Documentation: reword rebase summary

[git.git] / ref-filter.c

#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"

typedef enum { FIELD_STR, FIELD_ULONG, FIELD_TIME } cmp_type;

static struct {
        const char *name;
        cmp_type cmp_type;
} valid_atom[] = {
        { "refname" },
        { "objecttype" },
        { "objectsize", FIELD_ULONG },
        { "objectname" },
        { "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" },
        { "body" },
        { "contents" },
        { "upstream" },
        { "push" },
        { "symref" },
        { "flag" },
        { "HEAD" },
        { "color" },
        { "align" },
        { "end" },
};

#define REF_FORMATTING_STATE_INIT  { 0, NULL }

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

struct contents {
        unsigned int lines;
        struct object_id oid;
};

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;
        union {
                struct align align;
                struct contents contents;
        } u;
        void (*handler)(struct atom_value *atomv, struct ref_formatting_state *state);
        unsigned long ul; /* used for sorting when not FIELD_STR */
};

/*
 * An atom is a valid field atom listed above, 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 const char **used_atom;
static cmp_type *used_atom_type;
static int used_atom_cnt, need_tagged, need_symref;
static int need_color_reset_at_eol;

/*
 * Used to parse format string and sort specifiers
 */
int parse_ref_filter_atom(const char *atom, const char *ep)
{
        const char *sp;
        int i, at;

        sp = atom;
        if (*sp == '*' && sp < ep)
                sp++; /* deref */
        if (ep <= sp)
                die("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]);
                if (len == ep - atom && !memcmp(used_atom[i], atom, len))
                        return i;
        }

        /* Is the atom a valid one? */
        for (i = 0; i < ARRAY_SIZE(valid_atom); i++) {
                int len = strlen(valid_atom[i].name);
                /*
                 * 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.
                 */
                const char *formatp = strchr(sp, ':');
                if (!formatp || ep < formatp)
                        formatp = ep;
                if (len == formatp - sp && !memcmp(valid_atom[i].name, sp, len))
                        break;
        }

        if (ARRAY_SIZE(valid_atom) <= i)
                die("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);
        REALLOC_ARRAY(used_atom_type, used_atom_cnt);
        used_atom[at] = xmemdupz(atom, ep - atom);
        used_atom_type[at] = valid_atom[i].cmp_type;
        if (*atom == '*')
                need_tagged = 1;
        if (!strcmp(used_atom[at], "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 void append_atom(struct atom_value *v, struct ref_formatting_state *state)
{
        /*
         * 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);
}

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 align *align = (struct align *)stack->at_end_data;
        struct strbuf s = STRBUF_INIT;

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

static void align_atom_handler(struct atom_value *atomv, struct ref_formatting_state *state)
{
        struct ref_formatting_stack *new;

        push_stack_element(&state->stack);
        new = state->stack;
        new->at_end = end_align_handler;
        new->at_end_data = &atomv->u.align;
}

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

        if (!current->at_end)
                die(_("format: %%(end) atom used without corresponding atom"));
        current->at_end(current);

        /*
         * 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 (!state->stack->prev->prev) {
                quote_formatting(&s, current->output.buf, state->quote_style);
                strbuf_swap(&current->output, &s);
        }
        strbuf_release(&s);
        pop_stack_element(&state->stack);
}

static int match_atom_name(const char *name, const char *atom_name, const char **val)
{
        const char *body;

        if (!skip_prefix(name, atom_name, &body))
                return 0; /* doesn't even begin with "atom_name" */
        if (!body[0]) {
                *val = NULL; /* %(atom_name) and no customization */
                return 1;
        }
        if (body[0] != ':')
                return 0; /* "atom_namefoo" is not "atom_name" or "atom_name:..." */
        *val = body + 1; /* "atom_name:val" */
        return 1;
}

