Remove frontmatter interface

Former-commit-id: bd8ab54a13b08f223cc00a5372dc885c5b7b49e6 [formerly 169211b32940ffa9a157bf140579e1946b8df75d] [formerly 1795b434a35c2f9dc3c6940b7555542f62f3d74d [formerly 1ae2afb9985b82c7c101395c8a65fd122200c808]]
Former-commit-id: 1ed1a0402184384c37b80d51ef1460d036d5201e [formerly e068d59a1b531635e6ccad4d2203c1ef9eab7c86]
Former-commit-id: 391cbcefcd6b9f98b054bc02aec5cf808ccd199f

frontmatter/runes.go

@@ -1,7 +1,6 @@
 package frontmatter
 
 import (
-	"errors"
 	"strings"
 )
 
@@ -27,31 +26,3 @@ func AppendRune(frontmatter string, mark rune) string {
 
 	return frontmatter
 }
-
-// RuneToStringFormat converts the rune to a string with the format
-func RuneToStringFormat(mark rune) (string, error) {
-	switch mark {
-	case '-':
-		return "yaml", nil
-	case '+':
-		return "toml", nil
-	case '{', '}':
-		return "json", nil
-	default:
-		return "", errors.New("Unsupported format type")
-	}
-}
-
-// StringFormatToRune converts the format name to its rune
-func StringFormatToRune(format string) (rune, error) {
-	switch format {
-	case "yaml":
-		return '-', nil
-	case "toml":
-		return '+', nil
-	case "json":
-		return '{', nil
-	default:
-		return '0', errors.New("Unsupported format type")
-	}
-}