Add plainify template function

To strip away any HTML. May be useful for the .Title in head etc.

People may shoot themself in the foot with this, maybe ...

But if someone wants to merge this, I guess it would be fine.

The replacement function is pretty fast.

docs/content/templates/functions.md

@@ -448,6 +448,12 @@ Runs the string through the Markdown processor. The result will be declared as "
 
 e.g. `{{ .Title | markdownify }}`
 
+### plainify
+
+Strips any HTML and returns the plain text version.
+
+e.g. `{{ "<b>BatMan</b>" | plainify }}` → "BatMan"
+
 ### pluralize
 Pluralize the given word with a set of common English pluralization rules.
 

tpl/template_funcs.go

@@ -1168,9 +1168,21 @@ func emojify(in interface{}) (template.HTML, error) {
 	if err != nil {
 		return "", err
 	}
+
 	return template.HTML(helpers.Emojify([]byte(str))), nil
 }
 
+// plainify strips any HTML and returns the plain text version.
+func plainify(in interface{}) (string, error) {
+	s, err := cast.ToStringE(in)
+
+	if err != nil {
+		return "", err
+	}
+
+	return helpers.StripHTML(s), nil
+}
+
 func refPage(page interface{}, ref, methodName string) template.HTML {
 	value := reflect.ValueOf(page)
 
@@ -1757,6 +1769,7 @@ func init() {
 		"mul":          func(a, b interface{}) (interface{}, error) { return doArithmetic(a, b, '*') },
 		"ne":           ne,
 		"partial":      partial,
+		"plainify":     plainify,
 		"pluralize":    pluralize,
 		"readDir":      readDir,
 		"ref":          ref,

tpl/template_funcs_test.go

@@ -102,6 +102,7 @@ delimit: {{ delimit (slice "A" "B" "C") ", " " and " }}
 jsonify: {{ (slice "A" "B" "C") | jsonify }}
 md5: {{ md5 "Hello world, gophers!" }}
 sha1: {{ sha1 "Hello world, gophers!" }}
+plainify: {{ plainify  "Hello <strong>world</strong>, gophers!" }}
 `
 	expected := `chomp: <p>Blockhead</p>
 dateFormat: Wednesday, Jan 21, 2015
@@ -139,6 +140,7 @@ delimit: A, B and C
 jsonify: ["A","B","C"]
 md5: b3029f756f98f79e7f1b7f1d1f0dd53b
 sha1: c8b5b0e33d408246e30f53e32b8f7627a7a649d4
+plainify: Hello world, gophers!
 `
 
 	var b bytes.Buffer