Detect markdown line width, resolve relative URLs (#332)

~~this is semi-blocked by https://github.com/charmbracelet/glamour/pull/96, but behaviour isn't really worse than the previous behaviour (most links work, some are still broken)~~

#### testcase for link resolver
```
tea pr 332
tea checkout 332 && make install && tea pr 332
```

- [rel](./332)
- [abs](/gitea/tea/pulls/332)
- [full](https://gitea.com/gitea/tea/pulls/332)

Co-authored-by: Norwin Roosen <git@nroo.de>
Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/332
Reviewed-by: 6543 <6543@obermui.de>
Reviewed-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Norwin <noerw@noreply.gitea.io>
Co-committed-by: Norwin <noerw@noreply.gitea.io>

vendor/github.com/yuin/goldmark-emoji/.gitignore

@@ -0,0 +1,15 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, build with `go test -c`
+*.test
+*.pprof
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+.DS_Store

vendor/github.com/yuin/goldmark-emoji/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2020 Yusuke Inuzuka
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

vendor/github.com/yuin/goldmark-emoji/README.md

@@ -0,0 +1,71 @@
+goldmark-emoji
+=========================
+
+[![GoDev][godev-image]][godev-url]
+
+[godev-image]: https://pkg.go.dev/badge/github.com/yuin/goldmark-emoji
+[godev-url]: https://pkg.go.dev/github.com/yuin/goldmark-emoji
+
+goldmark-emoji is an extension for the [goldmark](http://github.com/yuin/goldmark) 
+that parses `:joy:` style emojis.
+
+Installation
+--------------------
+
+```
+go get github.com/yuin/goldmark-emoji
+```
+
+Usage
+--------------------
+
+```go
+import (
+    "bytes"
+    "fmt"
+
+    "github.com/yuin/goldmark"
+    "github.com/yuin/goldmark-emoji"
+    "github.com/yuin/goldmark-emoji/definition"
+)
+
+func main() {
+    markdown := goldmark.New(
+        goldmark.WithExtensions(
+            emoji.Emoji,
+        ),
+    )
+    source := `
+    Joy :joy:
+    `
+    var buf bytes.Buffer
+    if err := markdown.Convert([]byte(source), &buf); err != nil {
+        panic(err)
+    }
+    fmt.Print(buf.String())
+}
+```
+
+See `emoji_test.go` for detailed usage.
+
+### Options
+
+Options for the extension
+
+| Option | Description |
+| ------ | ----------- |
+| `WithEmojis` | Definition of emojis. This defaults to github emoji set |
+| `WithRenderingMethod` | `Entity` : renders as HTML entities, `Twemoji` : renders as an img tag that uses [twemoji](https://github.com/twitter/twemoji), `Func` : renders using a go function |
+| `WithTwemojiTemplate` | Twemoji img tag printf template |
+| `WithRendererFunc` | renders by a go function |
+
+
+
+License
+--------------------
+MIT
+
+Author
+--------------------
+Yusuke Inuzuka
+

vendor/github.com/yuin/goldmark-emoji/ast/emoji.go

@@ -0,0 +1,42 @@
+// Package ast defines AST nodes that represetns emoji extension's elements.
+package ast
+
+import (
+	"fmt"
+
+	"github.com/yuin/goldmark-emoji/definition"
+	gast "github.com/yuin/goldmark/ast"
+)
+
+// Emoji represents an inline emoji.
+type Emoji struct {
+	gast.BaseInline
+
+	ShortName []byte
+	Value     *definition.Emoji
+}
+
+// Dump implements Node.Dump.
+func (n *Emoji) Dump(source []byte, level int) {
+	m := map[string]string{
+		"ShortName": string(n.ShortName),
+		"Value":     fmt.Sprintf("%#v", n.Value),
+	}
+	gast.DumpHelper(n, source, level, m, nil)
+}
+
+// KindEmoji is a NodeKind of the emoji node.
+var KindEmoji = gast.NewNodeKind("Emoji")
+
+// Kind implements Node.Kind.
+func (n *Emoji) Kind() gast.NodeKind {
+	return KindEmoji
+}
+
+// NewEmoji returns a new Emoji node.
+func NewEmoji(shortName []byte, value *definition.Emoji) *Emoji {
+	return &Emoji{
+		ShortName: shortName,
+		Value:     value,
+	}
+}

vendor/github.com/yuin/goldmark-emoji/definition/definition.go

@@ -0,0 +1,106 @@
+package definition
+
+// Emoji is a data structure that holds a single emoji.
+type Emoji struct {
+	// Name is a name of this emoji.
+	Name string
+
+	// ShortNames is a shorter representation of this emoji.
+	ShortNames []string
+
+	// Unicode is an unicode representation of this emoji.
+	Unicode []rune
+}
+
+// NewEmoji returns a new Emoji.
+func NewEmoji(name string, unicode []rune, shortNames ...string) Emoji {
+	if len(shortNames) == 0 {
+		panic("Emoji must have at leat 1 short name.")
+	}
+	if unicode == nil || len(unicode) == 0 {
+		unicode = []rune{0xFFFD}
+	}
+	return Emoji{
+		Name:       name,
+		ShortNames: shortNames,
+		Unicode:    unicode,
+	}
+}
+
+// IsUnicode returns true if this emoji is defined in unicode, otherwise false.
+func (em *Emoji) IsUnicode() bool {
+	return !(len(em.Unicode) == 1 && em.Unicode[0] == 0xFFFD)
+}
+
+// Emojis is a collection of emojis.
+type Emojis interface {
+	// Get returns (*Emoji, true) if found mapping associated with given short name, otherwise (nil, false).
+	Get(shortName string) (*Emoji, bool)
+
+	// Add adds new emojis to this collection.
+	Add(Emojis)
+
+	// Clone clones this collection.
+	Clone() Emojis
+}
+
+type emojis struct {
+	list     []Emoji
+	m        map[string]*Emoji
+	children []Emojis
+}
+
+// NewEmojis returns a new Emojis.
+func NewEmojis(es ...Emoji) Emojis {
+	m := &emojis{
+		list:     es,
+		m:        map[string]*Emoji{},
+		children: []Emojis{},
+	}
+	for i, _ := range es {
+		emoji := &m.list[i]
+		for _, s := range emoji.ShortNames {
+			m.m[s] = emoji
+		}
+	}
+	return m
+}
+
+func (m *emojis) Add(emojis Emojis) {
+	m.children = append(m.children, emojis)
+}
+
+func (m *emojis) Clone() Emojis {
+	es := &emojis{
+		list:     m.list,
+		m:        m.m,
+		children: make([]Emojis, len(m.children)),
+	}
+	copy(es.children, m.children)
+	return es
+}
+
+func (m *emojis) Get(shortName string) (*Emoji, bool) {
+	v, ok := m.m[shortName]
+	if ok {
+		return v, ok
+	}
+
+	for _, es := range m.children {
+		v, ok := es.Get(shortName)
+		if ok {
+			return v, ok
+		}
+	}
+	return nil, false
+}
+
+// EmojisOption sets options for Emojis.
+type EmojisOption func(Emojis)
+
+// WithEmojis is an EmojisOption that adds emojis to the Emojis.
+func WithEmojis(emojis ...Emoji) EmojisOption {
+	return func(m Emojis) {
+		m.Add(NewEmojis(emojis...))
+	}
+}

