Merge branch 'cp/submodule-custom-update'

[git.git] / remote.c

#include "cache.h"
#include "remote.h"
#include "refs.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "dir.h"
#include "tag.h"
#include "string-list.h"
#include "mergesort.h"

enum map_direction { FROM_SRC, FROM_DST };

static struct refspec s_tag_refspec = {
        0,
        1,
        0,
        0,
        "refs/tags/*",
        "refs/tags/*"
};

const struct refspec *tag_refspec = &s_tag_refspec;

struct counted_string {
        size_t len;
        const char *s;
};
struct rewrite {
        const char *base;
        size_t baselen;
        struct counted_string *instead_of;
        int instead_of_nr;
        int instead_of_alloc;
};
struct rewrites {
        struct rewrite **rewrite;
        int rewrite_alloc;
        int rewrite_nr;
};

static struct remote **remotes;
static int remotes_alloc;
static int remotes_nr;

static struct branch **branches;
static int branches_alloc;
static int branches_nr;

static struct branch *current_branch;
static const char *default_remote_name;
static const char *pushremote_name;
static int explicit_default_remote_name;

static struct rewrites rewrites;
static struct rewrites rewrites_push;

#define BUF_SIZE (2048)
static char buffer[BUF_SIZE];

static int valid_remote(const struct remote *remote)
{
        return (!!remote->url) || (!!remote->foreign_vcs);
}

static const char *alias_url(const char *url, struct rewrites *r)
{
        int i, j;
        char *ret;
        struct counted_string *longest;
        int longest_i;

        longest = NULL;
        longest_i = -1;
        for (i = 0; i < r->rewrite_nr; i++) {
                if (!r->rewrite[i])
                        continue;
                for (j = 0; j < r->rewrite[i]->instead_of_nr; j++) {
                        if (!prefixcmp(url, r->rewrite[i]->instead_of[j].s) &&
                            (!longest ||
                             longest->len < r->rewrite[i]->instead_of[j].len)) {
                                longest = &(r->rewrite[i]->instead_of[j]);
                                longest_i = i;
                        }
                }
        }
        if (!longest)
                return url;

        ret = xmalloc(r->rewrite[longest_i]->baselen +
                     (strlen(url) - longest->len) + 1);
        strcpy(ret, r->rewrite[longest_i]->base);
        strcpy(ret + r->rewrite[longest_i]->baselen, url + longest->len);
        return ret;
}

static void add_push_refspec(struct remote *remote, const char *ref)
{
        ALLOC_GROW(remote->push_refspec,
                   remote->push_refspec_nr + 1,
                   remote->push_refspec_alloc);
        remote->push_refspec[remote->push_refspec_nr++] = ref;
}

static void add_fetch_refspec(struct remote *remote, const char *ref)
{
        ALLOC_GROW(remote->fetch_refspec,
                   remote->fetch_refspec_nr + 1,
                   remote->fetch_refspec_alloc);
        remote->fetch_refspec[remote->fetch_refspec_nr++] = ref;
}

static void add_url(struct remote *remote, const char *url)
{
        ALLOC_GROW(remote->url, remote->url_nr + 1, remote->url_alloc);
        remote->url[remote->url_nr++] = url;
}

static void add_pushurl(struct remote *remote, const char *pushurl)
{
        ALLOC_GROW(remote->pushurl, remote->pushurl_nr + 1, remote->pushurl_alloc);
        remote->pushurl[remote->pushurl_nr++] = pushurl;
}

static void add_pushurl_alias(struct remote *remote, const char *url)
{
        const char *pushurl = alias_url(url, &rewrites_push);
        if (pushurl != url)
                add_pushurl(remote, pushurl);
}

static void add_url_alias(struct remote *remote, const char *url)
{
        add_url(remote, alias_url(url, &rewrites));
        add_pushurl_alias(remote, url);
}

static struct remote *make_remote(const char *name, int len)
{
        struct remote *ret;
        int i;

        for (i = 0; i < remotes_nr; i++) {
                if (len ? (!strncmp(name, remotes[i]->name, len) &&
                           !remotes[i]->name[len]) :
                    !strcmp(name, remotes[i]->name))
                        return remotes[i];
        }

        ret = xcalloc(1, sizeof(struct remote));
        ALLOC_GROW(remotes, remotes_nr + 1, remotes_alloc);
        remotes[remotes_nr++] = ret;
        if (len)
                ret->name = xstrndup(name, len);
        else
                ret->name = xstrdup(name);
        return ret;
}

static void add_merge(struct branch *branch, const char *name)
{
        ALLOC_GROW(branch->merge_name, branch->merge_nr + 1,
                   branch->merge_alloc);
        branch->merge_name[branch->merge_nr++] = name;
}

static struct branch *make_branch(const char *name, int len)
{
        struct branch *ret;
        int i;
        char *refname;

        for (i = 0; i < branches_nr; i++) {
                if (len ? (!strncmp(name, branches[i]->name, len) &&
                           !branches[i]->name[len]) :
                    !strcmp(name, branches[i]->name))
                        return branches[i];
        }

        ALLOC_GROW(branches, branches_nr + 1, branches_alloc);
        ret = xcalloc(1, sizeof(struct branch));
        branches[branches_nr++] = ret;
        if (len)
                ret->name = xstrndup(name, len);
        else
                ret->name = xstrdup(name);
        refname = xmalloc(strlen(name) + strlen("refs/heads/") + 1);
        strcpy(refname, "refs/heads/");
        strcpy(refname + strlen("refs/heads/"), ret->name);
        ret->refname = refname;

        return ret;
}

static struct rewrite *make_rewrite(struct rewrites *r, const char *base, int len)
{
        struct rewrite *ret;
        int i;

        for (i = 0; i < r->rewrite_nr; i++) {
                if (len
                    ? (len == r->rewrite[i]->baselen &&
                       !strncmp(base, r->rewrite[i]->base, len))
                    : !strcmp(base, r->rewrite[i]->base))
                        return r->rewrite[i];
        }

        ALLOC_GROW(r->rewrite, r->rewrite_nr + 1, r->rewrite_alloc);
        ret = xcalloc(1, sizeof(struct rewrite));
        r->rewrite[r->rewrite_nr++] = ret;
        if (len) {
                ret->base = xstrndup(base, len);
                ret->baselen = len;
        }
        else {
                ret->base = xstrdup(base);
                ret->baselen = strlen(base);
        }
        return ret;
}

static void add_instead_of(struct rewrite *rewrite, const char *instead_of)
{
        ALLOC_GROW(rewrite->instead_of, rewrite->instead_of_nr + 1, rewrite->instead_of_alloc);
        rewrite->instead_of[rewrite->instead_of_nr].s = instead_of;
        rewrite->instead_of[rewrite->instead_of_nr].len = strlen(instead_of);
        rewrite->instead_of_nr++;
}

static void read_remotes_file(struct remote *remote)
{
        FILE *f = fopen(git_path("remotes/%s", remote->name), "r");

        if (!f)
                return;
        remote->origin = REMOTE_REMOTES;
        while (fgets(buffer, BUF_SIZE, f)) {
                int value_list;
                char *s, *p;

