+static char update_hook[] = "hooks/update";
+
+static int run_update_hook(const char *refname,
+ char *old_hex, char *new_hex)
+{
+ int code;
+
+ if (access(update_hook, X_OK) < 0)
+ return 0;
+ code = run_command(update_hook, refname, old_hex, new_hex, NULL);
+ switch (code) {
+ case 0:
+ return 0;
+ case -ERR_RUN_COMMAND_FORK:
+ die("hook fork failed");
+ case -ERR_RUN_COMMAND_EXEC:
+ die("hook execute failed");
+ case -ERR_RUN_COMMAND_WAITPID:
+ die("waitpid failed");
+ case -ERR_RUN_COMMAND_WAITPID_WRONG_PID:
+ die("waitpid is confused");
+ case -ERR_RUN_COMMAND_WAITPID_SIGNAL:
+ fprintf(stderr, "%s died of signal", update_hook);
+ return -1;
+ case -ERR_RUN_COMMAND_WAITPID_NOEXIT:
+ die("%s died strangely", update_hook);
+ default:
+ error("%s exited with error code %d", update_hook, -code);
+ return -code;
+ }
+}
+
+static int update(const char *name,
+ unsigned char *old_sha1, unsigned char *new_sha1)