vendor/github.com/yuin/goldmark-emoji/emoji.go

@@ -0,0 +1,360 @@
+// package emoji is a extension for the goldmark(http://github.com/yuin/goldmark).
+package emoji
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/yuin/goldmark"
+	east "github.com/yuin/goldmark-emoji/ast"
+	"github.com/yuin/goldmark-emoji/definition"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// Option interface sets options for this extension.
+type Option interface {
+	emojiOption()
+}
+
+// ParserConfig struct is a data structure that holds configuration of
+// the Emoji extension.
+type ParserConfig struct {
+	Emojis definition.Emojis
+}
+
+const optEmojis parser.OptionName = "EmojiEmojis"
+
+// SetOption implements parser.SetOptioner
+func (c *ParserConfig) SetOption(name parser.OptionName, value interface{}) {
+	switch name {
+	case optEmojis:
+		c.Emojis = value.(definition.Emojis)
+	}
+}
+
+// A ParserOption interface sets options for the emoji parser.
+type ParserOption interface {
+	Option
+	parser.Option
+
+	SetEmojiOption(*ParserConfig)
+}
+
+var _ ParserOption = &withEmojis{}
+
+type withEmojis struct {
+	value definition.Emojis
+}
+
+func (o *withEmojis) emojiOption() {}
+
+func (o *withEmojis) SetParserOption(c *parser.Config) {
+	c.Options[optEmojis] = o.value
+}
+
+func (o *withEmojis) SetEmojiOption(c *ParserConfig) {
+	c.Emojis = o.value
+}
+
+// WithMaping is a functional option that defines links names to unicode emojis.
+func WithEmojis(value definition.Emojis) Option {
+	return &withEmojis{
+		value: value,
+	}
+}
+
+// RenderingMethod indicates how emojis are rendered.
+type RenderingMethod int
+
+// RendererFunc will be used for rendering emojis.
+type RendererFunc func(w util.BufWriter, source []byte, n *east.Emoji, config *RendererConfig)
+
+const (
+	// Entity renders an emoji as an html entity.
+	Entity RenderingMethod = iota
+
+	// Unicode renders an emoji as unicode character.
+	Unicode
+
+	// Twemoji renders an emoji as an img tag with [twemoji](https://github.com/twitter/twemoji).
+	Twemoji
+
+	// Func renders an emoji using RendererFunc.
+	Func
+)
+
+// RendererConfig struct holds options for the emoji renderer.
+type RendererConfig struct {
+	html.Config
+
+	// Method indicates how emojis are rendered.
+	Method RenderingMethod
+
+	// TwemojiTemplate is a printf template for twemoji. This value is valid only when Method is set to Twemoji.
+	// `printf` arguments are:
+	//
+	//     1: name (e.g. "face with tears of joy")
+	//     2: file name without an extension (e.g. 1f646-2642)
+	//     3: '/' if XHTML, otherwise ''
+	//
+	TwemojiTemplate string
+
+	// RendererFunc is a RendererFunc that renders emojis. This value is valid only when Method is set to Func.
+	RendererFunc RendererFunc
+}
+
+// DefaultTwemojiTemplate is a default value for RendererConfig.TwemojiTemplate.
+const DefaultTwemojiTemplate = `<img class="emoji" draggable="false" alt="%[1]s" src="https://twemoji.maxcdn.com/v/latest/72x72/%[2]s.png"%[3]s>`
+
+// SetOption implements renderer.SetOptioner.
+func (c *RendererConfig) SetOption(name renderer.OptionName, value interface{}) {
+	switch name {
+	case optRenderingMethod:
+		c.Method = value.(RenderingMethod)
+	case optTwemojiTemplate:
+		c.TwemojiTemplate = value.(string)
+	case optRendererFunc:
+		c.RendererFunc = value.(RendererFunc)
+	default:
+		c.Config.SetOption(name, value)
+	}
+}
+
+// A RendererOption interface sets options for the emoji renderer.
+type RendererOption interface {
+	Option
+	renderer.Option
+
+	SetEmojiOption(*RendererConfig)
+}
+
+var _ RendererOption = &withRenderingMethod{}
+
+type withRenderingMethod struct {
+	value RenderingMethod
+}
+
+func (o *withRenderingMethod) emojiOption() {
+}
+
+// SetConfig implements renderer.Option#SetConfig.
+func (o *withRenderingMethod) SetConfig(c *renderer.Config) {
+	c.Options[optRenderingMethod] = o.value
+}
+
+// SetEmojiOption implements RendererOption#SetEmojiOption
+func (o *withRenderingMethod) SetEmojiOption(c *RendererConfig) {
+	c.Method = o.value
+}
+
+const optRenderingMethod renderer.OptionName = "EmojiRenderingMethod"
+
+// WithRenderingMethod is a functional option that indicates how emojis are rendered.
+func WithRenderingMethod(a RenderingMethod) Option {
+	return &withRenderingMethod{a}
+}
+
+type withTwemojiTemplate struct {
+	value string
+}
+
+func (o *withTwemojiTemplate) emojiOption() {
+}
+
+// SetConfig implements renderer.Option#SetConfig.
+func (o *withTwemojiTemplate) SetConfig(c *renderer.Config) {
+	c.Options[optTwemojiTemplate] = o.value
+}
+
+// SetEmojiOption implements RendererOption#SetEmojiOption
+func (o *withTwemojiTemplate) SetEmojiOption(c *RendererConfig) {
+	c.TwemojiTemplate = o.value
+}
+
+const optTwemojiTemplate renderer.OptionName = "EmojiTwemojiTemplate"
+
+// WithTwemojiTemplate is a functional option that changes a twemoji img tag.
+func WithTwemojiTemplate(s string) Option {
+	return &withTwemojiTemplate{s}
+}
+
+var _ RendererOption = &withRendererFunc{}
+
+type withRendererFunc struct {
+	value RendererFunc
+}
+
+func (o *withRendererFunc) emojiOption() {
+}
+
+// SetConfig implements renderer.Option#SetConfig.
+func (o *withRendererFunc) SetConfig(c *renderer.Config) {
+	c.Options[optRendererFunc] = o.value
+}
+
+// SetEmojiOption implements RendererOption#SetEmojiOption
+func (o *withRendererFunc) SetEmojiOption(c *RendererConfig) {
+	c.RendererFunc = o.value
+}
+
+const optRendererFunc renderer.OptionName = "EmojiRendererFunc"
+
+// WithRendererFunc is a functional option that changes a renderer func.
+func WithRendererFunc(f RendererFunc) Option {
+	return &withRendererFunc{f}
+}
+
+type emojiParser struct {
+	ParserConfig
+}
+
+// NewParser returns a new parser.InlineParser that can parse emoji expressions.
+func NewParser(opts ...ParserOption) parser.InlineParser {
+	p := &emojiParser{
+		ParserConfig: ParserConfig{
+			Emojis: definition.Github(),
+		},
+	}
+	for _, o := range opts {
+		o.SetEmojiOption(&p.ParserConfig)
+	}
+	return p
+}
+
+func (s *emojiParser) Trigger() []byte {
+	return []byte{':'}
+}
+
+func (s *emojiParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
+	line, _ := block.PeekLine()
+	if len(line) < 1 {
+		return nil
+	}
+	i := 1
+	for ; i < len(line); i++ {
+		c := line[i]
+		if !(util.IsAlphaNumeric(c) || c == '_' || c == '-' || c == '+') {
+			break
+		}
+	}
+	if i >= len(line) || line[i] != ':' {
+		return nil
+	}
+	block.Advance(i + 1)
+	shortName := line[1:i]
+	emoji, ok := s.Emojis.Get(util.BytesToReadOnlyString(shortName))
+	if !ok {
+		return nil
+	}
+	return east.NewEmoji(shortName, emoji)
+}
+
+type emojiHTMLRenderer struct {
+	RendererConfig
+}
+
+// NewHTMLRenderer returns a new HTMLRenderer.
+func NewHTMLRenderer(opts ...RendererOption) renderer.NodeRenderer {
+	r := &emojiHTMLRenderer{
+		RendererConfig: RendererConfig{
+			Config:          html.NewConfig(),
+			Method:          Entity,
+			TwemojiTemplate: DefaultTwemojiTemplate,
+			RendererFunc:    nil,
+		},
+	}
+	for _, opt := range opts {
+		opt.SetEmojiOption(&r.RendererConfig)
+	}
+	return r
+}
+
+// RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
+func (r *emojiHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(east.KindEmoji, r.renderEmoji)
+}
+
+const slash = " /"
+const empty = ""
+
+func (r *emojiHTMLRenderer) renderEmoji(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+	node := n.(*east.Emoji)
+	if !node.Value.IsUnicode() && r.Method != Func {
+		fmt.Fprintf(w, `<span title="%s">:%s:</span>`, util.EscapeHTML(util.StringToReadOnlyBytes(node.Value.Name)), node.ShortName)
+		return ast.WalkContinue, nil
+	}
+
+	switch r.Method {
+	case Entity:
+		for _, r := range node.Value.Unicode {
+			if r == 0x200D {
+				_, _ = w.WriteString("&zwj;")
+				continue
+			}
+			fmt.Fprintf(w, "&#x%x;", r)
+		}
+	case Unicode:
+		fmt.Fprintf(w, "%s", string(node.Value.Unicode))
+	case Twemoji:
+		s := slash
+		if !r.XHTML {
+			s = empty
+		}
+		values := []string{}
+		for _, r := range node.Value.Unicode {
+			values = append(values, fmt.Sprintf("%x", r))
+		}
+		fmt.Fprintf(w, r.TwemojiTemplate, util.EscapeHTML(util.StringToReadOnlyBytes(node.Value.Name)), strings.Join(values, "-"), s)
+	case Func:
+		r.RendererFunc(w, source, node, &r.RendererConfig)
+	}
+	return ast.WalkContinue, nil
+}
+
+type emoji struct {
+	options []Option
+}
+
+// Emoji is a goldmark.Extender implementation.
+var Emoji = &emoji{
+	options: []Option{},
+}
+
+// New returns a new extension with given options.
+func New(opts ...Option) goldmark.Extender {
+	return &emoji{
+		options: opts,
+	}
+}
+
+// Extend implements goldmark.Extender.
+func (e *emoji) Extend(m goldmark.Markdown) {
+	pOpts := []ParserOption{}
+	rOpts := []RendererOption{}
+	for _, o := range e.options {
+		if po, ok := o.(ParserOption); ok {
+			pOpts = append(pOpts, po)
+			continue
+		}
+		if ro, ok := o.(RendererOption); ok {
+			rOpts = append(rOpts, ro)
+		}
+	}
+
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(NewHTMLRenderer(rOpts...), 200),
+	))
+
+	m.Parser().AddOptions(parser.WithInlineParsers(
+		util.Prioritized(NewParser(pOpts...), 999),
+	))
+
+}

