Partial merge of devmapper/ in order to integrate it as a backend

plugin.

The merge is inert, in other words the devmapper code is not called
and the primary aufs backend is untouched.

utils/utils.go

@@ -1114,6 +1114,41 @@ func (e *StatusError) Error() string {
 	return fmt.Sprintf("Status: %d", e.Status)
 }
 
+func quote(word string, buf *bytes.Buffer) {
+	// Bail out early for "simple" strings
+	if word != "" && !strings.ContainsAny(word, "\\'\"`${[|&;<>()~*?! \t\n") {
+		buf.WriteString(word)
+		return
+	}
+
+	buf.WriteString("'")
+
+	for i := 0; i < len(word); i++ {
+		b := word[i]
+		if b == '\'' {
+			// Replace literal ' with a close ', a \', and a open '
+			buf.WriteString("'\\''")
+		} else {
+			buf.WriteByte(b)
+		}
+	}
+
+	buf.WriteString("'")
+}
+
+// Take a list of strings and escape them so they will be handled right
+// when passed as arguments to an program via a shell
+func ShellQuoteArguments(args []string) string {
+	var buf bytes.Buffer
+	for i, arg := range args {
+		if i != 0 {
+			buf.WriteByte(' ')
+		}
+		quote(arg, &buf)
+	}
+	return buf.String()
+}
+
 func IsClosedError(err error) bool {
 	/* This comparison is ugly, but unfortunately, net.go doesn't export errClosing.
 	 * See: