Better error handling for list dir and cli

src/file/file.odin

@@ -5,12 +5,26 @@ import "core:os"
 
 // -----------------------------------------
 
-get_working_dir :: proc(allocator := context.allocator) -> string {
+Error :: union #shared_nil {
+	os.Error,
+	File_Error,
+}
+
+File_Error :: enum u8 {
+	None            = 0,
+	Not_A_Directory = 1,
+	Unimplemented   = 127,
+	Okay            = None,
+}
+
+// -----------------------------------------
+
+get_working_dir :: proc(allocator := context.allocator) -> (string, Error) {
 	wd, err := os.get_working_directory(allocator)
 	if err != nil {
 		fmt.eprintln("error: get working directory failed:", err)
-		os.exit(1)
+		return {}, err
 	}
 
-	return wd
+	return wd, nil
 }