1 files changed, 21 insertions, 0 deletions
diff --git a/common/collections/collections.go b/common/collections/collections.go
new file mode 100644
index 000000000..bb47c8acc
--- /dev/null
+++ b/common/collections/collections.go
@@ -0,0 +1,21 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package collections contains common Hugo functionality related to collection
+// handling.
+package collections
+
+// Grouper defines a very generic way to group items by a given key.
+type Grouper interface {
+	Group(key interface{}, items interface{}) (interface{}, error)
+}