no of '/' separated path-components */
                for (i = 0; p[i]; p[i] == '/' ? i++ : *p++)
                        ;
                /*
                 * The number of components we need to strip is now
                 * the total minus the components to be left (Plus one
                 * because we count the number of '/', but the number
                 * of components is one more than the no of '/').
                 */
                remaining = i + len + 1;
        }

        while (remaining-- > 0) {
                char *p = strrchr(start, '/');
                if (p == NULL)
                        return "";
                else
                        p[0] = '\0';
        }
        return start;
}

static const char *show_ref(struct refname_atom *atom, const char *refname)
{
        if (atom->option == R_SHORT)
                return shorten_unambiguous_ref(refname, warn_ambiguous_refs);
        else if (atom->option == R_LSTRIP)
                return lstrip_ref_components(refname, atom->lstrip);
        else if (atom->option == R_RSTRIP)
                return rstrip_ref_components(refname, atom->rstrip);
        else
                return refname;
}

static void fill_remote_ref_details(struct used_atom *atom, const char *refname,
                                    struct branch *branch, const char **s)
{
        int num_ours, num_theirs;
        if (atom->u.remote_ref.option == RR_REF)
                *s = show_ref(&atom->u.remote_ref.refname, refname);
        else if (atom->u.remote_ref.option == RR_TRACK) {
                if (stat_tracking_info(branch, &num_ours, &num_theirs,
                                       NULL, AHEAD_BEHIND_FULL) < 0) {
                        *s = xstrdup(msgs.gone);
                } else if (!num_ours && !num_theirs)
                        *s = "";
                else if (!num_ours)
                        *s = xstrfmt(msgs.behind, num_theirs);
                else if (!num_theirs)
                        *s = xstrfmt(msgs.ahead, num_ours);
                else
                        *s = xstrfmt(msgs.ahead_behind,
                                     num_ours, num_theirs);
                if (!atom->u.remote_ref.nobracket && *s[0]) {
                        const char *to_free = *s;
                        *s = xstrfmt("[%s]", *s);
                        free((void *)to_free);
                }
        } else if (atom->u.remote_ref.option == RR_TRACKSHORT) {
                if (stat_tracking_info(branch, &num_ours, &num_theirs,
                                       NULL, AHEAD_BEHIND_FULL) < 0)
                        return;

                if (!num_ours && !num_theirs)
                        *s = "=";
                else if (!num_ours)
                        *s = "<";
                else if (!num_theirs)
                        *s = ">";
                else
                        *s = "<>";
        } else if (atom->u.remote_ref.option == RR_REMOTE_NAME) {
                int explicit;
                const char *remote = atom->u.remote_ref.push ?
                        pushremote_for_branch(branch, &explicit) :
                        remote_for_branch(branch, &explicit);
                if (explicit)
                        *s = xstrdup(remote);
                else
                        *s = "";
        } else if (atom->u.remote_ref.option == RR_REMOTE_REF) {
                int explicit;
                const char *merge;

                merge = remote_ref_for_branch(branch, atom->u.remote_ref.push,
                                              &explicit);
                if (explicit)
                        *s = xstrdup(merge);
                else
                        *s = "";
        } else
                die("BUG: unhandled RR_* enum");
}

char *get_head_description(void)
{
        struct strbuf desc = STRBUF_INIT;
        struct wt_status_state state;
        memset(&state, 0, sizeof(state));
        wt_status_get_state(&state, 1);
        if (state.rebase_in_progress ||
            state.rebase_interactive_in_progress)
                strbuf_addf(&desc, _("(no branch, rebasing %s)"),
                            state.branch);
        else if (state.bisect_in_progress)
                strbuf_addf(&desc, _("(no branch, bisect started on %s)"),
                            state.branch);
        else if (state.detached_from) {
                if (state.detached_at)
                        /*
                         * TRANSLATORS: make sure this matches "HEAD
                         * detached at " in wt-status.c
                         */
                        strbuf_addf(&desc, _("(HEAD detached at %s)"),
                                state.detached_from);
                else
                        /*
                         * TRANSLATORS: make sure this matches "HEAD
                         * detached from " in wt-status.c
                         */
                        strbuf_addf(&desc, _("(HEAD detached from %s)"),
                                state.detached_from);
        }
        else
                strbuf_addstr(&desc, _("(no branch)"));
        free(state.branch);
        free(state.onto);
        free(state.detached_from);
        return strbuf_detach(&desc, NULL);
}

