Code

api-run-command.txt: talk about run_hook()
[git.git] / remote.c
index 2d9af4023eba6f8b2fe528ccbf03569fcaa265ee..570e11286ea295e825a23b1d5ed40c9fbd02be57 100644 (file)
--- a/remote.c
+++ b/remote.c
@@ -1,6 +1,19 @@
 #include "cache.h"
 #include "remote.h"
 #include "refs.h"
+#include "commit.h"
+#include "diff.h"
+#include "revision.h"
+
+static struct refspec s_tag_refspec = {
+       0,
+       1,
+       0,
+       "refs/tags/",
+       "refs/tags/"
+};
+
+const struct refspec *tag_refspec = &s_tag_refspec;
 
 struct counted_string {
        size_t len;
@@ -56,7 +69,7 @@ static const char *alias_url(const char *url)
        if (!longest)
                return url;
 
-       ret = malloc(rewrite[longest_i]->baselen +
+       ret = xmalloc(rewrite[longest_i]->baselen +
                     (strlen(url) - longest->len) + 1);
        strcpy(ret, rewrite[longest_i]->base);
        strcpy(ret + rewrite[longest_i]->baselen, url + longest->len);
@@ -139,7 +152,7 @@ static struct branch *make_branch(const char *name, int len)
                ret->name = xstrndup(name, len);
        else
                ret->name = xstrdup(name);
-       refname = malloc(strlen(name) + strlen("refs/heads/") + 1);
+       refname = xmalloc(strlen(name) + strlen("refs/heads/") + 1);
        strcpy(refname, "refs/heads/");
        strcpy(refname + strlen("refs/heads/"), ret->name);
        ret->refname = refname;
@@ -188,6 +201,7 @@ static void read_remotes_file(struct remote *remote)
 
        if (!f)
                return;
+       remote->origin = REMOTE_REMOTES;
        while (fgets(buffer, BUF_SIZE, f)) {
                int value_list;
                char *s, *p;
@@ -232,7 +246,7 @@ static void read_branches_file(struct remote *remote)
 {
        const char *slash = strchr(remote->name, '/');
        char *frag;
-       struct strbuf branch;
+       struct strbuf branch = STRBUF_INIT;
        int n = slash ? slash - remote->name : 1000;
        FILE *f = fopen(git_path("branches/%.*s", n, remote->name), "r");
        char *s, *p;
@@ -248,6 +262,7 @@ static void read_branches_file(struct remote *remote)
                s++;
        if (!*s)
                return;
+       remote->origin = REMOTE_BRANCHES;
        p = s + strlen(s);
        while (isspace(p[-1]))
                *--p = 0;
@@ -270,7 +285,6 @@ static void read_branches_file(struct remote *remote)
         * #branch specified.  The "master" (or specified) branch is
         * fetched and stored in the local branch of the same name.
         */
-       strbuf_init(&branch, 0);
        frag = strchr(p, '#');
        if (frag) {
                *(frag++) = '\0';
@@ -285,10 +299,21 @@ static void read_branches_file(struct remote *remote)
        }
        add_url_alias(remote, p);
        add_fetch_refspec(remote, strbuf_detach(&branch, 0));
+       /*
+        * Cogito compatible push: push current HEAD to remote #branch
+        * (master if missing)
+        */
+       strbuf_init(&branch, 0);
+       strbuf_addstr(&branch, "HEAD");
+       if (frag)
+               strbuf_addf(&branch, ":refs/heads/%s", frag);
+       else
+               strbuf_addstr(&branch, ":refs/heads/master");
+       add_push_refspec(remote, strbuf_detach(&branch, 0));
        remote->fetch_tags = 1; /* always auto-follow */
 }
 