/*
 * 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(const char *format)
{
        const char *cp, *sp;

        need_color_reset_at_eol = 0;
        for (cp = format; *cp && (sp = find_next(cp)); ) {
                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(sp + 2, ep);
                cp = ep + 1;

                if (skip_prefix(used_atom[at], "color:", &color))
                        need_color_reset_at_eol = !!strcmp(color, "reset");
        }
        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 unsigned char *sha1, struct object **obj, unsigned long *sz, int *eaten)
{
        enum object_type type;
        void *buf = read_sha1_file(sha1, &type, sz);

        if (buf)
                *obj = parse_object_buffer(sha1, type, *sz, buf, eaten);
        else
                *obj = NULL;
        return buf;
}

static int grab_objectname(const char *name, const unsigned char *sha1,
                            struct atom_value *v)
{
        if (!strcmp(name, "objectname")) {
                v->s = xstrdup(sha1_to_hex(sha1));
                return 1;
        }
        if (!strcmp(name, "objectname:short")) {
                v->s = xstrdup(find_unique_abbrev(sha1, DEFAULT_ABBREV));
                return 1;
        }
        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];
                struct atom_value *v = &val[i];
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (!strcmp(name, "objecttype"))
                        v->s = typename(obj->type);
                else if (!strcmp(name, "objectsize")) {
                        v->ul = sz;
                        v->s = xstrfmt("%lu", sz);
                }
                else if (deref)
                        grab_objectname(name, obj->oid.hash, v);
        }
}

/* 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];
                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 = typename(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];
                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->ul = commit_list_count(commit->parents);
                        v->s = xstrfmt("%lu", v->ul);
                }
                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;
        unsigned long 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 = strtoul(eoemail + 2, &zone, 10);
        if (timestamp == ULONG_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->ul = timestamp;
        return;
 bad:
        v->s = "";
        v->ul = 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];
                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];
                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++) {
                const char *name = used_atom[i];
                struct atom_value *v = &val[i];
                const char *valp = NULL;
                if (!!deref != (*name == '*'))
                        continue;
                if (deref)
                        name++;
                if (strcmp(name, "subject") &&
                    strcmp(name, "body") &&
                    strcmp(name, "contents") &&
                    strcmp(name, "contents:subject") &&
                    strcmp(name, "contents:body") &&
                    strcmp(name, "contents:signature") &&
                    !starts_with(name, "contents:lines="))
                        continue;
                if (!subpos)
                        find_subpos(buf, sz,
                                    &subpos, &sublen,
                                    &bodypos, &bodylen, &nonsiglen,
                                    &sigpos, &siglen);

                if (!strcmp(name, "subject"))
                        v->s = copy_subject(subpos, sublen);
                else if (!strcmp(name, "contents:subject"))
                        v->s = copy_subject(subpos, sublen);
                else if (!strcmp(name, "body"))
                        v->s = xmemdupz(bodypos, bodylen);
                else if (!strcmp(name, "contents:body"))
                        v->s = xmemdupz(bodypos, nonsiglen);
                else if (!strcmp(name, "contents:signature"))
                        v->s = xmemdupz(sigpos, siglen);
                else if (!strcmp(name, "contents"))
                        v->s = xstrdup(subpos);
                else if (skip_prefix(name, "contents:lines=", &valp)) {
                        struct strbuf s = STRBUF_INIT;
                        const char *contents_end = bodylen + bodypos - siglen;

                        if (strtoul_ui(valp, 10, &v->u.contents.lines))
                                die(_("positive value expected contents:lines=%s"), valp);
                        /*  Size is the length of the message after removing the signature */
                        append_lines(&s, subpos, contents_end - subpos, v->u.contents.lines);
                        v->s = strbuf_detach(&s, NULL);
                }
        }
}

/*
 * 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 *strip_ref_components(const char *refname, const char *nr_arg)
{
        char *end;
        long nr = strtol(nr_arg, &end, 10);
        long remaining = nr;
        const char *start = refname;

        if (nr < 1 || *end != '\0')
                die(":strip= requires a positive integer argument");

        while (remaining) {
                switch (*start++) {
                case '\0':
                        die("ref '%s' does not have %ld components to :strip",
                            refname, nr);
                case '/':
                        remaining--;
                        break;
                }
        }
        return start;
}

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

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

        if (need_symref && (ref->flag & REF_ISSYMREF) && !ref->symref) {
                unsigned char unused1[20];
                ref->symref = resolve_refdup(ref->refname, RESOLVE_REF_READING,
                                             unused1, NULL);
                if (!ref->symref)
                        ref->symref = "";
        }

