Add Repository Validation for local backend mountPath (#947)

apis/stash/v1alpha1/validator.go

@@ -89,5 +89,15 @@ func (r Repository) IsValid() error {
 			return fmt.Errorf("wipe out operation is not supported for B2 backend")
 		}
 	}
+
+	if r.Spec.Backend.Local != nil && r.Spec.Backend.Local.MountPath != "" {
+		parts := strings.Split(r.Spec.Backend.Local.MountPath, "/")
+		if len(parts) >= 2 && parts[1] == "stash" {
+			return fmt.Errorf("\n\t" +
+				"Error: Invalid `mountPath` specification for local backend.\n\t" +
+				"Reason: We have put `stash` binary  in the root directory. Hence, you can not use `/stash` or `/stash/*` as `mountPath` \n\t" +
+				"Hints: Use `/stash-backup` or anything else except the forbidden ones as `mountPath`.")
+		}
+	}
 	return nil
 }