-static int handle_config(const char *key, const char *value)
+static int handle_config(const char *key, const char *value, void *cb)
 {
        const char *name;
        const char *subkey;
@@ -329,52 +354,59 @@ static int handle_config(const char *key, const char *value)
        if (prefixcmp(key,  "remote."))
                return 0;
        name = key + 7;
+       if (*name == '/') {
+               warning("Config remote shorthand cannot begin with '/': %s",
+                       name);
+               return 0;
+       }
        subkey = strrchr(name, '.');
        if (!subkey)
                return error("Config with no key for remote %s", name);
-       if (*subkey == '/') {
-               warning("Config remote shorthand cannot begin with '/': %s", name);
-               return 0;
-       }
        remote = make_remote(name, subkey - name);
-       if (!value) {
-               /* if we ever have a boolean variable, e.g. "remote.*.disabled"
-                * [remote "frotz"]
-                *      disabled
-                * is a valid way to set it to true; we get NULL in value so
-                * we need to handle it here.
-                *
-                * if (!strcmp(subkey, ".disabled")) {
-                *      val = git_config_bool(key, value);
-                *      return 0;
-                * } else
-                *
-                */
-               return 0; /* ignore unknown booleans */
-       }
-       if (!strcmp(subkey, ".url")) {
-               add_url(remote, xstrdup(value));
+       remote->origin = REMOTE_CONFIG;
+       if (!strcmp(subkey, ".mirror"))
+               remote->mirror = git_config_bool(key, value);
+       else if (!strcmp(subkey, ".skipdefaultupdate"))
+               remote->skip_default_update = git_config_bool(key, value);
+
+       else if (!strcmp(subkey, ".url")) {
+               const char *v;
+               if (git_config_string(&v, key, value))
+                       return -1;
+               add_url(remote, v);
        } else if (!strcmp(subkey, ".push")) {
-               add_push_refspec(remote, xstrdup(value));
+               const char *v;
+               if (git_config_string(&v, key, value))
+                       return -1;
+               add_push_refspec(remote, v);
        } else if (!strcmp(subkey, ".fetch")) {
-               add_fetch_refspec(remote, xstrdup(value));
+               const char *v;
+               if (git_config_string(&v, key, value))
+                       return -1;
+               add_fetch_refspec(remote, v);
        } else if (!strcmp(subkey, ".receivepack")) {
+               const char *v;
+               if (git_config_string(&v, key, value))
+                       return -1;
                if (!remote->receivepack)
-                       remote->receivepack = xstrdup(value);
+                       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 = xstrdup(value);
+                       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(subkey, ".proxy")) {
-               remote->http_proxy = xstrdup(value);
-       } else if (!strcmp(subkey, ".skipdefaultupdate"))
-               remote->skip_default_update = 1;
+               return git_config_string((const char **)&remote->http_proxy,
+                                        key, value);
+       }
        return 0;
 }
 
@@ -405,10 +437,52 @@ static void read_config(void)
                current_branch =
                        make_branch(head_ref + strlen("refs/heads/"), 0);
        }
-       git_config(handle_config);
+       git_config(handle_config, NULL);
        alias_all_urls();
 }
 
+/*
+ * We need to make sure the tracking branches are well formed, but a
+ * wildcard refspec in "struct refspec" must have a trailing slash. We
+ * temporarily drop the trailing '/' while calling check_ref_format(),
+ * and put it back.  The caller knows that a CHECK_REF_FORMAT_ONELEVEL
+ * error return is Ok for a wildcard refspec.
+ */
+static int verify_refname(char *name, int is_glob)
+{
+       int result, len = -1;
+
+       if (is_glob) {
+               len = strlen(name);
+               assert(name[len - 1] == '/');
+               name[len - 1] = '\0';
+       }
+       result = check_ref_format(name);
+       if (is_glob)
+               name[len - 1] = '/';
+       return result;
+}
+
+/*
+ * This function frees a refspec array.
+ * Warning: code paths should be checked to ensure that the src
+ *          and dst pointers are always freeable pointers as well
+ *          as the refspec pointer itself.
+ */
+static void free_refspecs(struct refspec *refspec, int nr_refspec)
+{
+       int i;
+
+       if (!refspec)
+               return;
+
+       for (i = 0; i < nr_refspec; i++) {
+               free(refspec[i].src);
+               free(refspec[i].dst);
+       }
+       free(refspec);
+}
+
 static struct refspec *parse_refspec_internal(int nr_refspec, const char **refspec, int fetch, int verify)
 {
        int i;
@@ -416,11 +490,11 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
        struct refspec *rs = xcalloc(sizeof(*rs), nr_refspec);
 
        for (i = 0; i < nr_refspec; i++) {
-               size_t llen, rlen;
+               size_t llen;
                int is_glob;
                const char *lhs, *rhs;
 
