support replacing [refid][] syntax link content with alternate content

inline.go

@@ -213,7 +213,7 @@ func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
 	var (
 		i                        = 1
 		noteId                   int
-		title, link []byte
+		title, link, alt_content []byte
 		textHasNl                = false
 	)
 
@@ -350,6 +350,7 @@ func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
 	// reference style link
 	case i < len(data) && data[i] == '[':
 		var id []byte
+		alt_content_considered := false
 
 		// look for the id
 		i++
@@ -379,6 +380,7 @@ func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
 				id = b.Bytes()
 			} else {
 				id = data[1:txtE]
+				alt_content_considered = true
 			}
 		} else {
 			id = data[linkB:linkE]
@@ -394,6 +396,9 @@ func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
 		// keep link and title from reference
 		link = lr.link
 		title = lr.title
+		if alt_content_considered {
+			alt_content = lr.text
+		}
 		i++
 
 	// shortcut reference style link or reference or inline footnote
@@ -503,7 +508,11 @@ func link(p *parser, out *bytes.Buffer, data []byte, offset int) int {
 	// call the relevant rendering function
 	switch t {
 	case linkNormal:
+		if len(alt_content) > 0 {
+			p.r.Link(out, uLink, title, alt_content)
+		} else {
 			p.r.Link(out, uLink, title, content.Bytes())
+		}
 
 	case linkImg:
 		outSize := out.Len()

markdown.go

@@ -222,7 +222,8 @@ func (p *parser) getRef(refid string) (ref *reference, found bool) {
 				link:     []byte(r.Link),
 				title:    []byte(r.Title),
 				noteId:   0,
-				hasBlock: false}, true
+				hasBlock: false,
+				text:     []byte(r.Text)}, true
 		}
 	}
 	// refs are case insensitive
@@ -243,6 +244,9 @@ type Reference struct {
 	Link string
 	// Title is the alternate text describing the link in more detail.
 	Title string
+	// Text is the optional text to override the ref with if the syntax used was
+	// [refid][]
+	Text string
 }
 
 // ReferenceOverrideFunc is expected to be called with a reference string and
@@ -508,6 +512,7 @@ type reference struct {
 	title    []byte
 	noteId   int // 0 if not a footnote ref
 	hasBlock bool
+	text     []byte
 }
 
 // Check whether or not data starts with a reference link.