vendor/github.com/yuin/goldmark-emoji/go.mod

@@ -0,0 +1,5 @@
+module github.com/yuin/goldmark-emoji
+
+go 1.15
+
+require github.com/yuin/goldmark v1.2.1

vendor/github.com/yuin/goldmark-emoji/go.sum

@@ -0,0 +1,2 @@
+github.com/yuin/goldmark v1.2.1 h1:ruQGxdhGHe7FWOJPT0mKs5+pD2Xs1Bm/kdGlHO04FmM=
+github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=

vendor/github.com/yuin/goldmark/README.md

@@ -1,7 +1,7 @@
 goldmark
 ==========================================
 
-[![http://godoc.org/github.com/yuin/goldmark](https://godoc.org/github.com/yuin/goldmark?status.svg)](http://godoc.org/github.com/yuin/goldmark)
+[![https://pkg.go.dev/github.com/yuin/goldmark](https://pkg.go.dev/badge/github.com/yuin/goldmark.svg)](https://pkg.go.dev/github.com/yuin/goldmark)
 [![https://github.com/yuin/goldmark/actions?query=workflow:test](https://github.com/yuin/goldmark/workflows/test/badge.svg?branch=master&event=push)](https://github.com/yuin/goldmark/actions?query=workflow:test)
 [![https://coveralls.io/github/yuin/goldmark](https://coveralls.io/repos/github/yuin/goldmark/badge.svg?branch=master)](https://coveralls.io/github/yuin/goldmark)
 [![https://goreportcard.com/report/github.com/yuin/goldmark](https://goreportcard.com/badge/github.com/yuin/goldmark)](https://goreportcard.com/report/github.com/yuin/goldmark)
@@ -173,6 +173,7 @@ Parser and Renderer options
     - This extension enables Table, Strikethrough, Linkify and TaskList.
     - This extension does not filter tags defined in [6.11: Disallowed Raw HTML (extension)](https://github.github.com/gfm/#disallowed-raw-html-extension-).
     If you need to filter HTML tags, see [Security](#security).
+    - If you need to parse github emojis, you can use [goldmark-emoji](https://github.com/yuin/goldmark-emoji) extension.
 - `extension.DefinitionList`
     - [PHP Markdown Extra: Definition lists](https://michelf.ca/projects/php-markdown/extra/#def-list)
 - `extension.Footnote`
@@ -286,6 +287,89 @@ markdown := goldmark.New(
 )
 ```
 
+### Footnotes extension
+
+The Footnote extension implements [PHP Markdown Extra: Footnotes](https://michelf.ca/projects/php-markdown/extra/#footnotes).
+
+This extension has some options:
+
+| Functional option | Type | Description |
+| ----------------- | ---- | ----------- |
+| `extension.WithFootnoteIDPrefix` | `[]byte` |  a prefix for the id attributes.|
+| `extension.WithFootnoteIDPrefixFunction` | `func(gast.Node) []byte` |  a function that determines the id attribute for given Node.|
+| `extension.WithFootnoteLinkTitle` | `[]byte` |  an optional title attribute for footnote links.|
+| `extension.WithFootnoteBacklinkTitle` | `[]byte` |  an optional title attribute for footnote backlinks. |
+| `extension.WithFootnoteLinkClass` | `[]byte` |  a class for footnote links. This defaults to `footnote-ref`. |
+| `extension.WithFootnoteBacklinkClass` | `[]byte` |  a class for footnote backlinks. This defaults to `footnote-backref`. |
+| `extension.WithFootnoteBacklinkHTML` | `[]byte` |  a class for footnote backlinks. This defaults to `↩︎`. |
+
+Some options can have special substitutions. Occurances of “^^” in the string will be replaced by the corresponding footnote number in the HTML output. Occurances of “%%” will be replaced by a number for the reference (footnotes can have multiple references).
+
+`extension.WithFootnoteIDPrefix` and `extension.WithFootnoteIDPrefixFunction` are useful if you have multiple Markdown documents displayed inside one HTML document to avoid footnote ids to clash each other.
+
+`extension.WithFootnoteIDPrefix` sets fixed id prefix, so you may write codes like the following:
+
+```go
+for _, path := range files {
+    source := readAll(path)
+    prefix := getPrefix(path)
+
+    markdown := goldmark.New(
+        goldmark.WithExtensions(
+            NewFootnote(
+                WithFootnoteIDPrefix([]byte(path)),
+            ),
+        ),
+    )
+    var b bytes.Buffer
+    err := markdown.Convert(source, &b)
+    if err != nil {
+        t.Error(err.Error())
+    }
+}
+```
+
+`extension.WithFootnoteIDPrefixFunction` determines an id prefix by calling given function, so you may write codes like the following:
+
+```go
+markdown := goldmark.New(
+    goldmark.WithExtensions(
+        NewFootnote(
+                WithFootnoteIDPrefixFunction(func(n gast.Node) []byte {
+                    v, ok := n.OwnerDocument().Meta()["footnote-prefix"]
+                    if ok {
+                        return util.StringToReadOnlyBytes(v.(string))
+                    }
+                    return nil
+                }),
+        ),
+    ),
+)
+
+for _, path := range files {
+    source := readAll(path)
+    var b bytes.Buffer
+
+    doc := markdown.Parser().Parse(text.NewReader(source))
+    doc.Meta()["footnote-prefix"] = getPrefix(path)
+    err := markdown.Renderer().Render(&b, source, doc)
+}
+```
+
+You can use [goldmark-meta](https://github.com/yuin/goldmark-meta) to define a id prefix in the markdown document:
+
+
+```markdown
+---
+title: document title
+slug: article1
+footnote-prefix: article1
+---
+
+# My article
+
+```
+ 
 Security
 --------------------
 By default, goldmark does not render raw HTML or potentially-dangerous URLs.
@@ -336,6 +420,8 @@ Extensions
   extension for the goldmark Markdown parser.
 - [goldmark-highlighting](https://github.com/yuin/goldmark-highlighting): A syntax-highlighting extension
   for the goldmark markdown parser.
+- [goldmark-emoji](https://github.com/yuin/goldmark-emoji): An emoji
+  extension for the goldmark Markdown parser.
 - [goldmark-mathjax](https://github.com/litao91/goldmark-mathjax): Mathjax support for the goldmark markdown parser
 
 goldmark internal(for extension developers)

vendor/github.com/yuin/goldmark/ast/ast.go

@@ -45,11 +45,6 @@ type Attribute struct {
 	Value interface{}
 }
 
-var attrNameIDS = []byte("#")
-var attrNameID = []byte("id")
-var attrNameClassS = []byte(".")
-var attrNameClass = []byte("class")
-
 // A Node interface defines basic AST node functionalities.
 type Node interface {
 	// Type returns a type of this node.
@@ -116,6 +111,11 @@ type Node interface {
 	// tail of the children.
 	InsertAfter(self, v1, insertee Node)
 