static const char *get_symref(struct used_atom *atom, struct ref_array_item *ref)
{
        if (!ref->symref)
                return "";
        else
                return show_ref(&atom->u.refname, ref->symref);
}

static const char *get_refname(struct used_atom *atom, struct ref_array_item *ref)
{
        if (ref->kind & FILTER_REFS_DETACHED_HEAD)
                return get_head_description();
        return show_ref(&atom->u.refname, ref->refname);
}

static void get_object(struct ref_array_item *ref, const struct object_id *oid,
                       int deref, struct object **obj)
{
        int eaten;
        unsigned long size;
        void *buf = get_obj(oid, obj, &size, &eaten);
        if (!buf)
                die(_("missing object %s for %s"),
                    oid_to_hex(oid), ref->refname);
        if (!*obj)
                die(_("parse_object_buffer failed on %s for %s"),
                    oid_to_hex(oid), ref->refname);

        grab_values(ref->value, deref, *obj, buf, size);
        if (!eaten)
                free(buf);
}

/*
 * Parse the object referred by ref, and grab needed value.
 */
static void populate_value(struct ref_array_item *ref)
{
        struct object *obj;
        int i;
        const struct object_id *tagged;

        ref->value = xcalloc(used_atom_cnt, sizeof(struct atom_value));

        if (need_symref && (ref->flag & REF_ISSYMREF) && !ref->symref) {
                ref->symref = resolve_refdup(ref->refname, RESOLVE_REF_READING,
                                             NULL, NULL);
                if (!ref->symref)
                        ref->symref = "";
        }

        /* Fill in specials first */
        for (i = 0; i < used_atom_cnt; i++) {
                struct used_atom *atom = &used_atom[i];
                const char *name = used_atom[i].name;
                struct atom_value *v = &ref->value[i];
                int deref = 0;
                const char *refname;
                struct branch *branch = NULL;

                v->handler = append_atom;
                v->atom = atom;

                if (*name == '*') {
                        deref = 1;
                        name++;
                }

                if (starts_with(name, "refname"))
                        refname = get_refname(atom, ref);
                else if (starts_with(name, "symref"))
                        refname = get_symref(atom, ref);
                else if (starts_with(name, "upstream")) {
                        const char *branch_name;
                        /* only local branches may have an upstream */
                        if (!skip_prefix(ref->refname, "refs/heads/",
                                         &branch_name))
                                continue;
                        branch = branch_get(branch_name);

                        refname = branch_get_upstream(branch, NULL);
                        if (refname)
                                fill_remote_ref_details(atom, refname, branch, &v->s);
                        continue;
                } else if (atom->u.remote_ref.push) {
                        const char *branch_name;
                        if (!skip_prefix(ref->refname, "refs/heads/",
                                         &branch_name))
                                continue;
                        branch = branch_get(branch_name);

                        if (atom->u.remote_ref.push_remote)
                                refname = NULL;
                        else {
                                refname = branch_get_push(branch, NULL);
                                if (!refname)
                                        continue;
                        }
                        fill_remote_ref_details(atom, refname, branch, &v->s);
                        continue;
                } else if (starts_with(name, "color:")) {
                        v->s = atom->u.color;
                        continue;
                } else if (!strcmp(name, "flag")) {
                        char buf[256], *cp = buf;
                        if (ref->flag & REF_ISSYMREF)
                                cp = copy_advance(cp, ",symref");
                        if (ref->flag & REF_ISPACKED)
                                cp = copy_advance(cp, ",packed");
                        if (cp == buf)
                                v->s = "";
                        else {
                                *cp = '\0';
                                v->s = xstrdup(buf + 1);
                        }
                        continue;
                } else if (!deref && grab_objectname(name, ref->objectname.hash, v, atom)) {
                        continue;
                } else if (!strcmp(name, "HEAD")) {
                        if (atom->u.head && !strcmp(ref->refname, atom->u.head))
                                v->s = "*";
                        else
                                v->s = " ";
                        continue;
                } else if (starts_with(name, "align")) {
                        v->handler = align_atom_handler;
                        continue;
                } else if (!strcmp(name, "end")) {
                        v->handler = end_atom_handler;
                        continue;
                } else if (starts_with(name, "if")) {
                        const char *s;

