fs: add OverrideDirectory for overriding path of directory

fs/override_dir.go

@@ -0,0 +1,34 @@
+package fs
+
+// OverrideDirectory is a wrapper to override the Remote for an
+// Directory
+type OverrideDirectory struct {
+	Directory
+	remote string
+}
+
+// NewOverrideDirectory returns an OverrideDirectoryObject which will
+// return the remote specified
+func NewOverrideDirectory(oi Directory, remote string) *OverrideDirectory {
+	// re-wrap an OverrideDirectory
+	if or, ok := oi.(*OverrideDirectory); ok {
+		return &OverrideDirectory{
+			Directory: or.Directory,
+			remote:    remote,
+		}
+	}
+	return &OverrideDirectory{
+		Directory: oi,
+		remote:    remote,
+	}
+}
+
+// Remote returns the overridden remote name
+func (o *OverrideDirectory) Remote() string {
+	return o.remote
+}
+
+// String returns the overridden remote name
+func (o *OverrideDirectory) String() string {
+	return o.remote
+}

fs/override_dir_test.go

@@ -0,0 +1,4 @@
+package fs
+
+// Check interfaces satisfied
+var _ Directory = (*OverrideDirectory)(nil)