Add sandbox branch to mage

mage_helpers/file_system.go

@@ -141,7 +141,7 @@ func CurrentEnv() string {
 		}
 	}
 
-	if env != "dev" && env != "stage" && env != "prod" {
+	if env != "dev" && env != "stage" && env != "sandbox" && env != "prod" {
 		env = "dev"
 	}
 	return env