remote: use remote_state parameter internally

[thirdparty/git.git] / remote.c

#include "cache.h"
#include "config.h"
#include "remote.h"
#include "refs.h"
#include "refspec.h"
#include "object-store.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "dir.h"
#include "tag.h"
#include "string-list.h"
#include "mergesort.h"
#include "strvec.h"
#include "commit-reach.h"
#include "advice.h"

enum map_direction { FROM_SRC, FROM_DST };

struct counted_string {
        size_t len;
        const char *s;
};

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;
        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 (starts_with(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;

        return xstrfmt("%s%s", r->rewrite[longest_i]->base, url + longest->len);
}

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_state *remote_state,
                              struct remote *remote, const char *url)
{
        const char *pushurl = alias_url(url, &remote_state->rewrites_push);
        if (pushurl != url)
                add_pushurl(remote, pushurl);
}

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

struct remotes_hash_key {
        const char *str;
        int len;
};

static int remotes_hash_cmp(const void *unused_cmp_data,
                            const struct hashmap_entry *eptr,
                            const struct hashmap_entry *entry_or_key,
                            const void *keydata)
{
        const struct remote *a, *b;
        const struct remotes_hash_key *key = keydata;

        a = container_of(eptr, const struct remote, ent);
        b = container_of(entry_or_key, const struct remote, ent);

        if (key)
                return strncmp(a->name, key->str, key->len) || a->name[key->len];
        else
                return strcmp(a->name, b->name);
}

static struct remote *make_remote(struct remote_state *remote_state,
                                  const char *name, int len)
{
        struct remote *ret;
        struct remotes_hash_key lookup;
        struct hashmap_entry lookup_entry, *e;

        if (!len)
                len = strlen(name);

        lookup.str = name;
        lookup.len = len;
        hashmap_entry_init(&lookup_entry, memhash(name, len));

        e = hashmap_get(&remote_state->remotes_hash, &lookup_entry, &lookup);
        if (e)
                return container_of(e, struct remote, ent);

        CALLOC_ARRAY(ret, 1);
        ret->prune = -1;  /* unspecified */
        ret->prune_tags = -1;  /* unspecified */
        ret->name = xstrndup(name, len);
        refspec_init(&ret->push, REFSPEC_PUSH);
        refspec_init(&ret->fetch, REFSPEC_FETCH);

        ALLOC_GROW(remote_state->remotes, remote_state->remotes_nr + 1,
                   remote_state->remotes_alloc);
        remote_state->remotes[remote_state->remotes_nr++] = ret;

        hashmap_entry_init(&ret->ent, lookup_entry.hash);
        if (hashmap_put_entry(&remote_state->remotes_hash, ret, ent))
                BUG("hashmap_put overwrote entry after hashmap_get returned NULL");
        return ret;
}

static void remote_clear(struct remote *remote)
{
        int i;

        free((char *)remote->name);
        free((char *)remote->foreign_vcs);

        for (i = 0; i < remote->url_nr; i++) {
                free((char *)remote->url[i]);
        }
        FREE_AND_NULL(remote->pushurl);

        for (i = 0; i < remote->pushurl_nr; i++) {
                free((char *)remote->pushurl[i]);
        }
        FREE_AND_NULL(remote->pushurl);
        free((char *)remote->receivepack);
        free((char *)remote->uploadpack);
        FREE_AND_NULL(remote->http_proxy);
        FREE_AND_NULL(remote->http_proxy_authmethod);
}

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(struct remote_state *remote_state,
                                  const char *name, size_t len)
{
        struct branch *ret;
        int i;

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

        ALLOC_GROW(remote_state->branches, remote_state->branches_nr + 1,
                   remote_state->branches_alloc);
        CALLOC_ARRAY(ret, 1);
        remote_state->branches[remote_state->branches_nr++] = ret;
        ret->name = xstrndup(name, len);
        ret->refname = xstrfmt("refs/heads/%s", ret->name);

        return ret;
}

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

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

        ALLOC_GROW(r->rewrite, r->rewrite_nr + 1, r->rewrite_alloc);
        CALLOC_ARRAY(ret, 1);
        r->rewrite[r->rewrite_nr++] = ret;
        ret->base = xstrndup(base, len);
        ret->baselen = len;
        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 const char *skip_spaces(const char *s)
{
        while (isspace(*s))
                s++;
        return s;
}

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

        if (!f)
                return;
        remote->configured_in_repo = 1;
        remote->origin = REMOTE_REMOTES;
        while (strbuf_getline(&buf, f) != EOF) {
                const char *v;

                strbuf_rtrim(&buf);

                if (skip_prefix(buf.buf, "URL:", &v))
                        add_url_alias(remote_state, remote,
                                      xstrdup(skip_spaces(v)));
                else if (skip_prefix(buf.buf, "Push:", &v))
                        refspec_append(&remote->push, skip_spaces(v));
                else if (skip_prefix(buf.buf, "Pull:", &v))
                        refspec_append(&remote->fetch, skip_spaces(v));
        }
        strbuf_release(&buf);
        fclose(f);
}

static void read_branches_file(struct remote_state *remote_state,
                               struct remote *remote)
{
        char *frag;
        struct strbuf buf = STRBUF_INIT;
        FILE *f = fopen_or_warn(git_path("branches/%s", remote->name), "r");

        if (!f)
                return;

        strbuf_getline_lf(&buf, f);
        fclose(f);
        strbuf_trim(&buf);
        if (!buf.len) {
                strbuf_release(&buf);
                return;
        }

        remote->configured_in_repo = 1;
        remote->origin = REMOTE_BRANCHES;

        /*
         * The branches file would have URL and optionally
         * #branch specified.  The default (or specified) branch is
         * fetched and stored in the local branch matching the
         * remote name.
         */
        frag = strchr(buf.buf, '#');
        if (frag)
                *(frag++) = '\0';
        else
                frag = (char *)git_default_branch_name(0);

        add_url_alias(remote_state, remote, strbuf_detach(&buf, NULL));
        refspec_appendf(&remote->fetch, "refs/heads/%s:refs/heads/%s",
                        frag, remote->name);

        /*
         * Cogito compatible push: push current HEAD to remote #branch
         * (master if missing)
         */
        refspec_appendf(&remote->push, "HEAD:refs/heads/%s", frag);
        remote->fetch_tags = 1; /* always auto-follow */
}

static int handle_config(const char *key, const char *value, void *cb)
{
        const char *name;
        size_t namelen;
        const char *subkey;
        struct remote *remote;
        struct branch *branch;
        struct remote_state *remote_state = cb;

        if (parse_config_key(key, "branch", &name, &namelen, &subkey) >= 0) {
                if (!name)
                        return 0;
                branch = make_branch(remote_state, name, namelen);
                if (!strcmp(subkey, "remote")) {
                        return git_config_string(&branch->remote_name, key, value);
                } else if (!strcmp(subkey, "pushremote")) {
                        return git_config_string(&branch->pushremote_name, key, value);
                } else if (!strcmp(subkey, "merge")) {
                        if (!value)
                                return config_error_nonbool(key);
                        add_merge(branch, xstrdup(value));
                }
                return 0;
        }
        if (parse_config_key(key, "url", &name, &namelen, &subkey) >= 0) {
                struct rewrite *rewrite;
                if (!name)
                        return 0;
                if (!strcmp(subkey, "insteadof")) {
                        if (!value)
                                return config_error_nonbool(key);
                        rewrite = make_rewrite(&remote_state->rewrites, name,
                                               namelen);
                        add_instead_of(rewrite, xstrdup(value));
                } else if (!strcmp(subkey, "pushinsteadof")) {
                        if (!value)
                                return config_error_nonbool(key);
                        rewrite = make_rewrite(&remote_state->rewrites_push,
                                               name, namelen);
                        add_instead_of(rewrite, xstrdup(value));
                }
        }

        if (parse_config_key(key, "remote", &name, &namelen, &subkey) < 0)
                return 0;

