Add Goldmark as the new default markdown handler

This commit adds the fast and CommonMark compliant Goldmark as the new default markdown handler in Hugo.

If you want to continue using BlackFriday as the default for md/markdown extensions, you can use this configuration:

```toml
[markup]
defaultMarkdownHandler="blackfriday"
```

Fixes #5963
Fixes #1778
Fixes #6355

1 files changed, 12 insertions, 0 deletions

diff --git a/hugolib/shortcode_test.go b/hugolib/shortcode_test.go
index eb763b2a0..fdf37b6c2 100644
--- a/hugolib/shortcode_test.go
+++ b/hugolib/shortcode_test.go
@@ -44,6 +44,11 @@ func CheckShortCodeMatch(t *testing.T, input, expected string, withTemplate func
 func CheckShortCodeMatchAndError(t *testing.T, input, expected string, withTemplate func(templ tpl.TemplateHandler) error, expectError bool) {
 	t.Helper()
 	cfg, fs := newTestCfg()
+
+	cfg.Set("markup", map[string]interface{}{
+		"defaultMarkdownHandler": "blackfriday", // TODO(bep)
+	})
+
 	c := qt.New(t)
 
 	// Need some front matter, see https://github.com/gohugoio/hugo/issues/2337
@@ -584,6 +589,9 @@ title: "Foo"
 
 	cfg.Set("pygmentsUseClasses", true)
 	cfg.Set("pygmentsCodefences", true)
+	cfg.Set("markup", map[string]interface{}{
+		"defaultMarkdownHandler": "blackfriday", // TODO(bep)
+	})
 
 	writeSourcesToSource(t, "content", fs, sources...)
 
@@ -597,6 +605,7 @@ title: "Foo"
 			th := newTestHelper(s.Cfg, s.Fs, t)
 
 			expected := cast.ToStringSlice(test.expected)
+
 			th.assertFileContent(filepath.FromSlash(test.outFile), expected...)
 		})
 
@@ -1245,6 +1254,9 @@ func TestShortcodeRef(t *testing.T) {
 			v.Set("blackfriday", map[string]interface{}{
 				"plainIDAnchors": plainIDAnchors,
 			})
+			v.Set("markup", map[string]interface{}{
+				"defaultMarkdownHandler": "blackfriday", // TODO(bep)
+			})
 
 			builder := newTestSitesBuilder(t).WithViper(v)