                if (!prefixcmp(buffer, "URL:")) {
                        value_list = 0;
                        s = buffer + 4;
                } else if (!prefixcmp(buffer, "Push:")) {
                        value_list = 1;
                        s = buffer + 5;
                } else if (!prefixcmp(buffer, "Pull:")) {
                        value_list = 2;
                        s = buffer + 5;
                } else
                        continue;

                while (isspace(*s))
                        s++;
                if (!*s)
                        continue;

                p = s + strlen(s);
                while (isspace(p[-1]))
                        *--p = 0;

                switch (value_list) {
                case 0:
                        add_url_alias(remote, xstrdup(s));
                        break;
                case 1:
                        add_push_refspec(remote, xstrdup(s));
                        break;
                case 2:
                        add_fetch_refspec(remote, xstrdup(s));
                        break;
                }
        }
        fclose(f);
}

static void read_branches_file(struct remote *remote)
{
        char *frag;
        struct strbuf branch = STRBUF_INIT;
        int n = 1000;
        FILE *f = fopen(git_path("branches/%.*s", n, remote->name), "r");
        char *s, *p;
        int len;

        if (!f)
                return;
        s = fgets(buffer, BUF_SIZE, f);
        fclose(f);
        if (!s)
                return;
        while (isspace(*s))
                s++;
        if (!*s)
                return;
        remote->origin = REMOTE_BRANCHES;
        p = s + strlen(s);
        while (isspace(p[-1]))
                *--p = 0;
        len = p - s;
        p = xmalloc(len + 1);
        strcpy(p, s);

        /*
         * The branches file would have URL and optionally
         * #branch specified.  The "master" (or specified) branch is
         * fetched and stored in the local branch of the same name.
         */
        frag = strchr(p, '#');
        if (frag) {
                *(frag++) = '\0';
                strbuf_addf(&branch, "refs/heads/%s", frag);
        } else
                strbuf_addstr(&branch, "refs/heads/master");

        strbuf_addf(&branch, ":refs/heads/%s", remote->name);
        add_url_alias(remote, p);
        add_fetch_refspec(remote, strbuf_detach(&branch, NULL));
        /*
         * Cogito compatible push: push current HEAD to remote #branch
         * (master if missing)
         */
        strbuf_init(&branch, 0);
        strbuf_addstr(&branch, "HEAD");
        if (frag)
                strbuf_addf(&branch, ":refs/heads/%s", frag);
        else
                strbuf_addstr(&branch, ":refs/heads/master");
        add_push_refspec(remote, strbuf_detach(&branch, NULL));
        remote->fetch_tags = 1; /* always auto-follow */
}

static int handle_config(const char *key, const char *value, void *cb)
{
        const char *name;
        const char *subkey;
        struct remote *remote;
        struct branch *branch;
        if (!prefixcmp(key, "branch.")) {
                name = key + 7;
                subkey = strrchr(name, '.');
                if (!subkey)
                        return 0;
                branch = make_branch(name, subkey - name);
                if (!strcmp(subkey, ".remote")) {
                        if (git_config_string(&branch->remote_name, key, value))
                                return -1;
                        if (branch == current_branch) {
                                default_remote_name = branch->remote_name;
                                explicit_default_remote_name = 1;
                        }
                } else if (!strcmp(subkey, ".pushremote")) {
                        if (branch == current_branch)
                                if (git_config_string(&pushremote_name, key, value))
                                        return -1;
                } else if (!strcmp(subkey, ".merge")) {
                        if (!value)
                                return config_error_nonbool(key);
                        add_merge(branch, xstrdup(value));
                }
                return 0;
        }
        if (!prefixcmp(key, "url.")) {
                struct rewrite *rewrite;
                name = key + 4;
                subkey = strrchr(name, '.');
                if (!subkey)
                        return 0;
                if (!strcmp(subkey, ".insteadof")) {
                        rewrite = make_rewrite(&rewrites, name, subkey - name);
                        if (!value)
                                return config_error_nonbool(key);
                        add_instead_of(rewrite, xstrdup(value));
                } else if (!strcmp(subkey, ".pushinsteadof")) {
                        rewrite = make_rewrite(&rewrites_push, name, subkey - name);
                        if (!value)
                                return config_error_nonbool(key);
                        add_instead_of(rewrite, xstrdup(value));
                }
        }

        if (prefixcmp(key,  "remote."))
                return 0;
        name = key + 7;

        /* Handle remote.* variables */
        if (!strcmp(name, "pushdefault"))
                return git_config_string(&pushremote_name, key, value);

        /* Handle remote.<name>.* variables */
        if (*name == '/') {
                warning("Config remote shorthand cannot begin with '/': %s",
                        name);
                return 0;
        }
        subkey = strrchr(name, '.');
        if (!subkey)
                return 0;
        remote = make_remote(name, subkey - name);
        remote->origin = REMOTE_CONFIG;
        if (!strcmp(subkey, ".mirror"))
                remote->mirror = git_config_bool(key, value);
        else if (!strcmp(subkey, ".skipdefaultupdate"))
                remote->skip_default_update = git_config_bool(key, value);
        else if (!strcmp(subkey, ".skipfetchall"))
                remote->skip_default_update = git_config_bool(key, value);
        else if (!strcmp(subkey, ".url")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                add_url(remote, v);
        } else if (!strcmp(subkey, ".pushurl")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                add_pushurl(remote, v);
        } else if (!strcmp(subkey, ".push")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                add_push_refspec(remote, v);
        } else if (!strcmp(subkey, ".fetch")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                add_fetch_refspec(remote, v);
        } else if (!strcmp(subkey, ".receivepack")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                if (!remote->receivepack)
                        remote->receivepack = v;
                else
                        error("more than one receivepack given, using the first");
        } else if (!strcmp(subkey, ".uploadpack")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                if (!remote->uploadpack)
                        remote->uploadpack = v;
                else
                        error("more than one uploadpack given, using the first");
        } else if (!strcmp(subkey, ".tagopt")) {
                if (!strcmp(value, "--no-tags"))
                        remote->fetch_tags = -1;
                else if (!strcmp(value, "--tags"))
                        remote->fetch_tags = 2;
        } else if (!strcmp(subkey, ".proxy")) {
                return git_config_string((const char **)&remote->http_proxy,
                                         key, value);
        } else if (!strcmp(subkey, ".vcs")) {
                return git_config_string(&remote->foreign_vcs, key, value);
        }
        return 0;
}

static void alias_all_urls(void)
{
        int i, j;
        for (i = 0; i < remotes_nr; i++) {
                int add_pushurl_aliases;
                if (!remotes[i])
                        continue;
                for (j = 0; j < remotes[i]->pushurl_nr; j++) {
                        remotes[i]->pushurl[j] = alias_url(remotes[i]->pushurl[j], &rewrites);
                }
                add_pushurl_aliases = remotes[i]->pushurl_nr == 0;
                for (j = 0; j < remotes[i]->url_nr; j++) {
                        if (add_pushurl_aliases)
                                add_pushurl_alias(remotes[i], remotes[i]->url[j]);
                        remotes[i]->url[j] = alias_url(remotes[i]->url[j], &rewrites);
                }
        }
}

static void read_config(void)
{
        unsigned char sha1[20];
        const char *head_ref;
        int flag;
        if (default_remote_name) /* did this already */
                return;
        default_remote_name = xstrdup("origin");
        current_branch = NULL;
        head_ref = resolve_ref_unsafe("HEAD", sha1, 0, &flag);
        if (head_ref && (flag & REF_ISSYMREF) &&
            !prefixcmp(head_ref, "refs/heads/")) {
                current_branch =
                        make_branch(head_ref + strlen("refs/heads/"), 0);
        }
        git_config(handle_config, NULL);
        alias_all_urls();
}