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

        if (!name)
                return 0;
        /* Handle remote.<name>.* variables */
        if (*name == '/') {
                warning(_("config remote shorthand cannot begin with '/': %s"),
                        name);
                return 0;
        }
        remote = make_remote(remote_state, name, namelen);
        remote->origin = REMOTE_CONFIG;
        if (current_config_scope() == CONFIG_SCOPE_LOCAL ||
            current_config_scope() == CONFIG_SCOPE_WORKTREE)
                remote->configured_in_repo = 1;
        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, "prune"))
                remote->prune = git_config_bool(key, value);
        else if (!strcmp(subkey, "prunetags"))
                remote->prune_tags = 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;
                refspec_append(&remote->push, v);
                free((char *)v);
        } else if (!strcmp(subkey, "fetch")) {
                const char *v;
                if (git_config_string(&v, key, value))
                        return -1;
                refspec_append(&remote->fetch, v);
                free((char *)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, "proxyauthmethod")) {
                return git_config_string((const char **)&remote->http_proxy_authmethod,
                                         key, value);
        } else if (!strcmp(subkey, "vcs")) {
                return git_config_string(&remote->foreign_vcs, key, value);
        }
        return 0;
}

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

static void read_config(struct repository *repo)
{
        int flag;

        if (repo->remote_state->initialized)
                return;
        repo->remote_state->initialized = 1;

        repo->remote_state->current_branch = NULL;
        if (startup_info->have_repository) {
                const char *head_ref = refs_resolve_ref_unsafe(
                        get_main_ref_store(repo), "HEAD", 0, NULL, &flag);
                if (head_ref && (flag & REF_ISSYMREF) &&
                    skip_prefix(head_ref, "refs/heads/", &head_ref)) {
                        repo->remote_state->current_branch = make_branch(
                                repo->remote_state, head_ref, strlen(head_ref));
                }
        }
        repo_config(repo, handle_config, repo->remote_state);
        alias_all_urls(repo->remote_state);
}

static int valid_remote_nick(const char *name)
{
        if (!name[0] || is_dot_or_dotdot(name))
                return 0;

        /* remote nicknames cannot contain slashes */
        while (*name)
                if (is_dir_sep(*name++))
                        return 0;
        return 1;
}

const char *remote_for_branch(struct branch *branch, int *explicit)
{
        if (branch && branch->remote_name) {
                if (explicit)
                        *explicit = 1;
                return branch->remote_name;
        }
        if (explicit)
                *explicit = 0;
        return "origin";
}

const char *pushremote_for_branch(struct branch *branch, int *explicit)
{
        if (branch && branch->pushremote_name) {
                if (explicit)
                        *explicit = 1;
                return branch->pushremote_name;
        }
        if (the_repository->remote_state->pushremote_name) {
                if (explicit)
                        *explicit = 1;
                return the_repository->remote_state->pushremote_name;
        }
        return remote_for_branch(branch, explicit);
}

const char *remote_ref_for_branch(struct branch *branch, int for_push)
{
        if (branch) {
                if (!for_push) {
                        if (branch->merge_nr) {
                                return branch->merge_name[0];
                        }
                } else {
                        const char *dst, *remote_name =
                                pushremote_for_branch(branch, NULL);
                        struct remote *remote = remote_get(remote_name);

                        if (remote && remote->push.nr &&
                            (dst = apply_refspecs(&remote->push,
                                                  branch->refname))) {
                                return dst;
                        }
                }
        }
        return NULL;
}

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

        read_config(the_repository);

        if (name)
                name_given = 1;
        else
                name = get_default(the_repository->remote_state->current_branch,
                                   &name_given);

        ret = make_remote(the_repository->remote_state, name, 0);
        if (valid_remote_nick(name) && have_git_dir()) {
                if (!valid_remote(ret))
                        read_remotes_file(the_repository->remote_state, ret);
                if (!valid_remote(ret))
                        read_branches_file(the_repository->remote_state, ret);
        }
        if (name_given && !valid_remote(ret))
                add_url_alias(the_repository->remote_state, ret, name);
        if (!valid_remote(ret))
                return NULL;
        return ret;
}

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

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

int remote_is_configured(struct remote *remote, int in_repo)
{
        if (!remote)
                return 0;
        if (in_repo)
                return remote->configured_in_repo;
        return !!remote->origin;
}

int for_each_remote(each_remote_fn fn, void *priv)
{
        int i, result = 0;
        read_config(the_repository);
        for (i = 0; i < the_repository->remote_state->remotes_nr && !result;
             i++) {
                struct remote *remote =
                        the_repository->remote_state->remotes[i];
                if (!remote)
                        continue;
                result = fn(remote, priv);
        }
        return result;
}

static void handle_duplicate(struct ref *ref1, struct ref *ref2)
{
        if (strcmp(ref1->name, ref2->name)) {
                if (ref1->fetch_head_status != FETCH_HEAD_IGNORE &&
                    ref2->fetch_head_status != FETCH_HEAD_IGNORE) {
                        die(_("Cannot fetch both %s and %s to %s"),
                            ref1->name, ref2->name, ref2->peer_ref->name);
                } else if (ref1->fetch_head_status != FETCH_HEAD_IGNORE &&
                           ref2->fetch_head_status == FETCH_HEAD_IGNORE) {
                        warning(_("%s usually tracks %s, not %s"),
                                ref2->peer_ref->name, ref2->name, ref1->name);
                } else if (ref1->fetch_head_status == FETCH_HEAD_IGNORE &&
                           ref2->fetch_head_status == FETCH_HEAD_IGNORE) {
                        die(_("%s tracks both %s and %s"),
                            ref2->peer_ref->name, ref1->name, ref2->name);
                } else {
                        /*
                         * This last possibility doesn't occur because
                         * FETCH_HEAD_IGNORE entries always appear at
                         * the end of the list.
                         */
                        BUG("Internal error");
                }
        }
        free(ref2->peer_ref);
        free(ref2);
}

struct ref *ref_remove_duplicates(struct ref *ref_map)
{
        struct string_list refs = STRING_LIST_INIT_NODUP;
        struct ref *retval = NULL;
        struct ref **p = &retval;

        while (ref_map) {
                struct ref *ref = ref_map;

                ref_map = ref_map->next;
                ref->next = NULL;

                if (!ref->peer_ref) {
                        *p = ref;
                        p = &ref->next;
                } else {
                        struct string_list_item *item =
                                string_list_insert(&refs, ref->peer_ref->name);

