[chore/bugfix] Switch markdown from blackfriday to goldmark (#1267)

Co-authored-by: Autumn! <autumnull@posteo.net>

19 files changed, 4133 insertions, 0 deletions

diff --git a/vendor/github.com/yuin/goldmark/parser/attribute.go b/vendor/github.com/yuin/goldmark/parser/attribute.go
new file mode 100644
index 000000000..f86c83610
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/attribute.go
@@ -0,0 +1,328 @@
+package parser
+
+import (
+	"bytes"
+	"io"
+	"strconv"
+
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var attrNameID = []byte("id")
+var attrNameClass = []byte("class")
+
+// An Attribute is an attribute of the markdown elements
+type Attribute struct {
+	Name  []byte
+	Value interface{}
+}
+
+// An Attributes is a collection of attributes.
+type Attributes []Attribute
+
+// Find returns a (value, true) if an attribute correspond with given name is found, otherwise (nil, false).
+func (as Attributes) Find(name []byte) (interface{}, bool) {
+	for _, a := range as {
+		if bytes.Equal(a.Name, name) {
+			return a.Value, true
+		}
+	}
+	return nil, false
+}
+
+func (as Attributes) findUpdate(name []byte, cb func(v interface{}) interface{}) bool {
+	for i, a := range as {
+		if bytes.Equal(a.Name, name) {
+			as[i].Value = cb(a.Value)
+			return true
+		}
+	}
+	return false
+}
+
+// ParseAttributes parses attributes into a map.
+// ParseAttributes returns a parsed attributes and true if could parse
+// attributes, otherwise nil and false.
+func ParseAttributes(reader text.Reader) (Attributes, bool) {
+	savedLine, savedPosition := reader.Position()
+	reader.SkipSpaces()
+	if reader.Peek() != '{' {
+		reader.SetPosition(savedLine, savedPosition)
+		return nil, false
+	}
+	reader.Advance(1)
+	attrs := Attributes{}
+	for {
+		if reader.Peek() == '}' {
+			reader.Advance(1)
+			return attrs, true
+		}
+		attr, ok := parseAttribute(reader)
+		if !ok {
+			reader.SetPosition(savedLine, savedPosition)
+			return nil, false
+		}
+		if bytes.Equal(attr.Name, attrNameClass) {
+			if !attrs.findUpdate(attrNameClass, func(v interface{}) interface{} {
+				ret := make([]byte, 0, len(v.([]byte))+1+len(attr.Value.([]byte)))
+				ret = append(ret, v.([]byte)...)
+				return append(append(ret, ' '), attr.Value.([]byte)...)
+			}) {
+				attrs = append(attrs, attr)
+			}
+		} else {
+			attrs = append(attrs, attr)
+		}
+		reader.SkipSpaces()
+		if reader.Peek() == ',' {
+			reader.Advance(1)
+			reader.SkipSpaces()
+		}
+	}
+}
+
+func parseAttribute(reader text.Reader) (Attribute, bool) {
+	reader.SkipSpaces()
+	c := reader.Peek()
+	if c == '#' || c == '.' {
+		reader.Advance(1)
+		line, _ := reader.PeekLine()
+		i := 0
+		// HTML5 allows any kind of characters as id, but XHTML restricts characters for id.
+		// CommonMark is basically defined for XHTML(even though it is legacy).
+		// So we restrict id characters.
+		for ; i < len(line) && !util.IsSpace(line[i]) &&
+			(!util.IsPunct(line[i]) || line[i] == '_' || line[i] == '-' || line[i] == ':' || line[i] == '.'); i++ {
+		}
+		name := attrNameClass
+		if c == '#' {
+			name = attrNameID
+		}
+		reader.Advance(i)
+		return Attribute{Name: name, Value: line[0:i]}, true
+	}
+	line, _ := reader.PeekLine()
+	if len(line) == 0 {
+		return Attribute{}, false
+	}
+	c = line[0]
+	if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+		c == '_' || c == ':') {
+		return Attribute{}, false
+	}
+	i := 0
+	for ; i < len(line); i++ {
+		c = line[i]
+		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+			(c >= '0' && c <= '9') ||
+			c == '_' || c == ':' || c == '.' || c == '-') {
+			break
+		}
+	}
+	name := line[:i]
+	reader.Advance(i)
+	reader.SkipSpaces()
+	c = reader.Peek()
+	if c != '=' {
+		return Attribute{}, false
+	}
+	reader.Advance(1)
+	reader.SkipSpaces()
+	value, ok := parseAttributeValue(reader)
+	if !ok {
+		return Attribute{}, false
+	}
+	if bytes.Equal(name, attrNameClass) {
+		if _, ok = value.([]byte); !ok {
+			return Attribute{}, false
+		}
+	}
+	return Attribute{Name: name, Value: value}, true
+}
+
+func parseAttributeValue(reader text.Reader) (interface{}, bool) {
+	reader.SkipSpaces()
+	c := reader.Peek()
+	var value interface{}
+	ok := false
+	switch c {
+	case text.EOF:
+		return Attribute{}, false
+	case '{':
+		value, ok = ParseAttributes(reader)
+	case '[':
+		value, ok = parseAttributeArray(reader)
+	case '"':
+		value, ok = parseAttributeString(reader)
+	default:
+		if c == '-' || c == '+' || util.IsNumeric(c) {
+			value, ok = parseAttributeNumber(reader)
+		} else {
+			value, ok = parseAttributeOthers(reader)
+		}
+	}
+	if !ok {
+		return nil, false
+	}
+	return value, true
+}
+
+func parseAttributeArray(reader text.Reader) ([]interface{}, bool) {
+	reader.Advance(1) // skip [
+	ret := []interface{}{}
+	for i := 0; ; i++ {
+		c := reader.Peek()
+		comma := false
+		if i != 0 && c == ',' {
+			reader.Advance(1)
+			comma = true
+		}
+		if c == ']' {
+			if !comma {
+				reader.Advance(1)
+				return ret, true
+			}
+			return nil, false
+		}
+		reader.SkipSpaces()
+		value, ok := parseAttributeValue(reader)
+		if !ok {
+			return nil, false
+		}
+		ret = append(ret, value)
+		reader.SkipSpaces()
+	}
+}
+
+func parseAttributeString(reader text.Reader) ([]byte, bool) {
+	reader.Advance(1) // skip "
+	line, _ := reader.PeekLine()
+	i := 0
+	l := len(line)
+	var buf bytes.Buffer
+	for i < l {
+		c := line[i]
+		if c == '\\' && i != l-1 {
+			n := line[i+1]
+			switch n {
+			case '"', '/', '\\':
+				buf.WriteByte(n)
+				i += 2
+			case 'b':
+				buf.WriteString("\b")
+				i += 2
+			case 'f':
+				buf.WriteString("\f")
+				i += 2
+			case 'n':
+				buf.WriteString("\n")
+				i += 2
+			case 'r':
+				buf.WriteString("\r")
+				i += 2
+			case 't':
+				buf.WriteString("\t")
+				i += 2
+			default:
+				buf.WriteByte('\\')
+				i++
+			}
+			continue
+		}
+		if c == '"' {
+			reader.Advance(i + 1)
+			return buf.Bytes(), true
+		}
+		buf.WriteByte(c)
+		i++
+	}
+	return nil, false
+}
+
+func scanAttributeDecimal(reader text.Reader, w io.ByteWriter) {
+	for {
+		c := reader.Peek()
+		if util.IsNumeric(c) {
+			w.WriteByte(c)
+		} else {
+			return
+		}
+		reader.Advance(1)
+	}
+}
+
+func parseAttributeNumber(reader text.Reader) (float64, bool) {
+	sign := 1
+	c := reader.Peek()
+	if c == '-' {
+		sign = -1
+		reader.Advance(1)
+	} else if c == '+' {
+		reader.Advance(1)
+	}
+	var buf bytes.Buffer
+	if !util.IsNumeric(reader.Peek()) {
+		return 0, false
+	}
+	scanAttributeDecimal(reader, &buf)
+	if buf.Len() == 0 {
+		return 0, false
+	}
+	c = reader.Peek()
+	if c == '.' {
+		buf.WriteByte(c)
+		reader.Advance(1)
+		scanAttributeDecimal(reader, &buf)
+	}
+	c = reader.Peek()
+	if c == 'e' || c == 'E' {
+		buf.WriteByte(c)
+		reader.Advance(1)
+		c = reader.Peek()
+		if c == '-' || c == '+' {
+			buf.WriteByte(c)
+			reader.Advance(1)
+		}
+		scanAttributeDecimal(reader, &buf)
+	}
+	f, err := strconv.ParseFloat(buf.String(), 10)
+	if err != nil {
+		return 0, false
+	}
+	return float64(sign) * f, true
+}
+
+var bytesTrue = []byte("true")
+var bytesFalse = []byte("false")
+var bytesNull = []byte("null")
+
+func parseAttributeOthers(reader text.Reader) (interface{}, bool) {
+	line, _ := reader.PeekLine()
+	c := line[0]
+	if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+		c == '_' || c == ':') {
+		return nil, false
+	}
+	i := 0
+	for ; i < len(line); i++ {
+		c := line[i]
+		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+			(c >= '0' && c <= '9') ||
+			c == '_' || c == ':' || c == '.' || c == '-') {
+			break
+		}
+	}
+	value := line[:i]
+	reader.Advance(i)
+	if bytes.Equal(value, bytesTrue) {
+		return true, true
+	}
+	if bytes.Equal(value, bytesFalse) {
+		return false, true
+	}
+	if bytes.Equal(value, bytesNull) {
+		return nil, true
+	}
+	return value, true
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/atx_heading.go b/vendor/github.com/yuin/goldmark/parser/atx_heading.go
new file mode 100644
index 000000000..13a198b52
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/atx_heading.go
@@ -0,0 +1,246 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// A HeadingConfig struct is a data structure that holds configuration of the renderers related to headings.
+type HeadingConfig struct {
+	AutoHeadingID bool
+	Attribute     bool
+}
+
+// SetOption implements SetOptioner.
+func (b *HeadingConfig) SetOption(name OptionName, value interface{}) {
+	switch name {
+	case optAutoHeadingID:
+		b.AutoHeadingID = true
+	case optAttribute:
+		b.Attribute = true
+	}
+}
+
+// A HeadingOption interface sets options for heading parsers.
+type HeadingOption interface {
+	Option
+	SetHeadingOption(*HeadingConfig)
+}
+
+// AutoHeadingID is an option name that enables auto IDs for headings.
+const optAutoHeadingID OptionName = "AutoHeadingID"
+
+type withAutoHeadingID struct {
+}
+
+func (o *withAutoHeadingID) SetParserOption(c *Config) {
+	c.Options[optAutoHeadingID] = true
+}
+
+func (o *withAutoHeadingID) SetHeadingOption(p *HeadingConfig) {
+	p.AutoHeadingID = true
+}
+
+// WithAutoHeadingID is a functional option that enables custom heading ids and
+// auto generated heading ids.
+func WithAutoHeadingID() HeadingOption {
+	return &withAutoHeadingID{}
+}
+
+type withHeadingAttribute struct {
+	Option
+}
+
+func (o *withHeadingAttribute) SetHeadingOption(p *HeadingConfig) {
+	p.Attribute = true
+}
+
+// WithHeadingAttribute is a functional option that enables custom heading attributes.
+func WithHeadingAttribute() HeadingOption {
+	return &withHeadingAttribute{WithAttribute()}
+}
+
+type atxHeadingParser struct {
+	HeadingConfig
+}
+
+// NewATXHeadingParser return a new BlockParser that can parse ATX headings.
+func NewATXHeadingParser(opts ...HeadingOption) BlockParser {
+	p := &atxHeadingParser{}
+	for _, o := range opts {
+		o.SetHeadingOption(&p.HeadingConfig)
+	}
+	return p
+}
+
+func (b *atxHeadingParser) Trigger() []byte {
+	return []byte{'#'}
+}
+
+func (b *atxHeadingParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	line, segment := reader.PeekLine()
+	pos := pc.BlockOffset()
+	if pos < 0 {
+		return nil, NoChildren
+	}
+	i := pos
+	for ; i < len(line) && line[i] == '#'; i++ {
+	}
+	level := i - pos
+	if i == pos || level > 6 {
+		return nil, NoChildren
+	}
+	if i == len(line) { // alone '#' (without a new line character)
+		return ast.NewHeading(level), NoChildren
+	}
+	l := util.TrimLeftSpaceLength(line[i:])
+	if l == 0 {
+		return nil, NoChildren
+	}
+	start := i + l
+	if start >= len(line) {
+		start = len(line) - 1
+	}
+	origstart := start
+	stop := len(line) - util.TrimRightSpaceLength(line)
+
+	node := ast.NewHeading(level)
+	parsed := false
+	if b.Attribute { // handles special case like ### heading ### {#id}
+		start--
+		closureClose := -1
+		closureOpen := -1
+		for j := start; j < stop; {
+			c := line[j]
+			if util.IsEscapedPunctuation(line, j) {
+				j += 2
+			} else if util.IsSpace(c) && j < stop-1 && line[j+1] == '#' {
+				closureOpen = j + 1
+				k := j + 1
+				for ; k < stop && line[k] == '#'; k++ {
+				}
+				closureClose = k
+				break
+			} else {
+				j++
+			}
+		}
+		if closureClose > 0 {
+			reader.Advance(closureClose)
+			attrs, ok := ParseAttributes(reader)
+			rest, _ := reader.PeekLine()
+			parsed = ok && util.IsBlank(rest)
+			if parsed {
+				for _, attr := range attrs {
+					node.SetAttribute(attr.Name, attr.Value)
+				}
+				node.Lines().Append(text.NewSegment(segment.Start+start+1-segment.Padding, segment.Start+closureOpen-segment.Padding))
+			}
+		}
+	}
+	if !parsed {
+		start = origstart
+		stop := len(line) - util.TrimRightSpaceLength(line)
+		if stop <= start { // empty headings like '##[space]'
+			stop = start
+		} else {
+			i = stop - 1
+			for ; line[i] == '#' && i >= start; i-- {
+			}
+			if i != stop-1 && !util.IsSpace(line[i]) {
+				i = stop - 1
+			}
+			i++
+			stop = i
+		}
+
+		if len(util.TrimRight(line[start:stop], []byte{'#'})) != 0 { // empty heading like '### ###'
+			node.Lines().Append(text.NewSegment(segment.Start+start-segment.Padding, segment.Start+stop-segment.Padding))
+		}
+	}
+	return node, NoChildren
+}
+
+func (b *atxHeadingParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	return Close
+}
+
+func (b *atxHeadingParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	if b.Attribute {
+		_, ok := node.AttributeString("id")
+		if !ok {
+			parseLastLineAttributes(node, reader, pc)
+		}
+	}
+
+	if b.AutoHeadingID {
+		id, ok := node.AttributeString("id")
+		if !ok {
+			generateAutoHeadingID(node.(*ast.Heading), reader, pc)
+		} else {
+			pc.IDs().Put(id.([]byte))
+		}
+	}
+}
+
+func (b *atxHeadingParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *atxHeadingParser) CanAcceptIndentedLine() bool {
+	return false
+}
+
+func generateAutoHeadingID(node *ast.Heading, reader text.Reader, pc Context) {
+	var line []byte
+	lastIndex := node.Lines().Len() - 1
+	if lastIndex > -1 {
+		lastLine := node.Lines().At(lastIndex)
+		line = lastLine.Value(reader.Source())
+	}
+	headingID := pc.IDs().Generate(line, ast.KindHeading)
+	node.SetAttribute(attrNameID, headingID)
+}
+
+func parseLastLineAttributes(node ast.Node, reader text.Reader, pc Context) {
+	lastIndex := node.Lines().Len() - 1
+	if lastIndex < 0 { // empty headings
+		return
+	}
+	lastLine := node.Lines().At(lastIndex)
+	line := lastLine.Value(reader.Source())
+	lr := text.NewReader(line)
+	var attrs Attributes
+	var ok bool
+	var start text.Segment
+	var sl int
+	var end text.Segment
+	for {
+		c := lr.Peek()
+		if c == text.EOF {
+			break
+		}
+		if c == '\\' {
+			lr.Advance(1)
+			if lr.Peek() == '{' {
+				lr.Advance(1)
+			}
+			continue
+		}
+		if c == '{' {
+			sl, start = lr.Position()
+			attrs, ok = ParseAttributes(lr)
+			_, end = lr.Position()
+			lr.SetPosition(sl, start)
+		}
+		lr.Advance(1)
+	}
+	if ok && util.IsBlank(line[end.Start:]) {
+		for _, attr := range attrs {
+			node.SetAttribute(attr.Name, attr.Value)
+		}
+		lastLine.Stop = lastLine.Start + start.Start
+		node.Lines().Set(lastIndex, lastLine)
+	}
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/auto_link.go b/vendor/github.com/yuin/goldmark/parser/auto_link.go
new file mode 100644
index 000000000..726a50571
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/auto_link.go
@@ -0,0 +1,42 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type autoLinkParser struct {
+}
+
+var defaultAutoLinkParser = &autoLinkParser{}
+
+// NewAutoLinkParser returns a new InlineParser that parses autolinks
+// surrounded by '<' and '>' .