+	// OwnerDocument returns this node's owner document.
+	// If this node is not a child of the Document node, OwnerDocument
+	// returns nil.
+	OwnerDocument() *Document
+
 	// Dump dumps an AST tree structure to stdout.
 	// This function completely aimed for debugging.
 	// level is a indent level. Implementer should indent informations with
@@ -169,7 +169,7 @@ type Node interface {
 	RemoveAttributes()
 }
 
-// A BaseNode struct implements the Node interface.
+// A BaseNode struct implements the Node interface partialliy.
 type BaseNode struct {
 	firstChild Node
 	lastChild  Node
@@ -358,6 +358,22 @@ func (n *BaseNode) InsertBefore(self, v1, insertee Node) {
 	}
 }
 
+// OwnerDocument implements Node.OwnerDocument
+func (n *BaseNode) OwnerDocument() *Document {
+	d := n.Parent()
+	for {
+		p := d.Parent()
+		if p == nil {
+			if v, ok := d.(*Document); ok {
+				return v
+			}
+			break
+		}
+		d = p
+	}
+	return nil
+}
+
 // Text implements Node.Text  .
 func (n *BaseNode) Text(source []byte) []byte {
 	var buf bytes.Buffer

vendor/github.com/yuin/goldmark/ast/block.go

@@ -7,7 +7,7 @@ import (
 	textm "github.com/yuin/goldmark/text"
 )
 
-// A BaseBlock struct implements the Node interface.
+// A BaseBlock struct implements the Node interface partialliy.
 type BaseBlock struct {
 	BaseNode
 	blankPreviousLines bool
@@ -50,6 +50,8 @@ func (b *BaseBlock) SetLines(v *textm.Segments) {
 // A Document struct is a root node of Markdown text.
 type Document struct {
 	BaseBlock
+
+	meta map[string]interface{}
 }
 
 // KindDocument is a NodeKind of the Document node.
@@ -70,10 +72,29 @@ func (n *Document) Kind() NodeKind {
 	return KindDocument
 }
 
+// OwnerDocument implements Node.OwnerDocument
+func (n *Document) OwnerDocument() *Document {
+	return n
+}
+
+// Meta returns metadata of this document.
+func (n *Document) Meta() map[string]interface{} {
+	if n.meta == nil {
+		n.meta = map[string]interface{}{}
+	}
+	return n.meta
+}
+
+// SetMeta sets given metadata to this document.
+func (n *Document) SetMeta(meta map[string]interface{}) {
+	n.meta = meta
+}
+
 // NewDocument returns a new Document node.
 func NewDocument() *Document {
 	return &Document{
 		BaseBlock: BaseBlock{},
+		meta:      nil,
 	}
 }
 

vendor/github.com/yuin/goldmark/ast/inline.go

@@ -8,7 +8,7 @@ import (
 	"github.com/yuin/goldmark/util"
 )
 
-// A BaseInline struct implements the Node interface.
+// A BaseInline struct implements the Node interface partialliy.
 type BaseInline struct {
 	BaseNode
 }

vendor/github.com/yuin/goldmark/extension/ast/footnote.go

@@ -2,6 +2,7 @@ package ast
 
 import (
 	"fmt"
+
 	gast "github.com/yuin/goldmark/ast"
 )
 
@@ -9,13 +10,15 @@ import (
 // (PHP Markdown Extra) text.
 type FootnoteLink struct {
 	gast.BaseInline
-	Index int
+	Index    int
+	RefCount int
 }
 
 // Dump implements Node.Dump.
 func (n *FootnoteLink) Dump(source []byte, level int) {
 	m := map[string]string{}
 	m["Index"] = fmt.Sprintf("%v", n.Index)
+	m["RefCount"] = fmt.Sprintf("%v", n.RefCount)
 	gast.DumpHelper(n, source, level, m, nil)
 }
 
@@ -30,36 +33,40 @@ func (n *FootnoteLink) Kind() gast.NodeKind {
 // NewFootnoteLink returns a new FootnoteLink node.
 func NewFootnoteLink(index int) *FootnoteLink {
 	return &FootnoteLink{
-		Index: index,
+		Index:    index,
+		RefCount: 0,
 	}
 }
 
-// A FootnoteBackLink struct represents a link to a footnote of Markdown
+// A FootnoteBacklink struct represents a link to a footnote of Markdown
 // (PHP Markdown Extra) text.
-type FootnoteBackLink struct {
+type FootnoteBacklink struct {
 	gast.BaseInline
-	Index int
+	Index    int
+	RefCount int
 }
 
 // Dump implements Node.Dump.
-func (n *FootnoteBackLink) Dump(source []byte, level int) {
+func (n *FootnoteBacklink) Dump(source []byte, level int) {
 	m := map[string]string{}
 	m["Index"] = fmt.Sprintf("%v", n.Index)
+	m["RefCount"] = fmt.Sprintf("%v", n.RefCount)
 	gast.DumpHelper(n, source, level, m, nil)
 }
 
-// KindFootnoteBackLink is a NodeKind of the FootnoteBackLink node.
-var KindFootnoteBackLink = gast.NewNodeKind("FootnoteBackLink")
+// KindFootnoteBacklink is a NodeKind of the FootnoteBacklink node.
+var KindFootnoteBacklink = gast.NewNodeKind("FootnoteBacklink")
 
 // Kind implements Node.Kind.
-func (n *FootnoteBackLink) Kind() gast.NodeKind {
-	return KindFootnoteBackLink
+func (n *FootnoteBacklink) Kind() gast.NodeKind {
+	return KindFootnoteBacklink
 }
 
-// NewFootnoteBackLink returns a new FootnoteBackLink node.
-func NewFootnoteBackLink(index int) *FootnoteBackLink {
-	return &FootnoteBackLink{
-		Index: index,
+// NewFootnoteBacklink returns a new FootnoteBacklink node.
+func NewFootnoteBacklink(index int) *FootnoteBacklink {
+	return &FootnoteBacklink{
+		Index:    index,
+		RefCount: 0,
 	}
 }
 

vendor/github.com/yuin/goldmark/extension/footnote.go

@@ -2,6 +2,8 @@ package extension
 
 import (
 	"bytes"
+	"strconv"
+
 	"github.com/yuin/goldmark"
 	gast "github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/extension/ast"
@@ -10,10 +12,10 @@ import (
 	"github.com/yuin/goldmark/renderer/html"
 	"github.com/yuin/goldmark/text"
 	"github.com/yuin/goldmark/util"
-	"strconv"
 )
 
 var footnoteListKey = parser.NewContextKey()
+var footnoteLinkListKey = parser.NewContextKey()
 
 type footnoteBlockParser struct {
 }
@@ -164,7 +166,20 @@ func (s *footnoteParser) Parse(parent gast.Node, block text.Reader, pc parser.Co
 		return nil
 	}
 
-	return ast.NewFootnoteLink(index)
+	fnlink := ast.NewFootnoteLink(index)
+	var fnlist []*ast.FootnoteLink
+	if tmp := pc.Get(footnoteLinkListKey); tmp != nil {
+		fnlist = tmp.([]*ast.FootnoteLink)
+	} else {
+		fnlist = []*ast.FootnoteLink{}
+		pc.Set(footnoteLinkListKey, fnlist)
+	}
+	pc.Set(footnoteLinkListKey, append(fnlist, fnlink))
+	if line[0] == '!' {
+		parent.AppendChild(parent, gast.NewTextSegment(text.NewSegment(segment.Start, segment.Start+1)))
+	}
+
+	return fnlink
 }
 
 type footnoteASTTransformer struct {
@@ -180,23 +195,46 @@ func NewFootnoteASTTransformer() parser.ASTTransformer {
 
 func (a *footnoteASTTransformer) Transform(node *gast.Document, reader text.Reader, pc parser.Context) {
 	var list *ast.FootnoteList