                        if (item->util) {
                                /* Entry already existed */
                                handle_duplicate((struct ref *)item->util, ref);
                        } else {
                                *p = ref;
                                p = &ref->next;
                                item->util = ref;
                        }
                }
        }

        string_list_clear(&refs, 0);
        return retval;
}

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) {
                struct strbuf sb = STRBUF_INIT;
                const char *vstar = strchr(value, '*');
                if (!vstar)
                        die(_("value '%s' of pattern has no '*'"), value);
                strbuf_add(&sb, value, vstar - value);
                strbuf_add(&sb, name + klen, namelen - klen - ksuffixlen);
                strbuf_addstr(&sb, vstar + 1);
                *result = strbuf_detach(&sb, NULL);
        }
        return ret;
}

static int refspec_match(const struct refspec_item *refspec,
                         const char *name)
{
        if (refspec->pattern)
                return match_name_with_pattern(refspec->src, name, NULL, NULL);

        return !strcmp(refspec->src, name);
}

static int omit_name_by_refspec(const char *name, struct refspec *rs)
{
        int i;

        for (i = 0; i < rs->nr; i++) {
                if (rs->items[i].negative && refspec_match(&rs->items[i], name))
                        return 1;
        }
        return 0;
}

struct ref *apply_negative_refspecs(struct ref *ref_map, struct refspec *rs)
{
        struct ref **tail;

        for (tail = &ref_map; *tail; ) {
                struct ref *ref = *tail;

                if (omit_name_by_refspec(ref->name, rs)) {
                        *tail = ref->next;
                        free(ref->peer_ref);
                        free(ref);
                } else
                        tail = &ref->next;
        }

        return ref_map;
}

static int query_matches_negative_refspec(struct refspec *rs, struct refspec_item *query)
{
        int i, matched_negative = 0;
        int find_src = !query->src;
        struct string_list reversed = STRING_LIST_INIT_NODUP;
        const char *needle = find_src ? query->dst : query->src;

        /*
         * Check whether the queried ref matches any negative refpsec. If so,
         * then we should ultimately treat this as not matching the query at
         * all.
         *
         * Note that negative refspecs always match the source, but the query
         * item uses the destination. To handle this, we apply pattern
         * refspecs in reverse to figure out if the query source matches any
         * of the negative refspecs.
         *
         * The first loop finds and expands all positive refspecs
         * matched by the queried ref.
         *
         * The second loop checks if any of the results of the first loop
         * match any negative refspec.
         */
        for (i = 0; i < rs->nr; i++) {
                struct refspec_item *refspec = &rs->items[i];
                char *expn_name;

                if (refspec->negative)
                        continue;

                /* Note the reversal of src and dst */
                if (refspec->pattern) {
                        const char *key = refspec->dst ? refspec->dst : refspec->src;
                        const char *value = refspec->src;

                        if (match_name_with_pattern(key, needle, value, &expn_name))
                                string_list_append_nodup(&reversed, expn_name);
                } else if (refspec->matching) {
                        /* For the special matching refspec, any query should match */
                        string_list_append(&reversed, needle);
                } else if (!refspec->src) {
                        BUG("refspec->src should not be null here");
                } else if (!strcmp(needle, refspec->src)) {
                        string_list_append(&reversed, refspec->src);
                }
        }

        for (i = 0; !matched_negative && i < reversed.nr; i++) {
                if (omit_name_by_refspec(reversed.items[i].string, rs))
                        matched_negative = 1;
        }

        string_list_clear(&reversed, 0);

        return matched_negative;
}

static void query_refspecs_multiple(struct refspec *rs,
                                    struct refspec_item *query,
                                    struct string_list *results)
{
        int i;
        int find_src = !query->src;

        if (find_src && !query->dst)
                BUG("query_refspecs_multiple: need either src or dst");

        if (query_matches_negative_refspec(rs, query))
                return;

        for (i = 0; i < rs->nr; i++) {
                struct refspec_item *refspec = &rs->items[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 || refspec->negative)
                        continue;
                if (refspec->pattern) {
                        if (match_name_with_pattern(key, needle, value, result))
                                string_list_append_nodup(results, *result);
                } else if (!strcmp(needle, key)) {
                        string_list_append(results, value);
                }
        }
}

int query_refspecs(struct refspec *rs, struct refspec_item *query)
{
        int i;
        int find_src = !query->src;
        const char *needle = find_src ? query->dst : query->src;
        char **result = find_src ? &query->src : &query->dst;

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

        if (query_matches_negative_refspec(rs, query))
                return -1;

        for (i = 0; i < rs->nr; i++) {
                struct refspec_item *refspec = &rs->items[i];
                const char *key = find_src ? refspec->dst : refspec->src;
                const char *value = find_src ? refspec->src : refspec->dst;

                if (!refspec->dst || refspec->negative)
                        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 *rs, const char *name)
{
        struct refspec_item query;

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

        if (query_refspecs(rs, &query))
                return NULL;

        return query.dst;
}

int remote_find_tracking(struct remote *remote, struct refspec_item *refspec)
{
        return query_refspecs(&remote->fetch, 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, st_add4(sizeof(*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 = st_add3(sizeof(struct ref), strlen(ref->name), 1);
        cpy = xmalloc(len);
        memcpy(cpy, ref, len);
        cpy->next = NULL;
        cpy->symref = xstrdup_or_null(ref->symref);
        cpy->remote_status = xstrdup_or_null(ref->remote_status);
        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;
}

void free_one_ref(struct ref *ref)
{
        if (!ref)
                return;
        free_one_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_one_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);
}

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))
                        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 &&
                    !starts_with(name, "refs/heads/") &&
                    !starts_with(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) {
                if (matched_ref)
                        *matched_ref = matched_weak;
                return weak_match;
        }
        else {
                if (matched_ref)
                        *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)");
        oidclr(&ref->new_oid);
        return ref;
}

static int try_explicit_object_name(const char *name,
                                    struct ref **match)
{
        struct object_id oid;

        if (!*name) {
                if (match)
                        *match = alloc_delete_ref();
                return 0;
        }

        if (get_oid(name, &oid))
                return -1;

        if (match) {
                *match = alloc_ref(name);
                oidcpy(&(*match)->new_oid, &oid);
        }
        return 0;
}

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;

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

        if (starts_with(r, "refs/heads/")) {
                strbuf_addstr(&buf, "refs/heads/");
        } else if (starts_with(r, "refs/tags/")) {
                strbuf_addstr(&buf, "refs/tags/");
        } else {
                return NULL;
        }

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

static int match_explicit_lhs(struct ref *src,
                              struct refspec_item *rs,
                              struct ref **match,
                              int *allocated_match)
{
        switch (count_refspec_match(rs->src, src, match)) {
        case 1:
                if (allocated_match)
                        *allocated_match = 0;
                return 0;
        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.
                 */
                if (try_explicit_object_name(rs->src, match) < 0)
                        return error(_("src refspec %s does not match any"), rs->src);
                if (allocated_match)
                        *allocated_match = 1;
                return 0;
        default:
                return error(_("src refspec %s matches more than one"), rs->src);
        }
}

static void show_push_unqualified_ref_name_error(const char *dst_value,
                                                 const char *matched_src_name)
{
        struct object_id oid;
        enum object_type type;