+func NewAutoLinkParser() InlineParser {
+	return defaultAutoLinkParser
+}
+
+func (s *autoLinkParser) Trigger() []byte {
+	return []byte{'<'}
+}
+
+func (s *autoLinkParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	line, segment := block.PeekLine()
+	stop := util.FindEmailIndex(line[1:])
+	typ := ast.AutoLinkType(ast.AutoLinkEmail)
+	if stop < 0 {
+		stop = util.FindURLIndex(line[1:])
+		typ = ast.AutoLinkURL
+	}
+	if stop < 0 {
+		return nil
+	}
+	stop++
+	if stop >= len(line) || line[stop] != '>' {
+		return nil
+	}
+	value := ast.NewTextSegment(text.NewSegment(segment.Start+1, segment.Start+stop))
+	block.Advance(stop + 1)
+	return ast.NewAutoLink(typ, value)
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/blockquote.go b/vendor/github.com/yuin/goldmark/parser/blockquote.go
new file mode 100644
index 000000000..e7778dca7
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/blockquote.go
@@ -0,0 +1,69 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type blockquoteParser struct {
+}
+
+var defaultBlockquoteParser = &blockquoteParser{}
+
+// NewBlockquoteParser returns a new BlockParser that
+// parses blockquotes.
+func NewBlockquoteParser() BlockParser {
+	return defaultBlockquoteParser
+}
+
+func (b *blockquoteParser) process(reader text.Reader) bool {
+	line, _ := reader.PeekLine()
+	w, pos := util.IndentWidth(line, reader.LineOffset())
+	if w > 3 || pos >= len(line) || line[pos] != '>' {
+		return false
+	}
+	pos++
+	if pos >= len(line) || line[pos] == '\n' {
+		reader.Advance(pos)
+		return true
+	}
+	if line[pos] == ' ' || line[pos] == '\t' {
+		pos++
+	}
+	reader.Advance(pos)
+	if line[pos-1] == '\t' {
+		reader.SetPadding(2)
+	}
+	return true
+}
+
+func (b *blockquoteParser) Trigger() []byte {
+	return []byte{'>'}
+}
+
+func (b *blockquoteParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	if b.process(reader) {
+		return ast.NewBlockquote(), HasChildren
+	}
+	return nil, NoChildren
+}
+
+func (b *blockquoteParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	if b.process(reader) {
+		return Continue | HasChildren
+	}
+	return Close
+}
+
+func (b *blockquoteParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	// nothing to do
+}
+
+func (b *blockquoteParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *blockquoteParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/code_block.go b/vendor/github.com/yuin/goldmark/parser/code_block.go
new file mode 100644
index 000000000..732f18c65
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/code_block.go
@@ -0,0 +1,100 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type codeBlockParser struct {
+}
+
+// CodeBlockParser is a BlockParser implementation that parses indented code blocks.
+var defaultCodeBlockParser = &codeBlockParser{}
+
+// NewCodeBlockParser returns a new BlockParser that
+// parses code blocks.
+func NewCodeBlockParser() BlockParser {
+	return defaultCodeBlockParser
+}
+
+func (b *codeBlockParser) Trigger() []byte {
+	return nil
+}
+
+func (b *codeBlockParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	line, segment := reader.PeekLine()
+	pos, padding := util.IndentPosition(line, reader.LineOffset(), 4)
+	if pos < 0 || util.IsBlank(line) {
+		return nil, NoChildren
+	}
+	node := ast.NewCodeBlock()
+	reader.AdvanceAndSetPadding(pos, padding)
+	_, segment = reader.PeekLine()
+	// if code block line starts with a tab, keep a tab as it is.
+	if segment.Padding != 0 {
+		preserveLeadingTabInCodeBlock(&segment, reader, 0)
+	}
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len() - 1)
+	return node, NoChildren
+
+}
+
+func (b *codeBlockParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	line, segment := reader.PeekLine()
+	if util.IsBlank(line) {
+		node.Lines().Append(segment.TrimLeftSpaceWidth(4, reader.Source()))
+		return Continue | NoChildren
+	}
+	pos, padding := util.IndentPosition(line, reader.LineOffset(), 4)
+	if pos < 0 {
+		return Close
+	}
+	reader.AdvanceAndSetPadding(pos, padding)
+	_, segment = reader.PeekLine()
+
+	// if code block line starts with a tab, keep a tab as it is.
+	if segment.Padding != 0 {
+		preserveLeadingTabInCodeBlock(&segment, reader, 0)
+	}
+
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len() - 1)
+	return Continue | NoChildren
+}
+
+func (b *codeBlockParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	// trim trailing blank lines
+	lines := node.Lines()
+	length := lines.Len() - 1
+	source := reader.Source()
+	for length >= 0 {
+		line := lines.At(length)
+		if util.IsBlank(line.Value(source)) {
+			length--
+		} else {
+			break
+		}
+	}
+	lines.SetSliced(0, length+1)
+}
+
+func (b *codeBlockParser) CanInterruptParagraph() bool {
+	return false
+}
+
+func (b *codeBlockParser) CanAcceptIndentedLine() bool {
+	return true
+}
+
+func preserveLeadingTabInCodeBlock(segment *text.Segment, reader text.Reader, indent int) {
+	offsetWithPadding := reader.LineOffset() + indent
+	sl, ss := reader.Position()
+	reader.SetPosition(sl, text.NewSegment(ss.Start-1, ss.Stop))
+	if offsetWithPadding == reader.LineOffset() {
+		segment.Padding = 0
+		segment.Start--
+	}
+	reader.SetPosition(sl, ss)
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/code_span.go b/vendor/github.com/yuin/goldmark/parser/code_span.go
new file mode 100644
index 000000000..a74b09bc4
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/code_span.go
@@ -0,0 +1,84 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+type codeSpanParser struct {
+}
+
+var defaultCodeSpanParser = &codeSpanParser{}
+
+// NewCodeSpanParser return a new InlineParser that parses inline codes
+// surrounded by '`' .
+func NewCodeSpanParser() InlineParser {
+	return defaultCodeSpanParser
+}
+
+func (s *codeSpanParser) Trigger() []byte {
+	return []byte{'`'}
+}
+
+func (s *codeSpanParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	line, startSegment := block.PeekLine()
+	opener := 0
+	for ; opener < len(line) && line[opener] == '`'; opener++ {
+	}
+	block.Advance(opener)
+	l, pos := block.Position()
+	node := ast.NewCodeSpan()
+	for {
+		line, segment := block.PeekLine()
+		if line == nil {
+			block.SetPosition(l, pos)
+			return ast.NewTextSegment(startSegment.WithStop(startSegment.Start + opener))
+		}
+		for i := 0; i < len(line); i++ {
+			c := line[i]
+			if c == '`' {
+				oldi := i
+				for ; i < len(line) && line[i] == '`'; i++ {
+				}
+				closure := i - oldi
+				if closure == opener && (i >= len(line) || line[i] != '`') {
+					segment = segment.WithStop(segment.Start + i - closure)
+					if !segment.IsEmpty() {
+						node.AppendChild(node, ast.NewRawTextSegment(segment))
+					}
+					block.Advance(i)
+					goto end
+				}
+			}
+		}
+		node.AppendChild(node, ast.NewRawTextSegment(segment))
+		block.AdvanceLine()
+	}
+end:
+	if !node.IsBlank(block.Source()) {
+		// trim first halfspace and last halfspace
+		segment := node.FirstChild().(*ast.Text).Segment
+		shouldTrimmed := true
+		if !(!segment.IsEmpty() && isSpaceOrNewline(block.Source()[segment.Start])) {
+			shouldTrimmed = false
+		}
+		segment = node.LastChild().(*ast.Text).Segment
+		if !(!segment.IsEmpty() && isSpaceOrNewline(block.Source()[segment.Stop-1])) {
+			shouldTrimmed = false
+		}
+		if shouldTrimmed {
+			t := node.FirstChild().(*ast.Text)
+			segment := t.Segment
+			t.Segment = segment.WithStart(segment.Start + 1)
+			t = node.LastChild().(*ast.Text)
+			segment = node.LastChild().(*ast.Text).Segment
+			t.Segment = segment.WithStop(segment.Stop - 1)
+		}
+
+	}
+	return node
+}
+
+func isSpaceOrNewline(c byte) bool {
+	return c == ' ' || c == '\n'
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/delimiter.go b/vendor/github.com/yuin/goldmark/parser/delimiter.go
new file mode 100644
index 000000000..eb843af44
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/delimiter.go
@@ -0,0 +1,238 @@
+package parser
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// A DelimiterProcessor interface provides a set of functions about
+// Delimiter nodes.
+type DelimiterProcessor interface {
+	// IsDelimiter returns true if given character is a delimiter, otherwise false.
+	IsDelimiter(byte) bool
+
+	// CanOpenCloser returns true if given opener can close given closer, otherwise false.
+	CanOpenCloser(opener, closer *Delimiter) bool
+
+	// OnMatch will be called when new matched delimiter found.
+	// OnMatch should return a new Node correspond to the matched delimiter.
+	OnMatch(consumes int) ast.Node
+}
+
+// A Delimiter struct represents a delimiter like '*' of the Markdown text.
+type Delimiter struct {
+	ast.BaseInline
+
+	Segment text.Segment
+
+	// CanOpen is set true if this delimiter can open a span for a new node.
+	// See https://spec.commonmark.org/0.30/#can-open-emphasis for details.
+	CanOpen bool
+
+	// CanClose is set true if this delimiter can close a span for a new node.
+	// See https://spec.commonmark.org/0.30/#can-open-emphasis for details.
+	CanClose bool
+
+	// Length is a remaining length of this delimiter.
+	Length int
+
+	// OriginalLength is a original length of this delimiter.
+	OriginalLength int
+
+	// Char is a character of this delimiter.
+	Char byte
+
+	// PreviousDelimiter is a previous sibling delimiter node of this delimiter.
+	PreviousDelimiter *Delimiter
+
+	// NextDelimiter is a next sibling delimiter node of this delimiter.
+	NextDelimiter *Delimiter
+
+	// Processor is a DelimiterProcessor associated with this delimiter.
+	Processor DelimiterProcessor
+}
+
+// Inline implements Inline.Inline.
+func (d *Delimiter) Inline() {}
+
+// Dump implements Node.Dump.
+func (d *Delimiter) Dump(source []byte, level int) {
+	fmt.Printf("%sDelimiter: \"%s\"\n", strings.Repeat("    ", level), string(d.Text(source)))
+}
+
+var kindDelimiter = ast.NewNodeKind("Delimiter")
+
+// Kind implements Node.Kind
+func (d *Delimiter) Kind() ast.NodeKind {
+	return kindDelimiter
+}
+
+// Text implements Node.Text
+func (d *Delimiter) Text(source []byte) []byte {
+	return d.Segment.Value(source)
+}
+
+// ConsumeCharacters consumes delimiters.
+func (d *Delimiter) ConsumeCharacters(n int) {
+	d.Length -= n
+	d.Segment = d.Segment.WithStop(d.Segment.Start + d.Length)
+}
+
+// CalcComsumption calculates how many characters should be used for opening
+// a new span correspond to given closer.
+func (d *Delimiter) CalcComsumption(closer *Delimiter) int {
+	if (d.CanClose || closer.CanOpen) && (d.OriginalLength+closer.OriginalLength)%3 == 0 && closer.OriginalLength%3 != 0 {
+		return 0
+	}
+	if d.Length >= 2 && closer.Length >= 2 {
+		return 2
+	}
+	return 1
+}
+
+// NewDelimiter returns a new Delimiter node.
+func NewDelimiter(canOpen, canClose bool, length int, char byte, processor DelimiterProcessor) *Delimiter {
+	c := &Delimiter{
+		BaseInline:        ast.BaseInline{},
+		CanOpen:           canOpen,
+		CanClose:          canClose,
+		Length:            length,
+		OriginalLength:    length,
+		Char:              char,
+		PreviousDelimiter: nil,
+		NextDelimiter:     nil,
+		Processor:         processor,
+	}
+	return c
+}
+
+// ScanDelimiter scans a delimiter by given DelimiterProcessor.
+func ScanDelimiter(line []byte, before rune, min int, processor DelimiterProcessor) *Delimiter {
+	i := 0
+	c := line[i]
+	j := i
+	if !processor.IsDelimiter(c) {
+		return nil
+	}
+	for ; j < len(line) && c == line[j]; j++ {
+	}
+	if (j - i) >= min {
+		after := rune(' ')
+		if j != len(line) {
+			after = util.ToRune(line, j)
+		}
+
+		canOpen, canClose := false, false
+		beforeIsPunctuation := util.IsPunctRune(before)
+		beforeIsWhitespace := util.IsSpaceRune(before)
+		afterIsPunctuation := util.IsPunctRune(after)
+		afterIsWhitespace := util.IsSpaceRune(after)
+
+		isLeft := !afterIsWhitespace &&
+			(!afterIsPunctuation || beforeIsWhitespace || beforeIsPunctuation)
+		isRight := !beforeIsWhitespace &&
+			(!beforeIsPunctuation || afterIsWhitespace || afterIsPunctuation)
+
+		if line[i] == '_' {
+			canOpen = isLeft && (!isRight || beforeIsPunctuation)
+			canClose = isRight && (!isLeft || afterIsPunctuation)
+		} else {
+			canOpen = isLeft
+			canClose = isRight
+		}
+		return NewDelimiter(canOpen, canClose, j-i, c, processor)
+	}
+	return nil
+}
+
+// ProcessDelimiters processes the delimiter list in the context.
+// Processing will be stop when reaching the bottom.
+//
+// If you implement an inline parser that can have other inline nodes as
+// children, you should call this function when nesting span has closed.
