[PATCH v2 10/12] initial_ref_transaction_commit(): check for duplicate refs

@@ -4068,12 +4068,22 @@ int initial_ref_transaction_commit(struct ref_transaction *transaction,
 	int ret = 0, i;
 	int n = transaction->nr;
 	struct ref_update **updates = transaction->updates;
+	struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
 
 	assert(err);
 
 	if (transaction->state != REF_TRANSACTION_OPEN)
 		die("BUG: commit called for transaction that is not open");
 
+	/* Fail if a refname appears more than once in the transaction: */
+	for (i = 0; i < n; i++)
+		string_list_append(&affected_refnames, updates[i]->refname);
+	string_list_sort(&affected_refnames);
+	if (ref_update_reject_duplicates(&affected_refnames, err)) {
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];
 

@@ -4106,6 +4116,7 @@ int initial_ref_transaction_commit(struct ref_transaction *transaction,
 
 cleanup:
 	transaction->state = REF_TRANSACTION_CLOSED;
+	string_list_clear(&affected_refnames, 0);
 	return ret;
 }