                        if (skip_prefix(name, "if:", &s))
                                v->s = xstrdup(s);
                        v->handler = if_atom_handler;
                        continue;
                } else if (!strcmp(name, "then")) {
                        v->handler = then_atom_handler;
                        continue;
                } else if (!strcmp(name, "else")) {
                        v->handler = else_atom_handler;
                        continue;
                } else
                        continue;

                if (!deref)
                        v->s = refname;
                else
                        v->s = xstrfmt("%s^{}", refname);
        }

        for (i = 0; i < used_atom_cnt; i++) {
                struct atom_value *v = &ref->value[i];
                if (v->s == NULL)
                        break;
        }
        if (used_atom_cnt <= i)
                return;

        get_object(ref, &ref->objectname, 0, &obj);

        /*
         * If there is no atom that wants to know about tagged
         * object, we are done.
         */
        if (!need_tagged || (obj->type != OBJ_TAG))
                return;

        /*
         * If it is a tag object, see if we use a value that derefs
         * the object, and if we do grab the object it refers to.
         */
        tagged = &((struct tag *)obj)->tagged->oid;

        /*
         * NEEDSWORK: This derefs tag only once, which
         * is good to deal with chains of trust, but
         * is not consistent with what deref_tag() does
         * which peels the onion to the core.
         */
        get_object(ref, tagged, 1, &obj);
}

/*
 * Given a ref, return the value for the atom.  This lazily gets value
 * out of the object by calling populate value.
 */
static void get_ref_atom_value(struct ref_array_item *ref, int atom, struct atom_value **v)
{
        if (!ref->value) {
                populate_value(ref);
                fill_missing_values(ref->value);
        }
        *v = &ref->value[atom];
}

/*
 * Unknown has to be "0" here, because that's the default value for
 * contains_cache slab entries that have not yet been assigned.
 */
enum contains_result {
        CONTAINS_UNKNOWN = 0,
        CONTAINS_NO,
        CONTAINS_YES
};

define_commit_slab(contains_cache, enum contains_result);

struct ref_filter_cbdata {
        struct ref_array *array;
        struct ref_filter *filter;
        struct contains_cache contains_cache;
        struct contains_cache no_contains_cache;
};

/*
 * Mimicking the real stack, this stack lives on the heap, avoiding stack
 * overflows.
 *
 * At each recursion step, the stack items points to the commits whose
 * ancestors are to be inspected.
 */
struct contains_stack {
        int nr, alloc;
        struct contains_stack_entry {
                struct commit *commit;
                struct commit_list *parents;
        } *contains_stack;
};

static int in_commit_list(const struct commit_list *want, struct commit *c)
{
        for (; want; want = want->next)
                if (!oidcmp(&want->item->object.oid, &c->object.oid))
                        return 1;
        return 0;
}

/*
 * Test whether the candidate or one of its parents is contained in the list.
 * Do not recurse to find out, though, but return -1 if inconclusive.
 */
static enum contains_result contains_test(struct commit *candidate,
                                          const struct commit_list *want,
                                          struct contains_cache *cache)
{
        enum contains_result *cached = contains_cache_at(cache, candidate);

        /* If we already have the answer cached, return that. */
        if (*cached)
                return *cached;

        /* or are we it? */
        if (in_commit_list(want, candidate)) {
                *cached = CONTAINS_YES;
                return CONTAINS_YES;
        }

        /* Otherwise, we don't know; prepare to recurse */
        parse_commit_or_die(candidate);
        return CONTAINS_UNKNOWN;
}

static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
{
        ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
        contains_stack->contains_stack[contains_stack->nr].commit = candidate;
        contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
}

static enum contains_result contains_tag_algo(struct commit *candidate,
                                              const struct commit_list *want,
                                              struct contains_cache *cache)
{
        struct contains_stack contains_stack = { 0, 0, NULL };
        enum contains_result result = contains_test(candidate, want, cache);

        if (result != CONTAINS_UNKNOWN)
                return result;

        push_to_contains_stack(candidate, &contains_stack);
        while (contains_stack.nr) {
                struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
                struct commit *commit = entry->commit;
                struct commit_list *parents = entry->parents;

