+static int replace_object(const char *object_ref, const char *replace_ref,
+ int force)
+{
+ unsigned char object[20], prev[20], repl[20];
+ char ref[PATH_MAX];
+ struct ref_lock *lock;
+
+ if (get_sha1(object_ref, object))
+ die("Failed to resolve '%s' as a valid ref.", object_ref);
+ if (get_sha1(replace_ref, repl))
+ die("Failed to resolve '%s' as a valid ref.", replace_ref);
+
+ if (snprintf(ref, sizeof(ref),
+ "refs/replace/%s",
+ sha1_to_hex(object)) > sizeof(ref) - 1)
+ die("replace ref name too long: %.*s...", 50, ref);
+ if (check_ref_format(ref))
+ die("'%s' is not a valid ref name.", ref);
+
+ if (!resolve_ref(ref, prev, 1, NULL))
+ hashclr(prev);
+ else if (!force)
+ die("replace ref '%s' already exists", ref);
+
+ lock = lock_any_ref_for_update(ref, prev, 0);
+ if (!lock)
+ die("%s: cannot lock the ref", ref);
+ if (write_ref_sha1(lock, repl, NULL) < 0)
+ die("%s: cannot update the ref", ref);
+
+ return 0;
+}
+