/*
 * This function frees a refspec array.
 * Warning: code paths should be checked to ensure that the src
 *          and dst pointers are always freeable pointers as well
 *          as the refspec pointer itself.
 */
static void free_refspecs(struct refspec *refspec, int nr_refspec)
{
        int i;

        if (!refspec)
                return;

        for (i = 0; i < nr_refspec; i++) {
                free(refspec[i].src);
                free(refspec[i].dst);
        }
        free(refspec);
}

static struct refspec *parse_refspec_internal(int nr_refspec, const char **refspec, int fetch, int verify)
{
        int i;
        struct refspec *rs = xcalloc(sizeof(*rs), nr_refspec);

        for (i = 0; i < nr_refspec; i++) {
                size_t llen;
                int is_glob;
                const char *lhs, *rhs;
                int flags;

                is_glob = 0;

                lhs = refspec[i];
                if (*lhs == '+') {
                        rs[i].force = 1;
                        lhs++;
                }

                rhs = strrchr(lhs, ':');

                /*
                 * Before going on, special case ":" (or "+:") as a refspec
                 * for pushing matching refs.
                 */
                if (!fetch && rhs == lhs && rhs[1] == '\0') {
                        rs[i].matching = 1;
                        continue;
                }

                if (rhs) {
                        size_t rlen = strlen(++rhs);
                        is_glob = (1 <= rlen && strchr(rhs, '*'));
                        rs[i].dst = xstrndup(rhs, rlen);
                }

                llen = (rhs ? (rhs - lhs - 1) : strlen(lhs));
                if (1 <= llen && memchr(lhs, '*', llen)) {
                        if ((rhs && !is_glob) || (!rhs && fetch))
                                goto invalid;
                        is_glob = 1;
                } else if (rhs && is_glob) {
                        goto invalid;
                }

                rs[i].pattern = is_glob;
                rs[i].src = xstrndup(lhs, llen);
                flags = REFNAME_ALLOW_ONELEVEL | (is_glob ? REFNAME_REFSPEC_PATTERN : 0);

                if (fetch) {
                        unsigned char unused[40];

                        /* LHS */
                        if (!*rs[i].src)
                                ; /* empty is ok; it means "HEAD" */
                        else if (llen == 40 && !get_sha1_hex(rs[i].src, unused))
                                rs[i].exact_sha1 = 1; /* ok */
                        else if (!check_refname_format(rs[i].src, flags))
                                ; /* valid looking ref is ok */
                        else
                                goto invalid;
                        /* RHS */
                        if (!rs[i].dst)
                                ; /* missing is ok; it is the same as empty */
                        else if (!*rs[i].dst)
                                ; /* empty is ok; it means "do not store" */
                        else if (!check_refname_format(rs[i].dst, flags))
                                ; /* valid looking ref is ok */
                        else
                                goto invalid;
                } else {
                        /*
                         * LHS
                         * - empty is allowed; it means delete.
                         * - when wildcarded, it must be a valid looking ref.
                         * - otherwise, it must be an extended SHA-1, but
                         *   there is no existing way to validate this.
                         */
                        if (!*rs[i].src)
                                ; /* empty is ok */
                        else if (is_glob) {
                                if (check_refname_format(rs[i].src, flags))
                                        goto invalid;
                        }
                        else
                                ; /* anything goes, for now */
                        /*
                         * RHS
                         * - missing is allowed, but LHS then must be a
                         *   valid looking ref.
                         * - empty is not allowed.
                         * - otherwise it must be a valid looking ref.
                         */
                        if (!rs[i].dst) {
                                if (check_refname_format(rs[i].src, flags))
                                        goto invalid;
                        } else if (!*rs[i].dst) {
                                goto invalid;
                        } else {
                                if (check_refname_format(rs[i].dst, flags))
                                        goto invalid;
                        }
                }
        }
        return rs;

 invalid:
        if (verify) {
                /*
                 * nr_refspec must be greater than zero and i must be valid
                 * since it is only possible to reach this point from within
                 * the for loop above.
                 */
                free_refspecs(rs, i+1);
                return NULL;
        }
        die("Invalid refspec '%s'", refspec[i]);
}

int valid_fetch_refspec(const char *fetch_refspec_str)
{
        struct refspec *refspec;

        refspec = parse_refspec_internal(1, &fetch_refspec_str, 1, 1);
        free_refspecs(refspec, 1);
        return !!refspec;
}

struct refspec *parse_fetch_refspec(int nr_refspec, const char **refspec)
{
        return parse_refspec_internal(nr_refspec, refspec, 1, 0);
}

static struct refspec *parse_push_refspec(int nr_refspec, const char **refspec)
{
        return parse_refspec_internal(nr_refspec, refspec, 0, 0);
}

void free_refspec(int nr_refspec, struct refspec *refspec)
{
        int i;
        for (i = 0; i < nr_refspec; i++) {
                free(refspec[i].src);
                free(refspec[i].dst);
        }
        free(refspec);
}

static int valid_remote_nick(const char *name)
{
        if (!name[0] || is_dot_or_dotdot(name))
                return 0;
        return !strchr(name, '/'); /* no slash */
}

static struct remote *remote_get_1(const char *name, const char *pushremote_name)
{
        struct remote *ret;
        int name_given = 0;

        if (name)
                name_given = 1;
        else {
                if (pushremote_name) {
                        name = pushremote_name;
                        name_given = 1;
                } else {
                        name = default_remote_name;
                        name_given = explicit_default_remote_name;
                }
        }

        ret = make_remote(name, 0);
        if (valid_remote_nick(name)) {
                if (!valid_remote(ret))
                        read_remotes_file(ret);
                if (!valid_remote(ret))
                        read_branches_file(ret);
        }
        if (name_given && !valid_remote(ret))
                add_url_alias(ret, name);
        if (!valid_remote(ret))
                return NULL;
        ret->fetch = parse_fetch_refspec(ret->fetch_refspec_nr, ret->fetch_refspec);
        ret->push = parse_push_refspec(ret->push_refspec_nr, ret->push_refspec);
        return ret;
}

struct remote *remote_get(const char *name)
{
        read_config();
        return remote_get_1(name, NULL);
}

struct remote *pushremote_get(const char *name)
{
        read_config();
        return remote_get_1(name, pushremote_name);
}

int remote_is_configured(const char *name)
{
        int i;
        read_config();

        for (i = 0; i < remotes_nr; i++)
                if (!strcmp(name, remotes[i]->name))
                        return 1;
        return 0;
}