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

                v->handler = append_atom;

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

                if (starts_with(name, "refname"))
                        refname = ref->refname;
                else if (starts_with(name, "symref"))
                        refname = ref->symref ? ref->symref : "";
                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)
                                continue;
                } else if (starts_with(name, "push")) {
                        const char *branch_name;
                        if (!skip_prefix(ref->refname, "refs/heads/",
                                         &branch_name))
                                continue;
                        branch = branch_get(branch_name);

                        refname = branch_get_push(branch, NULL);
                        if (!refname)
                                continue;
                } else if (match_atom_name(name, "color", &valp)) {
                        char color[COLOR_MAXLEN] = "";

                        if (!valp)
                                die(_("expected format: %%(color:<color>)"));
                        if (color_parse(valp, color) < 0)
                                die(_("unable to parse format"));
                        v->s = xstrdup(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, v)) {
                        continue;
                } else if (!strcmp(name, "HEAD")) {
                        const char *head;
                        unsigned char sha1[20];

                        head = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
                                                  sha1, NULL);
                        if (!strcmp(ref->refname, head))
                                v->s = "*";
                        else
                                v->s = " ";
                        continue;
                } else if (match_atom_name(name, "align", &valp)) {
                        struct align *align = &v->u.align;
                        struct strbuf **s, **to_free;
                        int width = -1;

                        if (!valp)
                                die(_("expected format: %%(align:<width>,<position>)"));

                        /*
                         * TODO: Implement a function similar to strbuf_split_str()
                         * which would omit the separator from the end of each value.
                         */
                        s = to_free = strbuf_split_str(valp, ',', 0);

                        align->position = ALIGN_LEFT;

                        while (*s) {
                                /*  Strip trailing comma */
                                if (s[1])
                                        strbuf_setlen(s[0], s[0]->len - 1);
                                if (!strtoul_ui(s[0]->buf, 10, (unsigned int *)&width))
                                        ;
                                else if (!strcmp(s[0]->buf, "left"))
                                        align->position = ALIGN_LEFT;
                                else if (!strcmp(s[0]->buf, "right"))
                                        align->position = ALIGN_RIGHT;
                                else if (!strcmp(s[0]->buf, "middle"))
                                        align->position = ALIGN_MIDDLE;
                                else
                                        die(_("improper format entered align:%s"), s[0]->buf);
                                s++;
                        }

                        if (width < 0)
                                die(_("positive width expected with the %%(align) atom"));
                        align->width = width;
                        strbuf_list_free(to_free);
                        v->handler = align_atom_handler;
                        continue;
                } else if (!strcmp(name, "end")) {
                        v->handler = end_atom_handler;
                        continue;
                } else
                        continue;

                formatp = strchr(name, ':');
                if (formatp) {
                        int num_ours, num_theirs;
                        const char *arg;

                        formatp++;
                        if (!strcmp(formatp, "short"))
                                refname = shorten_unambiguous_ref(refname,
                                                      warn_ambiguous_refs);
                        else if (skip_prefix(formatp, "strip=", &arg))
                                refname = strip_ref_components(refname, arg);
                        else if (!strcmp(formatp, "track") &&
                                 (starts_with(name, "upstream") ||
                                  starts_with(name, "push"))) {

                                if (stat_tracking_info(branch, &num_ours,
                                                       &num_theirs, NULL))
                                        continue;

                                if (!num_ours && !num_theirs)
                                        v->s = "";
                                else if (!num_ours)
                                        v->s = xstrfmt("[behind %d]", num_theirs);
                                else if (!num_theirs)
                                        v->s = xstrfmt("[ahead %d]", num_ours);
                                else
                                        v->s = xstrfmt("[ahead %d, behind %d]",
                                                       num_ours, num_theirs);
                                continue;
                        } else if (!strcmp(formatp, "trackshort") &&
                                   (starts_with(name, "upstream") ||
                                    starts_with(name, "push"))) {
                                assert(branch);

                                if (stat_tracking_info(branch, &num_ours,
                                                        &num_theirs, NULL))
                                        continue;

