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

2 files changed, 36 insertions, 0 deletions

diff --git a/helpers/hugo.go b/helpers/hugo.go
index c4c3f4a76..b9b42e6cf 100644
--- a/helpers/hugo.go
+++ b/helpers/hugo.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/gohugoio/hugo/compare"
 	"github.com/spf13/cast"
 )
 
@@ -34,10 +35,40 @@ type HugoVersion struct {
 	Suffix string
 }
 
+var (
+	_ compare.Eqer     = (*HugoVersionString)(nil)
+	_ compare.Comparer = (*HugoVersionString)(nil)
+)
+
+type HugoVersionString string
+
 func (v HugoVersion) String() string {
 	return hugoVersion(v.Number, v.PatchLevel, v.Suffix)
 }
 
+func (v HugoVersion) Version() HugoVersionString {
+	return HugoVersionString(v.String())
+}
+
+func (h HugoVersionString) String() string {
+	return string(h)
+}
+
+// Implements compare.Comparer
+func (h HugoVersionString) Compare(other interface{}) int {
+	v := MustParseHugoVersion(h.String())
+	return compareVersions(v.Number, v.PatchLevel, other)
+}
+
+// Implements compare.Eqer
+func (h HugoVersionString) Eq(other interface{}) bool {
+	s, err := cast.ToStringE(other)
+	if err != nil {
+		return false
+	}
+	return s == h.String()
+}
+
 // ParseHugoVersion parses a version string.
 func ParseHugoVersion(s string) (HugoVersion, error) {
 	var vv HugoVersion
diff --git a/helpers/hugo_test.go b/helpers/hugo_test.go
index 1f5e5193f..78742c705 100644
--- a/helpers/hugo_test.go
+++ b/helpers/hugo_test.go
@@ -29,6 +29,11 @@ func TestHugoVersion(t *testing.T) {
 	require.Equal(t, v.ReleaseVersion().String(), "0.21")
 	require.Equal(t, "0.21-DEV", v.String())
 	require.Equal(t, "0.22", v.Next().String())
+	nextVersionString := v.Next().Version()
+	require.Equal(t, "0.22", nextVersionString.String())
+	require.True(t, nextVersionString.Eq("0.22"))
+	require.False(t, nextVersionString.Eq("0.21"))
+	require.True(t, nextVersionString.Eq(nextVersionString))
 	require.Equal(t, "0.20.3", v.NextPatchLevel(3).String())
 }