\begin{frame}{Maintaining Patch Series}
  The \ext{mq} extension makes it easy to maintain a patch series:
  \begin{center}
    \begin{tikzpicture}[start chain=stack going above, node distance=5mm]
      \tikzstyle{rev}+=[on chain,join]
      \tikzstyle{patch}=[rev,
        draw=green!30!black!50, bottom color=green!30!black!20]
      \path[use as bounding box] (0,0) -- (0, 4.5);

      \node[on chain] {$\vdots$};
      \node[rev] {};
      \node<2->[patch] {code};
      \node<3->[patch] {test};
      \node<4->[patch] {doc};

      \draw<5->[->] ([xshift=-1cm] stack-3.center)
        -- node[left, anchor=mid east] {\cmd{qpush}}
                    ([xshift=-1cm] stack-5.center);
      \draw<5->[->] ([xshift=1cm] stack-5.center)
        -- node[right, anchor=mid west] {\cmd{qpop}}
                    ([xshift=1cm] stack-3.center);
    \end{tikzpicture}
  \end{center}
  Works nicely for local modification for upstream sources.
\end{frame}