-               llen = rlen = is_glob = 0;
+               llen = is_glob = 0;
 
                lhs = refspec[i];
                if (*lhs == '+') {
@@ -429,13 +503,20 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                }
 
                rhs = strrchr(lhs, ':');
+
+               /*
+                * Before going on, special case ":" (or "+:") as a refspec
+                * for matching refs.
+                */
+               if (!fetch && rhs == lhs && rhs[1] == '\0') {
+                       rs[i].matching = 1;
+                       continue;
+               }
+
                if (rhs) {
-                       rhs++;
-                       rlen = strlen(rhs);
+                       size_t rlen = strlen(++rhs);
                        is_glob = (2 <= rlen && !strcmp(rhs + rlen - 2, "/*"));
-                       if (is_glob)
-                               rlen -= 2;
-                       rs[i].dst = xstrndup(rhs, rlen);
+                       rs[i].dst = xstrndup(rhs, rlen - is_glob);
                }
 
                llen = (rhs ? (rhs - lhs - 1) : strlen(lhs));
@@ -443,7 +524,7 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                        if ((rhs && !is_glob) || (!rhs && fetch))
                                goto invalid;
                        is_glob = 1;
-                       llen -= 2;
+                       llen--;
                } else if (rhs && is_glob) {
                        goto invalid;
                }
@@ -460,7 +541,7 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                        if (!*rs[i].src)
                                ; /* empty is ok */
                        else {
-                               st = check_ref_format(rs[i].src);
+                               st = verify_refname(rs[i].src, is_glob);
                                if (st && st != CHECK_REF_FORMAT_ONELEVEL)
                                        goto invalid;
                        }
@@ -475,7 +556,7 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                        } else if (!*rs[i].dst) {
                                ; /* ok */
                        } else {
-                               st = check_ref_format(rs[i].dst);
+                               st = verify_refname(rs[i].dst, is_glob);
                                if (st && st != CHECK_REF_FORMAT_ONELEVEL)
                                        goto invalid;
                        }
@@ -490,7 +571,7 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                        if (!*rs[i].src)
                                ; /* empty is ok */
                        else if (is_glob) {
-                               st = check_ref_format(rs[i].src);
+                               st = verify_refname(rs[i].src, is_glob);
                                if (st && st != CHECK_REF_FORMAT_ONELEVEL)
                                        goto invalid;
                        }
@@ -504,13 +585,13 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
                         * - otherwise it must be a valid looking ref.
                         */
                        if (!rs[i].dst) {
-                               st = check_ref_format(rs[i].src);
+                               st = verify_refname(rs[i].src, is_glob);
                                if (st && st != CHECK_REF_FORMAT_ONELEVEL)
                                        goto invalid;
                        } else if (!*rs[i].dst) {
                                goto invalid;
                        } else {
-                               st = check_ref_format(rs[i].dst);
+                               st = verify_refname(rs[i].dst, is_glob);
                                if (st && st != CHECK_REF_FORMAT_ONELEVEL)
                                        goto invalid;
                        }
@@ -520,7 +601,12 @@ static struct refspec *parse_refspec_internal(int nr_refspec, const char **refsp
 
  invalid:
        if (verify) {
-               free(rs);
+               /*
+                * nr_refspec must be greater than zero and i must be valid
+                * since it is only possible to reach this point from within
+                * the for loop above.
+                */
+               free_refspecs(rs, i+1);
                return NULL;
        }
        die("Invalid refspec '%s'", refspec[i]);
@@ -532,8 +618,7 @@ int valid_fetch_refspec(const char *fetch_refspec_str)
        struct refspec *refspec;
 
        refspec = parse_refspec_internal(1, fetch_refspec, 1, 1);
-       if (refspec)
-               free(refspec);
+       free_refspecs(refspec, 1);
        return !!refspec;
 }
 