                if (!parents) {
                        *contains_cache_at(cache, commit) = CONTAINS_NO;
                        contains_stack.nr--;
                }
                /*
                 * If we just popped the stack, parents->item has been marked,
                 * therefore contains_test will return a meaningful yes/no.
                 */
                else switch (contains_test(parents->item, want, cache)) {
                case CONTAINS_YES:
                        *contains_cache_at(cache, commit) = CONTAINS_YES;
                        contains_stack.nr--;
                        break;
                case CONTAINS_NO:
                        entry->parents = parents->next;
                        break;
                case CONTAINS_UNKNOWN:
                        push_to_contains_stack(parents->item, &contains_stack);
                        break;
                }
        }
        free(contains_stack.contains_stack);
        return contains_test(candidate, want, cache);
}

static int commit_contains(struct ref_filter *filter, struct commit *commit,
                           struct commit_list *list, struct contains_cache *cache)
{
        if (filter->with_commit_tag_algo)
                return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
        return is_descendant_of(commit, list);
}

/*
 * Return 1 if the refname matches one of the patterns, otherwise 0.
 * A pattern can be a literal prefix (e.g. a refname "refs/heads/master"
 * matches a pattern "refs/heads/mas") or a wildcard (e.g. the same ref
 * matches "refs/heads/mas*", too).
 */
static int match_pattern(const struct ref_filter *filter, const char *refname)
{
        const char **patterns = filter->name_patterns;
        unsigned flags = 0;

        if (filter->ignore_case)
                flags |= WM_CASEFOLD;

        /*
         * When no '--format' option is given we need to skip the prefix
         * for matching refs of tags and branches.
         */
        (void)(skip_prefix(refname, "refs/tags/", &refname) ||
               skip_prefix(refname, "refs/heads/", &refname) ||
               skip_prefix(refname, "refs/remotes/", &refname) ||
               skip_prefix(refname, "refs/", &refname));

        for (; *patterns; patterns++) {
                if (!wildmatch(*patterns, refname, flags))
                        return 1;
        }
        return 0;
}

/*
 * Return 1 if the refname matches one of the patterns, otherwise 0.
 * A pattern can be path prefix (e.g. a refname "refs/heads/master"
 * matches a pattern "refs/heads/" but not "refs/heads/m") or a
 * wildcard (e.g. the same ref matches "refs/heads/m*", too).
 */
static int match_name_as_path(const struct ref_filter *filter, const char *refname)
{
        const char **pattern = filter->name_patterns;
        int namelen = strlen(refname);
        unsigned flags = WM_PATHNAME;

        if (filter->ignore_case)
                flags |= WM_CASEFOLD;

        for (; *pattern; pattern++) {
                const char *p = *pattern;
                int plen = strlen(p);

                if ((plen <= namelen) &&
                    !strncmp(refname, p, plen) &&
                    (refname[plen] == '\0' ||
                     refname[plen] == '/' ||
                     p[plen-1] == '/'))
                        return 1;
                if (!wildmatch(p, refname, WM_PATHNAME))
                        return 1;
        }
        return 0;
}

/* Return 1 if the refname matches one of the patterns, otherwise 0. */
static int filter_pattern_match(struct ref_filter *filter, const char *refname)
{
        if (!*filter->name_patterns)
                return 1; /* No pattern always matches */
        if (filter->match_as_path)
                return match_name_as_path(filter, refname);
        return match_pattern(filter, refname);
}

/*
 * Find the longest prefix of pattern we can pass to
 * `for_each_fullref_in()`, namely the part of pattern preceding the
 * first glob character. (Note that `for_each_fullref_in()` is
 * perfectly happy working with a prefix that doesn't end at a
 * pathname component boundary.)
 */
static void find_longest_prefix(struct strbuf *out, const char *pattern)
{
        const char *p;

        for (p = pattern; *p && !is_glob_special(*p); p++)
                ;

        strbuf_add(out, pattern, p - pattern);
}

/*
 * This is the same as for_each_fullref_in(), but it tries to iterate
 * only over the patterns we'll care about. Note that it _doesn't_ do a full
 * pattern match, so the callback still has to match each ref individually.
 */
static int for_each_fullref_in_pattern(struct ref_filter *filter,
                                       each_ref_fn cb,
                                       void *cb_data,
                                       int broken)
{
        struct strbuf prefix = STRBUF_INIT;
        int ret;

