Fix infinite recursive call

fmt.Sprint would call the String function on the FileMode, which
again would call fmt.Sprint, looping like this forever.

Instead, we now call the String function that's already implemented
on os.FileMode

Author: SimonBarendse

internals/cli/filemode/filemode.go

@@ -2,7 +2,6 @@
 package filemode
 
 import (
-	"fmt"
 	"os"
 	"strconv"
 
@@ -48,7 +47,7 @@ func (m *FileMode) Set(value string) error {
 
 // String implements the flag.Value interface.
 func (m FileMode) String() string {
-	return fmt.Sprint(m)
+	return m.FileMode().String()
 }
 
 // FileMode returns the file mode as an os.FileMode.