The Debian packaging of s-el is maintained in git, using the merging
workflow described in dgit-maint-merge(7).  There isn't a patch queue
that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/s-el
    % cd s-el
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone s-el`, rather than plain `git
clone`.)

A single combined diff, containing all the changes, follows.
--- s-el-1.11.0.orig/s.el
+++ s-el-1.11.0/s.el
@@ -3,7 +3,7 @@
 ;; Copyright (C) 2012-2015 Magnar Sveen
 
 ;; Author: Magnar Sveen <magnars@gmail.com>
-;; Version: 1.10.0
+;; Version: 1.11.0
 ;; Keywords: strings
 
 ;; This program is free software; you can redistribute it and/or modify