        if (!filter->match_as_path) {
                /*
                 * in this case, the patterns are applied after
                 * prefixes like "refs/heads/" etc. are stripped off,
                 * so we have to look at everything:
                 */
                return for_each_fullref_in("", cb, cb_data, broken);
        }

        if (!filter->name_patterns[0]) {
                /* no patterns; we have to look at everything */
                return for_each_fullref_in("", cb, cb_data, broken);
        }

        if (filter->name_patterns[1]) {
                /*
                 * multiple patterns; in theory this could still work as long
                 * as the patterns are disjoint. We'd just make multiple calls
                 * to for_each_ref(). But if they're not disjoint, we'd end up
                 * reporting the same ref multiple times. So let's punt on that
                 * for now.
                 */
                return for_each_fullref_in("", cb, cb_data, broken);
        }

        find_longest_prefix(&prefix, filter->name_patterns[0]);

        ret = for_each_fullref_in(prefix.buf, cb, cb_data, broken);
        strbuf_release(&prefix);
        return ret;
}

/*
 * Given a ref (sha1, refname), check if the ref belongs to the array
 * of sha1s. If the given ref is a tag, check if the given tag points
 * at one of the sha1s in the given sha1 array.
 * the given sha1_array.
 * NEEDSWORK:
 * 1. Only a single level of inderection is obtained, we might want to
 * change this to account for multiple levels (e.g. annotated tags
 * pointing to annotated tags pointing to a commit.)
 * 2. As the refs are cached we might know what refname peels to without
 * the need to parse the object via parse_object(). peel_ref() might be a
 * more efficient alternative to obtain the pointee.
 */
static const struct object_id *match_points_at(struct oid_array *points_at,
                                               const struct object_id *oid,
                                               const char *refname)
{
        const struct object_id *tagged_oid = NULL;
        struct object *obj;

        if (oid_array_lookup(points_at, oid) >= 0)
                return oid;
        obj = parse_object(oid);
        if (!obj)
                die(_("malformed object at '%s'"), refname);
        if (obj->type == OBJ_TAG)
                tagged_oid = &((struct tag *)obj)->tagged->oid;
        if (tagged_oid && oid_array_lookup(points_at, tagged_oid) >= 0)
                return tagged_oid;
        return NULL;
}

/* Allocate space for a new ref_array_item and copy the objectname and flag to it */
static struct ref_array_item *new_ref_array_item(const char *refname,
                                                 const unsigned char *objectname,
                                                 int flag)
{
        struct ref_array_item *ref;
        FLEX_ALLOC_STR(ref, refname, refname);
        hashcpy(ref->objectname.hash, objectname);
        ref->flag = flag;

        return ref;
}

static int ref_kind_from_refname(const char *refname)
{
        unsigned int i;

        static struct {
                const char *prefix;
                unsigned int kind;
        } ref_kind[] = {
                { "refs/heads/" , FILTER_REFS_BRANCHES },
                { "refs/remotes/" , FILTER_REFS_REMOTES },
                { "refs/tags/", FILTER_REFS_TAGS}
        };

        if (!strcmp(refname, "HEAD"))
                return FILTER_REFS_DETACHED_HEAD;

        for (i = 0; i < ARRAY_SIZE(ref_kind); i++) {
                if (starts_with(refname, ref_kind[i].prefix))
                        return ref_kind[i].kind;
        }

        return FILTER_REFS_OTHERS;
}

static int filter_ref_kind(struct ref_filter *filter, const char *refname)
{
        if (filter->kind == FILTER_REFS_BRANCHES ||
            filter->kind == FILTER_REFS_REMOTES ||
            filter->kind == FILTER_REFS_TAGS)
                return filter->kind;
        return ref_kind_from_refname(refname);
}

/*
 * A call-back given to for_each_ref().  Filter refs and keep them for
 * later object processing.
 */
static int ref_filter_handler(const char *refname, const struct object_id *oid, int flag, void *cb_data)
{
        struct ref_filter_cbdata *ref_cbdata = cb_data;
        struct ref_filter *filter = ref_cbdata->filter;
        struct ref_array_item *ref;
        struct commit *commit = NULL;
        unsigned int kind;

        if (flag & REF_BAD_NAME) {
                warning(_("ignoring ref with broken name %s"), refname);
                return 0;
        }

        if (flag & REF_ISBROKEN) {
                warning(_("ignoring broken ref %s"), refname);
                return 0;
        }

