Fix handling of taxonomy terms containing slashes

Fixes #4090

helpers/path.go

@@ -74,6 +74,35 @@ func (filepathBridge) Separator() string {
 
 var fpb filepathBridge
 
+// segmentReplacer replaces some URI-reserved characters in a path segments.
+var segmentReplacer = strings.NewReplacer("/", "-", "#", "-")
+
+// MakeSegment returns a copy of string s that is appropriate for a path
+// segment.  MakeSegment is similar to MakePath but disallows the '/' and
+// '#' characters because of their reserved meaning in URIs.
+func (p *PathSpec) MakeSegment(s string) string {
+	s = p.MakePathSanitized(strings.Trim(segmentReplacer.Replace(s), "- "))
+
+	var pos int
+	var last byte
+	b := make([]byte, len(s))
+
+	for i := 0; i < len(s); i++ {
+		// consolidate dashes
+		if s[i] == '-' && last == '-' {
+			continue
+		}
+
+		b[pos], last = s[i], s[i]
+		pos++
+	}
+
+	if p.DisablePathToLower {
+		return string(b[:pos])
+	}
+	return strings.ToLower(string(b[:pos]))
+}
+
 // MakePath takes a string with any characters and replace it
 // so the string could be used in a path.
 // It does so by creating a Unicode-sanitized string, with the spaces replaced,