+func ProcessDelimiters(bottom ast.Node, pc Context) {
+	lastDelimiter := pc.LastDelimiter()
+	if lastDelimiter == nil {
+		return
+	}
+	var closer *Delimiter
+	if bottom != nil {
+		if bottom != lastDelimiter {
+			for c := lastDelimiter.PreviousSibling(); c != nil && c != bottom; {
+				if d, ok := c.(*Delimiter); ok {
+					closer = d
+				}
+				c = c.PreviousSibling()
+			}
+		}
+	} else {
+		closer = pc.FirstDelimiter()
+	}
+	if closer == nil {
+		pc.ClearDelimiters(bottom)
+		return
+	}
+	for closer != nil {
+		if !closer.CanClose {
+			closer = closer.NextDelimiter
+			continue
+		}
+		consume := 0
+		found := false
+		maybeOpener := false
+		var opener *Delimiter
+		for opener = closer.PreviousDelimiter; opener != nil && opener != bottom; opener = opener.PreviousDelimiter {
+			if opener.CanOpen && opener.Processor.CanOpenCloser(opener, closer) {
+				maybeOpener = true
+				consume = opener.CalcComsumption(closer)
+				if consume > 0 {
+					found = true
+					break
+				}
+			}
+		}
+		if !found {
+			next := closer.NextDelimiter
+			if !maybeOpener && !closer.CanOpen {
+				pc.RemoveDelimiter(closer)
+			}
+			closer = next
+			continue
+		}
+		opener.ConsumeCharacters(consume)
+		closer.ConsumeCharacters(consume)
+
+		node := opener.Processor.OnMatch(consume)
+
+		parent := opener.Parent()
+		child := opener.NextSibling()
+
+		for child != nil && child != closer {
+			next := child.NextSibling()
+			node.AppendChild(node, child)
+			child = next
+		}
+		parent.InsertAfter(parent, opener, node)
+
+		for c := opener.NextDelimiter; c != nil && c != closer; {
+			next := c.NextDelimiter
+			pc.RemoveDelimiter(c)
+			c = next
+		}
+
+		if opener.Length == 0 {
+			pc.RemoveDelimiter(opener)
+		}
+
+		if closer.Length == 0 {
+			next := closer.NextDelimiter
+			pc.RemoveDelimiter(closer)
+			closer = next
+		}
+	}
+	pc.ClearDelimiters(bottom)
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/emphasis.go b/vendor/github.com/yuin/goldmark/parser/emphasis.go
new file mode 100644
index 000000000..488647117
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/emphasis.go
@@ -0,0 +1,50 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+type emphasisDelimiterProcessor struct {
+}
+
+func (p *emphasisDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '*' || b == '_'
+}
+
+func (p *emphasisDelimiterProcessor) CanOpenCloser(opener, closer *Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *emphasisDelimiterProcessor) OnMatch(consumes int) ast.Node {
+	return ast.NewEmphasis(consumes)
+}
+
+var defaultEmphasisDelimiterProcessor = &emphasisDelimiterProcessor{}
+
+type emphasisParser struct {
+}
+
+var defaultEmphasisParser = &emphasisParser{}
+
+// NewEmphasisParser return a new InlineParser that parses emphasises.
+func NewEmphasisParser() InlineParser {
+	return defaultEmphasisParser
+}
+
+func (s *emphasisParser) Trigger() []byte {
+	return []byte{'*', '_'}
+}
+
+func (s *emphasisParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := ScanDelimiter(line, before, 1, defaultEmphasisDelimiterProcessor)
+	if node == nil {
+		return nil
+	}
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/fcode_block.go b/vendor/github.com/yuin/goldmark/parser/fcode_block.go
new file mode 100644
index 000000000..e51a35ace
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/fcode_block.go
@@ -0,0 +1,121 @@
+package parser
+
+import (
+	"bytes"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type fencedCodeBlockParser struct {
+}
+
+var defaultFencedCodeBlockParser = &fencedCodeBlockParser{}
+
+// NewFencedCodeBlockParser returns a new BlockParser that
+// parses fenced code blocks.
+func NewFencedCodeBlockParser() BlockParser {
+	return defaultFencedCodeBlockParser
+}
+
+type fenceData struct {
+	char   byte
+	indent int
+	length int
+	node   ast.Node
+}
+
+var fencedCodeBlockInfoKey = NewContextKey()
+
+func (b *fencedCodeBlockParser) Trigger() []byte {
+	return []byte{'~', '`'}
+}
+
+func (b *fencedCodeBlockParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	line, segment := reader.PeekLine()
+	pos := pc.BlockOffset()
+	if pos < 0 || (line[pos] != '`' && line[pos] != '~') {
+		return nil, NoChildren
+	}
+	findent := pos
+	fenceChar := line[pos]
+	i := pos
+	for ; i < len(line) && line[i] == fenceChar; i++ {
+	}
+	oFenceLength := i - pos
+	if oFenceLength < 3 {
+		return nil, NoChildren
+	}
+	var info *ast.Text
+	if i < len(line)-1 {
+		rest := line[i:]
+		left := util.TrimLeftSpaceLength(rest)
+		right := util.TrimRightSpaceLength(rest)
+		if left < len(rest)-right {
+			infoStart, infoStop := segment.Start-segment.Padding+i+left, segment.Stop-right
+			value := rest[left : len(rest)-right]
+			if fenceChar == '`' && bytes.IndexByte(value, '`') > -1 {
+				return nil, NoChildren
+			} else if infoStart != infoStop {
+				info = ast.NewTextSegment(text.NewSegment(infoStart, infoStop))
+			}
+		}
+	}
+	node := ast.NewFencedCodeBlock(info)
+	pc.Set(fencedCodeBlockInfoKey, &fenceData{fenceChar, findent, oFenceLength, node})
+	return node, NoChildren
+
+}
+
+func (b *fencedCodeBlockParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	line, segment := reader.PeekLine()
+	fdata := pc.Get(fencedCodeBlockInfoKey).(*fenceData)
+
+	w, pos := util.IndentWidth(line, reader.LineOffset())
+	if w < 4 {
+		i := pos
+		for ; i < len(line) && line[i] == fdata.char; i++ {
+		}
+		length := i - pos
+		if length >= fdata.length && util.IsBlank(line[i:]) {
+			newline := 1
+			if line[len(line)-1] != '\n' {
+				newline = 0
+			}
+			reader.Advance(segment.Stop - segment.Start - newline + segment.Padding)
+			return Close
+		}
+	}
+	pos, padding := util.IndentPositionPadding(line, reader.LineOffset(), segment.Padding, fdata.indent)
+	if pos < 0 {
+		pos = util.FirstNonSpacePosition(line)
+		if pos < 0 {
+			pos = 0
+		}
+		padding = 0
+	}
+	seg := text.NewSegmentPadding(segment.Start+pos, segment.Stop, padding)
+	// if code block line starts with a tab, keep a tab as it is.
+	if padding != 0 {
+		preserveLeadingTabInCodeBlock(&seg, reader, fdata.indent)
+	}
+	node.Lines().Append(seg)
+	reader.AdvanceAndSetPadding(segment.Stop-segment.Start-pos-1, padding)
+	return Continue | NoChildren
+}
+
+func (b *fencedCodeBlockParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	fdata := pc.Get(fencedCodeBlockInfoKey).(*fenceData)
+	if fdata.node == node {
+		pc.Set(fencedCodeBlockInfoKey, nil)
+	}
+}
+
+func (b *fencedCodeBlockParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *fencedCodeBlockParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/html_block.go b/vendor/github.com/yuin/goldmark/parser/html_block.go
new file mode 100644
index 000000000..380e723f2
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/html_block.go
@@ -0,0 +1,228 @@
+package parser
+
+import (
+	"bytes"
+	"regexp"
+	"strings"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var allowedBlockTags = map[string]bool{
+	"address":    true,
+	"article":    true,
+	"aside":      true,
+	"base":       true,
+	"basefont":   true,
+	"blockquote": true,
+	"body":       true,
+	"caption":    true,
+	"center":     true,
+	"col":        true,
+	"colgroup":   true,
+	"dd":         true,
+	"details":    true,
+	"dialog":     true,
+	"dir":        true,
+	"div":        true,
+	"dl":         true,
+	"dt":         true,
+	"fieldset":   true,
+	"figcaption": true,
+	"figure":     true,
+	"footer":     true,
+	"form":       true,
+	"frame":      true,
+	"frameset":   true,
+	"h1":         true,
+	"h2":         true,
+	"h3":         true,
+	"h4":         true,
+	"h5":         true,
+	"h6":         true,
+	"head":       true,
+	"header":     true,
+	"hr":         true,
+	"html":       true,
+	"iframe":     true,
+	"legend":     true,
+	"li":         true,
+	"link":       true,
+	"main":       true,
+	"menu":       true,
+	"menuitem":   true,
+	"meta":       true,
+	"nav":        true,
+	"noframes":   true,
+	"ol":         true,
+	"optgroup":   true,
+	"option":     true,
+	"p":          true,
+	"param":      true,
+	"section":    true,
+	"source":     true,
+	"summary":    true,
+	"table":      true,
+	"tbody":      true,
+	"td":         true,
+	"tfoot":      true,
+	"th":         true,
+	"thead":      true,
+	"title":      true,
+	"tr":         true,
+	"track":      true,
+	"ul":         true,
+}
+
+var htmlBlockType1OpenRegexp = regexp.MustCompile(`(?i)^[ ]{0,3}<(script|pre|style|textarea)(?:\s.*|>.*|/>.*|)(?:\r\n|\n)?$`)
+var htmlBlockType1CloseRegexp = regexp.MustCompile(`(?i)^.*</(?:script|pre|style|textarea)>.*`)
+
+var htmlBlockType2OpenRegexp = regexp.MustCompile(`^[ ]{0,3}<!\-\-`)
+var htmlBlockType2Close = []byte{'-', '-', '>'}
+
+var htmlBlockType3OpenRegexp = regexp.MustCompile(`^[ ]{0,3}<\?`)
+var htmlBlockType3Close = []byte{'?', '>'}
+
+var htmlBlockType4OpenRegexp = regexp.MustCompile(`^[ ]{0,3}<![A-Z]+.*(?:\r\n|\n)?$`)
+var htmlBlockType4Close = []byte{'>'}
+
+var htmlBlockType5OpenRegexp = regexp.MustCompile(`^[ ]{0,3}<\!\[CDATA\[`)
+var htmlBlockType5Close = []byte{']', ']', '>'}
+
+var htmlBlockType6Regexp = regexp.MustCompile(`^[ ]{0,3}<(?:/[ ]*)?([a-zA-Z]+[a-zA-Z0-9\-]*)(?:[ ].*|>.*|/>.*|)(?:\r\n|\n)?$`)
+
+var htmlBlockType7Regexp = regexp.MustCompile(`^[ ]{0,3}<(/[ ]*)?([a-zA-Z]+[a-zA-Z0-9\-]*)(` + attributePattern + `*)[ ]*(?:>|/>)[ ]*(?:\r\n|\n)?$`)
+
+type htmlBlockParser struct {
+}
+
+var defaultHTMLBlockParser = &htmlBlockParser{}
+
+// NewHTMLBlockParser return a new BlockParser that can parse html
+// blocks.
+func NewHTMLBlockParser() BlockParser {
+	return defaultHTMLBlockParser
+}
+
+func (b *htmlBlockParser) Trigger() []byte {
+	return []byte{'<'}
+}
+
+func (b *htmlBlockParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	var node *ast.HTMLBlock
+	line, segment := reader.PeekLine()
+	last := pc.LastOpenedBlock().Node
+	if pos := pc.BlockOffset(); pos < 0 || line[pos] != '<' {
+		return nil, NoChildren
+	}
+
+	if m := htmlBlockType1OpenRegexp.FindSubmatchIndex(line); m != nil {
+		node = ast.NewHTMLBlock(ast.HTMLBlockType1)
+	} else if htmlBlockType2OpenRegexp.Match(line) {
+		node = ast.NewHTMLBlock(ast.HTMLBlockType2)
+	} else if htmlBlockType3OpenRegexp.Match(line) {
+		node = ast.NewHTMLBlock(ast.HTMLBlockType3)
+	} else if htmlBlockType4OpenRegexp.Match(line) {
+		node = ast.NewHTMLBlock(ast.HTMLBlockType4)
+	} else if htmlBlockType5OpenRegexp.Match(line) {
+		node = ast.NewHTMLBlock(ast.HTMLBlockType5)
+	} else if match := htmlBlockType7Regexp.FindSubmatchIndex(line); match != nil {
+		isCloseTag := match[2] > -1 && bytes.Equal(line[match[2]:match[3]], []byte("/"))
+		hasAttr := match[6] != match[7]
+		tagName := strings.ToLower(string(line[match[4]:match[5]]))
+		_, ok := allowedBlockTags[tagName]
+		if ok {
+			node = ast.NewHTMLBlock(ast.HTMLBlockType6)
+		} else if tagName != "script" && tagName != "style" && tagName != "pre" && !ast.IsParagraph(last) && !(isCloseTag && hasAttr) { // type 7 can not interrupt paragraph
+			node = ast.NewHTMLBlock(ast.HTMLBlockType7)
+		}
+	}
+	if node == nil {
+		if match := htmlBlockType6Regexp.FindSubmatchIndex(line); match != nil {
+			tagName := string(line[match[2]:match[3]])
+			_, ok := allowedBlockTags[strings.ToLower(tagName)]
+			if ok {
+				node = ast.NewHTMLBlock(ast.HTMLBlockType6)
+			}
+		}
+	}
+	if node != nil {
+		reader.Advance(segment.Len() - 1)
+		node.Lines().Append(segment)
+		return node, NoChildren
+	}
+	return nil, NoChildren
+}
+
+func (b *htmlBlockParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	htmlBlock := node.(*ast.HTMLBlock)
+	lines := htmlBlock.Lines()
+	line, segment := reader.PeekLine()
+	var closurePattern []byte
+
+	switch htmlBlock.HTMLBlockType {
+	case ast.HTMLBlockType1:
+		if lines.Len() == 1 {
+			firstLine := lines.At(0)
+			if htmlBlockType1CloseRegexp.Match(firstLine.Value(reader.Source())) {
+				return Close
+			}
+		}
+		if htmlBlockType1CloseRegexp.Match(line) {
+			htmlBlock.ClosureLine = segment
+			reader.Advance(segment.Len() - 1)
+			return Close
+		}
+	case ast.HTMLBlockType2:
+		closurePattern = htmlBlockType2Close
+		fallthrough
+	case ast.HTMLBlockType3:
+		if closurePattern == nil {
+			closurePattern = htmlBlockType3Close
+		}
+		fallthrough
+	case ast.HTMLBlockType4:
+		if closurePattern == nil {
+			closurePattern = htmlBlockType4Close
+		}
+		fallthrough
+	case ast.HTMLBlockType5:
+		if closurePattern == nil {
+			closurePattern = htmlBlockType5Close
+		}
+
+		if lines.Len() == 1 {
+			firstLine := lines.At(0)
+			if bytes.Contains(firstLine.Value(reader.Source()), closurePattern) {
+				return Close
+			}
+		}
+		if bytes.Contains(line, closurePattern) {
+			htmlBlock.ClosureLine = segment
+			reader.Advance(segment.Len())
+			return Close
+		}
+
+	case ast.HTMLBlockType6, ast.HTMLBlockType7:
+		if util.IsBlank(line) {
+			return Close
+		}
+	}
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len() - 1)
+	return Continue | NoChildren
+}
+
+func (b *htmlBlockParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	// nothing to do
+}
+
+func (b *htmlBlockParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *htmlBlockParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/link.go b/vendor/github.com/yuin/goldmark/parser/link.go
new file mode 100644
index 000000000..99583ac2a
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/link.go
@@ -0,0 +1,409 @@
+package parser
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var linkLabelStateKey = NewContextKey()
+
+type linkLabelState struct {
+	ast.BaseInline
+
+	Segment text.Segment
+
+	IsImage bool
+
+	Prev *linkLabelState
+
+	Next *linkLabelState
+
+	First *linkLabelState
+
+	Last *linkLabelState
+}
+
+func newLinkLabelState(segment text.Segment, isImage bool) *linkLabelState {
+	return &linkLabelState{
+		Segment: segment,
+		IsImage: isImage,
+	}
+}
+
+func (s *linkLabelState) Text(source []byte) []byte {
+	return s.Segment.Value(source)
+}
+
+func (s *linkLabelState) Dump(source []byte, level int) {
+	fmt.Printf("%slinkLabelState: \"%s\"\n", strings.Repeat("    ", level), s.Text(source))
+}
+
+var kindLinkLabelState = ast.NewNodeKind("LinkLabelState")
+
+func (s *linkLabelState) Kind() ast.NodeKind {
+	return kindLinkLabelState
+}
+
+func linkLabelStateLength(v *linkLabelState) int {
+	if v == nil || v.Last == nil || v.First == nil {
+		return 0
+	}
+	return v.Last.Segment.Stop - v.First.Segment.Start
+}
+
+func pushLinkLabelState(pc Context, v *linkLabelState) {
+	tlist := pc.Get(linkLabelStateKey)
+	var list *linkLabelState
+	if tlist == nil {
+		list = v
+		v.First = v
+		v.Last = v
+		pc.Set(linkLabelStateKey, list)
+	} else {
+		list = tlist.(*linkLabelState)
+		l := list.Last
+		list.Last = v
+		l.Next = v
+		v.Prev = l
+	}
+}
+
+func removeLinkLabelState(pc Context, d *linkLabelState) {
+	tlist := pc.Get(linkLabelStateKey)
+	var list *linkLabelState
+	if tlist == nil {
+		return
+	}
+	list = tlist.(*linkLabelState)
+
+	if d.Prev == nil {
+		list = d.Next
+		if list != nil {
+			list.First = d
+			list.Last = d.Last
+			list.Prev = nil
+			pc.Set(linkLabelStateKey, list)
+		} else {
+			pc.Set(linkLabelStateKey, nil)
+		}
+	} else {
+		d.Prev.Next = d.Next
+		if d.Next != nil {
+			d.Next.Prev = d.Prev
+		}
+	}
+	if list != nil && d.Next == nil {
+		list.Last = d.Prev
+	}
+	d.Next = nil
+	d.Prev = nil
+	d.First = nil
+	d.Last = nil
+}
+
+type linkParser struct {
+}
+
+var defaultLinkParser = &linkParser{}
+
+// NewLinkParser return a new InlineParser that parses links.