        /*
         * TRANSLATORS: "matches '%s'%" is the <dst> part of "git push
         * <remote> <src>:<dst>" push, and "being pushed ('%s')" is
         * the <src>.
         */
        error(_("The destination you provided is not a full refname (i.e.,\n"
                "starting with \"refs/\"). We tried to guess what you meant by:\n"
                "\n"
                "- Looking for a ref that matches '%s' on the remote side.\n"
                "- Checking if the <src> being pushed ('%s')\n"
                "  is a ref in \"refs/{heads,tags}/\". If so we add a corresponding\n"
                "  refs/{heads,tags}/ prefix on the remote side.\n"
                "\n"
                "Neither worked, so we gave up. You must fully qualify the ref."),
              dst_value, matched_src_name);

        if (!advice_enabled(ADVICE_PUSH_UNQUALIFIED_REF_NAME))
                return;

        if (get_oid(matched_src_name, &oid))
                BUG("'%s' is not a valid object, "
                    "match_explicit_lhs() should catch this!",
                    matched_src_name);
        type = oid_object_info(the_repository, &oid, NULL);
        if (type == OBJ_COMMIT) {
                advise(_("The <src> part of the refspec is a commit object.\n"
                         "Did you mean to create a new branch by pushing to\n"
                         "'%s:refs/heads/%s'?"),
                       matched_src_name, dst_value);
        } else if (type == OBJ_TAG) {
                advise(_("The <src> part of the refspec is a tag object.\n"
                         "Did you mean to create a new tag by pushing to\n"
                         "'%s:refs/tags/%s'?"),
                       matched_src_name, dst_value);
        } else if (type == OBJ_TREE) {
                advise(_("The <src> part of the refspec is a tree object.\n"
                         "Did you mean to tag a new tree by pushing to\n"
                         "'%s:refs/tags/%s'?"),
                       matched_src_name, dst_value);
        } else if (type == OBJ_BLOB) {
                advise(_("The <src> part of the refspec is a blob object.\n"
                         "Did you mean to tag a new blob by pushing to\n"
                         "'%s:refs/tags/%s'?"),
                       matched_src_name, dst_value);
        } else {
                BUG("'%s' should be commit/tag/tree/blob, is '%d'",
                    matched_src_name, type);
        }
}

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

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

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

        matched_src = matched_dst = NULL;
        if (match_explicit_lhs(src, rs, &matched_src, &allocated_src) < 0)
                return -1;

        if (!dst_value) {
                int flag;

                dst_value = resolve_ref_unsafe(matched_src->name,
                                               RESOLVE_REF_READING,
                                               NULL, &flag);
                if (!dst_value ||
                    ((flag & REF_ISSYMREF) &&
                     !starts_with(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 (starts_with(dst_value, "refs/")) {
                        matched_dst = make_linked_ref(dst_value, dst_tail);
                } else if (is_null_oid(&matched_src->new_oid)) {
                        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);
                        free(dst_guess);
                } else {
                        show_push_unqualified_ref_name_error(dst_value,
                                                             matched_src->name);
                }
                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 = allocated_src ?
                                        matched_src :
                                        copy_ref(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 i, errs;
        for (i = errs = 0; i < rs->nr; i++)
                errs += match_explicit(src, dst, dst_tail, &rs->items[i]);
        return errs;
}

static char *get_ref_match(const struct refspec *rs, const struct ref *ref,
                           int send_mirror, int direction,
                           const struct refspec_item **ret_pat)
{
        const struct refspec_item *pat;
        char *name;
        int i;
        int matching_refs = -1;
        for (i = 0; i < rs->nr; i++) {
                const struct refspec_item *item = &rs->items[i];

                if (item->negative)
                        continue;

                if (item->matching &&
                    (matching_refs == -1 || item->force)) {
                        matching_refs = i;
                        continue;
                }

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

        pat = &rs->items[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 && !starts_with(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 struct object_id *oid)
{
        struct commit *commit;

        if (is_null_oid(oid))
                return;
        commit = lookup_commit_reference_gently(the_repository, oid, 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_oid(&ref->peer_ref->new_oid))
                        add_to_tips(&sent_tips, &ref->peer_ref->new_oid);
                else
                        add_to_tips(&sent_tips, &ref->old_oid);
                if (starts_with(ref->name, "refs/tags/"))
                        string_list_append(&dst_tag, ref->name);
        }
        clear_commit_marks_many(sent_tips.nr, sent_tips.tip, TMP_MARK);

        string_list_sort(&dst_tag);

        /* Collect tags they do not have. */
        for (ref = src; ref; ref = ref->next) {
                if (!starts_with(ref->name, "refs/tags/"))
                        continue; /* not a tag */
                if (string_list_has_string(&dst_tag, ref->name))
                        continue; /* they already have it */
                if (oid_object_info(the_repository, &ref->new_oid, 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) {
                const int reachable_flag = 1;
                struct commit_list *found_commits;
                struct commit **src_commits;
                int nr_src_commits = 0, alloc_src_commits = 16;
                ALLOC_ARRAY(src_commits, alloc_src_commits);

                for_each_string_list_item(item, &src_tag) {
                        struct ref *ref = item->util;
                        struct commit *commit;

                        if (is_null_oid(&ref->new_oid))
                                continue;
                        commit = lookup_commit_reference_gently(the_repository,
                                                                &ref->new_oid,
                                                                1);
                        if (!commit)
                                /* not pushing a commit, which is not an error */
                                continue;

                        ALLOC_GROW(src_commits, nr_src_commits + 1, alloc_src_commits);
                        src_commits[nr_src_commits++] = commit;
                }

                found_commits = get_reachable_subset(sent_tips.tip, sent_tips.nr,
                                                     src_commits, nr_src_commits,
                                                     reachable_flag);

                for_each_string_list_item(item, &src_tag) {
                        struct ref *dst_ref;
                        struct ref *ref = item->util;
                        struct commit *commit;

                        if (is_null_oid(&ref->new_oid))
                                continue;
                        commit = lookup_commit_reference_gently(the_repository,
                                                                &ref->new_oid,
                                                                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 (!(commit->object.flags & reachable_flag))
                                continue;

