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1 \chapter*{Preface}
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2 \addcontentsline{toc}{chapter}{Preface}
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3 \label{chap:preface}
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4
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5 Distributed revision control is a relatively new territory, and has
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6 thus far grown due to people's willingness to strike out into
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7 ill-charted territory.
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8
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9 I am writing a book about distributed revision control because I
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10 believe that it is an important subject that deserves a field guide.
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11 I chose to write about Mercurial because it is the easiest tool to
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12 learn the terrain with, and yet it scales to the demands of real,
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13 challenging environments where many other revision control tools fail.
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14
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15 \section{This book is a work in progress}
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16
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17 I am releasing this book while I am still writing it, in the hope that
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18 it will prove useful to others. I also hope that readers will
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19 contribute as they see fit.
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20
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21 \section{About the examples in this book}
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22
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23 This book takes an unusual approach to code samples. Every example is
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24 ``live''---each one is actually the result of a shell script that
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25 executes the Mercurial commands you see. Every time an image of the
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26 book is built from its sources, all the example scripts are
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27 automatically run, and their current results compared against their
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28 expected results.
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29
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30 The advantage of this approach is that the examples are always
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31 accurate; they describe \emph{exactly} the behaviour of the version of
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32 Mercurial that's mentioned at the front of the book. If I update the
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33 version of Mercurial that I'm documenting, and the output of some
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34 command changes, the build fails.
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35
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36 There is a small disadvantage to this approach, which is that the
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37 dates and times you'll see in examples tend to be ``squashed''
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38 together in a way that they wouldn't be if the same commands were
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39 being typed by a human. Where a human can issue no more than one
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40 command every few seconds, with any resulting timestamps
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41 correspondingly spread out, my automated example scripts run many
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42 commands in one second.
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43
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44 As an instance of this, several consecutive commits in an example can
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45 show up as having occurred during the same second. You can see this
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46 occur in the \hgext{bisect} example in section~\ref{sec:undo:bisect},
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47 for instance.
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48
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49 So when you're reading examples, don't place too much weight on the
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50 dates or times you see in the output of commands. But \emph{do} be
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51 confident that the behaviour you're seeing is consistent and
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52 reproducible.
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53
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54 \section{Colophon---this book is Free}
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55
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56 This book is licensed under the Open Publication License, and is
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57 produced entirely using Free Software tools. It is typeset with
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58 \LaTeX{}; illustrations are drawn and rendered with
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59 \href{http://www.inkscape.org/}{Inkscape}.
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60
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61 The complete source code for this book is published as a Mercurial
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62 repository, at \url{http://hg.serpentine.com/mercurial/book}.
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63
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64 %%% Local Variables:
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65 %%% mode: latex
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66 %%% TeX-master: "00book"
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67 %%% End:
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