int for_each_remote(each_remote_fn fn, void *priv)
{
        int i, result = 0;
        read_config();
        for (i = 0; i < remotes_nr && !result; i++) {
                struct remote *r = remotes[i];
                if (!r)
                        continue;
                if (!r->fetch)
                        r->fetch = parse_fetch_refspec(r->fetch_refspec_nr,
                                                       r->fetch_refspec);
                if (!r->push)
                        r->push = parse_push_refspec(r->push_refspec_nr,
                                                     r->push_refspec);
                result = fn(r, priv);
        }
        return result;
}

void ref_remove_duplicates(struct ref *ref_map)
{
        struct string_list refs = STRING_LIST_INIT_NODUP;
        struct string_list_item *item = NULL;
        struct ref *prev = NULL, *next = NULL;
        for (; ref_map; prev = ref_map, ref_map = next) {
                next = ref_map->next;
                if (!ref_map->peer_ref)
                        continue;

                item = string_list_lookup(&refs, ref_map->peer_ref->name);
                if (item) {
                        if (strcmp(((struct ref *)item->util)->name,
                                   ref_map->name))
                                die("%s tracks both %s and %s",
                                    ref_map->peer_ref->name,
                                    ((struct ref *)item->util)->name,
                                    ref_map->name);
                        prev->next = ref_map->next;
                        free(ref_map->peer_ref);
                        free(ref_map);
                        ref_map = prev; /* skip this; we freed it */
                        continue;
                }

                item = string_list_insert(&refs, ref_map->peer_ref->name);
                item->util = ref_map;
        }
        string_list_clear(&refs, 0);
}

int remote_has_url(struct remote *remote, const char *url)
{
        int i;
        for (i = 0; i < remote->url_nr; i++) {
                if (!strcmp(remote->url[i], url))
                        return 1;
        }
        return 0;
}

static int match_name_with_pattern(const char *key, const char *name,
                                   const char *value, char **result)
{
        const char *kstar = strchr(key, '*');
        size_t klen;
        size_t ksuffixlen;
        size_t namelen;
        int ret;
        if (!kstar)
                die("Key '%s' of pattern had no '*'", key);
        klen = kstar - key;
        ksuffixlen = strlen(kstar + 1);
        namelen = strlen(name);
        ret = !strncmp(name, key, klen) && namelen >= klen + ksuffixlen &&
                !memcmp(name + namelen - ksuffixlen, kstar + 1, ksuffixlen);
        if (ret && value) {
                const char *vstar = strchr(value, '*');
                size_t vlen;
                size_t vsuffixlen;
                if (!vstar)
                        die("Value '%s' of pattern has no '*'", value);
                vlen = vstar - value;
                vsuffixlen = strlen(vstar + 1);
                *result = xmalloc(vlen + vsuffixlen +
                                  strlen(name) -
                                  klen - ksuffixlen + 1);
                strncpy(*result, value, vlen);
                strncpy(*result + vlen,
                        name + klen, namelen - klen - ksuffixlen);
                strcpy(*result + vlen + namelen - klen - ksuffixlen,
                       vstar + 1);
        }
        return ret;
}

static int query_refspecs(struct refspec *refs, int ref_count, struct refspec *query)
{
        int i;
        int find_src = !query->src;

        if (find_src && !query->dst)
                return error("query_refspecs: need either src or dst");

        for (i = 0; i < ref_count; i++) {
                struct refspec *refspec = &refs[i];
                const char *key = find_src ? refspec->dst : refspec->src;
                const char *value = find_src ? refspec->src : refspec->dst;
                const char *needle = find_src ? query->dst : query->src;
                char **result = find_src ? &query->src : &query->dst;

                if (!refspec->dst)
                        continue;
                if (refspec->pattern) {
                        if (match_name_with_pattern(key, needle, value, result)) {
                                query->force = refspec->force;
                                return 0;
                        }
                } else if (!strcmp(needle, key)) {
                        *result = xstrdup(value);
                        query->force = refspec->force;
                        return 0;
                }
        }
        return -1;
}

char *apply_refspecs(struct refspec *refspecs, int nr_refspec,
                     const char *name)
{
        struct refspec query;

        memset(&query, 0, sizeof(struct refspec));
        query.src = (char *)name;

        if (query_refspecs(refspecs, nr_refspec, &query))
                return NULL;

        return query.dst;
}

int remote_find_tracking(struct remote *remote, struct refspec *refspec)
{
        return query_refspecs(remote->fetch, remote->fetch_refspec_nr, refspec);
}

static struct ref *alloc_ref_with_prefix(const char *prefix, size_t prefixlen,
                const char *name)
{
        size_t len = strlen(name);
        struct ref *ref = xcalloc(1, sizeof(struct ref) + prefixlen + len + 1);
        memcpy(ref->name, prefix, prefixlen);
        memcpy(ref->name + prefixlen, name, len);
        return ref;
}

struct ref *alloc_ref(const char *name)
{
        return alloc_ref_with_prefix("", 0, name);
}

struct ref *copy_ref(const struct ref *ref)
{
        struct ref *cpy;
        size_t len;
        if (!ref)
                return NULL;
        len = strlen(ref->name);
        cpy = xmalloc(sizeof(struct ref) + len + 1);
        memcpy(cpy, ref, sizeof(struct ref) + len + 1);
        cpy->next = NULL;
        cpy->symref = ref->symref ? xstrdup(ref->symref) : NULL;
        cpy->remote_status = ref->remote_status ? xstrdup(ref->remote_status) : NULL;
        cpy->peer_ref = copy_ref(ref->peer_ref);
        return cpy;
}

struct ref *copy_ref_list(const struct ref *ref)
{
        struct ref *ret = NULL;
        struct ref **tail = &ret;
        while (ref) {
                *tail = copy_ref(ref);
                ref = ref->next;
                tail = &((*tail)->next);
        }
        return ret;
}

static void free_ref(struct ref *ref)
{
        if (!ref)
                return;
        free_ref(ref->peer_ref);
        free(ref->remote_status);
        free(ref->symref);
        free(ref);
}

void free_refs(struct ref *ref)
{
        struct ref *next;
        while (ref) {
                next = ref->next;
                free_ref(ref);
                ref = next;
        }
}

int ref_compare_name(const void *va, const void *vb)
{
        const struct ref *a = va, *b = vb;
        return strcmp(a->name, b->name);
}

static void *ref_list_get_next(const void *a)
{
        return ((const struct ref *)a)->next;
}

static void ref_list_set_next(void *a, void *next)
{
        ((struct ref *)a)->next = next;
}

void sort_ref_list(struct ref **l, int (*cmp)(const void *, const void *))
{
        *l = llist_mergesort(*l, ref_list_get_next, ref_list_set_next, cmp);
}

static int count_refspec_match(const char *pattern,
                               struct ref *refs,
                               struct ref **matched_ref)
{
        int patlen = strlen(pattern);
        struct ref *matched_weak = NULL;
        struct ref *matched = NULL;
        int weak_match = 0;
        int match = 0;

        for (weak_match = match = 0; refs; refs = refs->next) {
                char *name = refs->name;
                int namelen = strlen(name);

                if (!refname_match(pattern, name, ref_rev_parse_rules))
                        continue;

