Make ge, le etc. work with the Hugo Version number

This means that you can do something ala:

```html
{{ if ge .Hugo.Version "0.36" }}Reasonable new Hugo version!{{ end }}
```

The intented use is feature toggling, but please note that it will take some time and Hugo versions until this can be trusted. It does not work in older Hugo versions.

Fixes #4443

1 files changed, 29 insertions, 0 deletions

diff --git a/compare/compare.go b/compare/compare.go
new file mode 100644
index 000000000..19a5deaa2
--- /dev/null
+++ b/compare/compare.go
@@ -0,0 +1,29 @@
+// Copyright 2017-present 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 compare
+
+// Eqer can be used to determine if this value is equal to the other.
+// The semantics of equals is that the two value are interchangeable
+// in the Hugo templates.
+type Eqer interface {
+	Eq(other interface{}) bool
+}
+
+// Comparer can be used to compare two values.
+// This will be used when using the le, ge etc. operators in the templates.
+// Compare returns -1 if the given version is less than, 0 if equal and 1 if greater than
+// the running version.
+type Comparer interface {
+	Compare(other interface{}) int
+}