@@ -542,7 +627,7 @@ struct refspec *parse_fetch_refspec(int nr_refspec, const char **refspec)
        return parse_refspec_internal(nr_refspec, refspec, 1, 0);
 }
 
-struct refspec *parse_push_refspec(int nr_refspec, const char **refspec)
+static struct refspec *parse_push_refspec(int nr_refspec, const char **refspec)
 {
        return parse_refspec_internal(nr_refspec, refspec, 0, 0);
 }
@@ -659,8 +744,7 @@ int remote_find_tracking(struct remote *remote, struct refspec *refspec)
                if (!fetch->dst)
                        continue;
                if (fetch->pattern) {
-                       if (!prefixcmp(needle, key) &&
-                           needle[strlen(key)] == '/') {
+                       if (!prefixcmp(needle, key)) {
                                *result = xmalloc(strlen(value) +
                                                  strlen(needle) -
                                                  strlen(key) + 1);
@@ -679,11 +763,19 @@ int remote_find_tracking(struct remote *remote, struct refspec *refspec)
        return -1;
 }
 
-struct ref *alloc_ref(unsigned namelen)
+static struct ref *alloc_ref_with_prefix(const char *prefix, size_t prefixlen,
+               const char *name)
 {
-       struct ref *ret = xmalloc(sizeof(struct ref) + namelen);
-       memset(ret, 0, sizeof(struct ref) + namelen);
-       return ret;
+       size_t len = strlen(name);
+       struct ref *ref = xcalloc(1, sizeof(struct ref) + prefixlen + len + 1);
+       memcpy(ref->name, prefix, prefixlen);
+       memcpy(ref->name + prefixlen, name, len);
+       return ref;
+}
+
+struct ref *alloc_ref(const char *name)
+{
+       return alloc_ref_with_prefix("", 0, name);
 }
 
 static struct ref *copy_ref(const struct ref *ref)
@@ -706,13 +798,22 @@ struct ref *copy_ref_list(const struct ref *ref)
        return ret;
 }
 
+static void free_ref(struct ref *ref)
+{
+       if (!ref)
+               return;
+       free(ref->remote_status);
+       free(ref->symref);
+       free(ref);
+}
+
 void free_refs(struct ref *ref)
 {
        struct ref *next;
        while (ref) {
                next = ref->next;
                free(ref->peer_ref);
-               free(ref);
+               free_ref(ref);
                ref = next;
        }
 }
@@ -783,31 +884,22 @@ static struct ref *try_explicit_object_name(const char *name)
 {
        unsigned char sha1[20];
        struct ref *ref;
-       int len;
 
        if (!*name) {
-               ref = alloc_ref(20);
-               strcpy(ref->name, "(delete)");
+               ref = alloc_ref("(delete)");
                hashclr(ref->new_sha1);
                return ref;
        }
        if (get_sha1(name, sha1))
                return NULL;
-       len = strlen(name) + 1;
-       ref = alloc_ref(len);
-       memcpy(ref->name, name, len);
+       ref = alloc_ref(name);
        hashcpy(ref->new_sha1, sha1);
        return ref;
 }
 
 static struct ref *make_linked_ref(const char *name, struct ref ***tail)
 {
-       struct ref *ret;
-       size_t len;
-
-       len = strlen(name) + 1;
-       ret = alloc_ref(len);
-       memcpy(ret->name, name, len);
+       struct ref *ret = alloc_ref(name);
        tail_link_ref(ret, tail);
        return ret;
 }
@@ -834,16 +926,15 @@ static char *guess_ref(const char *name, struct ref *peer)
 
 static int match_explicit(struct ref *src, struct ref *dst,
                          struct ref ***dst_tail,
-                         struct refspec *rs,
-                         int errs)
+                         struct refspec *rs)
 {
        struct ref *matched_src, *matched_dst;
 
        const char *dst_value = rs->dst;
        char *dst_guess;
 