        /* Obtain the current ref kind from filter_ref_kind() and ignore unwanted refs. */
        kind = filter_ref_kind(filter, refname);
        if (!(kind & filter->kind))
                return 0;

        if (!filter_pattern_match(filter, refname))
                return 0;

        if (filter->points_at.nr && !match_points_at(&filter->points_at, oid, refname))
                return 0;

        /*
         * A merge filter is applied on refs pointing to commits. Hence
         * obtain the commit using the 'oid' available and discard all
         * non-commits early. The actual filtering is done later.
         */
        if (filter->merge_commit || filter->with_commit || filter->no_commit || filter->verbose) {
                commit = lookup_commit_reference_gently(oid, 1);
                if (!commit)
                        return 0;
                /* We perform the filtering for the '--contains' option... */
                if (filter->with_commit &&
                    !commit_contains(filter, commit, filter->with_commit, &ref_cbdata->contains_cache))
                        return 0;
                /* ...or for the `--no-contains' option */
                if (filter->no_commit &&
                    commit_contains(filter, commit, filter->no_commit, &ref_cbdata->no_contains_cache))
                        return 0;
        }

        /*
         * We do not open the object yet; sort may only need refname
         * to do its job and the resulting list may yet to be pruned
         * by maxcount logic.
         */
        ref = new_ref_array_item(refname, oid->hash, flag);
        ref->commit = commit;

        REALLOC_ARRAY(ref_cbdata->array->items, ref_cbdata->array->nr + 1);
        ref_cbdata->array->items[ref_cbdata->array->nr++] = ref;
        ref->kind = kind;
        return 0;
}

/*  Free memory allocated for a ref_array_item */
static void free_array_item(struct ref_array_item *item)
{
        free((char *)item->symref);
        free(item);
}

/* Free all memory allocated for ref_array */
void ref_array_clear(struct ref_array *array)
{
        int i;

        for (i = 0; i < array->nr; i++)
                free_array_item(array->items[i]);
        FREE_AND_NULL(array->items);
        array->nr = array->alloc = 0;
}

static void do_merge_filter(struct ref_filter_cbdata *ref_cbdata)
{
        struct rev_info revs;
        int i, old_nr;
        struct ref_filter *filter = ref_cbdata->filter;
        struct ref_array *array = ref_cbdata->array;
        struct commit **to_clear = xcalloc(sizeof(struct commit *), array->nr);

        init_revisions(&revs, NULL);

        for (i = 0; i < array->nr; i++) {
                struct ref_array_item *item = array->items[i];
                add_pending_object(&revs, &item->commit->object, item->refname);
                to_clear[i] = item->commit;
        }

        filter->merge_commit->object.flags |= UNINTERESTING;
        add_pending_object(&revs, &filter->merge_commit->object, "");

        revs.limited = 1;
        if (prepare_revision_walk(&revs))
                die(_("revision walk setup failed"));

        old_nr = array->nr;
        array->nr = 0;

        for (i = 0; i < old_nr; i++) {
                struct ref_array_item *item = array->items[i];
                struct commit *commit = item->commit;

                int is_merged = !!(commit->object.flags & UNINTERESTING);

                if (is_merged == (filter->merge == REF_FILTER_MERGED_INCLUDE))
                        array->items[array->nr++] = array->items[i];
                else
                        free_array_item(item);
        }

        clear_commit_marks_many(old_nr, to_clear, ALL_REV_FLAGS);
        clear_commit_marks(filter->merge_commit, ALL_REV_FLAGS);
        free(to_clear);
}

/*
 * API for filtering a set of refs. Based on the type of refs the user
 * has requested, we iterate through those refs and apply filters
 * as per the given ref_filter structure and finally store the
 * filtered refs in the ref_array structure.
 */
int filter_refs(struct ref_array *array, struct ref_filter *filter, unsigned int type)
{
        struct ref_filter_cbdata ref_cbdata;
        int ret = 0;
        unsigned int broken = 0;

        ref_cbdata.array = array;
        ref_cbdata.filter = filter;

        if (type & FILTER_REFS_INCLUDE_BROKEN)
                broken = 1;
        filter->kind = type & FILTER_REFS_KIND_MASK;

        init_contains_cache(&ref_cbdata.contains_cache);
        init_contains_cache(&ref_cbdata.no_contains_cache);

