Refactor for issues loadattributes of a repository (#971)

* refactor for issues loadattributes of a repository

* refactors

models/helper.go

@@ -0,0 +1,21 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+func keysInt64(m map[int64]struct{}) []int64 {
+	var keys = make([]int64, 0, len(m))
+	for k, _ := range m {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+func valuesRepository(m map[int64]*Repository) []*Repository {
+	var values = make([]*Repository, 0, len(m))
+	for _, v := range m {
+		values = append(values, v)
+	}
+	return values
+}