-       if (rs->pattern)
-               return errs;
+       if (rs->pattern || rs->matching)
+               return 0;
 
        matched_src = matched_dst = NULL;
        switch (count_refspec_match(rs->src, src, &matched_src)) {
@@ -856,23 +947,16 @@ static int match_explicit(struct ref *src, struct ref *dst,
                 */
                matched_src = try_explicit_object_name(rs->src);
                if (!matched_src)
-                       error("src refspec %s does not match any.", rs->src);
+                       return error("src refspec %s does not match any.", rs->src);
                break;
        default:
-               matched_src = NULL;
-               error("src refspec %s matches more than one.", rs->src);
-               break;
+               return error("src refspec %s matches more than one.", rs->src);
        }
 
-       if (!matched_src)
-               errs = 1;
-
        if (!dst_value) {
                unsigned char sha1[20];
                int flag;
 
-               if (!matched_src)
-                       return errs;
                dst_value = resolve_ref(matched_src->name, sha1, 1, &flag);
                if (!dst_value ||
                    ((flag & REF_ISSYMREF) &&
@@ -903,18 +987,16 @@ static int match_explicit(struct ref *src, struct ref *dst,
                      dst_value);
                break;
        }
-       if (errs || !matched_dst)
-               return 1;
-       if (matched_dst->peer_ref) {
-               errs = 1;
-               error("dst ref %s receives from more than one src.",
+       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 = matched_src;
                matched_dst->force = rs->force;
        }
-       return errs;
+       return 0;
 }
 
 static int match_explicit_refs(struct ref *src, struct ref *dst,
@@ -923,8 +1005,8 @@ static int match_explicit_refs(struct ref *src, struct ref *dst,
 {
        int i, errs;
        for (i = errs = 0; i < rs_nr; i++)
-               errs |= match_explicit(src, dst, dst_tail, &rs[i], errs);
-       return -errs;
+               errs += match_explicit(src, dst, dst_tail, &rs[i]);
+       return errs;
 }
 
 static const struct refspec *check_pattern_match(const struct refspec *rs,
@@ -932,13 +1014,21 @@ static const struct refspec *check_pattern_match(const struct refspec *rs,
                                                 const struct ref *src)
 {
        int i;
+       int matching_refs = -1;
        for (i = 0; i < rs_nr; i++) {
-               if (rs[i].pattern &&
-                   !prefixcmp(src->name, rs[i].src) &&
-                   src->name[strlen(rs[i].src)] == '/')
+               if (rs[i].matching &&
+                   (matching_refs == -1 || rs[i].force)) {
+                       matching_refs = i;
+                       continue;
+               }
+
+               if (rs[i].pattern && !prefixcmp(src->name, rs[i].src))
                        return rs + i;
        }
-       return NULL;
+       if (matching_refs != -1)
+               return rs + matching_refs;
+       else
+               return NULL;
 }
 
 /*
@@ -949,11 +1039,16 @@ static const struct refspec *check_pattern_match(const struct refspec *rs,
 int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
               int nr_refspec, const char **refspec, int flags)
 {
-       struct refspec *rs =
-               parse_push_refspec(nr_refspec, (const char **) refspec);
+       struct refspec *rs;
        int send_all = flags & MATCH_REFS_ALL;
        int send_mirror = flags & MATCH_REFS_MIRROR;
+       static const char *default_refspec[] = { ":", 0 };
 
+       if (!nr_refspec) {
+               nr_refspec = 1;
+               refspec = default_refspec;
+       }
+       rs = parse_push_refspec(nr_refspec, (const char **) refspec);
        if (match_explicit_refs(src, dst, dst_tail, rs, nr_refspec))
                return -1;
 
