feat: hiding only directories instead of files (#175)

A `--hidden` pattern with `/` suffix means hiding only directories not files.
A `--hidden` pattern without `/` will hide matching files and directories.

tests/fixtures.rs

@@ -65,6 +65,7 @@ pub fn tmpdir() -> TempDir {
             }
         }
     }
+    tmpdir.child("dir4/hidden").touch().unwrap();
 
     tmpdir
 }