\begin{frame}{Distributed Revision Control}
  Mercurial duplicates the history on many servers:
  \begin{center}
    \begin{tikzpicture}[remember picture]
      \tikzstyle{working copy}+=[below=3pt]

      \begin{scope}[xshift=-3cm]
        \node[repository] (a) {};
        \node[rev] (ar1) at (-7mm, 0) {};
        \node[rev] (ar2) at (0, 0) {};
        \draw[->] (ar1) -- (ar2);
      \end{scope}

      \begin{scope}[xshift=3cm]
        \node[repository] (b) {};
        \node[rev] (br1) at (-7mm, 0) {};
        \node[rev] (br2) at (0, 0) {};
        \node[rev] (br3) at (7mm, 0) {};
        \draw[->] (br1) -- (br2);
        \draw[->] (br2) -- (br3);
      \end{scope}

      \node[working copy] (wa) at (a.south) {
        hello.c\\
        Makefile
      };

      \node[working copy, text width=18mm] (wb) at (b.south) {
        goodbye.c\\
        Makefile
      };

      \begin{pgfonlayer}{background}
        \node[label=below:Alice, highlight, fit=(a) (wa)] {};
        \node[label=below:Bob, highlight, fit=(b) (wb)] {};
      \end{pgfonlayer}

      \node<2->[box, text width=6cm] at (current page.center) {
        Advantages:
        \begin{itemize}
        \item no network latency
        \item distributed, off-line operations
        \item no imposed workflow
        \end{itemize}

        Drawback(?):
        \begin{itemize}
        \item must synchronize repositories
        \end{itemize}
      };
    \end{tikzpicture}
  \end{center}
\end{frame}