Skip non-file inputs when using --diff

src/printer.rs

@@ -101,7 +101,7 @@ impl<'a> InteractivePrinter<'a> {
         config: &'a Config,
         assets: &'a HighlightingAssets,
         input: &mut OpenedInput,
-        #[cfg(feature = "git")] line_changes: &'a Option<LineChanges>,
+        line_changes: &'a Option<LineChanges>,
     ) -> Self {
         let theme = assets.get_theme(&config.theme);