                        /* Add it in */
                        dst_ref = make_linked_ref(ref->name, dst_tail);
                        oidcpy(&dst_ref->new_oid, &ref->new_oid);
                        dst_ref->peer_ref = copy_ref(ref);
                }

                clear_commit_marks_many(nr_src_commits, src_commits, reachable_flag);
                free(src_commits);
                free_commit_list(found_commits);
        }

        string_list_clear(&src_tag, 0);
        free(sent_tips.tip);
}

struct ref *find_ref_by_name(const struct ref *list, const char *name)
{
        for ( ; list; list = list->next)
                if (!strcmp(list->name, name))
                        return (struct ref *)list;
        return NULL;
}

static void prepare_ref_index(struct string_list *ref_index, struct ref *ref)
{
        for ( ; ref; ref = ref->next)
                string_list_append_nodup(ref_index, ref->name)->util = ref;

        string_list_sort(ref_index);
}

/*
 * Given only the set of local refs, sanity-check the set of push
 * refspecs. We can't catch all errors that match_push_refs would,
 * but we can catch some errors early before even talking to the
 * remote side.
 */
int check_push_refs(struct ref *src, struct refspec *rs)
{
        int ret = 0;
        int i;

        for (i = 0; i < rs->nr; i++) {
                struct refspec_item *item = &rs->items[i];

                if (item->pattern || item->matching || item->negative)
                        continue;

                ret |= match_explicit_lhs(src, item, NULL, NULL);
        }

        return ret;
}

/*
 * 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,
                    struct refspec *rs, int flags)
{
        int send_all = flags & MATCH_REFS_ALL;
        int send_mirror = flags & MATCH_REFS_MIRROR;
        int send_prune = flags & MATCH_REFS_PRUNE;
        int errs;
        struct ref *ref, **dst_tail = tail_ref(dst);
        struct string_list dst_ref_index = STRING_LIST_INIT_NODUP;

        /* If no refspec is provided, use the default ":" */
        if (!rs->nr)
                refspec_append(rs, ":");

        errs = match_explicit_refs(src, *dst, &dst_tail, rs);

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

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

                if (!dst_ref_index.nr)
                        prepare_ref_index(&dst_ref_index, *dst);

                dst_item = string_list_lookup(&dst_ref_index, dst_name);
                dst_peer = dst_item ? dst_item->util : NULL;
                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 or --mirror.
                                 */
                                goto free_name;

                        /* Create a new one and link it */
                        dst_peer = make_linked_ref(dst_name, &dst_tail);
                        oidcpy(&dst_peer->new_oid, &ref->new_oid);
                        string_list_insert(&dst_ref_index,
                                dst_peer->name)->util = dst_peer;
                }
                dst_peer->peer_ref = copy_ref(ref);
                dst_peer->force = pat->force;
        free_name:
                free(dst_name);
        }

        string_list_clear(&dst_ref_index, 0);

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

        if (send_prune) {
                struct string_list src_ref_index = STRING_LIST_INIT_NODUP;
                /* 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, ref, send_mirror, FROM_DST, NULL);
                        if (src_name) {
                                if (!src_ref_index.nr)
                                        prepare_ref_index(&src_ref_index, src);
                                if (!string_list_has_string(&src_ref_index,
                                            src_name))
                                        ref->peer_ref = alloc_delete_ref();
                                free(src_name);
                        }
                }
                string_list_clear(&src_ref_index, 0);
        }

        *dst = apply_negative_refspecs(*dst, rs);

        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;
                int reject_reason = 0;

                if (ref->peer_ref)
                        oidcpy(&ref->new_oid, &ref->peer_ref->new_oid);
                else if (!send_mirror)
                        continue;

                ref->deletion = is_null_oid(&ref->new_oid);
                if (!ref->deletion &&
                        oideq(&ref->old_oid, &ref->new_oid)) {
                        ref->status = REF_STATUS_UPTODATE;
                        continue;
                }

                /*
                 * If the remote ref has moved and is now different
                 * from what we expect, reject any push.
                 *
                 * It also is an error if the user told us to check
                 * with the remote-tracking branch to find the value
                 * to expect, but we did not have such a tracking
                 * branch.
                 *
                 * If the tip of the remote-tracking ref is unreachable
                 * from any reflog entry of its local ref indicating a
                 * possible update since checkout; reject the push.
                 */
                if (ref->expect_old_sha1) {
                        if (!oideq(&ref->old_oid, &ref->old_oid_expect))
                                reject_reason = REF_STATUS_REJECT_STALE;
                        else if (ref->check_reachable && ref->unreachable)
                                reject_reason =
                                        REF_STATUS_REJECT_REMOTE_UPDATED;
                        else
                                /*
                                 * If the ref isn't stale, and is reachable
                                 * from one of the reflog entries of
                                 * the local branch, force the update.
                                 */
                                force_ref_update = 1;
                }

                /*
                 * If the update isn't already rejected then check
                 * the usual "must fast-forward" rules.
                 *
                 * 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 (!reject_reason && !ref->deletion && !is_null_oid(&ref->old_oid)) {
                        if (starts_with(ref->name, "refs/tags/"))
                                reject_reason = REF_STATUS_REJECT_ALREADY_EXISTS;
                        else if (!has_object_file(&ref->old_oid))
                                reject_reason = REF_STATUS_REJECT_FETCH_FIRST;
                        else if (!lookup_commit_reference_gently(the_repository, &ref->old_oid, 1) ||
                                 !lookup_commit_reference_gently(the_repository, &ref->new_oid, 1))
                                reject_reason = REF_STATUS_REJECT_NEEDS_FORCE;
                        else if (!ref_newer(&ref->new_oid, &ref->old_oid))
                                reject_reason = REF_STATUS_REJECT_NONFASTFORWARD;
                }

                /*
                 * "--force" will defeat any rejection implemented
                 * by the rules above.
                 */
                if (!force_ref_update)
                        ref->status = reject_reason;
                else if (reject_reason)
                        ref->forced_update = 1;
        }
}

static void set_merge(struct branch *ret)
{
        struct remote *remote;
        char *ref;
        struct object_id oid;
        int i;

        if (!ret)
                return; /* no branch */
        if (ret->merge)
                return; /* already run */
        if (!ret->remote_name || !ret->merge_nr) {
                /*
                 * no merge config; let's make sure we don't confuse callers
                 * with a non-zero merge_nr but a NULL merge
                 */
                ret->merge_nr = 0;
                return;
        }

        remote = remote_get(ret->remote_name);

        CALLOC_ARRAY(ret->merge, ret->merge_nr);
        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(remote, ret->merge[i]) ||
                    strcmp(ret->remote_name, "."))
                        continue;
                if (dwim_ref(ret->merge_name[i], strlen(ret->merge_name[i]),
                             &oid, &ref, 0) == 1)
                        ret->merge[i]->dst = ref;
                else
                        ret->merge[i]->dst = xstrdup(ret->merge_name[i]);
        }
}

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

        read_config(the_repository);
        if (!name || !*name || !strcmp(name, "HEAD"))
                ret = the_repository->remote_state->current_branch;
        else
                ret = make_branch(the_repository->remote_state, name,
                                  strlen(name));
        set_merge(ret);
        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);
}

