Prevent `.max-width-marker` to break layout on mobile

app/assets/stylesheets/pages/commit.scss

@@ -90,6 +90,7 @@
   position: relative;
   font-family: $monospace_font;
   $left: 12px;
+  overflow: hidden; // Issue #13987
   .max-width-marker {
     width: 72ch;
     color: rgba(0, 0, 0, 0.0);