\begin{frame}{Branches in SVN}
  Subversion knows nothing about branches!
  \begin{itemize}
  \item but SVN has a cheap copy mechanism
  \item used for tags and branches
  \end{itemize}

  \begin{tikzpicture}
    \node<2->[working copy, below, text width=20mm, label=above:r10]
             (a) at (0, 0) {
      trunk/\\
      \quad hello.c\\
      \quad Makefile\\
      branches/\\
      tags/
    };
    \node<3->[working copy, below, text width=25mm, label=above:r11]
             (b) at (3.5, 0) {
      trunk/\\
      \quad hello.c\\
      \quad Makefile\\
      branches/\\
      \quad \alert<3>{goodbye/}\\
      \qquad \alert<3>{hello.c}\\
      \qquad \alert<3>{Makefile}\\
      tags/
    };
    \node<4->[working copy, below, text width=30mm, label=above:r12]
             (c) at (7.5, 0) {
      trunk/\\
      \quad hello.c\\
      \quad Makefile\\
      branches/\\
      \quad goodbye/\\
      \qquad hello.c\\
      \qquad \alert<4>{goodbye.c}\\
      \qquad Makefile\\
      tags/
    };

    \tikzstyle{s}=[yshift=-5mm]
    \tikzstyle{every pin edge}=[draw, red, <-]

    \draw<3->[->, short] ([s] a.north east) -- ([s] b.north west);
    \draw<4->[->, short] ([s] b.north east) -- ([s] c.north west);
  \end{tikzpicture}
\end{frame}