__attribute__((format (printf,2,3)))
static const char *error_buf(struct strbuf *err, const char *fmt, ...)
{
        if (err) {
                va_list ap;
                va_start(ap, fmt);
                strbuf_vaddf(err, fmt, ap);
                va_end(ap);
        }
        return NULL;
}

const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
{
        if (!branch)
                return error_buf(err, _("HEAD does not point to a branch"));

        if (!branch->merge || !branch->merge[0]) {
                /*
                 * no merge config; is it because the user didn't define any,
                 * or because it is not a real branch, and get_branch
                 * auto-vivified it?
                 */
                if (!ref_exists(branch->refname))
                        return error_buf(err, _("no such branch: '%s'"),
                                         branch->name);
                return error_buf(err,
                                 _("no upstream configured for branch '%s'"),
                                 branch->name);
        }

        if (!branch->merge[0]->dst)
                return error_buf(err,
                                 _("upstream branch '%s' not stored as a remote-tracking branch"),
                                 branch->merge[0]->src);

        return branch->merge[0]->dst;
}

static const char *tracking_for_push_dest(struct remote *remote,
                                          const char *refname,
                                          struct strbuf *err)
{
        char *ret;

        ret = apply_refspecs(&remote->fetch, refname);
        if (!ret)
                return error_buf(err,
                                 _("push destination '%s' on remote '%s' has no local tracking branch"),
                                 refname, remote->name);
        return ret;
}

static const char *branch_get_push_1(struct branch *branch, struct strbuf *err)
{
        struct remote *remote;

        remote = remote_get(pushremote_for_branch(branch, NULL));
        if (!remote)
                return error_buf(err,
                                 _("branch '%s' has no remote for pushing"),
                                 branch->name);

        if (remote->push.nr) {
                char *dst;
                const char *ret;

                dst = apply_refspecs(&remote->push, branch->refname);
                if (!dst)
                        return error_buf(err,
                                         _("push refspecs for '%s' do not include '%s'"),
                                         remote->name, branch->name);

                ret = tracking_for_push_dest(remote, dst, err);
                free(dst);
                return ret;
        }

        if (remote->mirror)
                return tracking_for_push_dest(remote, branch->refname, err);

        switch (push_default) {
        case PUSH_DEFAULT_NOTHING:
                return error_buf(err, _("push has no destination (push.default is 'nothing')"));

        case PUSH_DEFAULT_MATCHING:
        case PUSH_DEFAULT_CURRENT:
                return tracking_for_push_dest(remote, branch->refname, err);

        case PUSH_DEFAULT_UPSTREAM:
                return branch_get_upstream(branch, err);

        case PUSH_DEFAULT_UNSPECIFIED:
        case PUSH_DEFAULT_SIMPLE:
                {
                        const char *up, *cur;

                        up = branch_get_upstream(branch, err);
                        if (!up)
                                return NULL;
                        cur = tracking_for_push_dest(remote, branch->refname, err);
                        if (!cur)
                                return NULL;
                        if (strcmp(cur, up))
                                return error_buf(err,
                                                 _("cannot resolve 'simple' push to a single destination"));
                        return cur;
                }
        }

        BUG("unhandled push situation");
}

const char *branch_get_push(struct branch *branch, struct strbuf *err)
{
        if (!branch)
                return error_buf(err, _("HEAD does not point to a branch"));

        if (!branch->push_tracking_ref)
                branch->push_tracking_ref = branch_get_push_1(branch, err);
        return branch->push_tracking_ref;
}

static int ignore_symref_update(const char *refname)
{
        int flag;

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

/*
 * Create and return a list of (struct ref) consisting of copies of
 * each remote_ref that matches refspec.  refspec must be a pattern.
 * Fill in the copies' peer_ref to describe the local tracking refs to
 * which they map.  Omit any references that would map to an existing
 * local symbolic ref.
 */
static struct ref *get_expanded_map(const struct ref *remote_refs,
                                    const struct refspec_item *refspec)
{
        const struct ref *ref;
        struct ref *ret = NULL;
        struct ref **tail = &ret;

        for (ref = remote_refs; ref; ref = ref->next) {
                char *expn_name = NULL;

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

        return ret;
}

static const struct ref *find_ref_by_name_abbrev(const struct ref *refs, const char *name)
{
        const struct ref *ref;
        const struct ref *best_match = NULL;
        int best_score = 0;

        for (ref = refs; ref; ref = ref->next) {
                int score = refname_match(name, ref->name);

                if (best_score < score) {
                        best_match = ref;
                        best_score = score;
                }
        }
        return best_match;
}

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 (starts_with(name, "refs/"))
                return alloc_ref(name);

        if (starts_with(name, "heads/") ||
            starts_with(name, "tags/") ||
            starts_with(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_item *refspec,
                  struct ref ***tail,
                  int missing_ok)
{
        struct ref *ref_map, **rmp;

        if (refspec->negative)
                return 0;

        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_oid_hex(name, &ref_map->old_oid);
                        ref_map->exact_oid = 1;
                } 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 (!starts_with((*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)) {
                        oidcpy(&ref->old_oid, &list->old_oid);
                        return 0;
                }
        return 1;
}

/*
 * Compute the commit ahead/behind values for the pair branch_name, base.
 *
 * If abf is AHEAD_BEHIND_FULL, compute the full ahead/behind and return the
 * counts in *num_ours and *num_theirs.  If abf is AHEAD_BEHIND_QUICK, skip
 * the (potentially expensive) a/b computation (*num_ours and *num_theirs are
 * set to zero).
 *
 * Returns -1 if num_ours and num_theirs could not be filled in (e.g., ref
 * does not exist).  Returns 0 if the commits are identical.  Returns 1 if
 * commits are different.
 */

static int stat_branch_pair(const char *branch_name, const char *base,
                             int *num_ours, int *num_theirs,
                             enum ahead_behind_flags abf)
{
        struct object_id oid;
        struct commit *ours, *theirs;
        struct rev_info revs;
        struct strvec argv = STRVEC_INIT;

        /* Cannot stat if what we used to build on no longer exists */
        if (read_ref(base, &oid))
                return -1;
        theirs = lookup_commit_reference(the_repository, &oid);
        if (!theirs)
                return -1;

        if (read_ref(branch_name, &oid))
                return -1;
        ours = lookup_commit_reference(the_repository, &oid);
        if (!ours)
                return -1;

        *num_theirs = *num_ours = 0;

        /* are we the same? */
        if (theirs == ours)
                return 0;
        if (abf == AHEAD_BEHIND_QUICK)
                return 1;
        if (abf != AHEAD_BEHIND_FULL)
                BUG("stat_branch_pair: invalid abf '%d'", abf);

        /* Run "rev-list --left-right ours...theirs" internally... */
        strvec_push(&argv, ""); /* ignored */
        strvec_push(&argv, "--left-right");
        strvec_pushf(&argv, "%s...%s",
                     oid_to_hex(&ours->object.oid),
                     oid_to_hex(&theirs->object.oid));
        strvec_push(&argv, "--");

        repo_init_revisions(the_repository, &revs, NULL);
        setup_revisions(argv.nr, argv.v, &revs, NULL);
        if (prepare_revision_walk(&revs))
                die(_("revision walk setup failed"));

        /* ... and count the commits on each side. */
        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);

        strvec_clear(&argv);
        return 1;
}

/*
 * Lookup the tracking branch for the given branch and if present, optionally
 * compute the commit ahead/behind values for the pair.
 *
 * If for_push is true, the tracking branch refers to the push branch,
 * otherwise it refers to the upstream branch.
 *
 * The name of the tracking branch (or NULL if it is not defined) is
 * returned via *tracking_name, if it is not itself NULL.
 *
 * If abf is AHEAD_BEHIND_FULL, compute the full ahead/behind and return the
 * counts in *num_ours and *num_theirs.  If abf is AHEAD_BEHIND_QUICK, skip
 * the (potentially expensive) a/b computation (*num_ours and *num_theirs are
 * set to zero).
 *
 * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
 * upstream defined, or ref does not exist).  Returns 0 if the commits are
 * identical.  Returns 1 if commits are different.
 */
int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
                       const char **tracking_name, int for_push,
                       enum ahead_behind_flags abf)
{
        const char *base;