+func NewLinkParser() InlineParser {
+	return defaultLinkParser
+}
+
+func (s *linkParser) Trigger() []byte {
+	return []byte{'!', '[', ']'}
+}
+
+var linkBottom = NewContextKey()
+
+func (s *linkParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	line, segment := block.PeekLine()
+	if line[0] == '!' {
+		if len(line) > 1 && line[1] == '[' {
+			block.Advance(1)
+			pc.Set(linkBottom, pc.LastDelimiter())
+			return processLinkLabelOpen(block, segment.Start+1, true, pc)
+		}
+		return nil
+	}
+	if line[0] == '[' {
+		pc.Set(linkBottom, pc.LastDelimiter())
+		return processLinkLabelOpen(block, segment.Start, false, pc)
+	}
+
+	// line[0] == ']'
+	tlist := pc.Get(linkLabelStateKey)
+	if tlist == nil {
+		return nil
+	}
+	last := tlist.(*linkLabelState).Last
+	if last == nil {
+		return nil
+	}
+	block.Advance(1)
+	removeLinkLabelState(pc, last)
+	// CommonMark spec says:
+	//  > A link label can have at most 999 characters inside the square brackets.
+	if linkLabelStateLength(tlist.(*linkLabelState)) > 998 {
+		ast.MergeOrReplaceTextSegment(last.Parent(), last, last.Segment)
+		return nil
+	}
+
+	if !last.IsImage && s.containsLink(last) { // a link in a link text is not allowed
+		ast.MergeOrReplaceTextSegment(last.Parent(), last, last.Segment)
+		return nil
+	}
+
+	c := block.Peek()
+	l, pos := block.Position()
+	var link *ast.Link
+	var hasValue bool
+	if c == '(' { // normal link
+		link = s.parseLink(parent, last, block, pc)
+	} else if c == '[' { // reference link
+		link, hasValue = s.parseReferenceLink(parent, last, block, pc)
+		if link == nil && hasValue {
+			ast.MergeOrReplaceTextSegment(last.Parent(), last, last.Segment)
+			return nil
+		}
+	}
+
+	if link == nil {
+		// maybe shortcut reference link
+		block.SetPosition(l, pos)
+		ssegment := text.NewSegment(last.Segment.Stop, segment.Start)
+		maybeReference := block.Value(ssegment)
+		// CommonMark spec says:
+		//  > A link label can have at most 999 characters inside the square brackets.
+		if len(maybeReference) > 999 {
+			ast.MergeOrReplaceTextSegment(last.Parent(), last, last.Segment)
+			return nil
+		}
+
+		ref, ok := pc.Reference(util.ToLinkReference(maybeReference))
+		if !ok {
+			ast.MergeOrReplaceTextSegment(last.Parent(), last, last.Segment)
+			return nil
+		}
+		link = ast.NewLink()
+		s.processLinkLabel(parent, link, last, pc)
+		link.Title = ref.Title()
+		link.Destination = ref.Destination()
+	}
+	if last.IsImage {
+		last.Parent().RemoveChild(last.Parent(), last)
+		return ast.NewImage(link)
+	}
+	last.Parent().RemoveChild(last.Parent(), last)
+	return link
+}
+
+func (s *linkParser) containsLink(n ast.Node) bool {
+	if n == nil {
+		return false
+	}
+	for c := n; c != nil; c = c.NextSibling() {
+		if _, ok := c.(*ast.Link); ok {
+			return true
+		}
+		if s.containsLink(c.FirstChild()) {
+			return true
+		}
+	}
+	return false
+}
+
+func processLinkLabelOpen(block text.Reader, pos int, isImage bool, pc Context) *linkLabelState {
+	start := pos
+	if isImage {
+		start--
+	}
+	state := newLinkLabelState(text.NewSegment(start, pos+1), isImage)
+	pushLinkLabelState(pc, state)
+	block.Advance(1)
+	return state
+}
+
+func (s *linkParser) processLinkLabel(parent ast.Node, link *ast.Link, last *linkLabelState, pc Context) {
+	var bottom ast.Node
+	if v := pc.Get(linkBottom); v != nil {
+		bottom = v.(ast.Node)
+	}
+	pc.Set(linkBottom, nil)
+	ProcessDelimiters(bottom, pc)
+	for c := last.NextSibling(); c != nil; {
+		next := c.NextSibling()
+		parent.RemoveChild(parent, c)
+		link.AppendChild(link, c)
+		c = next
+	}
+}
+
+var linkFindClosureOptions text.FindClosureOptions = text.FindClosureOptions{
+	Nesting: false,
+	Newline: true,
+	Advance: true,
+}
+
+func (s *linkParser) parseReferenceLink(parent ast.Node, last *linkLabelState, block text.Reader, pc Context) (*ast.Link, bool) {
+	_, orgpos := block.Position()
+	block.Advance(1) // skip '['
+	segments, found := block.FindClosure('[', ']', linkFindClosureOptions)
+	if !found {
+		return nil, false
+	}
+
+	var maybeReference []byte
+	if segments.Len() == 1 { // avoid allocate a new byte slice
+		maybeReference = block.Value(segments.At(0))
+	} else {
+		maybeReference = []byte{}
+		for i := 0; i < segments.Len(); i++ {
+			s := segments.At(i)
+			maybeReference = append(maybeReference, block.Value(s)...)
+		}
+	}
+	if util.IsBlank(maybeReference) { // collapsed reference link
+		s := text.NewSegment(last.Segment.Stop, orgpos.Start-1)
+		maybeReference = block.Value(s)
+	}
+	// CommonMark spec says:
+	//  > A link label can have at most 999 characters inside the square brackets.
+	if len(maybeReference) > 999 {
+		return nil, true
+	}
+
+	ref, ok := pc.Reference(util.ToLinkReference(maybeReference))
+	if !ok {
+		return nil, true
+	}
+
+	link := ast.NewLink()
+	s.processLinkLabel(parent, link, last, pc)
+	link.Title = ref.Title()
+	link.Destination = ref.Destination()
+	return link, true
+}
+
+func (s *linkParser) parseLink(parent ast.Node, last *linkLabelState, block text.Reader, pc Context) *ast.Link {
+	block.Advance(1) // skip '('
+	block.SkipSpaces()
+	var title []byte
+	var destination []byte
+	var ok bool
+	if block.Peek() == ')' { // empty link like '[link]()'
+		block.Advance(1)
+	} else {
+		destination, ok = parseLinkDestination(block)
+		if !ok {
+			return nil
+		}
+		block.SkipSpaces()
+		if block.Peek() == ')' {
+			block.Advance(1)
+		} else {
+			title, ok = parseLinkTitle(block)
+			if !ok {
+				return nil
+			}
+			block.SkipSpaces()
+			if block.Peek() == ')' {
+				block.Advance(1)
+			} else {
+				return nil
+			}
+		}
+	}
+
+	link := ast.NewLink()
+	s.processLinkLabel(parent, link, last, pc)
+	link.Destination = destination
+	link.Title = title
+	return link
+}
+
+func parseLinkDestination(block text.Reader) ([]byte, bool) {
+	block.SkipSpaces()
+	line, _ := block.PeekLine()
+	if block.Peek() == '<' {
+		i := 1
+		for i < len(line) {
+			c := line[i]
+			if c == '\\' && i < len(line)-1 && util.IsPunct(line[i+1]) {
+				i += 2
+				continue
+			} else if c == '>' {
+				block.Advance(i + 1)
+				return line[1:i], true
+			}
+			i++
+		}
+		return nil, false
+	}
+	opened := 0
+	i := 0
+	for i < len(line) {
+		c := line[i]
+		if c == '\\' && i < len(line)-1 && util.IsPunct(line[i+1]) {
+			i += 2
+			continue
+		} else if c == '(' {
+			opened++
+		} else if c == ')' {
+			opened--
+			if opened < 0 {
+				break
+			}
+		} else if util.IsSpace(c) {
+			break
+		}
+		i++
+	}
+	block.Advance(i)
+	return line[:i], len(line[:i]) != 0
+}
+
+func parseLinkTitle(block text.Reader) ([]byte, bool) {
+	block.SkipSpaces()
+	opener := block.Peek()
+	if opener != '"' && opener != '\'' && opener != '(' {
+		return nil, false
+	}
+	closer := opener
+	if opener == '(' {
+		closer = ')'
+	}
+	block.Advance(1)
+	segments, found := block.FindClosure(opener, closer, linkFindClosureOptions)
+	if found {
+		if segments.Len() == 1 {
+			return block.Value(segments.At(0)), true
+		}
+		var title []byte
+		for i := 0; i < segments.Len(); i++ {
+			s := segments.At(i)
+			title = append(title, block.Value(s)...)
+		}
+		return title, true
+	}
+	return nil, false
+}
+
+func (s *linkParser) CloseBlock(parent ast.Node, block text.Reader, pc Context) {
+	pc.Set(linkBottom, nil)
+	tlist := pc.Get(linkLabelStateKey)
+	if tlist == nil {
+		return
+	}
+	for s := tlist.(*linkLabelState); s != nil; {
+		next := s.Next
+		removeLinkLabelState(pc, s)
+		s.Parent().ReplaceChild(s.Parent(), s, ast.NewTextSegment(s.Segment))
+		s = next
+	}
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/link_ref.go b/vendor/github.com/yuin/goldmark/parser/link_ref.go
new file mode 100644
index 000000000..ea3f6544a
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/link_ref.go
@@ -0,0 +1,152 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type linkReferenceParagraphTransformer struct {
+}
+
+// LinkReferenceParagraphTransformer is a ParagraphTransformer implementation
+// that parses and extracts link reference from paragraphs.
+var LinkReferenceParagraphTransformer = &linkReferenceParagraphTransformer{}
+
+func (p *linkReferenceParagraphTransformer) Transform(node *ast.Paragraph, reader text.Reader, pc Context) {
+	lines := node.Lines()
+	block := text.NewBlockReader(reader.Source(), lines)
+	removes := [][2]int{}
+	for {
+		start, end := parseLinkReferenceDefinition(block, pc)
+		if start > -1 {
+			if start == end {
+				end++
+			}
+			removes = append(removes, [2]int{start, end})
+			continue
+		}
+		break
+	}
+
+	offset := 0
+	for _, remove := range removes {
+		if lines.Len() == 0 {
+			break
+		}
+		s := lines.Sliced(remove[1]-offset, lines.Len())
+		lines.SetSliced(0, remove[0]-offset)
+		lines.AppendAll(s)
+		offset = remove[1]
+	}
+
+	if lines.Len() == 0 {
+		t := ast.NewTextBlock()
+		t.SetBlankPreviousLines(node.HasBlankPreviousLines())
+		node.Parent().ReplaceChild(node.Parent(), node, t)
+		return
+	}
+
+	node.SetLines(lines)
+}
+
+func parseLinkReferenceDefinition(block text.Reader, pc Context) (int, int) {
+	block.SkipSpaces()
+	line, _ := block.PeekLine()
+	if line == nil {
+		return -1, -1
+	}
+	startLine, _ := block.Position()
+	width, pos := util.IndentWidth(line, 0)
+	if width > 3 {
+		return -1, -1
+	}
+	if width != 0 {
+		pos++
+	}
+	if line[pos] != '[' {
+		return -1, -1
+	}
+	block.Advance(pos + 1)
+	segments, found := block.FindClosure('[', ']', linkFindClosureOptions)
+	if !found {
+		return -1, -1
+	}
+	var label []byte
+	if segments.Len() == 1 {
+		label = block.Value(segments.At(0))
+	} else {
+		for i := 0; i < segments.Len(); i++ {
+			s := segments.At(i)
+			label = append(label, block.Value(s)...)
+		}
+	}
+	if util.IsBlank(label) {
+		return -1, -1
+	}
+	if block.Peek() != ':' {
+		return -1, -1
+	}
+	block.Advance(1)
+	block.SkipSpaces()
+	destination, ok := parseLinkDestination(block)
+	if !ok {
+		return -1, -1
+	}
+	line, _ = block.PeekLine()
+	isNewLine := line == nil || util.IsBlank(line)
+
+	endLine, _ := block.Position()
+	_, spaces, _ := block.SkipSpaces()
+	opener := block.Peek()
+	if opener != '"' && opener != '\'' && opener != '(' {
+		if !isNewLine {
+			return -1, -1
+		}
+		ref := NewReference(label, destination, nil)
+		pc.AddReference(ref)
+		return startLine, endLine + 1
+	}
+	if spaces == 0 {
+		return -1, -1
+	}
+	block.Advance(1)
+	closer := opener
+	if opener == '(' {
+		closer = ')'
+	}
+	segments, found = block.FindClosure(opener, closer, linkFindClosureOptions)
+	if !found {
+		if !isNewLine {
+			return -1, -1
+		}
+		ref := NewReference(label, destination, nil)
+		pc.AddReference(ref)
+		block.AdvanceLine()
+		return startLine, endLine + 1
+	}
+	var title []byte
+	if segments.Len() == 1 {
+		title = block.Value(segments.At(0))
+	} else {
+		for i := 0; i < segments.Len(); i++ {
+			s := segments.At(i)
+			title = append(title, block.Value(s)...)
