Rewrite markdown rendering to blackfriday v2 and rewrite orgmode rendering to go-org (#8560)

* Rewrite markdown rendering to blackfriday v2.0

* Fix style

* Fix go mod with golang 1.13

* Fix blackfriday v2 import

* Inital orgmode renderer migration to go-org

* Vendor go-org dependency

* Ignore errors :/

* Update go-org to latest version

* Update test

* Fix go-org test

* Remove unneeded code

* Fix comments

* Fix markdown test

* Fix blackfriday regression rendering HTML block

vendor/github.com/niklasfasching/go-org/org/headline.go

@@ -0,0 +1,101 @@
+package org
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+	"unicode"
+)
+
+type Outline struct {
+	*Section
+	last  *Section
+	count int
+}
+
+type Section struct {
+	Headline *Headline
+	Parent   *Section
+	Children []*Section
+}
+
+type Headline struct {
+	Index      int
+	Lvl        int
+	Status     string
+	Priority   string
+	Properties *PropertyDrawer
+	Title      []Node
+	Tags       []string
+	Children   []Node
+}
+
+var headlineRegexp = regexp.MustCompile(`^([*]+)\s+(.*)`)
+var tagRegexp = regexp.MustCompile(`(.*?)\s+(:[A-Za-z0-9_@#%:]+:\s*$)`)
+
+func lexHeadline(line string) (token, bool) {
+	if m := headlineRegexp.FindStringSubmatch(line); m != nil {
+		return token{"headline", len(m[1]), m[2], m}, true
+	}
+	return nilToken, false
+}
+
+func (d *Document) parseHeadline(i int, parentStop stopFn) (int, Node) {
+	t, headline := d.tokens[i], Headline{}
+	headline.Lvl = t.lvl
+
+	headline.Index = d.addHeadline(&headline)
+
+	text := t.content
+	todoKeywords := strings.FieldsFunc(d.Get("TODO"), func(r rune) bool { return unicode.IsSpace(r) || r == '|' })
+	for _, k := range todoKeywords {
+		if strings.HasPrefix(text, k) && len(text) > len(k) && unicode.IsSpace(rune(text[len(k)])) {
+			headline.Status = k
+			text = text[len(k)+1:]
+			break
+		}
+	}
+
+	if len(text) >= 4 && text[0:2] == "[#" && strings.Contains("ABC", text[2:3]) && text[3] == ']' {
+		headline.Priority = text[2:3]
+		text = strings.TrimSpace(text[4:])
+	}
+
+	if m := tagRegexp.FindStringSubmatch(text); m != nil {
+		text = m[1]
+		headline.Tags = strings.FieldsFunc(m[2], func(r rune) bool { return r == ':' })
+	}
+
+	headline.Title = d.parseInline(text)
+
+	stop := func(d *Document, i int) bool {
+		return parentStop(d, i) || d.tokens[i].kind == "headline" && d.tokens[i].lvl <= headline.Lvl
+	}
+	consumed, nodes := d.parseMany(i+1, stop)
+	if len(nodes) > 0 {
+		if d, ok := nodes[0].(PropertyDrawer); ok {
+			headline.Properties = &d
+			nodes = nodes[1:]
+		}
+	}
+	headline.Children = nodes
+	return consumed + 1, headline
+}
+
+func (h Headline) ID() string {
+	if customID, ok := h.Properties.Get("CUSTOM_ID"); ok {
+		return customID
+	}
+	return fmt.Sprintf("headline-%d", h.Index)
+}
+
+func (parent *Section) add(current *Section) {
+	if parent.Headline == nil || parent.Headline.Lvl < current.Headline.Lvl {
+		parent.Children = append(parent.Children, current)
+		current.Parent = parent
+	} else {
+		parent.Parent.add(current)
+	}
+}
+
+func (n Headline) String() string { return orgWriter.nodesAsString(n) }