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1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
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2
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3 <preface id="chap.preface">
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4 <title>Preface</title>
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5
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6 <para>Distributed revision control is a relatively new territory,
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7 and has thus far grown due to people's willingness to strike out
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8 into ill-charted territory.</para>
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9
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10 <para>I am writing a book about distributed revision control because
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11 I believe that it is an important subject that deserves a field
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12 guide. I chose to write about Mercurial because it is the easiest
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13 tool to learn the terrain with, and yet it scales to the demands
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14 of real, challenging environments where many other revision
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15 control tools fail.</para>
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16
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17 <sect1>
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18 <title>This book is a work in progress</title>
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19
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20 <para>I am releasing this book while I am still writing it, in the
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21 hope that it will prove useful to others. I also hope that
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22 readers will contribute as they see fit.</para>
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23
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24 </sect1>
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25 <sect1>
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26 <title>About the examples in this book</title>
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27
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28 <para>This book takes an unusual approach to code samples. Every
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29 example is <quote>live</quote>---each one is actually the result
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30 of a shell script that executes the Mercurial commands you see.
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31 Every time an image of the book is built from its sources, all
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32 the example scripts are automatically run, and their current
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33 results compared against their expected results.</para>
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34
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35 <para>The advantage of this approach is that the examples are
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36 always accurate; they describe <emphasis>exactly</emphasis> the
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37 behaviour of the version of Mercurial that's mentioned at the
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38 front of the book. If I update the version of Mercurial that
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39 I'm documenting, and the output of some command changes, the
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40 build fails.</para>
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41
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42 <para>There is a small disadvantage to this approach, which is
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43 that the dates and times you'll see in examples tend to be
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44 <quote>squashed</quote> together in a way that they wouldn't be
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45 if the same commands were being typed by a human. Where a human
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46 can issue no more than one command every few seconds, with any
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47 resulting timestamps correspondingly spread out, my automated
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48 example scripts run many commands in one second.</para>
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49
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50 <para>As an instance of this, several consecutive commits in an
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51 example can show up as having occurred during the same second.
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52 You can see this occur in the <literal
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53 role="hg-ext">bisect</literal> example in section <xref
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54 id="sec.undo.bisect"/>, for instance.</para>
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55
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56 <para>So when you're reading examples, don't place too much weight
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57 on the dates or times you see in the output of commands. But
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58 <emphasis>do</emphasis> be confident that the behaviour you're
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59 seeing is consistent and reproducible.</para>
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60
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61 </sect1>
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62 <sect1>
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63 <title>Colophon---this book is Free</title>
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64
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65 <para>This book is licensed under the Open Publication License,
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66 and is produced entirely using Free Software tools. It is
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67 typeset with \LaTeX{}; illustrations are drawn and rendered with
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68 <ulink url="http://www.inkscape.org/">Inkscape</ulink>.</para>
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69
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70 <para>The complete source code for this book is published as a
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71 Mercurial repository, at <ulink
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72 url="http://hg.serpentine.com/mercurial/book">http://hg.serpentine.com/mercurial/book</ulink>.</para>
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73
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74 </sect1>
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75 </preface>
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76 <!--
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77 local variables:
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78 sgml-parent-document: ("00book.xml" "book" "preface")
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79 end:
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80 -->
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