                                if (!num_ours && !num_theirs)
                                        v->s = "=";
                                else if (!num_ours)
                                        v->s = "<";
                                else if (!num_theirs)
                                        v->s = ">";
                                else
                                        v->s = "<>";
                                continue;
                        } else
                                die("unknown %.*s format %s",
                                    (int)(formatp - name), name, formatp);
                }

                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)
                        goto need_obj;
        }
        return;

 need_obj:
        buf = get_obj(ref->objectname, &obj, &size, &eaten);
        if (!buf)
                die("missing object %s for %s",
                    sha1_to_hex(ref->objectname), ref->refname);
        if (!obj)
                die("parse_object_buffer failed on %s for %s",
                    sha1_to_hex(ref->objectname), ref->refname);

        grab_values(ref->value, 0, obj, buf, size);
        if (!eaten)
                free(buf);

        /*
         * 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.hash;

        /*
         * 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.
         */
        buf = get_obj(tagged, &obj, &size, &eaten);
        if (!buf)
                die("missing object %s for %s",
                    sha1_to_hex(tagged), ref->refname);
        if (!obj)
                die("parse_object_buffer failed on %s for %s",
                    sha1_to_hex(tagged), ref->refname);
        grab_values(ref->value, 1, obj, buf, size);
        if (!eaten)
                free(buf);
}

/*
 * 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];
}

enum contains_result {
        CONTAINS_UNKNOWN = -1,
        CONTAINS_NO = 0,
        CONTAINS_YES = 1
};

/*
 * 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)
{
        /* was it previously marked as containing a want commit? */
        if (candidate->object.flags & TMP_MARK)
                return 1;
        /* or marked as not possibly containing a want commit? */
        if (candidate->object.flags & UNINTERESTING)
                return 0;
        /* or are we it? */
        if (in_commit_list(want, candidate)) {
                candidate->object.flags |= TMP_MARK;
                return 1;
        }

        if (parse_commit(candidate) < 0)
                return 0;

        return -1;
}

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_stack contains_stack = { 0, 0, NULL };
        int result = contains_test(candidate, want);

        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) {
                        commit->object.flags |= UNINTERESTING;
                        contains_stack.nr--;
                }
                /*
                 * If we just popped the stack, parents->item has been marked,
                 * therefore contains_test will return a meaningful 0 or 1.
                 */
                else switch (contains_test(parents->item, want)) {
                case CONTAINS_YES:
                        commit->object.flags |= TMP_MARK;
                        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);
}

static int commit_contains(struct ref_filter *filter, struct commit *commit)
{
        if (filter->with_commit_tag_algo)
                return contains_tag_algo(commit, filter->with_commit);
        return is_descendant_of(commit, filter->with_commit);
}

/*
 * 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 char **patterns, const char *refname)
{
        /*
         * 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, 0, NULL))
                        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 char **pattern, const char *refname)
{
        int namelen = strlen(refname);
        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, NULL))
                        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->name_patterns, refname);
        return match_pattern(filter->name_patterns, refname);
}

/*
 * 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 unsigned char *match_points_at(struct sha1_array *points_at,
                                            const unsigned char *sha1,
                                            const char *refname)
{
        const unsigned char *tagged_sha1 = NULL;
        struct object *obj;

        if (sha1_array_lookup(points_at, sha1) >= 0)
                return sha1;
        obj = parse_object(sha1);
        if (!obj)
                die(_("malformed object at '%s'"), refname);
        if (obj->type == OBJ_TAG)
                tagged_sha1 = ((struct tag *)obj)->tagged->oid.hash;
        if (tagged_sha1 && sha1_array_lookup(points_at, tagged_sha1) >= 0)
                return tagged_sha1;
        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)
{
        size_t len = strlen(refname);
        struct ref_array_item *ref = xcalloc(1, sizeof(struct ref_array_item) + len + 1);
        memcpy(ref->refname, refname, len);
        ref->refname[len] = '\0';
        hashcpy(ref->objectname, objectname);
        ref->flag = flag;

        return ref;
}

static int filter_ref_kind(struct ref_filter *filter, 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 (filter->kind == FILTER_REFS_BRANCHES ||
            filter->kind == FILTER_REFS_REMOTES ||
            filter->kind == FILTER_REFS_TAGS)
                return filter->kind;
        else 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;
}