+		}
+	}
+
+	line, _ = block.PeekLine()
+	if line != nil && !util.IsBlank(line) {
+		if !isNewLine {
+			return -1, -1
+		}
+		ref := NewReference(label, destination, title)
+		pc.AddReference(ref)
+		return startLine, endLine
+	}
+
+	endLine, _ = block.Position()
+	ref := NewReference(label, destination, title)
+	pc.AddReference(ref)
+	return startLine, endLine + 1
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/list.go b/vendor/github.com/yuin/goldmark/parser/list.go
new file mode 100644
index 000000000..e5cad1173
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/list.go
@@ -0,0 +1,287 @@
+package parser
+
+import (
+	"strconv"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type listItemType int
+
+const (
+	notList listItemType = iota
+	bulletList
+	orderedList
+)
+
+var skipListParserKey = NewContextKey()
+var emptyListItemWithBlankLines = NewContextKey()
+var listItemFlagValue interface{} = true
+
+// Same as
+// `^(([ ]*)([\-\*\+]))(\s+.*)?\n?$`.FindSubmatchIndex or
+// `^(([ ]*)(\d{1,9}[\.\)]))(\s+.*)?\n?$`.FindSubmatchIndex
+func parseListItem(line []byte) ([6]int, listItemType) {
+	i := 0
+	l := len(line)
+	ret := [6]int{}
+	for ; i < l && line[i] == ' '; i++ {
+		c := line[i]
+		if c == '\t' {
+			return ret, notList
+		}
+	}
+	if i > 3 {
+		return ret, notList
+	}
+	ret[0] = 0
+	ret[1] = i
+	ret[2] = i
+	var typ listItemType
+	if i < l && (line[i] == '-' || line[i] == '*' || line[i] == '+') {
+		i++
+		ret[3] = i
+		typ = bulletList
+	} else if i < l {
+		for ; i < l && util.IsNumeric(line[i]); i++ {
+		}
+		ret[3] = i
+		if ret[3] == ret[2] || ret[3]-ret[2] > 9 {
+			return ret, notList
+		}
+		if i < l && (line[i] == '.' || line[i] == ')') {
+			i++
+			ret[3] = i
+		} else {
+			return ret, notList
+		}
+		typ = orderedList
+	} else {
+		return ret, notList
+	}
+	if i < l && line[i] != '\n' {
+		w, _ := util.IndentWidth(line[i:], 0)
+		if w == 0 {
+			return ret, notList
+		}
+	}
+	if i >= l {
+		ret[4] = -1
+		ret[5] = -1
+		return ret, typ
+	}
+	ret[4] = i
+	ret[5] = len(line)
+	if line[ret[5]-1] == '\n' && line[i] != '\n' {
+		ret[5]--
+	}
+	return ret, typ
+}
+
+func matchesListItem(source []byte, strict bool) ([6]int, listItemType) {
+	m, typ := parseListItem(source)
+	if typ != notList && (!strict || strict && m[1] < 4) {
+		return m, typ
+	}
+	return m, notList
+}
+
+func calcListOffset(source []byte, match [6]int) int {
+	offset := 0
+	if match[4] < 0 || util.IsBlank(source[match[4]:]) { // list item starts with a blank line
+		offset = 1
+	} else {
+		offset, _ = util.IndentWidth(source[match[4]:], match[4])
+		if offset > 4 { // offseted codeblock
+			offset = 1
+		}
+	}
+	return offset
+}
+
+func lastOffset(node ast.Node) int {
+	lastChild := node.LastChild()
+	if lastChild != nil {
+		return lastChild.(*ast.ListItem).Offset
+	}
+	return 0
+}
+
+type listParser struct {
+}
+
+var defaultListParser = &listParser{}
+
+// NewListParser returns a new BlockParser that
+// parses lists.
+// This parser must take precedence over the ListItemParser.
+func NewListParser() BlockParser {
+	return defaultListParser
+}
+
+func (b *listParser) Trigger() []byte {
+	return []byte{'-', '+', '*', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
+}
+
+func (b *listParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	last := pc.LastOpenedBlock().Node
+	if _, lok := last.(*ast.List); lok || pc.Get(skipListParserKey) != nil {
+		pc.Set(skipListParserKey, nil)
+		return nil, NoChildren
+	}
+	line, _ := reader.PeekLine()
+	match, typ := matchesListItem(line, true)
+	if typ == notList {
+		return nil, NoChildren
+	}
+	start := -1
+	if typ == orderedList {
+		number := line[match[2] : match[3]-1]
+		start, _ = strconv.Atoi(string(number))
+	}
+
+	if ast.IsParagraph(last) && last.Parent() == parent {
+		// we allow only lists starting with 1 to interrupt paragraphs.
+		if typ == orderedList && start != 1 {
+			return nil, NoChildren
+		}
+		//an empty list item cannot interrupt a paragraph:
+		if match[4] < 0 || util.IsBlank(line[match[4]:match[5]]) {
+			return nil, NoChildren
+		}
+	}
+
+	marker := line[match[3]-1]
+	node := ast.NewList(marker)
+	if start > -1 {
+		node.Start = start
+	}
+	pc.Set(emptyListItemWithBlankLines, nil)
+	return node, HasChildren
+}
+
+func (b *listParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	list := node.(*ast.List)
+	line, _ := reader.PeekLine()
+	if util.IsBlank(line) {
+		if node.LastChild().ChildCount() == 0 {
+			pc.Set(emptyListItemWithBlankLines, listItemFlagValue)
+		}
+		return Continue | HasChildren
+	}
+
+	// "offset" means a width that bar indicates.
+	//    -  aaaaaaaa
+	// |----|
+	//
+	// If the indent is less than the last offset like
+	// - a
+	//  - b          <--- current line
+	// it maybe a new child of the list.
+	//
+	// Empty list items can have multiple blanklines
+	//
+	// -             <--- 1st item is an empty thus "offset" is unknown
+	//
+	//
+	//   -           <--- current line
+	//
+	// -> 1 list with 2 blank items
+	//
+	// So if the last item is an empty, it maybe a new child of the list.
+	//
+	offset := lastOffset(node)
+	lastIsEmpty := node.LastChild().ChildCount() == 0
+	indent, _ := util.IndentWidth(line, reader.LineOffset())
+
+	if indent < offset || lastIsEmpty {
+		if indent < 4 {
+			match, typ := matchesListItem(line, false) // may have a leading spaces more than 3
+			if typ != notList && match[1]-offset < 4 {
+				marker := line[match[3]-1]
+				if !list.CanContinue(marker, typ == orderedList) {
+					return Close
+				}
+				// Thematic Breaks take precedence over lists
+				if isThematicBreak(line[match[3]-1:], 0) {
+					isHeading := false
+					last := pc.LastOpenedBlock().Node
+					if ast.IsParagraph(last) {
+						c, ok := matchesSetextHeadingBar(line[match[3]-1:])
+						if ok && c == '-' {
+							isHeading = true
+						}
+					}
+					if !isHeading {
+						return Close
+					}
+				}
+				return Continue | HasChildren
+			}
+		}
+		if !lastIsEmpty {
+			return Close
+		}
+	}
+
+	if lastIsEmpty && indent < offset {
+		return Close
+	}
+
+	// Non empty items can not exist next to an empty list item
+	// with blank lines. So we need to close the current list
+	//
+	// -
+	//
+	//   foo
+	//
+	// -> 1 list with 1 blank items and 1 paragraph
+	if pc.Get(emptyListItemWithBlankLines) != nil {
+		return Close
+	}
+	return Continue | HasChildren
+}
+
+func (b *listParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	list := node.(*ast.List)
+
+	for c := node.FirstChild(); c != nil && list.IsTight; c = c.NextSibling() {
+		if c.FirstChild() != nil && c.FirstChild() != c.LastChild() {
+			for c1 := c.FirstChild().NextSibling(); c1 != nil; c1 = c1.NextSibling() {
+				if bl, ok := c1.(ast.Node); ok && bl.HasBlankPreviousLines() {
+					list.IsTight = false
+					break
+				}
+			}
+		}
+		if c != node.FirstChild() {
+			if bl, ok := c.(ast.Node); ok && bl.HasBlankPreviousLines() {
+				list.IsTight = false
+			}
+		}
+	}
+
+	if list.IsTight {
+		for child := node.FirstChild(); child != nil; child = child.NextSibling() {
+			for gc := child.FirstChild(); gc != nil; {
+				paragraph, ok := gc.(*ast.Paragraph)
+				gc = gc.NextSibling()
+				if ok {
+					textBlock := ast.NewTextBlock()
+					textBlock.SetLines(paragraph.Lines())
+					child.ReplaceChild(child, paragraph, textBlock)
+				}
+			}
+		}
+	}
+}
+
+func (b *listParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *listParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/list_item.go b/vendor/github.com/yuin/goldmark/parser/list_item.go
new file mode 100644
index 000000000..81357a9ad
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/list_item.go
@@ -0,0 +1,90 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type listItemParser struct {
+}
+
+var defaultListItemParser = &listItemParser{}
+
+// NewListItemParser returns a new BlockParser that
+// parses list items.
+func NewListItemParser() BlockParser {
+	return defaultListItemParser
+}
+
+func (b *listItemParser) Trigger() []byte {
+	return []byte{'-', '+', '*', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
+}
+
+func (b *listItemParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	list, lok := parent.(*ast.List)
+	if !lok { // list item must be a child of a list
+		return nil, NoChildren
+	}
+	offset := lastOffset(list)
+	line, _ := reader.PeekLine()
+	match, typ := matchesListItem(line, false)
+	if typ == notList {
+		return nil, NoChildren
+	}
+	if match[1]-offset > 3 {
+		return nil, NoChildren
+	}
+
+	pc.Set(emptyListItemWithBlankLines, nil)
+
+	itemOffset := calcListOffset(line, match)
+	node := ast.NewListItem(match[3] + itemOffset)
+	if match[4] < 0 || util.IsBlank(line[match[4]:match[5]]) {
+		return node, NoChildren
+	}
+
+	pos, padding := util.IndentPosition(line[match[4]:], match[4], itemOffset)
+	child := match[3] + pos
+	reader.AdvanceAndSetPadding(child, padding)
+	return node, HasChildren
+}
+
+func (b *listItemParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	line, _ := reader.PeekLine()
+	if util.IsBlank(line) {
+		reader.Advance(len(line) - 1)
+		return Continue | HasChildren
+	}
+
+	offset := lastOffset(node.Parent())
+	isEmpty := node.ChildCount() == 0
+	indent, _ := util.IndentWidth(line, reader.LineOffset())
+	if (isEmpty || indent < offset) && indent < 4 {
+		_, typ := matchesListItem(line, true)
+		// new list item found
+		if typ != notList {
+			pc.Set(skipListParserKey, listItemFlagValue)
+			return Close
+		}
+		if !isEmpty {
+			return Close
+		}
+	}
+	pos, padding := util.IndentPosition(line, reader.LineOffset(), offset)
+	reader.AdvanceAndSetPadding(pos, padding)
+
+	return Continue | HasChildren
+}
+
+func (b *listItemParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	// nothing to do
+}
+
+func (b *listItemParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *listItemParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/paragraph.go b/vendor/github.com/yuin/goldmark/parser/paragraph.go
new file mode 100644
index 000000000..9d3fa38e0
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/paragraph.go
@@ -0,0 +1,72 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type paragraphParser struct {
+}
+
+var defaultParagraphParser = &paragraphParser{}
+
+// NewParagraphParser returns a new BlockParser that
+// parses paragraphs.
+func NewParagraphParser() BlockParser {
+	return defaultParagraphParser
+}
+
+func (b *paragraphParser) Trigger() []byte {
+	return nil
+}
+
+func (b *paragraphParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	_, segment := reader.PeekLine()
+	segment = segment.TrimLeftSpace(reader.Source())
+	if segment.IsEmpty() {
+		return nil, NoChildren
+	}
+	node := ast.NewParagraph()
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len() - 1)
+	return node, NoChildren
+}
+
+func (b *paragraphParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	line, segment := reader.PeekLine()
+	if util.IsBlank(line) {
+		return Close
+	}
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len() - 1)
+	return Continue | NoChildren
+}
+
+func (b *paragraphParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	lines := node.Lines()
+	if lines.Len() != 0 {
+		// trim leading spaces
+		for i := 0; i < lines.Len(); i++ {
+			l := lines.At(i)
+			lines.Set(i, l.TrimLeftSpace(reader.Source()))
+		}
+
+		// trim trailing spaces
+		length := lines.Len()
+		lastLine := node.Lines().At(length - 1)
+		node.Lines().Set(length-1, lastLine.TrimRightSpace(reader.Source()))
+	}
+	if lines.Len() == 0 {
+		node.Parent().RemoveChild(node.Parent(), node)
+		return
+	}
+}
+
+func (b *paragraphParser) CanInterruptParagraph() bool {
+	return false
+}
+
+func (b *paragraphParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/parser.go b/vendor/github.com/yuin/goldmark/parser/parser.go
new file mode 100644
index 000000000..a82369266
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/parser.go
@@ -0,0 +1,1253 @@
+// Package parser contains stuff that are related to parsing a Markdown text.
+package parser
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// A Reference interface represents a link reference in Markdown text.
+type Reference interface {
+	// String implements Stringer.
+	String() string
+
+	// Label returns a label of the reference.
+	Label() []byte
+
+	// Destination returns a destination(URL) of the reference.
+	Destination() []byte
+
+	// Title returns a title of the reference.
+	Title() []byte
+}
+
+type reference struct {
+	label       []byte
+	destination []byte
+	title       []byte
+}
+
+// NewReference returns a new Reference.
+func NewReference(label, destination, title []byte) Reference {
+	return &reference{label, destination, title}
+}
+
+func (r *reference) Label() []byte {
+	return r.label
+}
+
+func (r *reference) Destination() []byte {
+	return r.destination
+}
+
+func (r *reference) Title() []byte {
+	return r.title
+}
+
+func (r *reference) String() string {
+	return fmt.Sprintf("Reference{Label:%s, Destination:%s, Title:%s}", r.label, r.destination, r.title)
+}
+
+// An IDs interface is a collection of the element ids.
+type IDs interface {
+	// Generate generates a new element id.
+	Generate(value []byte, kind ast.NodeKind) []byte
+
+	// Put puts a given element id to the used ids table.
+	Put(value []byte)
+}
+
+type ids struct {
+	values map[string]bool
+}
+
+func newIDs() IDs {
+	return &ids{
+		values: map[string]bool{},
+	}
+}
+
+func (s *ids) Generate(value []byte, kind ast.NodeKind) []byte {
+	value = util.TrimLeftSpace(value)
+	value = util.TrimRightSpace(value)
+	result := []byte{}
+	for i := 0; i < len(value); {
+		v := value[i]
+		l := util.UTF8Len(v)
+		i += int(l)
+		if l != 1 {
+			continue
+		}
+		if util.IsAlphaNumeric(v) {
+			if 'A' <= v && v <= 'Z' {
+				v += 'a' - 'A'
+			}
+			result = append(result, v)
+		} else if util.IsSpace(v) || v == '-' || v == '_' {
+			result = append(result, '-')
+		}
+	}
+	if len(result) == 0 {
+		if kind == ast.KindHeading {
+			result = []byte("heading")
+		} else {
+			result = []byte("id")
+		}
+	}
+	if _, ok := s.values[util.BytesToReadOnlyString(result)]; !ok {
+		s.values[util.BytesToReadOnlyString(result)] = true
+		return result
+	}
+	for i := 1; ; i++ {
+		newResult := fmt.Sprintf("%s-%d", result, i)
+		if _, ok := s.values[newResult]; !ok {
+			s.values[newResult] = true
+			return []byte(newResult)
+		}
+
+	}
+}
+
+func (s *ids) Put(value []byte) {
+	s.values[util.BytesToReadOnlyString(value)] = true
+}
+
+// ContextKey is a key that is used to set arbitrary values to the context.
+type ContextKey int
+
+// ContextKeyMax is a maximum value of the ContextKey.
+var ContextKeyMax ContextKey
+
+// NewContextKey return a new ContextKey value.
+func NewContextKey() ContextKey {
+	ContextKeyMax++
+	return ContextKeyMax
+}
+
+// A Context interface holds a information that are necessary to parse
+// Markdown text.
+type Context interface {
+	// String implements Stringer.
+	String() string
+
+	// Get returns a value associated with the given key.
+	Get(ContextKey) interface{}
+
+	// ComputeIfAbsent computes a value if a value associated with the given key is absent and returns the value.
+	ComputeIfAbsent(ContextKey, func() interface{}) interface{}
+
+	// Set sets the given value to the context.
+	Set(ContextKey, interface{})
+
+	// AddReference adds the given reference to this context.
+	AddReference(Reference)
+
+	// Reference returns (a reference, true) if a reference associated with
+	// the given label exists, otherwise (nil, false).
+	Reference(label string) (Reference, bool)
+
+	// References returns a list of references.
+	References() []Reference
+
+	// IDs returns a collection of the element ids.
+	IDs() IDs
+
+	// BlockOffset returns a first non-space character position on current line.
+	// This value is valid only for BlockParser.Open.
+	// BlockOffset returns -1 if current line is blank.
+	BlockOffset() int
+
+	// BlockOffset sets a first non-space character position on current line.
+	// This value is valid only for BlockParser.Open.
