Revert c73aa1a

Fixes #4878

Author: maximd-g

opengrok-web/src/main/java/org/opengrok/web/PageConfig.java

@@ -1845,6 +1845,15 @@ public boolean isNotModified(HttpServletRequest request, HttpServletResponse res
         return false;
     }
 
+    /**
+     * @param root root path
+     * @param path path
+     * @return path relative to root
+     */
+    public static String getRelativePath(String root, String path) {
+        return Paths.get(root).relativize(Paths.get(path)).toString();
+    }
+
     @VisibleForTesting @NotNull String getEtag() {
         return String.format("W/\"%s\"",
                 Objects.hash(