@@ -964,48 +1059,50 @@ int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
                char *dst_name;
                if (src->peer_ref)
                        continue;
-               if (nr_refspec) {
-                       pat = check_pattern_match(rs, nr_refspec, src);
-                       if (!pat)
-                               continue;
-               }
-               else if (!send_mirror && prefixcmp(src->name, "refs/heads/"))
+
+               pat = check_pattern_match(rs, nr_refspec, src);
+               if (!pat)
+                       continue;
+
+               if (pat->matching) {
                        /*
                         * "matching refs"; traditionally we pushed everything
                         * including refs outside refs/heads/ hierarchy, but
                         * that does not make much sense these days.
                         */
-                       continue;
+                       if (!send_mirror && prefixcmp(src->name, "refs/heads/"))
+                               continue;
+                       dst_name = xstrdup(src->name);
 
-               if (pat) {
+               } else {
                        const char *dst_side = pat->dst ? pat->dst : pat->src;
                        dst_name = xmalloc(strlen(dst_side) +
                                           strlen(src->name) -
                                           strlen(pat->src) + 2);
                        strcpy(dst_name, dst_side);
                        strcat(dst_name, src->name + strlen(pat->src));
-               } else
-                       dst_name = xstrdup(src->name);
+               }
                dst_peer = find_ref_by_name(dst, dst_name);
-               if (dst_peer && dst_peer->peer_ref)
-                       /* We're already sending something to this ref. */
-                       goto free_name;
+               if (dst_peer) {
+                       if (dst_peer->peer_ref)
+                               /* We're already sending something to this ref. */
+                               goto free_name;
+
+               } else {
+                       if (pat->matching && !(send_all || send_mirror))
+                               /*
+                                * Remote doesn't have it, and we have no
+                                * explicit pattern, and we don't have
+                                * --all nor --mirror.
+                                */
+                               goto free_name;
 
-               if (!dst_peer && !nr_refspec && !(send_all || send_mirror))
-                       /*
-                        * Remote doesn't have it, and we have no
-                        * explicit pattern, and we don't have
-                        * --all nor --mirror.
-                        */
-                       goto free_name;
-               if (!dst_peer) {
                        /* Create a new one and link it */
                        dst_peer = make_linked_ref(dst_name, dst_tail);
                        hashcpy(dst_peer->new_sha1, src->new_sha1);
                }
                dst_peer->peer_ref = src;
-               if (pat)
-                       dst_peer->force = pat->force;
+               dst_peer->force = pat->force;
        free_name:
                free(dst_name);
        }
@@ -1070,10 +1167,8 @@ static struct ref *get_expanded_map(const struct ref *remote_refs,
                        struct ref *cpy = copy_ref(ref);
                        match = ref->name + remote_prefix_len;
 
-                       cpy->peer_ref = alloc_ref(local_prefix_len +
-                                                 strlen(match) + 1);
-                       sprintf(cpy->peer_ref->name, "%s%s",
-                               refspec->dst, match);
+                       cpy->peer_ref = alloc_ref_with_prefix(refspec->dst,
+                                       local_prefix_len, match);
                        if (refspec->force)
                                cpy->peer_ref->force = 1;
                        *tail = cpy;
@@ -1106,27 +1201,18 @@ struct ref *get_remote_ref(const struct ref *remote_refs, const char *name)
 
 static struct ref *get_local_ref(const char *name)
 {
-       struct ref *ret;
        if (!name)
                return NULL;
 
-       if (!prefixcmp(name, "refs/")) {
-               ret = alloc_ref(strlen(name) + 1);
-               strcpy(ret->name, name);
-               return ret;
-       }
+       if (!prefixcmp(name, "refs/"))
+               return alloc_ref(name);
 
        if (!prefixcmp(name, "heads/") ||
            !prefixcmp(name, "tags/") ||
-           !prefixcmp(name, "remotes/")) {
-               ret = alloc_ref(strlen(name) + 6);
-               sprintf(ret->name, "refs/%s", name);
-               return ret;
-       }
+           !prefixcmp(name, "remotes/"))
+               return alloc_ref_with_prefix("refs/", 5, name);
 