-	if tlist := pc.Get(footnoteListKey); tlist != nil {
-		list = tlist.(*ast.FootnoteList)
-	} else {
+	var fnlist []*ast.FootnoteLink
+	if tmp := pc.Get(footnoteListKey); tmp != nil {
+		list = tmp.(*ast.FootnoteList)
+	}
+	if tmp := pc.Get(footnoteLinkListKey); tmp != nil {
+		fnlist = tmp.([]*ast.FootnoteLink)
+	}
+
+	pc.Set(footnoteListKey, nil)
+	pc.Set(footnoteLinkListKey, nil)
+
+	if list == nil {
 		return
 	}
-	pc.Set(footnoteListKey, nil)
+
+	counter := map[int]int{}
+	if fnlist != nil {
+		for _, fnlink := range fnlist {
+			if fnlink.Index >= 0 {
+				counter[fnlink.Index]++
+			}
+		}
+		for _, fnlink := range fnlist {
+			fnlink.RefCount = counter[fnlink.Index]
+		}
+	}
 	for footnote := list.FirstChild(); footnote != nil; {
 		var container gast.Node = footnote
 		next := footnote.NextSibling()
 		if fc := container.LastChild(); fc != nil && gast.IsParagraph(fc) {
 			container = fc
 		}
-		index := footnote.(*ast.Footnote).Index
+		fn := footnote.(*ast.Footnote)
+		index := fn.Index
 		if index < 0 {
 			list.RemoveChild(list, footnote)
 		} else {
-			container.AppendChild(container, ast.NewFootnoteBackLink(index))
+			backLink := ast.NewFootnoteBacklink(index)
+			backLink.RefCount = counter[index]
+			container.AppendChild(container, backLink)
 		}
 		footnote = next
 	}
@@ -214,19 +252,250 @@ func (a *footnoteASTTransformer) Transform(node *gast.Document, reader text.Read
 	node.AppendChild(node, list)
 }
 
+// FootnoteConfig holds configuration values for the footnote extension.
+//
+// Link* and Backlink* configurations have some variables:
+// Occurrances of “^^” in the string will be replaced by the
+// corresponding footnote number in the HTML output.
+// Occurrances of “%%” will be replaced by a number for the
+// reference (footnotes can have multiple references).
+type FootnoteConfig struct {
+	html.Config
+
+	// IDPrefix is a prefix for the id attributes generated by footnotes.
+	IDPrefix []byte
+
+	// IDPrefix is a function that determines the id attribute for given Node.
+	IDPrefixFunction func(gast.Node) []byte
+
+	// LinkTitle is an optional title attribute for footnote links.
+	LinkTitle []byte
+
+	// BacklinkTitle is an optional title attribute for footnote backlinks.
+	BacklinkTitle []byte
+
+	// LinkClass is a class for footnote links.
+	LinkClass []byte
+
+	// BacklinkClass is a class for footnote backlinks.
+	BacklinkClass []byte
+
+	// BacklinkHTML is an HTML content for footnote backlinks.
+	BacklinkHTML []byte
+}
+
+// FootnoteOption interface is a functional option interface for the extension.
+type FootnoteOption interface {
+	renderer.Option
+	// SetFootnoteOption sets given option to the extension.
+	SetFootnoteOption(*FootnoteConfig)
+}
+
+// NewFootnoteConfig returns a new Config with defaults.
+func NewFootnoteConfig() FootnoteConfig {
+	return FootnoteConfig{
+		Config:        html.NewConfig(),
+		LinkTitle:     []byte(""),
+		BacklinkTitle: []byte(""),
+		LinkClass:     []byte("footnote-ref"),
+		BacklinkClass: []byte("footnote-backref"),
+		BacklinkHTML:  []byte("&#x21a9;&#xfe0e;"),
+	}
+}
+
+// SetOption implements renderer.SetOptioner.
+func (c *FootnoteConfig) SetOption(name renderer.OptionName, value interface{}) {
+	switch name {
+	case optFootnoteIDPrefixFunction:
+		c.IDPrefixFunction = value.(func(gast.Node) []byte)
+	case optFootnoteIDPrefix:
+		c.IDPrefix = value.([]byte)
+	case optFootnoteLinkTitle:
+		c.LinkTitle = value.([]byte)
+	case optFootnoteBacklinkTitle:
+		c.BacklinkTitle = value.([]byte)
+	case optFootnoteLinkClass:
+		c.LinkClass = value.([]byte)
+	case optFootnoteBacklinkClass:
+		c.BacklinkClass = value.([]byte)
+	case optFootnoteBacklinkHTML:
+		c.BacklinkHTML = value.([]byte)
+	default:
+		c.Config.SetOption(name, value)
+	}
+}
+
+type withFootnoteHTMLOptions struct {
+	value []html.Option
+}
+
+func (o *withFootnoteHTMLOptions) SetConfig(c *renderer.Config) {
+	if o.value != nil {
+		for _, v := range o.value {
+			v.(renderer.Option).SetConfig(c)
+		}
+	}
+}
+
+func (o *withFootnoteHTMLOptions) SetFootnoteOption(c *FootnoteConfig) {
+	if o.value != nil {
+		for _, v := range o.value {
+			v.SetHTMLOption(&c.Config)
+		}
+	}
+}
+
+// WithFootnoteHTMLOptions is functional option that wraps goldmark HTMLRenderer options.
+func WithFootnoteHTMLOptions(opts ...html.Option) FootnoteOption {
+	return &withFootnoteHTMLOptions{opts}
+}
+
+const optFootnoteIDPrefix renderer.OptionName = "FootnoteIDPrefix"
+
+type withFootnoteIDPrefix struct {
+	value []byte
+}
+
+func (o *withFootnoteIDPrefix) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteIDPrefix] = o.value
+}
+
+func (o *withFootnoteIDPrefix) SetFootnoteOption(c *FootnoteConfig) {
+	c.IDPrefix = o.value
+}
+
+// WithFootnoteIDPrefix is a functional option that is a prefix for the id attributes generated by footnotes.
+func WithFootnoteIDPrefix(a []byte) FootnoteOption {
+	return &withFootnoteIDPrefix{a}
+}
+
+const optFootnoteIDPrefixFunction renderer.OptionName = "FootnoteIDPrefixFunction"
+
+type withFootnoteIDPrefixFunction struct {
+	value func(gast.Node) []byte
+}
+
+func (o *withFootnoteIDPrefixFunction) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteIDPrefixFunction] = o.value
+}
+
+func (o *withFootnoteIDPrefixFunction) SetFootnoteOption(c *FootnoteConfig) {
+	c.IDPrefixFunction = o.value
+}
+
+// WithFootnoteIDPrefixFunction is a functional option that is a prefix for the id attributes generated by footnotes.
+func WithFootnoteIDPrefixFunction(a func(gast.Node) []byte) FootnoteOption {
+	return &withFootnoteIDPrefixFunction{a}
+}
+
+const optFootnoteLinkTitle renderer.OptionName = "FootnoteLinkTitle"
+
+type withFootnoteLinkTitle struct {
+	value []byte
+}
+
+func (o *withFootnoteLinkTitle) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteLinkTitle] = o.value
+}
+
+func (o *withFootnoteLinkTitle) SetFootnoteOption(c *FootnoteConfig) {
+	c.LinkTitle = o.value
+}
+
+// WithFootnoteLinkTitle is a functional option that is an optional title attribute for footnote links.
+func WithFootnoteLinkTitle(a []byte) FootnoteOption {
+	return &withFootnoteLinkTitle{a}
+}
+
+const optFootnoteBacklinkTitle renderer.OptionName = "FootnoteBacklinkTitle"
+
+type withFootnoteBacklinkTitle struct {