+	SetBlockOffset(int)
+
+	// BlockIndent returns an indent width on current line.
+	// This value is valid only for BlockParser.Open.
+	// BlockIndent returns -1 if current line is blank.
+	BlockIndent() int
+
+	// BlockIndent sets an indent width on current line.
+	// This value is valid only for BlockParser.Open.
+	SetBlockIndent(int)
+
+	// FirstDelimiter returns a first delimiter of the current delimiter list.
+	FirstDelimiter() *Delimiter
+
+	// LastDelimiter returns a last delimiter of the current delimiter list.
+	LastDelimiter() *Delimiter
+
+	// PushDelimiter appends the given delimiter to the tail of the current
+	// delimiter list.
+	PushDelimiter(delimiter *Delimiter)
+
+	// RemoveDelimiter removes the given delimiter from the current delimiter list.
+	RemoveDelimiter(d *Delimiter)
+
+	// ClearDelimiters clears the current delimiter list.
+	ClearDelimiters(bottom ast.Node)
+
+	// OpenedBlocks returns a list of nodes that are currently in parsing.
+	OpenedBlocks() []Block
+
+	// SetOpenedBlocks sets a list of nodes that are currently in parsing.
+	SetOpenedBlocks([]Block)
+
+	// LastOpenedBlock returns a last node that is currently in parsing.
+	LastOpenedBlock() Block
+
+	// IsInLinkLabel returns true if current position seems to be in link label.
+	IsInLinkLabel() bool
+}
+
+// A ContextConfig struct is a data structure that holds configuration of the Context.
+type ContextConfig struct {
+	IDs IDs
+}
+
+// An ContextOption is a functional option type for the Context.
+type ContextOption func(*ContextConfig)
+
+// WithIDs is a functional option for the Context.
+func WithIDs(ids IDs) ContextOption {
+	return func(c *ContextConfig) {
+		c.IDs = ids
+	}
+}
+
+type parseContext struct {
+	store         []interface{}
+	ids           IDs
+	refs          map[string]Reference
+	blockOffset   int
+	blockIndent   int
+	delimiters    *Delimiter
+	lastDelimiter *Delimiter
+	openedBlocks  []Block
+}
+
+// NewContext returns a new Context.
+func NewContext(options ...ContextOption) Context {
+	cfg := &ContextConfig{
+		IDs: newIDs(),
+	}
+	for _, option := range options {
+		option(cfg)
+	}
+
+	return &parseContext{
+		store:         make([]interface{}, ContextKeyMax+1),
+		refs:          map[string]Reference{},
+		ids:           cfg.IDs,
+		blockOffset:   -1,
+		blockIndent:   -1,
+		delimiters:    nil,
+		lastDelimiter: nil,
+		openedBlocks:  []Block{},
+	}
+}
+
+func (p *parseContext) Get(key ContextKey) interface{} {
+	return p.store[key]
+}
+
+func (p *parseContext) ComputeIfAbsent(key ContextKey, f func() interface{}) interface{} {
+	v := p.store[key]
+	if v == nil {
+		v = f()
+		p.store[key] = v
+	}
+	return v
+}
+
+func (p *parseContext) Set(key ContextKey, value interface{}) {
+	p.store[key] = value
+}
+
+func (p *parseContext) IDs() IDs {
+	return p.ids
+}
+
+func (p *parseContext) BlockOffset() int {
+	return p.blockOffset
+}
+
+func (p *parseContext) SetBlockOffset(v int) {
+	p.blockOffset = v
+}
+
+func (p *parseContext) BlockIndent() int {
+	return p.blockIndent
+}
+
+func (p *parseContext) SetBlockIndent(v int) {
+	p.blockIndent = v
+}
+
+func (p *parseContext) LastDelimiter() *Delimiter {
+	return p.lastDelimiter
+}
+
+func (p *parseContext) FirstDelimiter() *Delimiter {
+	return p.delimiters
+}
+
+func (p *parseContext) PushDelimiter(d *Delimiter) {
+	if p.delimiters == nil {
+		p.delimiters = d
+		p.lastDelimiter = d
+	} else {
+		l := p.lastDelimiter
+		p.lastDelimiter = d
+		l.NextDelimiter = d
+		d.PreviousDelimiter = l
+	}
+}
+
+func (p *parseContext) RemoveDelimiter(d *Delimiter) {
+	if d.PreviousDelimiter == nil {
+		p.delimiters = d.NextDelimiter
+	} else {
+		d.PreviousDelimiter.NextDelimiter = d.NextDelimiter
+		if d.NextDelimiter != nil {
+			d.NextDelimiter.PreviousDelimiter = d.PreviousDelimiter
+		}
+	}
+	if d.NextDelimiter == nil {
+		p.lastDelimiter = d.PreviousDelimiter
+	}
+	if p.delimiters != nil {
+		p.delimiters.PreviousDelimiter = nil
+	}
+	if p.lastDelimiter != nil {
+		p.lastDelimiter.NextDelimiter = nil
+	}
+	d.NextDelimiter = nil
+	d.PreviousDelimiter = nil
+	if d.Length != 0 {
+		ast.MergeOrReplaceTextSegment(d.Parent(), d, d.Segment)
+	} else {
+		d.Parent().RemoveChild(d.Parent(), d)
+	}
+}
+
+func (p *parseContext) ClearDelimiters(bottom ast.Node) {
+	if p.lastDelimiter == nil {
+		return
+	}
+	var c ast.Node
+	for c = p.lastDelimiter; c != nil && c != bottom; {
+		prev := c.PreviousSibling()
+		if d, ok := c.(*Delimiter); ok {
+			p.RemoveDelimiter(d)
+		}
+		c = prev
+	}
+}
+
+func (p *parseContext) AddReference(ref Reference) {
+	key := util.ToLinkReference(ref.Label())
+	if _, ok := p.refs[key]; !ok {
+		p.refs[key] = ref
+	}
+}
+
+func (p *parseContext) Reference(label string) (Reference, bool) {
+	v, ok := p.refs[label]
+	return v, ok
+}
+
+func (p *parseContext) References() []Reference {
+	ret := make([]Reference, 0, len(p.refs))
+	for _, v := range p.refs {
+		ret = append(ret, v)
+	}
+	return ret
+}
+
+func (p *parseContext) String() string {
+	refs := []string{}
+	for _, r := range p.refs {
+		refs = append(refs, r.String())
+	}
+
+	return fmt.Sprintf("Context{Store:%#v, Refs:%s}", p.store, strings.Join(refs, ","))
+}
+
+func (p *parseContext) OpenedBlocks() []Block {
+	return p.openedBlocks
+}
+
+func (p *parseContext) SetOpenedBlocks(v []Block) {
+	p.openedBlocks = v
+}
+
+func (p *parseContext) LastOpenedBlock() Block {
+	if l := len(p.openedBlocks); l != 0 {
+		return p.openedBlocks[l-1]
+	}
+	return Block{}
+}
+
+func (p *parseContext) IsInLinkLabel() bool {
+	tlist := p.Get(linkLabelStateKey)
+	return tlist != nil
+}
+
+// State represents parser's state.
+// State is designed to use as a bit flag.
+type State int
+
+const (
+	none State = 1 << iota
+
+	// Continue indicates parser can continue parsing.
+	Continue
+
+	// Close indicates parser cannot parse anymore.
+	Close
+
+	// HasChildren indicates parser may have child blocks.
+	HasChildren
+
+	// NoChildren indicates parser does not have child blocks.
+	NoChildren
+
+	// RequireParagraph indicates parser requires that the last node
+	// must be a paragraph and is not converted to other nodes by
+	// ParagraphTransformers.
+	RequireParagraph
+)
+
+// A Config struct is a data structure that holds configuration of the Parser.
+type Config struct {
+	Options               map[OptionName]interface{}
+	BlockParsers          util.PrioritizedSlice /*<BlockParser>*/
+	InlineParsers         util.PrioritizedSlice /*<InlineParser>*/
+	ParagraphTransformers util.PrioritizedSlice /*<ParagraphTransformer>*/
+	ASTTransformers       util.PrioritizedSlice /*<ASTTransformer>*/
+	EscapedSpace          bool
+}
+
+// NewConfig returns a new Config.
+func NewConfig() *Config {
+	return &Config{
+		Options:               map[OptionName]interface{}{},
+		BlockParsers:          util.PrioritizedSlice{},
+		InlineParsers:         util.PrioritizedSlice{},
+		ParagraphTransformers: util.PrioritizedSlice{},
+		ASTTransformers:       util.PrioritizedSlice{},
+	}
+}
+
+// An Option interface is a functional option type for the Parser.
+type Option interface {
+	SetParserOption(*Config)
+}
+
+// OptionName is a name of parser options.
+type OptionName string
+
+// Attribute is an option name that spacify attributes of elements.
+const optAttribute OptionName = "Attribute"
+
+type withAttribute struct {
+}
+
+func (o *withAttribute) SetParserOption(c *Config) {
+	c.Options[optAttribute] = true
+}
+
+// WithAttribute is a functional option that enables custom attributes.
+func WithAttribute() Option {
+	return &withAttribute{}
+}
+
+// A Parser interface parses Markdown text into AST nodes.
+type Parser interface {
+	// Parse parses the given Markdown text into AST nodes.
+	Parse(reader text.Reader, opts ...ParseOption) ast.Node
+
+	// AddOption adds the given option to this parser.
+	AddOptions(...Option)
+}
+
+// A SetOptioner interface sets the given option to the object.
+type SetOptioner interface {
+	// SetOption sets the given option to the object.
+	// Unacceptable options may be passed.
+	// Thus implementations must ignore unacceptable options.
+	SetOption(name OptionName, value interface{})
+}
+
+// A BlockParser interface parses a block level element like Paragraph, List,
+// Blockquote etc.
+type BlockParser interface {
+	// Trigger returns a list of characters that triggers Parse method of
+	// this parser.
+	// If Trigger returns a nil, Open will be called with any lines.
+	Trigger() []byte
+
+	// Open parses the current line and returns a result of parsing.
+	//
+	// Open must not parse beyond the current line.
+	// If Open has been able to parse the current line, Open must advance a reader
+	// position by consumed byte length.
+	//
+	// If Open has not been able to parse the current line, Open should returns
+	// (nil, NoChildren). If Open has been able to parse the current line, Open
+	// should returns a new Block node and returns HasChildren or NoChildren.
+	Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State)
+
+	// Continue parses the current line and returns a result of parsing.
+	//
+	// Continue must not parse beyond the current line.
+	// If Continue has been able to parse the current line, Continue must advance
+	// a reader position by consumed byte length.
+	//
+	// If Continue has not been able to parse the current line, Continue should
+	// returns Close. If Continue has been able to parse the current line,
+	// Continue should returns (Continue | NoChildren) or
+	// (Continue | HasChildren)
+	Continue(node ast.Node, reader text.Reader, pc Context) State
+
+	// Close will be called when the parser returns Close.
+	Close(node ast.Node, reader text.Reader, pc Context)
+
+	// CanInterruptParagraph returns true if the parser can interrupt paragraphs,
+	// otherwise false.
+	CanInterruptParagraph() bool
+
+	// CanAcceptIndentedLine returns true if the parser can open new node when
+	// the given line is being indented more than 3 spaces.
+	CanAcceptIndentedLine() bool
+}
+
+// An InlineParser interface parses an inline level element like CodeSpan, Link etc.
+type InlineParser interface {
+	// Trigger returns a list of characters that triggers Parse method of
+	// this parser.
+	// Trigger characters must be a punctuation or a halfspace.
+	// Halfspaces triggers this parser when character is any spaces characters or
+	// a head of line
+	Trigger() []byte
+
+	// Parse parse the given block into an inline node.
+	//
+	// Parse can parse beyond the current line.
+	// If Parse has been able to parse the current line, it must advance a reader
+	// position by consumed byte length.
+	Parse(parent ast.Node, block text.Reader, pc Context) ast.Node
+}
+
+// A CloseBlocker interface is a callback function that will be
+// called when block is closed in the inline parsing.
+type CloseBlocker interface {
+	// CloseBlock will be called when a block is closed.
+	CloseBlock(parent ast.Node, block text.Reader, pc Context)
+}
+
+// A ParagraphTransformer transforms parsed Paragraph nodes.
+// For example, link references are searched in parsed Paragraphs.
+type ParagraphTransformer interface {
+	// Transform transforms the given paragraph.
+	Transform(node *ast.Paragraph, reader text.Reader, pc Context)
+}
+
+// ASTTransformer transforms entire Markdown document AST tree.
+type ASTTransformer interface {
+	// Transform transforms the given AST tree.
+	Transform(node *ast.Document, reader text.Reader, pc Context)
+}
+
+// DefaultBlockParsers returns a new list of default BlockParsers.
+// Priorities of default BlockParsers are:
+//
+//	SetextHeadingParser, 100
+//	ThematicBreakParser, 200
+//	ListParser, 300
+//	ListItemParser, 400
+//	CodeBlockParser, 500
+//	ATXHeadingParser, 600
+//	FencedCodeBlockParser, 700
+//	BlockquoteParser, 800
+//	HTMLBlockParser, 900
+//	ParagraphParser, 1000
+func DefaultBlockParsers() []util.PrioritizedValue {
+	return []util.PrioritizedValue{
+		util.Prioritized(NewSetextHeadingParser(), 100),
+		util.Prioritized(NewThematicBreakParser(), 200),
+		util.Prioritized(NewListParser(), 300),
+		util.Prioritized(NewListItemParser(), 400),
+		util.Prioritized(NewCodeBlockParser(), 500),
+		util.Prioritized(NewATXHeadingParser(), 600),
+		util.Prioritized(NewFencedCodeBlockParser(), 700),
+		util.Prioritized(NewBlockquoteParser(), 800),
+		util.Prioritized(NewHTMLBlockParser(), 900),
+		util.Prioritized(NewParagraphParser(), 1000),
+	}
+}
+
+// DefaultInlineParsers returns a new list of default InlineParsers.
+// Priorities of default InlineParsers are:
+//
+//	CodeSpanParser, 100
+//	LinkParser, 200
+//	AutoLinkParser, 300
+//	RawHTMLParser, 400
+//	EmphasisParser, 500
+func DefaultInlineParsers() []util.PrioritizedValue {
+	return []util.PrioritizedValue{
+		util.Prioritized(NewCodeSpanParser(), 100),
+		util.Prioritized(NewLinkParser(), 200),
+		util.Prioritized(NewAutoLinkParser(), 300),
+		util.Prioritized(NewRawHTMLParser(), 400),
+		util.Prioritized(NewEmphasisParser(), 500),
+	}
+}
+
+// DefaultParagraphTransformers returns a new list of default ParagraphTransformers.
+// Priorities of default ParagraphTransformers are:
+//
+//	LinkReferenceParagraphTransformer, 100
+func DefaultParagraphTransformers() []util.PrioritizedValue {
+	return []util.PrioritizedValue{
+		util.Prioritized(LinkReferenceParagraphTransformer, 100),
+	}
+}
+
+// A Block struct holds a node and correspond parser pair.
+type Block struct {
+	// Node is a BlockNode.
+	Node ast.Node
+	// Parser is a BlockParser.
+	Parser BlockParser
+}
+
+type parser struct {
+	options               map[OptionName]interface{}
+	blockParsers          [256][]BlockParser
+	freeBlockParsers      []BlockParser
+	inlineParsers         [256][]InlineParser
+	closeBlockers         []CloseBlocker
+	paragraphTransformers []ParagraphTransformer
+	astTransformers       []ASTTransformer
+	escapedSpace          bool
+	config                *Config
+	initSync              sync.Once
+}
+
+type withBlockParsers struct {
+	value []util.PrioritizedValue
+}
+
+func (o *withBlockParsers) SetParserOption(c *Config) {
+	c.BlockParsers = append(c.BlockParsers, o.value...)
+}
+
+// WithBlockParsers is a functional option that allow you to add
+// BlockParsers to the parser.
