static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
-#define MAXDEPTH 5
-
-const char *resolve_ref(const char *path, unsigned char *sha1)
+static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
{
- int depth = MAXDEPTH, len;
- char buffer[256];
-
- for (;;) {
- struct stat st;
- int fd;
-
- if (--depth < 0)
- return NULL;
-
- /* Special case: non-existing file */
- if (lstat(path, &st) < 0) {
- if (errno != ENOENT)
- return NULL;
- memset(sha1, 0, 20);
- return path;
- }
-
- /* Follow "normalized" - ie "refs/.." symlinks by hand */
- if (S_ISLNK(st.st_mode)) {
- len = readlink(path, buffer, sizeof(buffer)-1);
- if (len >= 5 && !memcmp("refs/", buffer, 5)) {
- path = git_path("%.*s", len, buffer);
- continue;
- }
- }
-
- /*
- * Anything else, just open it and try to use it as
- * a ref
- */
- fd = open(path, O_RDONLY);
- if (fd < 0)
- return NULL;
- len = read(fd, buffer, sizeof(buffer)-1);
- close(fd);
- break;
- }
- if (len < 40 || get_sha1_hex(buffer, sha1))
- return NULL;
- return path;
+ char buf[40];
+ int fd = open(path, O_RDONLY), nr;
+ if (fd < 0)
+ return -1;
+ nr = read(fd, buf, 40);
+ close(fd);
+ if (nr != 40 || get_sha1_hex(buf, currsha1) < 0)
+ return -1;
+ return memcmp(oldsha1, currsha1, 20) ? -1 : 0;
}
int main(int argc, char **argv)
if (oldval && get_sha1(oldval, oldsha1) < 0)
die("%s: not a valid old SHA1", oldval);
- path = resolve_ref(git_path("%s", refname), currsha1);
+ path = resolve_ref(git_path("%s", refname), currsha1, !!oldval);
if (!path)
die("No such ref: %s", refname);
}
/*
- * FIXME!
- *
- * We should re-read the old ref here, and re-verify that it
- * matches "oldsha1". Otherwise there's a small race.
+ * Re-read the ref after getting the lock to verify
*/
+ if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
+ unlink(lockpath);
+ die("Ref lock failed");
+ }
+ /*
+ * Finally, replace the old ref with the new one
+ */
if (rename(lockpath, path) < 0) {
unlink(lockpath);
die("Unable to create %s", path);