+	value []byte
+}
+
+func (o *withFootnoteBacklinkTitle) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteBacklinkTitle] = o.value
+}
+
+func (o *withFootnoteBacklinkTitle) SetFootnoteOption(c *FootnoteConfig) {
+	c.BacklinkTitle = o.value
+}
+
+// WithFootnoteBacklinkTitle is a functional option that is an optional title attribute for footnote backlinks.
+func WithFootnoteBacklinkTitle(a []byte) FootnoteOption {
+	return &withFootnoteBacklinkTitle{a}
+}
+
+const optFootnoteLinkClass renderer.OptionName = "FootnoteLinkClass"
+
+type withFootnoteLinkClass struct {
+	value []byte
+}
+
+func (o *withFootnoteLinkClass) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteLinkClass] = o.value
+}
+
+func (o *withFootnoteLinkClass) SetFootnoteOption(c *FootnoteConfig) {
+	c.LinkClass = o.value
+}
+
+// WithFootnoteLinkClass is a functional option that is a class for footnote links.
+func WithFootnoteLinkClass(a []byte) FootnoteOption {
+	return &withFootnoteLinkClass{a}
+}
+
+const optFootnoteBacklinkClass renderer.OptionName = "FootnoteBacklinkClass"
+
+type withFootnoteBacklinkClass struct {
+	value []byte
+}
+
+func (o *withFootnoteBacklinkClass) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteBacklinkClass] = o.value
+}
+
+func (o *withFootnoteBacklinkClass) SetFootnoteOption(c *FootnoteConfig) {
+	c.BacklinkClass = o.value
+}
+
+// WithFootnoteBacklinkClass is a functional option that is a class for footnote backlinks.
+func WithFootnoteBacklinkClass(a []byte) FootnoteOption {
+	return &withFootnoteBacklinkClass{a}
+}
+
+const optFootnoteBacklinkHTML renderer.OptionName = "FootnoteBacklinkHTML"
+
+type withFootnoteBacklinkHTML struct {
+	value []byte
+}
+
+func (o *withFootnoteBacklinkHTML) SetConfig(c *renderer.Config) {
+	c.Options[optFootnoteBacklinkHTML] = o.value
+}
+
+func (o *withFootnoteBacklinkHTML) SetFootnoteOption(c *FootnoteConfig) {
+	c.BacklinkHTML = o.value
+}
+
+// WithFootnoteBacklinkHTML is an HTML content for footnote backlinks.
+func WithFootnoteBacklinkHTML(a []byte) FootnoteOption {
+	return &withFootnoteBacklinkHTML{a}
+}
+
 // FootnoteHTMLRenderer is a renderer.NodeRenderer implementation that
 // renders FootnoteLink nodes.
 type FootnoteHTMLRenderer struct {
-	html.Config
+	FootnoteConfig
 }
 
 // NewFootnoteHTMLRenderer returns a new FootnoteHTMLRenderer.
-func NewFootnoteHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
+func NewFootnoteHTMLRenderer(opts ...FootnoteOption) renderer.NodeRenderer {
 	r := &FootnoteHTMLRenderer{
-		Config: html.NewConfig(),
+		FootnoteConfig: NewFootnoteConfig(),
 	}
 	for _, opt := range opts {
-		opt.SetHTMLOption(&r.Config)
+		opt.SetFootnoteOption(&r.FootnoteConfig)
 	}
 	return r
 }
@@ -234,7 +503,7 @@ func NewFootnoteHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
 // RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
 func (r *FootnoteHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
 	reg.Register(ast.KindFootnoteLink, r.renderFootnoteLink)
-	reg.Register(ast.KindFootnoteBackLink, r.renderFootnoteBackLink)
+	reg.Register(ast.KindFootnoteBacklink, r.renderFootnoteBacklink)
 	reg.Register(ast.KindFootnote, r.renderFootnote)
 	reg.Register(ast.KindFootnoteList, r.renderFootnoteList)
 }
@@ -243,25 +512,45 @@ func (r *FootnoteHTMLRenderer) renderFootnoteLink(w util.BufWriter, source []byt
 	if entering {
 		n := node.(*ast.FootnoteLink)
 		is := strconv.Itoa(n.Index)
-		_, _ = w.WriteString(`<sup id="fnref:`)
+		_, _ = w.WriteString(`<sup id="`)
+		_, _ = w.Write(r.idPrefix(node))
+		_, _ = w.WriteString(`fnref:`)
 		_, _ = w.WriteString(is)
-		_, _ = w.WriteString(`"><a href="#fn:`)
+		_, _ = w.WriteString(`"><a href="#`)
+		_, _ = w.Write(r.idPrefix(node))
+		_, _ = w.WriteString(`fn:`)
 		_, _ = w.WriteString(is)
-		_, _ = w.WriteString(`" class="footnote-ref" role="doc-noteref">`)
+		_, _ = w.WriteString(`" class="`)
+		_, _ = w.Write(applyFootnoteTemplate(r.FootnoteConfig.LinkClass,
+			n.Index, n.RefCount))
+		if len(r.FootnoteConfig.LinkTitle) > 0 {
+			_, _ = w.WriteString(`" title="`)
+			_, _ = w.Write(util.EscapeHTML(applyFootnoteTemplate(r.FootnoteConfig.LinkTitle, n.Index, n.RefCount)))
+		}
+		_, _ = w.WriteString(`" role="doc-noteref">`)
+
 		_, _ = w.WriteString(is)
 		_, _ = w.WriteString(`</a></sup>`)
 	}
 	return gast.WalkContinue, nil
 }
 
-func (r *FootnoteHTMLRenderer) renderFootnoteBackLink(w util.BufWriter, source []byte, node gast.Node, entering bool) (gast.WalkStatus, error) {
+func (r *FootnoteHTMLRenderer) renderFootnoteBacklink(w util.BufWriter, source []byte, node gast.Node, entering bool) (gast.WalkStatus, error) {
 	if entering {
-		n := node.(*ast.FootnoteBackLink)
+		n := node.(*ast.FootnoteBacklink)
 		is := strconv.Itoa(n.Index)
-		_, _ = w.WriteString(` <a href="#fnref:`)
+		_, _ = w.WriteString(` <a href="#`)
+		_, _ = w.Write(r.idPrefix(node))
+		_, _ = w.WriteString(`fnref:`)
 		_, _ = w.WriteString(is)
-		_, _ = w.WriteString(`" class="footnote-backref" role="doc-backlink">`)
-		_, _ = w.WriteString("&#x21a9;&#xfe0e;")
+		_, _ = w.WriteString(`" class="`)
+		_, _ = w.Write(applyFootnoteTemplate(r.FootnoteConfig.BacklinkClass, n.Index, n.RefCount))
+		if len(r.FootnoteConfig.BacklinkTitle) > 0 {
+			_, _ = w.WriteString(`" title="`)
+			_, _ = w.Write(util.EscapeHTML(applyFootnoteTemplate(r.FootnoteConfig.BacklinkTitle, n.Index, n.RefCount)))
+		}
+		_, _ = w.WriteString(`" role="doc-backlink">`)
+		_, _ = w.Write(applyFootnoteTemplate(r.FootnoteConfig.BacklinkHTML, n.Index, n.RefCount))
 		_, _ = w.WriteString(`</a>`)
 	}
 	return gast.WalkContinue, nil
@@ -271,7 +560,9 @@ func (r *FootnoteHTMLRenderer) renderFootnote(w util.BufWriter, source []byte, n
 	n := node.(*ast.Footnote)
 	is := strconv.Itoa(n.Index)
 	if entering {
-		_, _ = w.WriteString(`<li id="fn:`)
+		_, _ = w.WriteString(`<li id="`)
+		_, _ = w.Write(r.idPrefix(node))
+		_, _ = w.WriteString(`fn:`)
 		_, _ = w.WriteString(is)
 		_, _ = w.WriteString(`" role="doc-endnote"`)
 		if node.Attributes() != nil {
@@ -312,11 +603,54 @@ func (r *FootnoteHTMLRenderer) renderFootnoteList(w util.BufWriter, source []byt
 	return gast.WalkContinue, nil
 }
 
+func (r *FootnoteHTMLRenderer) idPrefix(node gast.Node) []byte {
