main: switch to urfave/cli/v2

For now this is a drop in replacement for all the flags curently
implemented

Fixes: #171

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

vendor/github.com/russross/blackfriday/v2/esc.go

@@ -0,0 +1,70 @@
+package blackfriday
+
+import (
+	"html"
+	"io"
+)
+
+var htmlEscaper = [256][]byte{
+	'&': []byte("&"),
+	'<': []byte("&lt;"),
+	'>': []byte("&gt;"),
+	'"': []byte("&quot;"),
+}
+
+func escapeHTML(w io.Writer, s []byte) {
+	escapeEntities(w, s, false)
+}
+
+func escapeAllHTML(w io.Writer, s []byte) {
+	escapeEntities(w, s, true)
+}
+
+func escapeEntities(w io.Writer, s []byte, escapeValidEntities bool) {
+	var start, end int
+	for end < len(s) {
+		escSeq := htmlEscaper[s[end]]
+		if escSeq != nil {
+			isEntity, entityEnd := nodeIsEntity(s, end)
+			if isEntity && !escapeValidEntities {
+				w.Write(s[start : entityEnd+1])
+				start = entityEnd + 1
+			} else {
+				w.Write(s[start:end])
+				w.Write(escSeq)
+				start = end + 1
+			}
+		}
+		end++
+	}
+	if start < len(s) && end <= len(s) {
+		w.Write(s[start:end])
+	}
+}
+
+func nodeIsEntity(s []byte, end int) (isEntity bool, endEntityPos int) {
+	isEntity = false
+	endEntityPos = end + 1
+
+	if s[end] == '&' {
+		for endEntityPos < len(s) {
+			if s[endEntityPos] == ';' {
+				if entities[string(s[end:endEntityPos+1])] {
+					isEntity = true
+					break
+				}
+			}
+			if !isalnum(s[endEntityPos]) && s[endEntityPos] != '&' && s[endEntityPos] != '#' {
+				break
+			}
+			endEntityPos++
+		}
+	}
+
+	return isEntity, endEntityPos
+}
+
+func escLink(w io.Writer, text []byte) {
+	unesc := html.UnescapeString(string(text))
+	escapeHTML(w, []byte(unesc))
+}