        /*  Simple per-ref filtering */
        if (!filter->kind)
                die("filter_refs: invalid type");
        else {
                /*
                 * For common cases where we need only branches or remotes or tags,
                 * we only iterate through those refs. If a mix of refs is needed,
                 * we iterate over all refs and filter out required refs with the help
                 * of filter_ref_kind().
                 */
                if (filter->kind == FILTER_REFS_BRANCHES)
                        ret = for_each_fullref_in("refs/heads/", ref_filter_handler, &ref_cbdata, broken);
                else if (filter->kind == FILTER_REFS_REMOTES)
                        ret = for_each_fullref_in("refs/remotes/", ref_filter_handler, &ref_cbdata, broken);
                else if (filter->kind == FILTER_REFS_TAGS)
                        ret = for_each_fullref_in("refs/tags/", ref_filter_handler, &ref_cbdata, broken);
                else if (filter->kind & FILTER_REFS_ALL)
                        ret = for_each_fullref_in_pattern(filter, ref_filter_handler, &ref_cbdata, broken);
                if (!ret && (filter->kind & FILTER_REFS_DETACHED_HEAD))
                        head_ref(ref_filter_handler, &ref_cbdata);
        }

        clear_contains_cache(&ref_cbdata.contains_cache);
        clear_contains_cache(&ref_cbdata.no_contains_cache);

        /*  Filters that need revision walking */
        if (filter->merge_commit)
                do_merge_filter(&ref_cbdata);

        return ret;
}

static int cmp_ref_sorting(struct ref_sorting *s, struct ref_array_item *a, struct ref_array_item *b)
{
        struct atom_value *va, *vb;
        int cmp;
        cmp_type cmp_type = used_atom[s->atom].type;
        int (*cmp_fn)(const char *, const char *);

        get_ref_atom_value(a, s->atom, &va);
        get_ref_atom_value(b, s->atom, &vb);
        cmp_fn = s->ignore_case ? strcasecmp : strcmp;
        if (s->version)
                cmp = versioncmp(va->s, vb->s);
        else if (cmp_type == FIELD_STR)
                cmp = cmp_fn(va->s, vb->s);
        else {
                if (va->value < vb->value)
                        cmp = -1;
                else if (va->value == vb->value)
                        cmp = cmp_fn(a->refname, b->refname);
                else
                        cmp = 1;
        }

        return (s->reverse) ? -cmp : cmp;
}

static int compare_refs(const void *a_, const void *b_, void *ref_sorting)
{
        struct ref_array_item *a = *((struct ref_array_item **)a_);
        struct ref_array_item *b = *((struct ref_array_item **)b_);
        struct ref_sorting *s;

        for (s = ref_sorting; s; s = s->next) {
                int cmp = cmp_ref_sorting(s, a, b);
                if (cmp)
                        return cmp;
        }
        return 0;
}

void ref_array_sort(struct ref_sorting *sorting, struct ref_array *array)
{
        QSORT_S(array->items, array->nr, compare_refs, sorting);
}

static void append_literal(const char *cp, const char *ep, struct ref_formatting_state *state)
{
        struct strbuf *s = &state->stack->output;

        while (*cp && (!ep || cp < ep)) {
                if (*cp == '%') {
                        if (cp[1] == '%')
                                cp++;
                        else {
                                int ch = hex2chr(cp + 1);
                                if (0 <= ch) {
                                        strbuf_addch(s, ch);
                                        cp += 3;
                                        continue;
                                }
                        }
                }
                strbuf_addch(s, *cp);
                cp++;
        }
}

int format_ref_array_item(struct ref_array_item *info,
                           const struct ref_format *format,
                           struct strbuf *final_buf,
                           struct strbuf *error_buf)
{
        const char *cp, *sp, *ep;
        struct ref_formatting_state state = REF_FORMATTING_STATE_INIT;

        state.quote_style = format->quote_style;
        push_stack_element(&state.stack);

        for (cp = format->format; *cp && (sp = find_next(cp)); cp = ep + 1) {
                struct atom_value *atomv;
                int pos;