+	if r.FootnoteConfig.IDPrefix != nil {
+		return r.FootnoteConfig.IDPrefix
+	}
+	if r.FootnoteConfig.IDPrefixFunction != nil {
+		return r.FootnoteConfig.IDPrefixFunction(node)
+	}
+	return []byte("")
+}
+
+func applyFootnoteTemplate(b []byte, index, refCount int) []byte {
+	fast := true
+	for i, c := range b {
+		if i != 0 {
+			if b[i-1] == '^' && c == '^' {
+				fast = false
+				break
+			}
+			if b[i-1] == '%' && c == '%' {
+				fast = false
+				break
+			}
+		}
+	}
+	if fast {
+		return b
+	}
+	is := []byte(strconv.Itoa(index))
+	rs := []byte(strconv.Itoa(refCount))
+	ret := bytes.Replace(b, []byte("^^"), is, -1)
+	return bytes.Replace(ret, []byte("%%"), rs, -1)
+}
+
 type footnote struct {
+	options []FootnoteOption
 }
 
 // Footnote is an extension that allow you to use PHP Markdown Extra Footnotes.
-var Footnote = &footnote{}
+var Footnote = &footnote{
+	options: []FootnoteOption{},
+}
+
+// NewFootnote returns a new extension with given options.
+func NewFootnote(opts ...FootnoteOption) goldmark.Extender {
+	return &footnote{
+		options: opts,
+	}
+}
 
 func (e *footnote) Extend(m goldmark.Markdown) {
 	m.Parser().AddOptions(
@@ -331,6 +665,6 @@ func (e *footnote) Extend(m goldmark.Markdown) {
 		),
 	)
 	m.Renderer().AddOptions(renderer.WithNodeRenderers(
-		util.Prioritized(NewFootnoteHTMLRenderer(), 500),
+		util.Prioritized(NewFootnoteHTMLRenderer(e.options...), 500),
 	))
 }

vendor/github.com/yuin/goldmark/extension/linkify.go

@@ -11,9 +11,9 @@ import (
 	"github.com/yuin/goldmark/util"
 )
 
-var wwwURLRegxp = regexp.MustCompile(`^www\.[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]+(?:(?:/|[#?])[-a-zA-Z0-9@:%_\+.~#!?&//=\(\);,'">\^{}\[\]` + "`" + `]*)?`)
+var wwwURLRegxp = regexp.MustCompile(`^www\.[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]+(?:[/#?][-a-zA-Z0-9@:%_\+.~#!?&/=\(\);,'">\^{}\[\]` + "`" + `]*)?`)
 
-var urlRegexp = regexp.MustCompile(`^(?:http|https|ftp):\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]+(?:(?:/|[#?])[-a-zA-Z0-9@:%_+.~#$!?&//=\(\);,'">\^{}\[\]` + "`" + `]*)?`)
+var urlRegexp = regexp.MustCompile(`^(?:http|https|ftp)://[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]+(?::\d+)?(?:[/#?][-a-zA-Z0-9@:%_+.~#$!?&/=\(\);,'">\^{}\[\]` + "`" + `]*)?`)
 
 // An LinkifyConfig struct is a data structure that holds configuration of the
 // Linkify extension.

vendor/github.com/yuin/goldmark/extension/table.go

@@ -15,6 +15,13 @@ import (
 	"github.com/yuin/goldmark/util"
 )
 
+var escapedPipeCellListKey = parser.NewContextKey()
+
+type escapedPipeCell struct {
+	Cell *ast.TableCell
+	Pos  []int
+}
+
 // TableCellAlignMethod indicates how are table cells aligned in HTML format.indicates how are table cells aligned in HTML format.
 type TableCellAlignMethod int
 
@@ -148,7 +155,7 @@ func (b *tableParagraphTransformer) Transform(node *gast.Paragraph, reader text.
 		if alignments == nil {
 			continue
 		}
-		header := b.parseRow(lines.At(i-1), alignments, true, reader)
+		header := b.parseRow(lines.At(i-1), alignments, true, reader, pc)
 		if header == nil || len(alignments) != header.ChildCount() {
 			return
 		}
@@ -156,7 +163,7 @@ func (b *tableParagraphTransformer) Transform(node *gast.Paragraph, reader text.
 		table.Alignments = alignments
 		table.AppendChild(table, ast.NewTableHeader(header))
 		for j := i + 1; j < lines.Len(); j++ {
-			table.AppendChild(table, b.parseRow(lines.At(j), alignments, false, reader))
+			table.AppendChild(table, b.parseRow(lines.At(j), alignments, false, reader, pc))
 		}
 		node.Lines().SetSliced(0, i-1)
 		node.Parent().InsertAfter(node.Parent(), node, table)
@@ -170,7 +177,7 @@ func (b *tableParagraphTransformer) Transform(node *gast.Paragraph, reader text.
 	}
 }
 
-func (b *tableParagraphTransformer) parseRow(segment text.Segment, alignments []ast.Alignment, isHeader bool, reader text.Reader) *ast.TableRow {
+func (b *tableParagraphTransformer) parseRow(segment text.Segment, alignments []ast.Alignment, isHeader bool, reader text.Reader, pc parser.Context) *ast.TableRow {
 	source := reader.Source()
 	line := segment.Value(source)
 	pos := 0
@@ -194,18 +201,39 @@ func (b *tableParagraphTransformer) parseRow(segment text.Segment, alignments []
 		} else {
 			alignment = alignments[i]
 		}
-		closure := util.FindClosure(line[pos:], byte(0), '|', true, false)
-		if closure < 0 {
-			closure = len(line[pos:])
-		}
+
+		var escapedCell *escapedPipeCell
 		node := ast.NewTableCell()
-		seg := text.NewSegment(segment.Start+pos, segment.Start+pos+closure)
+		node.Alignment = alignment
+		hasBacktick := false
+		closure := pos
+		for ; closure < limit; closure++ {
+			if line[closure] == '`' {
+				hasBacktick = true
+			}
+			if line[closure] == '|' {
+				if closure == 0 || line[closure-1] != '\\' {
+					break
+				} else if hasBacktick {
+					if escapedCell == nil {
+						escapedCell = &escapedPipeCell{node, []int{}}
+						escapedList := pc.ComputeIfAbsent(escapedPipeCellListKey,
+							func() interface{} {
+								return []*escapedPipeCell{}
+							}).([]*escapedPipeCell)
+						escapedList = append(escapedList, escapedCell)
+						pc.Set(escapedPipeCellListKey, escapedList)
+					}
+					escapedCell.Pos = append(escapedCell.Pos, segment.Start+closure-1)
+				}
+			}
+		}
+		seg := text.NewSegment(segment.Start+pos, segment.Start+closure)
 		seg = seg.TrimLeftSpace(source)
 		seg = seg.TrimRightSpace(source)
 		node.Lines().Append(seg)
-		node.Alignment = alignment
 		row.AppendChild(row, node)
-		pos += closure + 1
+		pos = closure + 1
 	}
 	for ; i < len(alignments); i++ {
 		row.AppendChild(row, ast.NewTableCell())
@@ -243,6 +271,49 @@ func (b *tableParagraphTransformer) parseDelimiter(segment text.Segment, reader
 	return alignments
 }
 
+type tableASTTransformer struct {
+}
+
+var defaultTableASTTransformer = &tableASTTransformer{}
+
+// NewTableASTTransformer returns a parser.ASTTransformer for tables.
+func NewTableASTTransformer() parser.ASTTransformer {
+	return defaultTableASTTransformer
+}
+
+func (a *tableASTTransformer) Transform(node *gast.Document, reader text.Reader, pc parser.Context) {
+	lst := pc.Get(escapedPipeCellListKey)
+	if lst == nil {
+		return