                /* A match is "weak" if it is with refs outside
                 * heads or tags, and did not specify the pattern
                 * in full (e.g. "refs/remotes/origin/master") or at
                 * least from the toplevel (e.g. "remotes/origin/master");
                 * otherwise "git push $URL master" would result in
                 * ambiguity between remotes/origin/master and heads/master
                 * at the remote site.
                 */
                if (namelen != patlen &&
                    patlen != namelen - 5 &&
                    prefixcmp(name, "refs/heads/") &&
                    prefixcmp(name, "refs/tags/")) {
                        /* We want to catch the case where only weak
                         * matches are found and there are multiple
                         * matches, and where more than one strong
                         * matches are found, as ambiguous.  One
                         * strong match with zero or more weak matches
                         * are acceptable as a unique match.
                         */
                        matched_weak = refs;
                        weak_match++;
                }
                else {
                        matched = refs;
                        match++;
                }
        }
        if (!matched) {
                *matched_ref = matched_weak;
                return weak_match;
        }
        else {
                *matched_ref = matched;
                return match;
        }
}

static void tail_link_ref(struct ref *ref, struct ref ***tail)
{
        **tail = ref;
        while (ref->next)
                ref = ref->next;
        *tail = &ref->next;
}

static struct ref *alloc_delete_ref(void)
{
        struct ref *ref = alloc_ref("(delete)");
        hashclr(ref->new_sha1);
        return ref;
}

static struct ref *try_explicit_object_name(const char *name)
{
        unsigned char sha1[20];
        struct ref *ref;

        if (!*name)
                return alloc_delete_ref();
        if (get_sha1(name, sha1))
                return NULL;
        ref = alloc_ref(name);
        hashcpy(ref->new_sha1, sha1);
        return ref;
}

static struct ref *make_linked_ref(const char *name, struct ref ***tail)
{
        struct ref *ret = alloc_ref(name);
        tail_link_ref(ret, tail);
        return ret;
}

static char *guess_ref(const char *name, struct ref *peer)
{
        struct strbuf buf = STRBUF_INIT;
        unsigned char sha1[20];

        const char *r = resolve_ref_unsafe(peer->name, sha1, 1, NULL);
        if (!r)
                return NULL;

        if (!prefixcmp(r, "refs/heads/"))
                strbuf_addstr(&buf, "refs/heads/");
        else if (!prefixcmp(r, "refs/tags/"))
                strbuf_addstr(&buf, "refs/tags/");
        else
                return NULL;

        strbuf_addstr(&buf, name);
        return strbuf_detach(&buf, NULL);
}

static int match_explicit(struct ref *src, struct ref *dst,
                          struct ref ***dst_tail,
                          struct refspec *rs)
{
        struct ref *matched_src, *matched_dst;
        int copy_src;

        const char *dst_value = rs->dst;
        char *dst_guess;

        if (rs->pattern || rs->matching)
                return 0;

        matched_src = matched_dst = NULL;
        switch (count_refspec_match(rs->src, src, &matched_src)) {
        case 1:
                copy_src = 1;
                break;
        case 0:
                /* The source could be in the get_sha1() format
                 * not a reference name.  :refs/other is a
                 * way to delete 'other' ref at the remote end.
                 */
                matched_src = try_explicit_object_name(rs->src);
                if (!matched_src)
                        return error("src refspec %s does not match any.", rs->src);
                copy_src = 0;
                break;
        default:
                return error("src refspec %s matches more than one.", rs->src);
        }

        if (!dst_value) {
                unsigned char sha1[20];
                int flag;

                dst_value = resolve_ref_unsafe(matched_src->name, sha1, 1, &flag);
                if (!dst_value ||
                    ((flag & REF_ISSYMREF) &&
                     prefixcmp(dst_value, "refs/heads/")))
                        die("%s cannot be resolved to branch.",
                            matched_src->name);
        }

        switch (count_refspec_match(dst_value, dst, &matched_dst)) {
        case 1:
                break;
        case 0:
                if (!memcmp(dst_value, "refs/", 5))
                        matched_dst = make_linked_ref(dst_value, dst_tail);
                else if (is_null_sha1(matched_src->new_sha1))
                        error("unable to delete '%s': remote ref does not exist",
                              dst_value);
                else if ((dst_guess = guess_ref(dst_value, matched_src)))
                        matched_dst = make_linked_ref(dst_guess, dst_tail);
                else
                        error("unable to push to unqualified destination: %s\n"
                              "The destination refspec neither matches an "
                              "existing ref on the remote nor\n"
                              "begins with refs/, and we are unable to "
                              "guess a prefix based on the source ref.",
                              dst_value);
                break;
        default:
                matched_dst = NULL;
                error("dst refspec %s matches more than one.",
                      dst_value);
                break;
        }
        if (!matched_dst)
                return -1;
        if (matched_dst->peer_ref)
                return error("dst ref %s receives from more than one src.",
                      matched_dst->name);
        else {
                matched_dst->peer_ref = copy_src ? copy_ref(matched_src) : matched_src;
                matched_dst->force = rs->force;
        }
        return 0;
}

static int match_explicit_refs(struct ref *src, struct ref *dst,
                               struct ref ***dst_tail, struct refspec *rs,
                               int rs_nr)
{
        int i, errs;
        for (i = errs = 0; i < rs_nr; i++)
                errs += match_explicit(src, dst, dst_tail, &rs[i]);
        return errs;
}

static char *get_ref_match(const struct refspec *rs, int rs_nr, const struct ref *ref,
                int send_mirror, int direction, const struct refspec **ret_pat)
{
        const struct refspec *pat;
        char *name;
        int i;
        int matching_refs = -1;
        for (i = 0; i < rs_nr; i++) {
                if (rs[i].matching &&
                    (matching_refs == -1 || rs[i].force)) {
                        matching_refs = i;
                        continue;
                }

                if (rs[i].pattern) {
                        const char *dst_side = rs[i].dst ? rs[i].dst : rs[i].src;
                        int match;
                        if (direction == FROM_SRC)
                                match = match_name_with_pattern(rs[i].src, ref->name, dst_side, &name);
                        else
                                match = match_name_with_pattern(dst_side, ref->name, rs[i].src, &name);
                        if (match) {
                                matching_refs = i;
                                break;
                        }
                }
        }
        if (matching_refs == -1)
                return NULL;

        pat = rs + matching_refs;
        if (pat->matching) {
                /*
                 * "matching refs"; traditionally we pushed everything
                 * including refs outside refs/heads/ hierarchy, but
                 * that does not make much sense these days.
                 */
                if (!send_mirror && prefixcmp(ref->name, "refs/heads/"))
                        return NULL;
                name = xstrdup(ref->name);
        }
        if (ret_pat)
                *ret_pat = pat;
        return name;
}

static struct ref **tail_ref(struct ref **head)
{
        struct ref **tail = head;
        while (*tail)
                tail = &((*tail)->next);
        return tail;
}

struct tips {
        struct commit **tip;
        int nr, alloc;
};

static void add_to_tips(struct tips *tips, const unsigned char *sha1)
{
        struct commit *commit;

        if (is_null_sha1(sha1))
                return;
        commit = lookup_commit_reference_gently(sha1, 1);
        if (!commit || (commit->object.flags & TMP_MARK))
                return;
        commit->object.flags |= TMP_MARK;
        ALLOC_GROW(tips->tip, tips->nr + 1, tips->alloc);
        tips->tip[tips->nr++] = commit;
}

static void add_missing_tags(struct ref *src, struct ref **dst, struct ref ***dst_tail)
{
        struct string_list dst_tag = STRING_LIST_INIT_NODUP;
        struct string_list src_tag = STRING_LIST_INIT_NODUP;
        struct string_list_item *item;
        struct ref *ref;
        struct tips sent_tips;

