*: cleaner Parent handling

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

hierarchy.go

@@ -3,6 +3,7 @@ package mtree
 import (
 	"fmt"
 	"io"
+	"path/filepath"
 	"sort"
 	"strings"
 )
@@ -45,6 +46,13 @@ type Entry struct {
 	Type          EntryType
 }
 
+func (e Entry) Path() string {
+	if e.Parent == nil {
+		return e.Name
+	}
+	return filepath.Join(e.Parent.Path(), e.Name)
+}
+
 func (e Entry) String() string {
 	if e.Raw != "" {
 		return e.Raw