+func WithBlockParsers(bs ...util.PrioritizedValue) Option {
+	return &withBlockParsers{bs}
+}
+
+type withInlineParsers struct {
+	value []util.PrioritizedValue
+}
+
+func (o *withInlineParsers) SetParserOption(c *Config) {
+	c.InlineParsers = append(c.InlineParsers, o.value...)
+}
+
+// WithInlineParsers is a functional option that allow you to add
+// InlineParsers to the parser.
+func WithInlineParsers(bs ...util.PrioritizedValue) Option {
+	return &withInlineParsers{bs}
+}
+
+type withParagraphTransformers struct {
+	value []util.PrioritizedValue
+}
+
+func (o *withParagraphTransformers) SetParserOption(c *Config) {
+	c.ParagraphTransformers = append(c.ParagraphTransformers, o.value...)
+}
+
+// WithParagraphTransformers is a functional option that allow you to add
+// ParagraphTransformers to the parser.
+func WithParagraphTransformers(ps ...util.PrioritizedValue) Option {
+	return &withParagraphTransformers{ps}
+}
+
+type withASTTransformers struct {
+	value []util.PrioritizedValue
+}
+
+func (o *withASTTransformers) SetParserOption(c *Config) {
+	c.ASTTransformers = append(c.ASTTransformers, o.value...)
+}
+
+// WithASTTransformers is a functional option that allow you to add
+// ASTTransformers to the parser.
+func WithASTTransformers(ps ...util.PrioritizedValue) Option {
+	return &withASTTransformers{ps}
+}
+
+type withEscapedSpace struct {
+}
+
+func (o *withEscapedSpace) SetParserOption(c *Config) {
+	c.EscapedSpace = true
+}
+
+// WithEscapedSpace is a functional option indicates that a '\' escaped half-space(0x20) should not trigger parsers.
+func WithEscapedSpace() Option {
+	return &withEscapedSpace{}
+}
+
+type withOption struct {
+	name  OptionName
+	value interface{}
+}
+
+func (o *withOption) SetParserOption(c *Config) {
+	c.Options[o.name] = o.value
+}
+
+// WithOption is a functional option that allow you to set
+// an arbitrary option to the parser.
+func WithOption(name OptionName, value interface{}) Option {
+	return &withOption{name, value}
+}
+
+// NewParser returns a new Parser with given options.
+func NewParser(options ...Option) Parser {
+	config := NewConfig()
+	for _, opt := range options {
+		opt.SetParserOption(config)
+	}
+
+	p := &parser{
+		options: map[OptionName]interface{}{},
+		config:  config,
+	}
+
+	return p
+}
+
+func (p *parser) AddOptions(opts ...Option) {
+	for _, opt := range opts {
+		opt.SetParserOption(p.config)
+	}
+}
+
+func (p *parser) addBlockParser(v util.PrioritizedValue, options map[OptionName]interface{}) {
+	bp, ok := v.Value.(BlockParser)
+	if !ok {
+		panic(fmt.Sprintf("%v is not a BlockParser", v.Value))
+	}
+	tcs := bp.Trigger()
+	so, ok := v.Value.(SetOptioner)
+	if ok {
+		for oname, ovalue := range options {
+			so.SetOption(oname, ovalue)
+		}
+	}
+	if tcs == nil {
+		p.freeBlockParsers = append(p.freeBlockParsers, bp)
+	} else {
+		for _, tc := range tcs {
+			if p.blockParsers[tc] == nil {
+				p.blockParsers[tc] = []BlockParser{}
+			}
+			p.blockParsers[tc] = append(p.blockParsers[tc], bp)
+		}
+	}
+}
+
+func (p *parser) addInlineParser(v util.PrioritizedValue, options map[OptionName]interface{}) {
+	ip, ok := v.Value.(InlineParser)
+	if !ok {
+		panic(fmt.Sprintf("%v is not a InlineParser", v.Value))
+	}
+	tcs := ip.Trigger()
+	so, ok := v.Value.(SetOptioner)
+	if ok {
+		for oname, ovalue := range options {
+			so.SetOption(oname, ovalue)
+		}
+	}
+	if cb, ok := ip.(CloseBlocker); ok {
+		p.closeBlockers = append(p.closeBlockers, cb)
+	}
+	for _, tc := range tcs {
+		if p.inlineParsers[tc] == nil {
+			p.inlineParsers[tc] = []InlineParser{}
+		}
+		p.inlineParsers[tc] = append(p.inlineParsers[tc], ip)
+	}
+}
+
+func (p *parser) addParagraphTransformer(v util.PrioritizedValue, options map[OptionName]interface{}) {
+	pt, ok := v.Value.(ParagraphTransformer)
+	if !ok {
+		panic(fmt.Sprintf("%v is not a ParagraphTransformer", v.Value))
+	}
+	so, ok := v.Value.(SetOptioner)
+	if ok {
+		for oname, ovalue := range options {
+			so.SetOption(oname, ovalue)
+		}
+	}
+	p.paragraphTransformers = append(p.paragraphTransformers, pt)
+}
+
+func (p *parser) addASTTransformer(v util.PrioritizedValue, options map[OptionName]interface{}) {
+	at, ok := v.Value.(ASTTransformer)
+	if !ok {
+		panic(fmt.Sprintf("%v is not a ASTTransformer", v.Value))
+	}
+	so, ok := v.Value.(SetOptioner)
+	if ok {
+		for oname, ovalue := range options {
+			so.SetOption(oname, ovalue)
+		}
+	}
+	p.astTransformers = append(p.astTransformers, at)
+}
+
+// A ParseConfig struct is a data structure that holds configuration of the Parser.Parse.
+type ParseConfig struct {
+	Context Context
+}
+
+// A ParseOption is a functional option type for the Parser.Parse.
+type ParseOption func(c *ParseConfig)
+
+// WithContext is a functional option that allow you to override
+// a default context.
+func WithContext(context Context) ParseOption {
+	return func(c *ParseConfig) {
+		c.Context = context
+	}
+}
+
+func (p *parser) Parse(reader text.Reader, opts ...ParseOption) ast.Node {
+	p.initSync.Do(func() {
+		p.config.BlockParsers.Sort()
+		for _, v := range p.config.BlockParsers {
+			p.addBlockParser(v, p.config.Options)
+		}
+		for i := range p.blockParsers {
+			if p.blockParsers[i] != nil {
+				p.blockParsers[i] = append(p.blockParsers[i], p.freeBlockParsers...)
+			}
+		}
+
+		p.config.InlineParsers.Sort()
+		for _, v := range p.config.InlineParsers {
+			p.addInlineParser(v, p.config.Options)
+		}
+		p.config.ParagraphTransformers.Sort()
+		for _, v := range p.config.ParagraphTransformers {
+			p.addParagraphTransformer(v, p.config.Options)
+		}
+		p.config.ASTTransformers.Sort()
+		for _, v := range p.config.ASTTransformers {
+			p.addASTTransformer(v, p.config.Options)
+		}
+		p.escapedSpace = p.config.EscapedSpace
+		p.config = nil
+	})
+	c := &ParseConfig{}
+	for _, opt := range opts {
+		opt(c)
+	}
+	if c.Context == nil {
+		c.Context = NewContext()
+	}
+	pc := c.Context
+	root := ast.NewDocument()
+	p.parseBlocks(root, reader, pc)
+
+	blockReader := text.NewBlockReader(reader.Source(), nil)
+	p.walkBlock(root, func(node ast.Node) {
+		p.parseBlock(blockReader, node, pc)
+	})
+	for _, at := range p.astTransformers {
+		at.Transform(root, reader, pc)
+	}
+	// root.Dump(reader.Source(), 0)
+	return root
+}
+
+func (p *parser) transformParagraph(node *ast.Paragraph, reader text.Reader, pc Context) bool {
+	for _, pt := range p.paragraphTransformers {
+		pt.Transform(node, reader, pc)
+		if node.Parent() == nil {
+			return true
+		}
+	}
+	return false
+}
+
+func (p *parser) closeBlocks(from, to int, reader text.Reader, pc Context) {
+	blocks := pc.OpenedBlocks()
+	for i := from; i >= to; i-- {
+		node := blocks[i].Node
+		paragraph, ok := node.(*ast.Paragraph)
+		if ok && node.Parent() != nil {
+			p.transformParagraph(paragraph, reader, pc)
+		}
+		if node.Parent() != nil { // closes only if node has not been transformed
+			blocks[i].Parser.Close(blocks[i].Node, reader, pc)
+		}
+	}
+	if from == len(blocks)-1 {
+		blocks = blocks[0:to]
+	} else {
+		blocks = append(blocks[0:to], blocks[from+1:]...)
+	}
+	pc.SetOpenedBlocks(blocks)
+}
+
+type blockOpenResult int
+
+const (
+	paragraphContinuation blockOpenResult = iota + 1
+	newBlocksOpened
+	noBlocksOpened
+)
+
+func (p *parser) openBlocks(parent ast.Node, blankLine bool, reader text.Reader, pc Context) blockOpenResult {
+	result := blockOpenResult(noBlocksOpened)
+	continuable := false
+	lastBlock := pc.LastOpenedBlock()
+	if lastBlock.Node != nil {
+		continuable = ast.IsParagraph(lastBlock.Node)
+	}
+retry:
+	var bps []BlockParser
+	line, _ := reader.PeekLine()
+	w, pos := util.IndentWidth(line, reader.LineOffset())
+	if w >= len(line) {
+		pc.SetBlockOffset(-1)
+		pc.SetBlockIndent(-1)
+	} else {
+		pc.SetBlockOffset(pos)
+		pc.SetBlockIndent(w)
+	}
+	if line == nil || line[0] == '\n' {
+		goto continuable
+	}
+	bps = p.freeBlockParsers
+	if pos < len(line) {
+		bps = p.blockParsers[line[pos]]
+		if bps == nil {
+			bps = p.freeBlockParsers
+		}
+	}
+	if bps == nil {
+		goto continuable
+	}
+
+	for _, bp := range bps {
+		if continuable && result == noBlocksOpened && !bp.CanInterruptParagraph() {
+			continue
+		}
+		if w > 3 && !bp.CanAcceptIndentedLine() {
+			continue
+		}
+		lastBlock = pc.LastOpenedBlock()
+		last := lastBlock.Node
+		node, state := bp.Open(parent, reader, pc)
+		if node != nil {
+			// Parser requires last node to be a paragraph.
+			// With table extension:
+			//
+			//     0
+			//     -:
+			//     -
+			//
+			// '-' on 3rd line seems a Setext heading because 1st and 2nd lines
+			// are being paragraph when the Settext heading parser tries to parse the 3rd
+			// line.
+			// But 1st line and 2nd line are a table. Thus this paragraph will be transformed
+			// by a paragraph transformer. So this text should be converted to a table and
+			// an empty list.
+			if state&RequireParagraph != 0 {
+				if last == parent.LastChild() {
+					// Opened paragraph may be transformed by ParagraphTransformers in
+					// closeBlocks().
+					lastBlock.Parser.Close(last, reader, pc)
+					blocks := pc.OpenedBlocks()
+					pc.SetOpenedBlocks(blocks[0 : len(blocks)-1])
+					if p.transformParagraph(last.(*ast.Paragraph), reader, pc) {
+						// Paragraph has been transformed.
+						// So this parser is considered as failing.
+						continuable = false
+						goto retry
+					}
+				}
+			}
+			node.SetBlankPreviousLines(blankLine)
+			if last != nil && last.Parent() == nil {
+				lastPos := len(pc.OpenedBlocks()) - 1
+				p.closeBlocks(lastPos, lastPos, reader, pc)
+			}
+			parent.AppendChild(parent, node)
+			result = newBlocksOpened
+			be := Block{node, bp}
+			pc.SetOpenedBlocks(append(pc.OpenedBlocks(), be))
+			if state&HasChildren != 0 {
+				parent = node
+				goto retry // try child block
+			}
+			break // no children, can not open more blocks on this line
+		}
+	}
+
+continuable:
+	if result == noBlocksOpened && continuable {
+		state := lastBlock.Parser.Continue(lastBlock.Node, reader, pc)
+		if state&Continue != 0 {
+			result = paragraphContinuation
+		}
+	}
+	return result
+}
+
+type lineStat struct {
+	lineNum int
+	level   int
+	isBlank bool
+}
+
+func isBlankLine(lineNum, level int, stats []lineStat) bool {
+	ret := true
+	for i := len(stats) - 1 - level; i >= 0; i-- {
+		ret = false
+		s := stats[i]
+		if s.lineNum == lineNum {
+			if s.level < level && s.isBlank {
+				return true
+			} else if s.level == level {
+				return s.isBlank
+			}
+		}
+		if s.lineNum < lineNum {
+			return ret
+		}
+	}
+	return ret
+}
+
+func (p *parser) parseBlocks(parent ast.Node, reader text.Reader, pc Context) {
+	pc.SetOpenedBlocks([]Block{})
+	blankLines := make([]lineStat, 0, 128)
+	isBlank := false
+	for { // process blocks separated by blank lines
+		_, lines, ok := reader.SkipBlankLines()
+		if !ok {
+			return
+		}
+		lineNum, _ := reader.Position()
+		if lines != 0 {
+			blankLines = blankLines[0:0]
+			l := len(pc.OpenedBlocks())
+			for i := 0; i < l; i++ {
+				blankLines = append(blankLines, lineStat{lineNum - 1, i, lines != 0})
+			}
+		}
+		isBlank = isBlankLine(lineNum-1, 0, blankLines)
+		// first, we try to open blocks
+		if p.openBlocks(parent, isBlank, reader, pc) != newBlocksOpened {
+			return
+		}
+		reader.AdvanceLine()
+		for { // process opened blocks line by line
+			openedBlocks := pc.OpenedBlocks()
+			l := len(openedBlocks)
+			if l == 0 {
+				break
+			}
+			lastIndex := l - 1
+			for i := 0; i < l; i++ {
+				be := openedBlocks[i]
+				line, _ := reader.PeekLine()
+				if line == nil {
+					p.closeBlocks(lastIndex, 0, reader, pc)
+					reader.AdvanceLine()
+					return
+				}
+				lineNum, _ := reader.Position()
+				blankLines = append(blankLines, lineStat{lineNum, i, util.IsBlank(line)})
+				// If node is a paragraph, p.openBlocks determines whether it is continuable.
+				// So we do not process paragraphs here.
+				if !ast.IsParagraph(be.Node) {
+					state := be.Parser.Continue(be.Node, reader, pc)
+					if state&Continue != 0 {
+						// When current node is a container block and has no children,
+						// we try to open new child nodes
+						if state&HasChildren != 0 && i == lastIndex {
+							isBlank = isBlankLine(lineNum-1, i, blankLines)
+							p.openBlocks(be.Node, isBlank, reader, pc)
+							break
+						}
+						continue
+					}
+				}
+				// current node may be closed or lazy continuation
+				isBlank = isBlankLine(lineNum-1, i, blankLines)
+				thisParent := parent
+				if i != 0 {
+					thisParent = openedBlocks[i-1].Node
+				}
+				lastNode := openedBlocks[lastIndex].Node
+				result := p.openBlocks(thisParent, isBlank, reader, pc)
+				if result != paragraphContinuation {
+					// lastNode is a paragraph and was transformed by the paragraph
+					// transformers.
