Update markdown parsing library to github.com/gomarkdown/markdown (#944)

vendor/github.com/gomarkdown/markdown/parser/ref.go

@@ -0,0 +1,89 @@
+package parser
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/gomarkdown/markdown/ast"
+)
+
+// parse '(#r)', where r does not contain spaces. Or.
+// (!item) (!item, subitem), for an index, (!!item) signals primary.
+func maybeShortRefOrIndex(p *Parser, data []byte, offset int) (int, ast.Node) {
+	if len(data[offset:]) < 4 {
+		return 0, nil
+	}
+	// short ref first
+	data = data[offset:]
+	i := 1
+	switch data[i] {
+	case '#': // cross ref
+		i++
+	Loop:
+		for i < len(data) {
+			c := data[i]
+			switch {
+			case c == ')':
+				break Loop
+			case !isAlnum(c):
+				if c == '_' || c == '-' || c == ':' {
+					i++
+					continue
+				}
+				i = 0
+				break Loop
+			}
+			i++
+		}
+		if i >= len(data) {
+			return 0, nil
+		}
+		if data[i] != ')' {
+			return 0, nil
+		}
+
+		id := data[2:i]
+		node := &ast.CrossReference{}
+		node.Destination = id
+
+		return i + 1, node
+
+	case '!': // index
+		i++
+		start := i
+		i = skipUntilChar(data, start, ')')
+
+		// did we reach the end of the buffer without a closing marker?
+		if i >= len(data) {
+			return 0, nil
+		}
+
+		if len(data[start:i]) < 1 {
+			return 0, nil
+		}
+
+		idx := &ast.Index{}
+
+		idx.ID = fmt.Sprintf("idxref:%d", p.indexCnt)
+		p.indexCnt++
+
+		idx.Primary = data[start] == '!'
+		buf := data[start:i]
+
+		if idx.Primary {
+			buf = buf[1:]
+		}
+		items := bytes.Split(buf, []byte(","))
+		switch len(items) {
+		case 1:
+			idx.Item = bytes.TrimSpace(items[0])
+			return i + 1, idx
+		case 2:
+			idx.Item = bytes.TrimSpace(items[0])
+			idx.Subitem = bytes.TrimSpace(items[1])
+			return i + 1, idx
+		}
+	}
+
+	return 0, nil
+}