        /*
         * Collect everything we know they would have at the end of
         * this push, and collect all tags they have.
         */
        memset(&sent_tips, 0, sizeof(sent_tips));
        for (ref = *dst; ref; ref = ref->next) {
                if (ref->peer_ref &&
                    !is_null_sha1(ref->peer_ref->new_sha1))
                        add_to_tips(&sent_tips, ref->peer_ref->new_sha1);
                else
                        add_to_tips(&sent_tips, ref->old_sha1);
                if (!prefixcmp(ref->name, "refs/tags/"))
                        string_list_append(&dst_tag, ref->name);
        }
        clear_commit_marks_many(sent_tips.nr, sent_tips.tip, TMP_MARK);

        sort_string_list(&dst_tag);

        /* Collect tags they do not have. */
        for (ref = src; ref; ref = ref->next) {
                if (prefixcmp(ref->name, "refs/tags/"))
                        continue; /* not a tag */
                if (string_list_has_string(&dst_tag, ref->name))
                        continue; /* they already have it */
                if (sha1_object_info(ref->new_sha1, NULL) != OBJ_TAG)
                        continue; /* be conservative */
                item = string_list_append(&src_tag, ref->name);
                item->util = ref;
        }
        string_list_clear(&dst_tag, 0);

        /*
         * At this point, src_tag lists tags that are missing from
         * dst, and sent_tips lists the tips we are pushing or those
         * that we know they already have. An element in the src_tag
         * that is an ancestor of any of the sent_tips needs to be
         * sent to the other side.
         */
        if (sent_tips.nr) {
                for_each_string_list_item(item, &src_tag) {
                        struct ref *ref = item->util;
                        struct ref *dst_ref;
                        struct commit *commit;

                        if (is_null_sha1(ref->new_sha1))
                                continue;
                        commit = lookup_commit_reference_gently(ref->new_sha1, 1);
                        if (!commit)
                                /* not pushing a commit, which is not an error */
                                continue;

                        /*
                         * Is this tag, which they do not have, reachable from
                         * any of the commits we are sending?
                         */
                        if (!in_merge_bases_many(commit, sent_tips.nr, sent_tips.tip))
                                continue;

                        /* Add it in */
                        dst_ref = make_linked_ref(ref->name, dst_tail);
                        hashcpy(dst_ref->new_sha1, ref->new_sha1);
                        dst_ref->peer_ref = copy_ref(ref);
                }
        }
        string_list_clear(&src_tag, 0);
        free(sent_tips.tip);
}

/*
 * Given the set of refs the local repository has, the set of refs the
 * remote repository has, and the refspec used for push, determine
 * what remote refs we will update and with what value by setting
 * peer_ref (which object is being pushed) and force (if the push is
 * forced) in elements of "dst". The function may add new elements to
 * dst (e.g. pushing to a new branch, done in match_explicit_refs).
 */
int match_push_refs(struct ref *src, struct ref **dst,
                    int nr_refspec, const char **refspec, int flags)
{
        struct refspec *rs;
        int send_all = flags & MATCH_REFS_ALL;
        int send_mirror = flags & MATCH_REFS_MIRROR;
        int send_prune = flags & MATCH_REFS_PRUNE;
        int errs;
        static const char *default_refspec[] = { ":", NULL };
        struct ref *ref, **dst_tail = tail_ref(dst);

        if (!nr_refspec) {
                nr_refspec = 1;
                refspec = default_refspec;
        }
        rs = parse_push_refspec(nr_refspec, (const char **) refspec);
        errs = match_explicit_refs(src, *dst, &dst_tail, rs, nr_refspec);

        /* pick the remainder */
        for (ref = src; ref; ref = ref->next) {
                struct ref *dst_peer;
                const struct refspec *pat = NULL;
                char *dst_name;

                dst_name = get_ref_match(rs, nr_refspec, ref, send_mirror, FROM_SRC, &pat);
                if (!dst_name)
                        continue;

                dst_peer = find_ref_by_name(*dst, dst_name);
                if (dst_peer) {
                        if (dst_peer->peer_ref)
                                /* We're already sending something to this ref. */
                                goto free_name;
                } else {
                        if (pat->matching && !(send_all || send_mirror))
                                /*
                                 * Remote doesn't have it, and we have no
                                 * explicit pattern, and we don't have
                                 * --all nor --mirror.
                                 */
                                goto free_name;

                        /* Create a new one and link it */
                        dst_peer = make_linked_ref(dst_name, &dst_tail);
                        hashcpy(dst_peer->new_sha1, ref->new_sha1);
                }
                dst_peer->peer_ref = copy_ref(ref);
                dst_peer->force = pat->force;
        free_name:
                free(dst_name);
        }

        if (flags & MATCH_REFS_FOLLOW_TAGS)
                add_missing_tags(src, dst, &dst_tail);

        if (send_prune) {
                /* check for missing refs on the remote */
                for (ref = *dst; ref; ref = ref->next) {
                        char *src_name;

                        if (ref->peer_ref)
                                /* We're already sending something to this ref. */
                                continue;

                        src_name = get_ref_match(rs, nr_refspec, ref, send_mirror, FROM_DST, NULL);
                        if (src_name) {
                                if (!find_ref_by_name(src, src_name))
                                        ref->peer_ref = alloc_delete_ref();
                                free(src_name);
                        }
                }
        }
        if (errs)
                return -1;
        return 0;
}

void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
        int force_update)
{
        struct ref *ref;

        for (ref = remote_refs; ref; ref = ref->next) {
                int force_ref_update = ref->force || force_update;

                if (ref->peer_ref)
                        hashcpy(ref->new_sha1, ref->peer_ref->new_sha1);
                else if (!send_mirror)
                        continue;

                ref->deletion = is_null_sha1(ref->new_sha1);
                if (!ref->deletion &&
                        !hashcmp(ref->old_sha1, ref->new_sha1)) {
                        ref->status = REF_STATUS_UPTODATE;
                        continue;
                }

                /*
                 * Decide whether an individual refspec A:B can be
                 * pushed.  The push will succeed if any of the
                 * following are true:
                 *
                 * (1) the remote reference B does not exist
                 *
                 * (2) the remote reference B is being removed (i.e.,
                 *     pushing :B where no source is specified)
                 *
                 * (3) the destination is not under refs/tags/, and
                 *     if the old and new value is a commit, the new
                 *     is a descendant of the old.
                 *
                 * (4) it is forced using the +A:B notation, or by
                 *     passing the --force argument
                 */

                if (!ref->deletion && !is_null_sha1(ref->old_sha1)) {
                        int why = 0; /* why would this push require --force? */