        /* Cannot stat unless we are marked to build on top of somebody else. */
        base = for_push ? branch_get_push(branch, NULL) :
                branch_get_upstream(branch, NULL);
        if (tracking_name)
                *tracking_name = base;
        if (!base)
                return -1;

        return stat_branch_pair(branch->refname, base, num_ours, num_theirs, abf);
}

/*
 * Return true when there is anything to report, otherwise false.
 */
int format_tracking_info(struct branch *branch, struct strbuf *sb,
                         enum ahead_behind_flags abf)
{
        int ours, theirs, sti;
        const char *full_base;
        char *base;
        int upstream_is_gone = 0;

        sti = stat_tracking_info(branch, &ours, &theirs, &full_base, 0, abf);
        if (sti < 0) {
                if (!full_base)
                        return 0;
                upstream_is_gone = 1;
        }

        base = shorten_unambiguous_ref(full_base, 0);
        if (upstream_is_gone) {
                strbuf_addf(sb,
                        _("Your branch is based on '%s', but the upstream is gone.\n"),
                        base);
                if (advice_enabled(ADVICE_STATUS_HINTS))
                        strbuf_addstr(sb,
                                _("  (use \"git branch --unset-upstream\" to fixup)\n"));
        } else if (!sti) {
                strbuf_addf(sb,
                        _("Your branch is up to date with '%s'.\n"),
                        base);
        } else if (abf == AHEAD_BEHIND_QUICK) {
                strbuf_addf(sb,
                            _("Your branch and '%s' refer to different commits.\n"),
                            base);
                if (advice_enabled(ADVICE_STATUS_HINTS))
                        strbuf_addf(sb, _("  (use \"%s\" for details)\n"),
                                    "git status --ahead-behind");
        } else if (!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",
                           ours),
                        base, ours);
                if (advice_enabled(ADVICE_STATUS_HINTS))
                        strbuf_addstr(sb,
                                _("  (use \"git push\" to publish your local commits)\n"));
        } else if (!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",
                           theirs),
                        base, theirs);
                if (advice_enabled(ADVICE_STATUS_HINTS))
                        strbuf_addstr(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",
                           ours + theirs),
                        base, ours, theirs);
                if (advice_enabled(ADVICE_STATUS_HINTS))
                        strbuf_addstr(sb,
                                _("  (use \"git pull\" to merge the remote branch into yours)\n"));
        }
        free(base);
        return 1;
}

static int one_local_ref(const char *refname, const struct object_id *oid,
                         int flag, void *cb_data)
{
        struct ref ***local_tail = cb_data;
        struct ref *ref;

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

        ref = alloc_ref(refname);
        oidcpy(&ref->new_oid, oid);
        **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 a remote branch exists with the default branch name, let's use it. */
        if (!all) {
                char *ref = xstrfmt("refs/heads/%s",
                                    git_default_branch_name(0));

                r = find_ref_by_name(refs, ref);
                free(ref);
                if (r && oideq(&r->old_oid, &head->old_oid))
                        return copy_ref(r);

                /* Fall back to the hard-coded historical default */
                r = find_ref_by_name(refs, "refs/heads/master");
                if (r && oideq(&r->old_oid, &head->old_oid))
                        return copy_ref(r);
        }

        /* Look for another ref that points there */
        for (r = refs; r; r = r->next) {
                if (r != head &&
                    starts_with(r->name, "refs/heads/") &&
                    oideq(&r->old_oid, &head->old_oid)) {
                        *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 *rs;
};

static int get_stale_heads_cb(const char *refname, const struct object_id *oid,
                              int flags, void *cb_data)
{
        struct stale_heads_info *info = cb_data;
        struct string_list matches = STRING_LIST_INIT_DUP;
        struct refspec_item query;
        int i, stale = 1;
        memset(&query, 0, sizeof(struct refspec_item));
        query.dst = (char *)refname;

        query_refspecs_multiple(info->rs, &query, &matches);
        if (matches.nr == 0)
                goto clean_exit; /* 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. In order to deal with
         * overlapping refspecs, we need to go over all of the
         * matching refs.
         */
        if (flags & REF_ISSYMREF)
                goto clean_exit;

        for (i = 0; stale && i < matches.nr; i++)
                if (string_list_has_string(info->ref_names, matches.items[i].string))
                        stale = 0;

        if (stale) {
                struct ref *ref = make_linked_ref(refname, &info->stale_refs_tail);
                oidcpy(&ref->new_oid, oid);
        }

clean_exit:
        string_list_clear(&matches, 0);
        return 0;
}

struct ref *get_stale_heads(struct refspec *rs, 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.rs = rs;
        for (ref = fetch_map; ref; ref = ref->next)
                string_list_append(&ref_names, ref->name);
        string_list_sort(&ref_names);
        for_each_ref(get_stale_heads_cb, &info);
        string_list_clear(&ref_names, 0);
        return stale_refs;
}

/*
 * Compare-and-swap
 */
static void clear_cas_option(struct push_cas_option *cas)
{
        int i;

        for (i = 0; i < cas->nr; i++)
                free(cas->entry[i].refname);
        free(cas->entry);
        memset(cas, 0, sizeof(*cas));
}

static struct push_cas *add_cas_entry(struct push_cas_option *cas,
                                      const char *refname,
                                      size_t refnamelen)
{
        struct push_cas *entry;
        ALLOC_GROW(cas->entry, cas->nr + 1, cas->alloc);
        entry = &cas->entry[cas->nr++];
        memset(entry, 0, sizeof(*entry));
        entry->refname = xmemdupz(refname, refnamelen);
        return entry;
}

static int parse_push_cas_option(struct push_cas_option *cas, const char *arg, int unset)
{
        const char *colon;
        struct push_cas *entry;

        if (unset) {
                /* "--no-<option>" */
                clear_cas_option(cas);
                return 0;
        }

        if (!arg) {
                /* just "--<option>" */
                cas->use_tracking_for_rest = 1;
                return 0;
        }

        /* "--<option>=refname" or "--<option>=refname:value" */
        colon = strchrnul(arg, ':');
        entry = add_cas_entry(cas, arg, colon - arg);
        if (!*colon)
                entry->use_tracking = 1;
        else if (!colon[1])
                oidclr(&entry->expect);
        else if (get_oid(colon + 1, &entry->expect))
                return error(_("cannot parse expected object name '%s'"),
                             colon + 1);
        return 0;
}

int parseopt_push_cas_option(const struct option *opt, const char *arg, int unset)
{
        return parse_push_cas_option(opt->value, arg, unset);
}

int is_empty_cas(const struct push_cas_option *cas)
{
        return !cas->use_tracking_for_rest && !cas->nr;
}

/*
 * Look at remote.fetch refspec and see if we have a remote
 * tracking branch for the refname there. Fill the name of
 * the remote-tracking branch in *dst_refname, and the name
 * of the commit object at its tip in oid[].
 * If we cannot do so, return negative to signal an error.
 */
static int remote_tracking(struct remote *remote, const char *refname,
                           struct object_id *oid, char **dst_refname)
{
        char *dst;

        dst = apply_refspecs(&remote->fetch, refname);
        if (!dst)
                return -1; /* no tracking ref for refname at remote */
        if (read_ref(dst, oid))
                return -1; /* we know what the tracking ref is but we cannot read it */