                ep = strchr(sp, ')');
                if (cp < sp)
                        append_literal(cp, sp, &state);
                pos = parse_ref_filter_atom(format, sp + 2, ep, error_buf);
                if (pos < 0) {
                        pop_stack_element(&state.stack);
                        return -1;
                }
                get_ref_atom_value(info, pos, &atomv);
                if (atomv->handler(atomv, &state, error_buf)) {
                        pop_stack_element(&state.stack);
                        return -1;
                }
        }
        if (*cp) {
                sp = cp + strlen(cp);
                append_literal(cp, sp, &state);
        }
        if (format->need_color_reset_at_eol) {
                struct atom_value resetv;
                resetv.s = GIT_COLOR_RESET;
                if (append_atom(&resetv, &state, error_buf)) {
                        pop_stack_element(&state.stack);
                        return -1;
                }
        }
        if (state.stack->prev) {
                pop_stack_element(&state.stack);
                return strbuf_addf_ret(error_buf, -1, _("format: %%(end) atom missing"));
        }
        strbuf_addbuf(final_buf, &state.stack->output);
        pop_stack_element(&state.stack);
        return 0;
}

void show_ref_array_item(struct ref_array_item *info,
                         const struct ref_format *format)
{
        struct strbuf final_buf = STRBUF_INIT;
        struct strbuf error_buf = STRBUF_INIT;

        if (format_ref_array_item(info, format, &final_buf, &error_buf))
                die("%s", error_buf.buf);
        fwrite(final_buf.buf, 1, final_buf.len, stdout);
        strbuf_release(&error_buf);
        strbuf_release(&final_buf);
        putchar('\n');
}

void pretty_print_ref(const char *name, const unsigned char *sha1,
                      const struct ref_format *format)
{
        struct ref_array_item *ref_item;
        ref_item = new_ref_array_item(name, sha1, 0);
        ref_item->kind = ref_kind_from_refname(name);
        show_ref_array_item(ref_item, format);
        free_array_item(ref_item);
}

static int parse_sorting_atom(const char *atom)
{
        /*
         * This parses an atom using a dummy ref_format, since we don't
         * actually care about the formatting details.
         */
        struct ref_format dummy = REF_FORMAT_INIT;
        const char *end = atom + strlen(atom);
        struct strbuf err = STRBUF_INIT;
        int res = parse_ref_filter_atom(&dummy, atom, end, &err);
        if (res < 0)
                die("%s", err.buf);
        strbuf_release(&err);
        return res;
}

/*  If no sorting option is given, use refname to sort as default */
struct ref_sorting *ref_default_sorting(void)
{
        static const char cstr_name[] = "refname";

        struct ref_sorting *sorting = xcalloc(1, sizeof(*sorting));

        sorting->next = NULL;
        sorting->atom = parse_sorting_atom(cstr_name);
        return sorting;
}

void parse_ref_sorting(struct ref_sorting **sorting_tail, const char *arg)
{
        struct ref_sorting *s;

        s = xcalloc(1, sizeof(*s));
        s->next = *sorting_tail;
        *sorting_tail = s;

        if (*arg == '-') {
                s->reverse = 1;
                arg++;
        }
        if (skip_prefix(arg, "version:", &arg) ||
            skip_prefix(arg, "v:", &arg))
                s->version = 1;
        s->atom = parse_sorting_atom(arg);
}

int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset)
{
        if (!arg) /* should --no-sort void the list ? */
                return -1;
        parse_ref_sorting(opt->value, arg);
        return 0;
}

int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
{
        struct ref_filter *rf = opt->value;
        struct object_id oid;
        int no_merged = starts_with(opt->long_name, "no");

        if (rf->merge) {
                if (no_merged) {
                        return opterror(opt, "is incompatible with --merged", 0);
                } else {
                        return opterror(opt, "is incompatible with --no-merged", 0);
                }
        }

        rf->merge = no_merged
                ? REF_FILTER_MERGED_OMIT
                : REF_FILTER_MERGED_INCLUDE;

        if (get_oid(arg, &oid))
                die(_("malformed object name %s"), arg);

        rf->merge_commit = lookup_commit_reference_gently(&oid, 0);
        if (!rf->merge_commit)
                return opterror(opt, "must point to a commit", 0);

        return 0;
}