                        if (!prefixcmp(ref->name, "refs/tags/"))
                                why = REF_STATUS_REJECT_ALREADY_EXISTS;
                        else if (!has_sha1_file(ref->old_sha1))
                                why = REF_STATUS_REJECT_FETCH_FIRST;
                        else if (!lookup_commit_reference_gently(ref->old_sha1, 1) ||
                                 !lookup_commit_reference_gently(ref->new_sha1, 1))
                                why = REF_STATUS_REJECT_NEEDS_FORCE;
                        else if (!ref_newer(ref->new_sha1, ref->old_sha1))
                                why = REF_STATUS_REJECT_NONFASTFORWARD;

                        if (!force_ref_update)
                                ref->status = why;
                        else if (why)
                                ref->forced_update = 1;
                }
        }
}

struct branch *branch_get(const char *name)
{
        struct branch *ret;

        read_config();
        if (!name || !*name || !strcmp(name, "HEAD"))
                ret = current_branch;
        else
                ret = make_branch(name, 0);
        if (ret && ret->remote_name) {
                ret->remote = remote_get(ret->remote_name);
                if (ret->merge_nr) {
                        int i;
                        ret->merge = xcalloc(ret->merge_nr, sizeof(*ret->merge));
                        for (i = 0; i < ret->merge_nr; i++) {
                                ret->merge[i] = xcalloc(1, sizeof(**ret->merge));
                                ret->merge[i]->src = xstrdup(ret->merge_name[i]);
                                if (remote_find_tracking(ret->remote, ret->merge[i])
                                    && !strcmp(ret->remote_name, "."))
                                        ret->merge[i]->dst = xstrdup(ret->merge_name[i]);
                        }
                }
        }
        return ret;
}

int branch_has_merge_config(struct branch *branch)
{
        return branch && !!branch->merge;
}

int branch_merge_matches(struct branch *branch,
                                 int i,
                                 const char *refname)
{
        if (!branch || i < 0 || i >= branch->merge_nr)
                return 0;
        return refname_match(branch->merge[i]->src, refname, ref_fetch_rules);
}

static int ignore_symref_update(const char *refname)
{
        unsigned char sha1[20];
        int flag;

        if (!resolve_ref_unsafe(refname, sha1, 0, &flag))
                return 0; /* non-existing refs are OK */
        return (flag & REF_ISSYMREF);
}

static struct ref *get_expanded_map(const struct ref *remote_refs,
                                    const struct refspec *refspec)
{
        const struct ref *ref;
        struct ref *ret = NULL;
        struct ref **tail = &ret;

        char *expn_name;

        for (ref = remote_refs; ref; ref = ref->next) {
                if (strchr(ref->name, '^'))
                        continue; /* a dereference item */
                if (match_name_with_pattern(refspec->src, ref->name,
                                            refspec->dst, &expn_name) &&
                    !ignore_symref_update(expn_name)) {
                        struct ref *cpy = copy_ref(ref);

                        cpy->peer_ref = alloc_ref(expn_name);
                        free(expn_name);
                        if (refspec->force)
                                cpy->peer_ref->force = 1;
                        *tail = cpy;
                        tail = &cpy->next;
                }
        }

        return ret;
}

static const struct ref *find_ref_by_name_abbrev(const struct ref *refs, const char *name)
{
        const struct ref *ref;
        for (ref = refs; ref; ref = ref->next) {
                if (refname_match(name, ref->name, ref_fetch_rules))
                        return ref;
        }
        return NULL;
}

struct ref *get_remote_ref(const struct ref *remote_refs, const char *name)
{
        const struct ref *ref = find_ref_by_name_abbrev(remote_refs, name);

        if (!ref)
                return NULL;

        return copy_ref(ref);
}

static struct ref *get_local_ref(const char *name)
{
        if (!name || name[0] == '\0')
                return NULL;

        if (!prefixcmp(name, "refs/"))
                return alloc_ref(name);

        if (!prefixcmp(name, "heads/") ||
            !prefixcmp(name, "tags/") ||
            !prefixcmp(name, "remotes/"))
                return alloc_ref_with_prefix("refs/", 5, name);

        return alloc_ref_with_prefix("refs/heads/", 11, name);
}

int get_fetch_map(const struct ref *remote_refs,
                  const struct refspec *refspec,
                  struct ref ***tail,
                  int missing_ok)
{
        struct ref *ref_map, **rmp;

        if (refspec->pattern) {
                ref_map = get_expanded_map(remote_refs, refspec);
        } else {
                const char *name = refspec->src[0] ? refspec->src : "HEAD";

                if (refspec->exact_sha1) {
                        ref_map = alloc_ref(name);
                        get_sha1_hex(name, ref_map->old_sha1);
                } else {
                        ref_map = get_remote_ref(remote_refs, name);
                }
                if (!missing_ok && !ref_map)
                        die("Couldn't find remote ref %s", name);
                if (ref_map) {
                        ref_map->peer_ref = get_local_ref(refspec->dst);
                        if (ref_map->peer_ref && refspec->force)
                                ref_map->peer_ref->force = 1;
                }
        }

        for (rmp = &ref_map; *rmp; ) {
                if ((*rmp)->peer_ref) {
                        if (prefixcmp((*rmp)->peer_ref->name, "refs/") ||
                            check_refname_format((*rmp)->peer_ref->name, 0)) {
                                struct ref *ignore = *rmp;
                                error("* Ignoring funny ref '%s' locally",
                                      (*rmp)->peer_ref->name);
                                *rmp = (*rmp)->next;
                                free(ignore->peer_ref);
                                free(ignore);
                                continue;
                        }
                }
                rmp = &((*rmp)->next);
        }

        if (ref_map)
                tail_link_ref(ref_map, tail);

        return 0;
}

int resolve_remote_symref(struct ref *ref, struct ref *list)
{
        if (!ref->symref)
                return 0;
        for (; list; list = list->next)
                if (!strcmp(ref->symref, list->name)) {
                        hashcpy(ref->old_sha1, list->old_sha1);
                        return 0;
                }
        return 1;
}

static void unmark_and_free(struct commit_list *list, unsigned int mark)
{
        while (list) {
                struct commit_list *temp = list;
                temp->item->object.flags &= ~mark;
                list = temp->next;
                free(temp);
        }
}

int ref_newer(const unsigned char *new_sha1, const unsigned char *old_sha1)
{
        struct object *o;
        struct commit *old, *new;
        struct commit_list *list, *used;
        int found = 0;

        /*
         * Both new and old must be commit-ish and new is descendant of
         * old.  Otherwise we require --force.
         */
        o = deref_tag(parse_object(old_sha1), NULL, 0);
        if (!o || o->type != OBJ_COMMIT)
                return 0;
        old = (struct commit *) o;

        o = deref_tag(parse_object(new_sha1), NULL, 0);
        if (!o || o->type != OBJ_COMMIT)
                return 0;
        new = (struct commit *) o;

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

        used = list = NULL;
        commit_list_insert(new, &list);
        while (list) {
                new = pop_most_recent_commit(&list, TMP_MARK);
                commit_list_insert(new, &used);
                if (new == old) {
                        found = 1;
                        break;
                }
        }
        unmark_and_free(list, TMP_MARK);
        unmark_and_free(used, TMP_MARK);
        return found;
}