-       ret = alloc_ref(strlen(name) + 12);
-       sprintf(ret->name, "refs/heads/%s", name);
-       return ret;
+       return alloc_ref_with_prefix("refs/heads/", 11, name);
 }
 
 int get_fetch_map(const struct ref *remote_refs,
@@ -1172,3 +1258,123 @@ int get_fetch_map(const struct ref *remote_refs,
 
        return 0;
 }
+
+int resolve_remote_symref(struct ref *ref, struct ref *list)
+{
+       if (!ref->symref)
+               return 0;
+       for (; list; list = list->next)
+               if (!strcmp(ref->symref, list->name)) {
+                       hashcpy(ref->old_sha1, list->old_sha1);
+                       return 0;
+               }
+       return 1;
+}
+
+/*
+ * Return true if there is anything to report, otherwise false.
+ */
+int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
+{
+       unsigned char sha1[20];
+       struct commit *ours, *theirs;
+       char symmetric[84];
+       struct rev_info revs;
+       const char *rev_argv[10], *base;
+       int rev_argc;
+
+       /*
+        * Nothing to report unless we are marked to build on top of
+        * somebody else.
+        */
+       if (!branch ||
+           !branch->merge || !branch->merge[0] || !branch->merge[0]->dst)
+               return 0;
+
+       /*
+        * If what we used to build on no longer exists, there is
+        * nothing to report.
+        */
+       base = branch->merge[0]->dst;
+       if (!resolve_ref(base, sha1, 1, NULL))
+               return 0;
+       theirs = lookup_commit(sha1);
+       if (!theirs)
+               return 0;
+
+       if (!resolve_ref(branch->refname, sha1, 1, NULL))
+               return 0;
+       ours = lookup_commit(sha1);
+       if (!ours)
+               return 0;
+
+       /* are we the same? */
+       if (theirs == ours)
+               return 0;
+
+       /* Run "rev-list --left-right ours...theirs" internally... */
+       rev_argc = 0;
+       rev_argv[rev_argc++] = NULL;
+       rev_argv[rev_argc++] = "--left-right";
+       rev_argv[rev_argc++] = symmetric;
+       rev_argv[rev_argc++] = "--";
+       rev_argv[rev_argc] = NULL;
+
+       strcpy(symmetric, sha1_to_hex(ours->object.sha1));
+       strcpy(symmetric + 40, "...");
+       strcpy(symmetric + 43, sha1_to_hex(theirs->object.sha1));
+
+       init_revisions(&revs, NULL);
+       setup_revisions(rev_argc, rev_argv, &revs, NULL);
+       prepare_revision_walk(&revs);
+
+       /* ... and count the commits on each side. */
+       *num_ours = 0;
+       *num_theirs = 0;
+       while (1) {
+               struct commit *c = get_revision(&revs);
+               if (!c)
+                       break;
+               if (c->object.flags & SYMMETRIC_LEFT)
+                       (*num_ours)++;
+               else
+                       (*num_theirs)++;
+       }
+
+       /* clear object flags smudged by the above traversal */
+       clear_commit_marks(ours, ALL_REV_FLAGS);
+       clear_commit_marks(theirs, ALL_REV_FLAGS);
+       return 1;
+}
+
+/*
+ * Return true when there is anything to report, otherwise false.
+ */
+int format_tracking_info(struct branch *branch, struct strbuf *sb)
+{
+       int num_ours, num_theirs;
+       const char *base;
+
+       if (!stat_tracking_info(branch, &num_ours, &num_theirs))
+               return 0;
+
+       base = branch->merge[0]->dst;
+       if (!prefixcmp(base, "refs/remotes/")) {
+               base += strlen("refs/remotes/");
+       }
+       if (!num_theirs)
+               strbuf_addf(sb, "Your branch is ahead of '%s' "
+                           "by %d commit%s.\n",
+                           base, num_ours, (num_ours == 1) ? "" : "s");
+       else if (!num_ours)
+               strbuf_addf(sb, "Your branch is behind '%s' "
+                           "by %d commit%s, "
+                           "and can be fast-forwarded.\n",
+                           base, num_theirs, (num_theirs == 1) ? "" : "s");
+       else
+               strbuf_addf(sb, "Your branch and '%s' have diverged,\n"
+                           "and have %d and %d different commit(s) each, "
+                           "respectively.\n",
+                           base, num_ours, num_theirs);
+       return 1;
+}