revert changes to mv, just keep overwrite option

vlib/os/os.v

@@ -138,24 +138,10 @@ pub fn mv_by_cp(source string, target string, opts MvParams) ! {
 
 // mv moves files or folders from `src` to `dst`.
 pub fn mv(source string, target string, opts MvParams) ! {
-	mut dst := target
 	if !opts.overwrite && exists(target) {
 		return error('Destination path already exist')
 	}
-	if exists(target) {
-		if source != target {
-			if !is_dir(target) {
-				rm(target)!
-			} else if is_dir(source) {
-				if is_dir_empty(source) {
-					rmdir_all(target)!
-				} else {
-					dst = join_path_single(target, file_name(source))
-				}
-			}
-		}
-	}
-	rename(source, dst) or { mv_by_cp(source, target, opts)! }
+	rename(source, target) or { mv_by_cp(source, target, opts)! }
 }
 
 // read_lines reads the file in `path` into an array of lines.