/*
 * 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->hash, 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->verbose) {
                commit = lookup_commit_reference_gently(oid->hash, 1);
                if (!commit)
                        return 0;
                /* We perform the filtering for the '--contains' option */
                if (filter->with_commit &&
                    !commit_contains(filter, commit))
                        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(array->items);
        array->items = NULL;
        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);
        }

        for (i = 0; i < old_nr; i++)
                clear_commit_marks(to_clear[i], 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;

        /*  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("", ref_filter_handler, &ref_cbdata, broken);
                if (!ret && (filter->kind & FILTER_REFS_DETACHED_HEAD))
                        head_ref(ref_filter_handler, &ref_cbdata);
        }


        /*  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_type[s->atom];

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

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

static struct ref_sorting *ref_sorting;
static int compare_refs(const void *a_, const void *b_)
{
        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)
{
        ref_sorting = sorting;
        qsort(array->items, array->nr, sizeof(struct ref_array_item *), compare_refs);
}

static int hex1(char ch)
{
        if ('0' <= ch && ch <= '9')
                return ch - '0';
        else if ('a' <= ch && ch <= 'f')
                return ch - 'a' + 10;
        else if ('A' <= ch && ch <= 'F')
                return ch - 'A' + 10;
        return -1;
}
static int hex2(const char *cp)
{
        if (cp[0] && cp[1])
                return (hex1(cp[0]) << 4) | hex1(cp[1]);
        else
                return -1;
}

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 = hex2(cp + 1);
                                if (0 <= ch) {
                                        strbuf_addch(s, ch);
                                        cp += 3;
                                        continue;
                                }
                        }
                }
                strbuf_addch(s, *cp);
                cp++;
        }
}

void show_ref_array_item(struct ref_array_item *info, const char *format, int quote_style)
{
        const char *cp, *sp, *ep;
        struct strbuf *final_buf;
        struct ref_formatting_state state = REF_FORMATTING_STATE_INIT;

        state.quote_style = quote_style;
        push_stack_element(&state.stack);

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

                ep = strchr(sp, ')');
                if (cp < sp)
                        append_literal(cp, sp, &state);
                get_ref_atom_value(info, parse_ref_filter_atom(sp + 2, ep), &atomv);
                atomv->handler(atomv, &state);
        }
        if (*cp) {
                sp = cp + strlen(cp);
                append_literal(cp, sp, &state);
        }
        if (need_color_reset_at_eol) {
                struct atom_value resetv;
                char color[COLOR_MAXLEN] = "";

                if (color_parse("reset", color) < 0)
                        die("BUG: couldn't parse 'reset' as a color");
                resetv.s = color;
                append_atom(&resetv, &state);
        }
        if (state.stack->prev)
                die(_("format: %%(end) atom missing"));
        final_buf = &state.stack->output;
        fwrite(final_buf->buf, 1, final_buf->len, stdout);
        pop_stack_element(&state.stack);
        putchar('\n');
}

/*  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_ref_filter_atom(cstr_name, cstr_name + strlen(cstr_name));
        return sorting;
}

int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset)
{
        struct ref_sorting **sorting_tail = opt->value;
        struct ref_sorting *s;
        int len;

        if (!arg) /* should --no-sort void the list ? */
                return -1;

        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;
        len = strlen(arg);
        s->atom = parse_ref_filter_atom(arg, arg+len);
        return 0;
}

int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
{
        struct ref_filter *rf = opt->value;
        unsigned char sha1[20];

        rf->merge = starts_with(opt->long_name, "no")
                ? REF_FILTER_MERGED_OMIT
                : REF_FILTER_MERGED_INCLUDE;

        if (get_sha1(arg, sha1))
                die(_("malformed object name %s"), arg);

        rf->merge_commit = lookup_commit_reference_gently(sha1, 0);
        if (!rf->merge_commit)
                return opterror(opt, "must point to a commit", 0);

        return 0;
}