        *dst_refname = dst;
        return 0;
}

/*
 * The struct "reflog_commit_array" and related helper functions
 * are used for collecting commits into an array during reflog
 * traversals in "check_and_collect_until()".
 */
struct reflog_commit_array {
        struct commit **item;
        size_t nr, alloc;
};

#define REFLOG_COMMIT_ARRAY_INIT { 0 }

/* Append a commit to the array. */
static void append_commit(struct reflog_commit_array *arr,
                          struct commit *commit)
{
        ALLOC_GROW(arr->item, arr->nr + 1, arr->alloc);
        arr->item[arr->nr++] = commit;
}

/* Free and reset the array. */
static void free_commit_array(struct reflog_commit_array *arr)
{
        FREE_AND_NULL(arr->item);
        arr->nr = arr->alloc = 0;
}

struct check_and_collect_until_cb_data {
        struct commit *remote_commit;
        struct reflog_commit_array *local_commits;
        timestamp_t remote_reflog_timestamp;
};

/* Get the timestamp of the latest entry. */
static int peek_reflog(struct object_id *o_oid, struct object_id *n_oid,
                       const char *ident, timestamp_t timestamp,
                       int tz, const char *message, void *cb_data)
{
        timestamp_t *ts = cb_data;
        *ts = timestamp;
        return 1;
}

static int check_and_collect_until(struct object_id *o_oid,
                                   struct object_id *n_oid,
                                   const char *ident, timestamp_t timestamp,
                                   int tz, const char *message, void *cb_data)
{
        struct commit *commit;
        struct check_and_collect_until_cb_data *cb = cb_data;

        /* An entry was found. */
        if (oideq(n_oid, &cb->remote_commit->object.oid))
                return 1;

        if ((commit = lookup_commit_reference(the_repository, n_oid)))
                append_commit(cb->local_commits, commit);

        /*
         * If the reflog entry timestamp is older than the remote ref's
         * latest reflog entry, there is no need to check or collect
         * entries older than this one.
         */
        if (timestamp < cb->remote_reflog_timestamp)
                return -1;

        return 0;
}

#define MERGE_BASES_BATCH_SIZE 8

/*
 * Iterate through the reflog of the local ref to check if there is an entry
 * for the given remote-tracking ref; runs until the timestamp of an entry is
 * older than latest timestamp of remote-tracking ref's reflog. Any commits
 * are that seen along the way are collected into an array to check if the
 * remote-tracking ref is reachable from any of them.
 */
static int is_reachable_in_reflog(const char *local, const struct ref *remote)
{
        timestamp_t date;
        struct commit *commit;
        struct commit **chunk;
        struct check_and_collect_until_cb_data cb;
        struct reflog_commit_array arr = REFLOG_COMMIT_ARRAY_INIT;
        size_t size = 0;
        int ret = 0;

        commit = lookup_commit_reference(the_repository, &remote->old_oid);
        if (!commit)
                goto cleanup_return;

        /*
         * Get the timestamp from the latest entry
         * of the remote-tracking ref's reflog.
         */
        for_each_reflog_ent_reverse(remote->tracking_ref, peek_reflog, &date);

        cb.remote_commit = commit;
        cb.local_commits = &arr;
        cb.remote_reflog_timestamp = date;
        ret = for_each_reflog_ent_reverse(local, check_and_collect_until, &cb);

        /* We found an entry in the reflog. */
        if (ret > 0)
                goto cleanup_return;

        /*
         * Check if the remote commit is reachable from any
         * of the commits in the collected array, in batches.
         */
        for (chunk = arr.item; chunk < arr.item + arr.nr; chunk += size) {
                size = arr.item + arr.nr - chunk;
                if (MERGE_BASES_BATCH_SIZE < size)
                        size = MERGE_BASES_BATCH_SIZE;

                if ((ret = in_merge_bases_many(commit, size, chunk)))
                        break;
        }

cleanup_return:
        free_commit_array(&arr);
        return ret;
}

/*
 * Check for reachability of a remote-tracking
 * ref in the reflog entries of its local ref.
 */
static void check_if_includes_upstream(struct ref *remote)
{
        struct ref *local = get_local_ref(remote->name);
        if (!local)
                return;

        if (is_reachable_in_reflog(local->name, remote) <= 0)
                remote->unreachable = 1;
}

static void apply_cas(struct push_cas_option *cas,
                      struct remote *remote,
                      struct ref *ref)
{
        int i;

        /* Find an explicit --<option>=<name>[:<value>] entry */
        for (i = 0; i < cas->nr; i++) {
                struct push_cas *entry = &cas->entry[i];
                if (!refname_match(entry->refname, ref->name))
                        continue;
                ref->expect_old_sha1 = 1;
                if (!entry->use_tracking)
                        oidcpy(&ref->old_oid_expect, &entry->expect);
                else if (remote_tracking(remote, ref->name,
                                         &ref->old_oid_expect,
                                         &ref->tracking_ref))
                        oidclr(&ref->old_oid_expect);
                else
                        ref->check_reachable = cas->use_force_if_includes;
                return;
        }

        /* Are we using "--<option>" to cover all? */
        if (!cas->use_tracking_for_rest)
                return;

        ref->expect_old_sha1 = 1;
        if (remote_tracking(remote, ref->name,
                            &ref->old_oid_expect,
                            &ref->tracking_ref))
                oidclr(&ref->old_oid_expect);
        else
                ref->check_reachable = cas->use_force_if_includes;
}

void apply_push_cas(struct push_cas_option *cas,
                    struct remote *remote,
                    struct ref *remote_refs)
{
        struct ref *ref;
        for (ref = remote_refs; ref; ref = ref->next) {
                apply_cas(cas, remote, ref);

                /*
                 * If "compare-and-swap" is in "use_tracking[_for_rest]"
                 * mode, and if "--force-if-includes" was specified, run
                 * the check.
                 */
                if (ref->check_reachable)
                        check_if_includes_upstream(ref);
        }
}

struct remote_state *remote_state_new(void)
{
        struct remote_state *r = xmalloc(sizeof(*r));

        memset(r, 0, sizeof(*r));

        hashmap_init(&r->remotes_hash, remotes_hash_cmp, NULL, 0);
        return r;
}

void remote_state_clear(struct remote_state *remote_state)
{
        int i;

        for (i = 0; i < remote_state->remotes_nr; i++) {
                remote_clear(remote_state->remotes[i]);
        }
        FREE_AND_NULL(remote_state->remotes);
        remote_state->remotes_alloc = 0;
        remote_state->remotes_nr = 0;

        hashmap_clear_and_free(&remote_state->remotes_hash, struct remote, ent);

        for (i = 0; i < remote_state->branches_nr; i++) {
                FREE_AND_NULL(remote_state->branches[i]);
        }
        FREE_AND_NULL(remote_state->branches);
        remote_state->branches_alloc = 0;
        remote_state->branches_nr = 0;
}