+	}
+	pc.Set(escapedPipeCellListKey, nil)
+	for _, v := range lst.([]*escapedPipeCell) {
+		_ = gast.Walk(v.Cell, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+			if n.Kind() != gast.KindCodeSpan {
+				return gast.WalkContinue, nil
+			}
+			c := n.FirstChild()
+			for c != nil {
+				next := c.NextSibling()
+				if c.Kind() == gast.KindText {
+					t := c.(*gast.Text)
+					for _, pos := range v.Pos {
+						if t.Segment.Start <= pos && t.Segment.Stop > pos {
+							n1 := gast.NewRawTextSegment(t.Segment.WithStop(pos))
+							n2 := gast.NewRawTextSegment(t.Segment.WithStart(pos + 1))
+							n.InsertAfter(n, c, n1)
+							n.InsertAfter(n, n1, n2)
+							n.RemoveChild(n, c)
+						}
+					}
+				}
+				c = next
+			}
+			return gast.WalkContinue, nil
+		})
+	}
+}
+
 // TableHTMLRenderer is a renderer.NodeRenderer implementation that
 // renders Table nodes.
 type TableHTMLRenderer struct {
@@ -419,7 +490,7 @@ func (r *TableHTMLRenderer) renderTableCell(w util.BufWriter, source []byte, nod
 					cob.AppendByte(';')
 				}
 				style := fmt.Sprintf("text-align:%s", n.Alignment.String())
-				cob.Append(util.StringToReadOnlyBytes(style))
+				cob.AppendString(style)
 				n.SetAttributeString("style", cob.Bytes())
 			}
 		}
@@ -454,9 +525,14 @@ func NewTable(opts ...TableOption) goldmark.Extender {
 }
 
 func (e *table) Extend(m goldmark.Markdown) {
-	m.Parser().AddOptions(parser.WithParagraphTransformers(
-		util.Prioritized(NewTableParagraphTransformer(), 200),
-	))
+	m.Parser().AddOptions(
+		parser.WithParagraphTransformers(
+			util.Prioritized(NewTableParagraphTransformer(), 200),
+		),
+		parser.WithASTTransformers(
+			util.Prioritized(defaultTableASTTransformer, 0),
+		),
+	)
 	m.Renderer().AddOptions(renderer.WithNodeRenderers(
 		util.Prioritized(NewTableHTMLRenderer(e.options...), 500),
 	))

vendor/github.com/yuin/goldmark/go.mod

@@ -1,3 +1,3 @@
 module github.com/yuin/goldmark
 
-go 1.13
+go 1.15

vendor/github.com/yuin/goldmark/parser/link.go

@@ -2,7 +2,6 @@ package parser
 
 import (
 	"fmt"
-	"regexp"
 	"strings"
 
 	"github.com/yuin/goldmark/ast"
@@ -113,8 +112,6 @@ func (s *linkParser) Trigger() []byte {
 	return []byte{'!', '[', ']'}
 }
 
-var linkDestinationRegexp = regexp.MustCompile(`\s*([^\s].+)`)
-var linkTitleRegexp = regexp.MustCompile(`\s+(\)|["'\(].+)`)
 var linkBottom = NewContextKey()
 
 func (s *linkParser) Parse(parent ast.Node, block text.Reader, pc Context) ast.Node {
@@ -293,20 +290,17 @@ func (s *linkParser) parseLink(parent ast.Node, last *linkLabelState, block text
 func parseLinkDestination(block text.Reader) ([]byte, bool) {
 	block.SkipSpaces()
 	line, _ := block.PeekLine()
-	buf := []byte{}
 	if block.Peek() == '<' {
 		i := 1
 		for i < len(line) {
 			c := line[i]
 			if c == '\\' && i < len(line)-1 && util.IsPunct(line[i+1]) {
-				buf = append(buf, '\\', line[i+1])
 				i += 2
 				continue
 			} else if c == '>' {
 				block.Advance(i + 1)
 				return line[1:i], true
 			}
-			buf = append(buf, c)
 			i++
 		}
 		return nil, false
@@ -316,7 +310,6 @@ func parseLinkDestination(block text.Reader) ([]byte, bool) {
 	for i < len(line) {
 		c := line[i]
 		if c == '\\' && i < len(line)-1 && util.IsPunct(line[i+1]) {
-			buf = append(buf, '\\', line[i+1])
 			i += 2
 			continue
 		} else if c == '(' {
@@ -329,7 +322,6 @@ func parseLinkDestination(block text.Reader) ([]byte, bool) {
 		} else if util.IsSpace(c) {
 			break
 		}
-		buf = append(buf, c)
 		i++
 	}
 	block.Advance(i)

vendor/github.com/yuin/goldmark/parser/parser.go

@@ -138,6 +138,9 @@ type Context interface {
 	// 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{})
 
@@ -252,6 +255,15 @@ 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
 }

vendor/github.com/yuin/goldmark/parser/raw_html.go

@@ -2,10 +2,11 @@ package parser
 
 import (
 	"bytes"
+	"regexp"
+
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/text"
 	"github.com/yuin/goldmark/util"
-	"regexp"
 )
 
 type rawHTMLParser struct {
@@ -67,8 +68,6 @@ func (s *rawHTMLParser) parseSingleLineRegexp(reg *regexp.Regexp, block text.Rea
 	return node
 }
 
-var dummyMatch = [][]byte{}
-
 func (s *rawHTMLParser) parseMultiLineRegexp(reg *regexp.Regexp, block text.Reader, pc Context) ast.Node {
 	sline, ssegment := block.Position()
 	if block.Match(reg) {
@@ -102,7 +101,3 @@ func (s *rawHTMLParser) parseMultiLineRegexp(reg *regexp.Regexp, block text.Read
 	}
 	return nil
 }
-
-func (s *rawHTMLParser) CloseBlock(parent ast.Node, pc Context) {
-	// nothing to do
-}

vendor/github.com/yuin/goldmark/util/util.go

@@ -37,6 +37,12 @@ func (b *CopyOnWriteBuffer) Write(value []byte) {
 	b.buffer = append(b.buffer, value...)
 }
 
+// WriteString writes given string to the buffer.
+// WriteString allocate new buffer and clears it at the first time.
+func (b *CopyOnWriteBuffer) WriteString(value string) {
+	b.Write(StringToReadOnlyBytes(value))
+}
+
 // Append appends given bytes to the buffer.
 // Append copy buffer at the first time.
 func (b *CopyOnWriteBuffer) Append(value []byte) {
@@ -49,6 +55,12 @@ func (b *CopyOnWriteBuffer) Append(value []byte) {
 	b.buffer = append(b.buffer, value...)
 }
 
+// AppendString appends given string to the buffer.
+// AppendString copy buffer at the first time.
+func (b *CopyOnWriteBuffer) AppendString(value string) {
+	b.Append(StringToReadOnlyBytes(value))
+}
+
 // WriteByte writes the given byte to the buffer.
 // WriteByte allocate new buffer and clears it at the first time.
 func (b *CopyOnWriteBuffer) WriteByte(c byte) {
@@ -804,7 +816,7 @@ func IsPunct(c byte) bool {
 	return punctTable[c] == 1
 }
 
-// IsPunct returns true if the given rune is a punctuation, otherwise false.
+// IsPunctRune returns true if the given rune is a punctuation, otherwise false.
 func IsPunctRune(r rune) bool {
 	return int32(r) <= 256 && IsPunct(byte(r)) || unicode.IsPunct(r)
 }
@@ -814,7 +826,7 @@ func IsSpace(c byte) bool {
 	return spaceTable[c] == 1
 }
 
-// IsSpace returns true if the given rune is a space, otherwise false.
+// IsSpaceRune returns true if the given rune is a space, otherwise false.
 func IsSpaceRune(r rune) bool {
 	return int32(r) <= 256 && IsSpace(byte(r)) || unicode.IsSpace(r)
 }