Merge branch 'ps/ref-transaction-hook'

The logic to find the ref transaction hook script attempted to
cache the path to the found hook without realizing that it needed
to keep a copied value, as the API it used returned a transitory
buffer space.  This has been corrected.

* ps/ref-transaction-hook:
  t1416: avoid hard-coded sha1 ids
  refs: fix interleaving hook calls with reference-transaction hook

refs.c

@@ -2044,7 +2044,7 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 	if (hook == &hook_not_found)
 		return ret;
 	if (!hook)
-		hook = find_hook("reference-transaction");
+		hook = xstrdup_or_null(find_hook("reference-transaction"));
 	if (!hook) {
 		hook = &hook_not_found;
 		return ret;