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1 \chapter{Introduction}
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2 \label{chap:intro}
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3
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4 \section{About revision control}
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5
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6 Revision control is the management of multiple versions of a piece of
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7 information. In its simplest form, it's a process that many people
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8 perform by hand: every time you modify a file, save it under a new
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9 name that contains a number, each one higher than the number of the
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10 preceding version.
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11
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12 Manually managing multiple versions of even a single file is an
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13 error-prone task, though, so software tools to help automate this
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14 process have long been available. The earliest automated revision
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15 control tools were intended to help a single user to manage revisions
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16 to a single file. Over the past several decades, the scope of
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17 revision control tools has expanded greatly; they now manage multiple
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18 files, and help multiple people to work together. The best modern
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19 revision control tools will have no problem coping with thousands of
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20 people working together on a single project, which might consist of
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21 hundreds of thousands of files.
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22
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23 \subsection{Why use revision control?}
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24
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25 There are a number of reasons why you or your team might want to use
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26 an automated revision control tool for a project.
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27 \begin{itemize}
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28 \item The software gives you a unified way of working with your
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29 project's files, and a single place to look in.
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30 \item When you're working with other people, it will make it easier
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31 for you to collaborate. When people more or less simultaneously
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32 make potentially incompatible changes, the software will help you to
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33 identify and resolve those conflicts.
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34 \item It will track the history of your project. For every change,
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35 you'll have a log of \emph{who} made it; \emph{why} they made it;
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36 \emph{when} they made it; and \emph{what} the change was.
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37 \item It can help you to recover from mistakes. If you make a change
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38 that later turns out to be in error, you can revert to an earlier
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39 version of one or more files. In fact, a \emph{really} good
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40 revision control tool will even help you to efficiently figure out
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41 exactly when a problem was introduced (see
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42 section~\ref{sec:undo:bisect} for details).
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43 \item It will help you to work simultaneously on multiple versions of
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44 your project.
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45 \end{itemize}
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46
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47 \subsection{The many names of revision control}
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48
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49 Revision control is a diverse field, so much so that it doesn't
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50 actually have a single name or acronym. Here are a few of the more
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51 common names and acronyms you'll encounter:
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52 \begin{itemize}
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53 \item Configuration management (CM)
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54 \item Revision control (RCS)
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55 \item Software configuration management (SCM)
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56 \item Version control (VCS)
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57 \end{itemize}
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58 Some people claim that these terms actually have different meanings,
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59 but in practice they overlap so much that there's no agreed or even
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60 useful way to tease them apart.
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61
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62 \section{The hierarchy of revision control}
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63
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64
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65 \subsection{On a single system}
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66
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67 \subsection{Network-based, but centralised}
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68
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69 \subsection{Fully distributed}
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70
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71
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72 \section{Advantages of distributed revision control}
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73
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74 \subsection{For open source projects}
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75
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76 \subsection{For commercial projects}
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77
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78 \subsection{Myths about distributed revision control}
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79
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80 \section{Why choose Mercurial?}
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81
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82
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83 %%% Local Variables:
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84 %%% mode: latex
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85 %%% TeX-master: "00book"
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86 %%% End:
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