/*
 * Return true if there is anything to report, otherwise false.
 */
int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
{
        unsigned char sha1[20];
        struct commit *ours, *theirs;
        char symmetric[84];
        struct rev_info revs;
        const char *rev_argv[10], *base;
        int rev_argc;

        /*
         * Nothing to report unless we are marked to build on top of
         * somebody else.
         */
        if (!branch ||
            !branch->merge || !branch->merge[0] || !branch->merge[0]->dst)
                return 0;

        /*
         * If what we used to build on no longer exists, there is
         * nothing to report.
         */
        base = branch->merge[0]->dst;
        if (read_ref(base, sha1))
                return 0;
        theirs = lookup_commit_reference(sha1);
        if (!theirs)
                return 0;

        if (read_ref(branch->refname, sha1))
                return 0;
        ours = lookup_commit_reference(sha1);
        if (!ours)
                return 0;

        /* are we the same? */
        if (theirs == ours)
                return 0;

        /* Run "rev-list --left-right ours...theirs" internally... */
        rev_argc = 0;
        rev_argv[rev_argc++] = NULL;
        rev_argv[rev_argc++] = "--left-right";
        rev_argv[rev_argc++] = symmetric;
        rev_argv[rev_argc++] = "--";
        rev_argv[rev_argc] = NULL;

        strcpy(symmetric, sha1_to_hex(ours->object.sha1));
        strcpy(symmetric + 40, "...");
        strcpy(symmetric + 43, sha1_to_hex(theirs->object.sha1));

        init_revisions(&revs, NULL);
        setup_revisions(rev_argc, rev_argv, &revs, NULL);
        prepare_revision_walk(&revs);

        /* ... and count the commits on each side. */
        *num_ours = 0;
        *num_theirs = 0;
        while (1) {
                struct commit *c = get_revision(&revs);
                if (!c)
                        break;
                if (c->object.flags & SYMMETRIC_LEFT)
                        (*num_ours)++;
                else
                        (*num_theirs)++;
        }

        /* clear object flags smudged by the above traversal */
        clear_commit_marks(ours, ALL_REV_FLAGS);
        clear_commit_marks(theirs, ALL_REV_FLAGS);
        return 1;
}

/*
 * Return true when there is anything to report, otherwise false.
 */
int format_tracking_info(struct branch *branch, struct strbuf *sb)
{
        int num_ours, num_theirs;
        const char *base;

        if (!stat_tracking_info(branch, &num_ours, &num_theirs))
                return 0;

        base = branch->merge[0]->dst;
        base = shorten_unambiguous_ref(base, 0);
        if (!num_theirs) {
                strbuf_addf(sb,
                        Q_("Your branch is ahead of '%s' by %d commit.\n",
                           "Your branch is ahead of '%s' by %d commits.\n",
                           num_ours),
                        base, num_ours);
                if (advice_status_hints)
                        strbuf_addf(sb,
                                _("  (use \"git push\" to publish your local commits)\n"));
        } else if (!num_ours) {
                strbuf_addf(sb,
                        Q_("Your branch is behind '%s' by %d commit, "
                               "and can be fast-forwarded.\n",
                           "Your branch is behind '%s' by %d commits, "
                               "and can be fast-forwarded.\n",
                           num_theirs),
                        base, num_theirs);
                if (advice_status_hints)
                        strbuf_addf(sb,
                                _("  (use \"git pull\" to update your local branch)\n"));
        } else {
                strbuf_addf(sb,
                        Q_("Your branch and '%s' have diverged,\n"
                               "and have %d and %d different commit each, "
                               "respectively.\n",
                           "Your branch and '%s' have diverged,\n"
                               "and have %d and %d different commits each, "
                               "respectively.\n",
                           num_theirs),
                        base, num_ours, num_theirs);
                if (advice_status_hints)
                        strbuf_addf(sb,
                                _("  (use \"git pull\" to merge the remote branch into yours)\n"));
        }
        return 1;
}

static int one_local_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
{
        struct ref ***local_tail = cb_data;
        struct ref *ref;
        int len;

        /* we already know it starts with refs/ to get here */
        if (check_refname_format(refname + 5, 0))
                return 0;

        len = strlen(refname) + 1;
        ref = xcalloc(1, sizeof(*ref) + len);
        hashcpy(ref->new_sha1, sha1);
        memcpy(ref->name, refname, len);
        **local_tail = ref;
        *local_tail = &ref->next;
        return 0;
}

struct ref *get_local_heads(void)
{
        struct ref *local_refs = NULL, **local_tail = &local_refs;
        for_each_ref(one_local_ref, &local_tail);
        return local_refs;
}

struct ref *guess_remote_head(const struct ref *head,
                              const struct ref *refs,
                              int all)
{
        const struct ref *r;
        struct ref *list = NULL;
        struct ref **tail = &list;

        if (!head)
                return NULL;

        /*
         * Some transports support directly peeking at
         * where HEAD points; if that is the case, then
         * we don't have to guess.
         */
        if (head->symref)
                return copy_ref(find_ref_by_name(refs, head->symref));

        /* If refs/heads/master could be right, it is. */
        if (!all) {
                r = find_ref_by_name(refs, "refs/heads/master");
                if (r && !hashcmp(r->old_sha1, head->old_sha1))
                        return copy_ref(r);
        }

        /* Look for another ref that points there */
        for (r = refs; r; r = r->next) {
                if (r != head &&
                    !prefixcmp(r->name, "refs/heads/") &&
                    !hashcmp(r->old_sha1, head->old_sha1)) {
                        *tail = copy_ref(r);
                        tail = &((*tail)->next);
                        if (!all)
                                break;
                }
        }

        return list;
}

struct stale_heads_info {
        struct string_list *ref_names;
        struct ref **stale_refs_tail;
        struct refspec *refs;
        int ref_count;
};

static int get_stale_heads_cb(const char *refname,
        const unsigned char *sha1, int flags, void *cb_data)
{
        struct stale_heads_info *info = cb_data;
        struct refspec query;
        memset(&query, 0, sizeof(struct refspec));
        query.dst = (char *)refname;

        if (query_refspecs(info->refs, info->ref_count, &query))
                return 0; /* No matches */

        /*
         * If we did find a suitable refspec and it's not a symref and
         * it's not in the list of refs that currently exist in that
         * remote we consider it to be stale.
         */
        if (!((flags & REF_ISSYMREF) ||
              string_list_has_string(info->ref_names, query.src))) {
                struct ref *ref = make_linked_ref(refname, &info->stale_refs_tail);
                hashcpy(ref->new_sha1, sha1);
        }

        free(query.src);
        return 0;
}

struct ref *get_stale_heads(struct refspec *refs, int ref_count, struct ref *fetch_map)
{
        struct ref *ref, *stale_refs = NULL;
        struct string_list ref_names = STRING_LIST_INIT_NODUP;
        struct stale_heads_info info;
        info.ref_names = &ref_names;
        info.stale_refs_tail = &stale_refs;
        info.refs = refs;
        info.ref_count = ref_count;
        for (ref = fetch_map; ref; ref = ref->next)
                string_list_append(&ref_names, ref->name);
        sort_string_list(&ref_names);
        for_each_ref(get_stale_heads_cb, &info);
        string_list_clear(&ref_names, 0);
        return stale_refs;
}