output: Fix permalink in sitemap etc. when multiple permalinkable output formats

In Hugo 0.55.0 we made AMP `permalinkable`. We also render the output formats in their natural sort order, meaning `AMP` will be rendered before `HTML`. References in the sitemap would then point to the AMP version, and this is normally not what you'd want.

This commit fixes that by making `HTML` by default sort before the others.

If this is not you want, you can set `weight` on the output format configuration.

Fixes #5910

output/outputFormat_test.go

@@ -15,6 +15,7 @@ package output
 
 import (
 	"fmt"
+	"sort"
 	"testing"
 
 	"github.com/gohugoio/hugo/media"
@@ -225,3 +226,25 @@ func TestDecodeFormats(t *testing.T) {
 		}
 	}
 }
+
+func TestSort(t *testing.T) {
+	assert := require.New(t)
+	assert.Equal("HTML", DefaultFormats[0].Name)
+	assert.Equal("AMP", DefaultFormats[1].Name)
+
+	json := JSONFormat
+	json.Weight = 1
+
+	formats := Formats{
+		AMPFormat,
+		HTMLFormat,
+		json,
+	}
+
+	sort.Sort(formats)
+
+	assert.Equal("JSON", formats[0].Name)
+	assert.Equal("HTML", formats[1].Name)
+	assert.Equal("AMP", formats[2].Name)
+
+}