+					if openedBlocks[lastIndex].Node != lastNode {
+						lastIndex--
+					}
+					p.closeBlocks(lastIndex, i, reader, pc)
+				}
+				break
+			}
+
+			reader.AdvanceLine()
+		}
+	}
+}
+
+func (p *parser) walkBlock(block ast.Node, cb func(node ast.Node)) {
+	for c := block.FirstChild(); c != nil; c = c.NextSibling() {
+		p.walkBlock(c, cb)
+	}
+	cb(block)
+}
+
+const (
+	lineBreakHard uint8 = 1 << iota
+	lineBreakSoft
+	lineBreakVisible
+)
+
+func (p *parser) parseBlock(block text.BlockReader, parent ast.Node, pc Context) {
+	if parent.IsRaw() {
+		return
+	}
+	escaped := false
+	source := block.Source()
+	block.Reset(parent.Lines())
+	for {
+	retry:
+		line, _ := block.PeekLine()
+		if line == nil {
+			break
+		}
+		lineLength := len(line)
+		var lineBreakFlags uint8 = 0
+		hasNewLine := line[lineLength-1] == '\n'
+		if ((lineLength >= 3 && line[lineLength-2] == '\\' && line[lineLength-3] != '\\') || (lineLength == 2 && line[lineLength-2] == '\\')) && hasNewLine { // ends with \\n
+			lineLength -= 2
+			lineBreakFlags |= lineBreakHard | lineBreakVisible
+		} else if ((lineLength >= 4 && line[lineLength-3] == '\\' && line[lineLength-2] == '\r' && line[lineLength-4] != '\\') || (lineLength == 3 && line[lineLength-3] == '\\' && line[lineLength-2] == '\r')) && hasNewLine { // ends with \\r\n
+			lineLength -= 3
+			lineBreakFlags |= lineBreakHard | lineBreakVisible
+		} else if lineLength >= 3 && line[lineLength-3] == ' ' && line[lineLength-2] == ' ' && hasNewLine { // ends with [space][space]\n
+			lineLength -= 3
+			lineBreakFlags |= lineBreakHard
+		} else if lineLength >= 4 && line[lineLength-4] == ' ' && line[lineLength-3] == ' ' && line[lineLength-2] == '\r' && hasNewLine { // ends with [space][space]\r\n
+			lineLength -= 4
+			lineBreakFlags |= lineBreakHard
+		} else if hasNewLine {
+			// If the line ends with a newline character, but it is not a hardlineBreak, then it is a softLinebreak
+			// If the line ends with a hardlineBreak, then it cannot end with a softLinebreak
+			// See https://spec.commonmark.org/0.30/#soft-line-breaks
+			lineBreakFlags |= lineBreakSoft
+		}
+
+		l, startPosition := block.Position()
+		n := 0
+		for i := 0; i < lineLength; i++ {
+			c := line[i]
+			if c == '\n' {
+				break
+			}
+			isSpace := util.IsSpace(c) && c != '\r' && c != '\n'
+			isPunct := util.IsPunct(c)
+			if (isPunct && !escaped) || isSpace && !(escaped && p.escapedSpace) || i == 0 {
+				parserChar := c
+				if isSpace || (i == 0 && !isPunct) {
+					parserChar = ' '
+				}
+				ips := p.inlineParsers[parserChar]
+				if ips != nil {
+					block.Advance(n)
+					n = 0
+					savedLine, savedPosition := block.Position()
+					if i != 0 {
+						_, currentPosition := block.Position()
+						ast.MergeOrAppendTextSegment(parent, startPosition.Between(currentPosition))
+						_, startPosition = block.Position()
+					}
+					var inlineNode ast.Node
+					for _, ip := range ips {
+						inlineNode = ip.Parse(parent, block, pc)
+						if inlineNode != nil {
+							break
+						}
+						block.SetPosition(savedLine, savedPosition)
+					}
+					if inlineNode != nil {
+						parent.AppendChild(parent, inlineNode)
+						goto retry
+					}
+				}
+			}
+			if escaped {
+				escaped = false
+				n++
+				continue
+			}
+
+			if c == '\\' {
+				escaped = true
+				n++
+				continue
+			}
+
+			escaped = false
+			n++
+		}
+		if n != 0 {
+			block.Advance(n)
+		}
+		currentL, currentPosition := block.Position()
+		if l != currentL {
+			continue
+		}
+		diff := startPosition.Between(currentPosition)
+		var text *ast.Text
+		if lineBreakFlags&(lineBreakHard|lineBreakVisible) == lineBreakHard|lineBreakVisible {
+			text = ast.NewTextSegment(diff)
+		} else {
+			text = ast.NewTextSegment(diff.TrimRightSpace(source))
+		}
+		text.SetSoftLineBreak(lineBreakFlags&lineBreakSoft != 0)
+		text.SetHardLineBreak(lineBreakFlags&lineBreakHard != 0)
+		parent.AppendChild(parent, text)
+		block.AdvanceLine()
+	}
+
+	ProcessDelimiters(nil, pc)
+	for _, ip := range p.closeBlockers {
+		ip.CloseBlock(parent, block, pc)
+	}
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/raw_html.go b/vendor/github.com/yuin/goldmark/parser/raw_html.go
new file mode 100644
index 000000000..55b9a9967
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/raw_html.go
@@ -0,0 +1,163 @@
+package parser
+
+import (
+	"bytes"
+	"regexp"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type rawHTMLParser struct {
+}
+
+var defaultRawHTMLParser = &rawHTMLParser{}
+
+// NewRawHTMLParser return a new InlineParser that can parse
+// inline htmls
+func NewRawHTMLParser() InlineParser {
+	return defaultRawHTMLParser
+}
+
+func (s *rawHTMLParser) Trigger() []byte {
+	return []byte{'<'}
+}
+
+func (s *rawHTMLParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
+	line, _ := block.PeekLine()
+	if len(line) > 1 && util.IsAlphaNumeric(line[1]) {
+		return s.parseMultiLineRegexp(openTagRegexp, block, pc)
+	}
+	if len(line) > 2 && line[1] == '/' && util.IsAlphaNumeric(line[2]) {
+		return s.parseMultiLineRegexp(closeTagRegexp, block, pc)
+	}
+	if bytes.HasPrefix(line, openComment) {
+		return s.parseComment(block, pc)
+	}
+	if bytes.HasPrefix(line, openProcessingInstruction) {
+		return s.parseUntil(block, closeProcessingInstruction, pc)
+	}
+	if len(line) > 2 && line[1] == '!' && line[2] >= 'A' && line[2] <= 'Z' {
+		return s.parseUntil(block, closeDecl, pc)
+	}
+	if bytes.HasPrefix(line, openCDATA) {
+		return s.parseUntil(block, closeCDATA, pc)
+	}
+	return nil
+}
+
+var tagnamePattern = `([A-Za-z][A-Za-z0-9-]*)`
+
+var attributePattern = `(?:[\r\n \t]+[a-zA-Z_:][a-zA-Z0-9:._-]*(?:[\r\n \t]*=[\r\n \t]*(?:[^\"'=<>` + "`" + `\x00-\x20]+|'[^']*'|"[^"]*"))?)`
+var openTagRegexp = regexp.MustCompile("^<" + tagnamePattern + attributePattern + `*[ \t]*/?>`)
+var closeTagRegexp = regexp.MustCompile("^</" + tagnamePattern + `\s*>`)
+
+var openProcessingInstruction = []byte("<?")
+var closeProcessingInstruction = []byte("?>")
+var openCDATA = []byte("<![CDATA[")
+var closeCDATA = []byte("]]>")
+var closeDecl = []byte(">")
+var emptyComment = []byte("<!---->")
+var invalidComment1 = []byte("<!-->")
+var invalidComment2 = []byte("<!--->")
+var openComment = []byte("<!--")
+var closeComment = []byte("-->")
+var doubleHyphen = []byte("--")
+
+func (s *rawHTMLParser) parseComment(block text.Reader, pc Context) ast.Node {
+	savedLine, savedSegment := block.Position()
+	node := ast.NewRawHTML()
+	line, segment := block.PeekLine()
+	if bytes.HasPrefix(line, emptyComment) {
+		node.Segments.Append(segment.WithStop(segment.Start + len(emptyComment)))
+		block.Advance(len(emptyComment))
+		return node
+	}
+	if bytes.HasPrefix(line, invalidComment1) || bytes.HasPrefix(line, invalidComment2) {
+		return nil
+	}
+	offset := len(openComment)
+	line = line[offset:]
+	for {
+		hindex := bytes.Index(line, doubleHyphen)
+		if hindex > -1 {
+			hindex += offset
+		}
+		index := bytes.Index(line, closeComment) + offset
+		if index > -1 && hindex == index {
+			if index == 0 || len(line) < 2 || line[index-offset-1] != '-' {
+				node.Segments.Append(segment.WithStop(segment.Start + index + len(closeComment)))
+				block.Advance(index + len(closeComment))
+				return node
+			}
+		}
+		if hindex > 0 {
+			break
+		}
+		node.Segments.Append(segment)
+		block.AdvanceLine()
+		line, segment = block.PeekLine()
+		offset = 0
+		if line == nil {
+			break
+		}
+	}
+	block.SetPosition(savedLine, savedSegment)
+	return nil
+}
+
+func (s *rawHTMLParser) parseUntil(block text.Reader, closer []byte, pc Context) ast.Node {
+	savedLine, savedSegment := block.Position()
+	node := ast.NewRawHTML()
+	for {
+		line, segment := block.PeekLine()
+		if line == nil {
+			break
+		}
+		index := bytes.Index(line, closer)
+		if index > -1 {
+			node.Segments.Append(segment.WithStop(segment.Start + index + len(closer)))
+			block.Advance(index + len(closer))
+			return node
+		}
+		node.Segments.Append(segment)
+		block.AdvanceLine()
+	}
+	block.SetPosition(savedLine, savedSegment)
+	return nil
+}
+
+func (s *rawHTMLParser) parseMultiLineRegexp(reg *regexp.Regexp, block text.Reader, pc Context) ast.Node {
+	sline, ssegment := block.Position()
+	if block.Match(reg) {
+		node := ast.NewRawHTML()
+		eline, esegment := block.Position()
+		block.SetPosition(sline, ssegment)
+		for {
+			line, segment := block.PeekLine()
+			if line == nil {
+				break
+			}
+			l, _ := block.Position()
+			start := segment.Start
+			if l == sline {
+				start = ssegment.Start
+			}
+			end := segment.Stop
+			if l == eline {
+				end = esegment.Start
+			}
+
+			node.Segments.Append(text.NewSegment(start, end))
+			if l == eline {
+				block.Advance(end - start)
+				break
+			} else {
+				block.AdvanceLine()
+			}
+		}
+		return node
+	}
+	return nil
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/setext_headings.go b/vendor/github.com/yuin/goldmark/parser/setext_headings.go
new file mode 100644
index 000000000..686efe179
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/setext_headings.go
@@ -0,0 +1,126 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var temporaryParagraphKey = NewContextKey()
+
+type setextHeadingParser struct {
+	HeadingConfig
+}
+
+func matchesSetextHeadingBar(line []byte) (byte, bool) {
+	start := 0
+	end := len(line)
+	space := util.TrimLeftLength(line, []byte{' '})
+	if space > 3 {
+		return 0, false
+	}
+	start += space
+	level1 := util.TrimLeftLength(line[start:end], []byte{'='})
+	c := byte('=')
+	var level2 int
+	if level1 == 0 {
+		level2 = util.TrimLeftLength(line[start:end], []byte{'-'})
+		c = '-'
+	}
+	if util.IsSpace(line[end-1]) {
+		end -= util.TrimRightSpaceLength(line[start:end])
+	}
+	if !((level1 > 0 && start+level1 == end) || (level2 > 0 && start+level2 == end)) {
+		return 0, false
+	}
+	return c, true
+}
+
+// NewSetextHeadingParser return a new BlockParser that can parse Setext headings.
+func NewSetextHeadingParser(opts ...HeadingOption) BlockParser {
+	p := &setextHeadingParser{}
+	for _, o := range opts {
+		o.SetHeadingOption(&p.HeadingConfig)
+	}
+	return p
+}
+
+func (b *setextHeadingParser) Trigger() []byte {
+	return []byte{'-', '='}
+}
+
+func (b *setextHeadingParser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	last := pc.LastOpenedBlock().Node
+	if last == nil {
+		return nil, NoChildren
+	}
+	paragraph, ok := last.(*ast.Paragraph)
+	if !ok || paragraph.Parent() != parent {
+		return nil, NoChildren
+	}
+	line, segment := reader.PeekLine()
+	c, ok := matchesSetextHeadingBar(line)
+	if !ok {
+		return nil, NoChildren
+	}
+	level := 1
+	if c == '-' {
+		level = 2
+	}
+	node := ast.NewHeading(level)
+	node.Lines().Append(segment)
+	pc.Set(temporaryParagraphKey, last)
+	return node, NoChildren | RequireParagraph
+}
+
+func (b *setextHeadingParser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	return Close
+}
+
+func (b *setextHeadingParser) Close(node ast.Node, reader text.Reader, pc Context) {
+	heading := node.(*ast.Heading)
+	segment := node.Lines().At(0)
+	heading.Lines().Clear()
+	tmp := pc.Get(temporaryParagraphKey).(*ast.Paragraph)
+	pc.Set(temporaryParagraphKey, nil)
+	if tmp.Lines().Len() == 0 {
+		next := heading.NextSibling()
+		segment = segment.TrimLeftSpace(reader.Source())
+		if next == nil || !ast.IsParagraph(next) {
+			para := ast.NewParagraph()
+			para.Lines().Append(segment)
+			heading.Parent().InsertAfter(heading.Parent(), heading, para)
+		} else {
+			next.(ast.Node).Lines().Unshift(segment)
+		}
+		heading.Parent().RemoveChild(heading.Parent(), heading)
+	} else {
+		heading.SetLines(tmp.Lines())
+		heading.SetBlankPreviousLines(tmp.HasBlankPreviousLines())
+		tp := tmp.Parent()
+		if tp != nil {
+			tp.RemoveChild(tp, tmp)
+		}
+	}
+
+	if b.Attribute {
+		parseLastLineAttributes(node, reader, pc)
+	}
+
+	if b.AutoHeadingID {
+		id, ok := node.AttributeString("id")
+		if !ok {
+			generateAutoHeadingID(heading, reader, pc)
+		} else {
+			pc.IDs().Put(id.([]byte))
+		}
+	}
+}
+
+func (b *setextHeadingParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *setextHeadingParser) CanAcceptIndentedLine() bool {
+	return false
+}
diff --git a/vendor/github.com/yuin/goldmark/parser/thematic_break.go b/vendor/github.com/yuin/goldmark/parser/thematic_break.go
new file mode 100644
index 000000000..db20a1e7a
--- /dev/null
+++ b/vendor/github.com/yuin/goldmark/parser/thematic_break.go
@@ -0,0 +1,75 @@
+package parser
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type thematicBreakPraser struct {
+}
+
+var defaultThematicBreakPraser = &thematicBreakPraser{}
+
+// NewThematicBreakParser returns a new BlockParser that
+// parses thematic breaks.
+func NewThematicBreakParser() BlockParser {
+	return defaultThematicBreakPraser
+}
+
+func isThematicBreak(line []byte, offset int) bool {
+	w, pos := util.IndentWidth(line, offset)
+	if w > 3 {
+		return false
+	}
+	mark := byte(0)
+	count := 0
+	for i := pos; i < len(line); i++ {
+		c := line[i]
+		if util.IsSpace(c) {
+			continue
+		}
+		if mark == 0 {
+			mark = c
+			count = 1
+			if mark == '*' || mark == '-' || mark == '_' {
+				continue
+			}
+			return false
+		}
+		if c != mark {
+			return false
+		}
+		count++
+	}
+	return count > 2
+}
+
+func (b *thematicBreakPraser) Trigger() []byte {
+	return []byte{'-', '*', '_'}
+}
+
+func (b *thematicBreakPraser) Open(parent ast.Node, reader text.Reader, pc Context) (ast.Node, State) {
+	line, segment := reader.PeekLine()
+	if isThematicBreak(line, reader.LineOffset()) {
+		reader.Advance(segment.Len() - 1)
+		return ast.NewThematicBreak(), NoChildren
+	}
+	return nil, NoChildren
+}
+
+func (b *thematicBreakPraser) Continue(node ast.Node, reader text.Reader, pc Context) State {
+	return Close
+}
+
+func (b *thematicBreakPraser) Close(node ast.Node, reader text.Reader, pc Context) {
+	// nothing to do
+}
+
+func (b *thematicBreakPraser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *thematicBreakPraser) CanAcceptIndentedLine() bool {
+	return false
+}