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1 \chapter{A tour of Mercurial: the basics}
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2 \label{chap:tour-basic}
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3
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4 \section{Installing Mercurial on your system}
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5 \label{sec:tour:install}
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6
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7 Prebuilt binary packages of Mercurial are available for every popular
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8 operating system. These make it easy to start using Mercurial on your
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9 computer immediately.
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10
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11 \subsection{Linux}
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12
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13 Because each Linux distribution has its own packaging tools, policies,
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14 and rate of development, it's difficult to give a comprehensive set of
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15 instructions on how to install Mercurial binaries. The version of
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16 Mercurial that you will end up with can vary depending on how active
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17 the person is who maintains the package for your distribution.
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18
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19 To keep things simple, I will focus on installing Mercurial from the
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20 command line under the most popular Linux distributions. Most of
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21 these distributions provide graphical package managers that will let
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22 you install Mercurial with a single click; the package name to look
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23 for is \texttt{mercurial}.
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24
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25 \begin{itemize}
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26 \item[Debian]
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27 \begin{codesample4}
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28 apt-get install mercurial
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29 \end{codesample4}
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30
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31 \item[Fedora Core]
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32 \begin{codesample4}
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33 yum install mercurial
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34 \end{codesample4}
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35
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36 \item[Gentoo]
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37 \begin{codesample4}
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38 emerge mercurial
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39 \end{codesample4}
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40
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41 \item[OpenSUSE]
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42 \begin{codesample4}
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43 yum install mercurial
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44 \end{codesample4}
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45
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46 \item[Ubuntu] Ubuntu's Mercurial package is based on Debian's. To
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47 install it, run the following command.
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48 \begin{codesample4}
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49 apt-get install mercurial
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50 \end{codesample4}
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51 The Ubuntu package for Mercurial tends to lag behind the Debian
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52 version by a considerable time margin (at the time of writing, seven
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53 months), which in some cases will mean that on Ubuntu, you may run
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54 into problems that have since been fixed in the Debian package.
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55 \end{itemize}
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56
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57 \subsection{Solaris}
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58
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59 XXX.
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60
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61 \subsection{Mac OS X}
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62
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63 Lee Cantey publishes an installer of Mercurial for Mac OS~X at
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64 \url{http://mercurial.berkwood.com}. This package works on both
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65 Intel-~and Power-based Macs. Before you can use it, you must install
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66 a compatible version of Universal MacPython~\cite{web:macpython}. This
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67 is easy to do; simply follow the instructions on Lee's site.
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68
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69 \subsection{Windows}
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70
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71 Lee Cantey also publishes an installer of Mercurial for Windows at
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72 \url{http://mercurial.berkwood.com}. This package has no external
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73 dependencies; it ``just works''.
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74
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75 \begin{note}
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76 The Windows version of Mercurial does not automatically convert line
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77 endings between Windows and Unix styles. If you want to share work
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78 with Unix users, you must do a little additional configuration
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79 work. XXX Flesh this out.
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80 \end{note}
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81
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82 \section{Getting started}
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83
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84 To begin, we'll use the \hgcmd{version} command to find out whether
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85 Mercurial is actually installed properly. The actual version
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86 information that it prints isn't so important; it's whether it prints
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87 anything at all that we care about.
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88 \interaction{tour.version}
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89
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90 \subsection{Built-in help}
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91
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92 Mercurial provides a built-in help system. This is invaluable for those
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93 times when you find yourself stuck trying to remember how to run a
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94 command. If you are completely stuck, simply run \hgcmd{help}; it
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95 will print a brief list of commands, along with a description of what
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96 each does. If you ask for help on a specific command (as below), it
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97 prints more detailed information.
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98 \interaction{tour.help}
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99 For a more impressive level of detail (which you won't usually need)
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100 run \hgcmdargs{help}{\hggopt{-v}}. The \hggopt{-v} option is short
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101 for \hggopt{--verbose}, and tells Mercurial to print more information
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102 than it usually would.
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103
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104 \section{Working with a repository}
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105
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106 In Mercurial, everything happens inside a \emph{repository}. The
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107 repository for a project contains all of the files that ``belong to''
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108 that project, along with a historical record of the project's files.
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109
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110 There's nothing particularly magical about a repository; it is simply
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111 a directory tree in your filesystem that Mercurial treats as special.
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112 You can rename or delete a repository any time you like, using either the
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113 command line or your file browser.
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114
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115 \subsection{Making a local copy of a repository}
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116
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117 \emph{Copying} a repository is just a little bit special. While you
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118 could use a normal file copying command to make a copy of a
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119 repository, it's best to use a built-in command that Mercurial
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120 provides. This command is called \hgcmd{clone}, because it creates an
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121 identical copy of an existing repository.
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122 \interaction{tour.clone}
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123 If our clone succeeded, we should now have a local directory called
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124 \dirname{hello}. This directory will contain some files.
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125 \interaction{tour.ls}
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126 These files have the same contents and history in our repository as
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127 they do in the repository we cloned.
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128
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129 Every Mercurial repository is complete, self-contained, and
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130 independent. It contains its own private copy of a project's files
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131 and history. A cloned repository remembers the location of the
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132 repository it was cloned from, but it does not communicate with that
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133 repository, or any other, unless you tell it to.
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134
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135 What this means for now is that we're free to experiment with our
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136 repository, safe in the knowledge that it's a private ``sandbox'' that
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137 won't affect anyone else.
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138
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139 \subsection{What's in a repository?}
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140
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141 When we take a more detailed look inside a repository, we can see that
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142 it contains a directory named \dirname{.hg}. This is where Mercurial
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143 keeps all of its metadata for the repository.
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144 \interaction{tour.ls-a}
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145
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146 The contents of the \dirname{.hg} directory and its subdirectories are
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147 private to Mercurial. Every other file and directory in the
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148 repository is yours to do with as you please.
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149
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150 To introduce a little terminology, the \dirname{.hg} directory is the
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151 ``real'' repository, and all of the files and directories that coexist
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152 with it are said to live in the \emph{working directory}. An easy way
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153 to remember the distinction is that the \emph{repository} contains the
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154 \emph{history} of your project, while the \emph{working directory}
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155 contains a \emph{snapshot} of your project at a particular point in
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156 history.
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157
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158 \section{A tour through history}
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159
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160 One of the first things we might want to do with a new, unfamiliar
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161 repository is understand its history. The \hgcmd{log} command gives
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162 us a view of history.
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163 \interaction{tour.log}
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164 By default, this command prints a brief paragraph of output for each
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165 change to the project that was recorded. In Mercurial terminology, we
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166 call each of these recorded events a \emph{changeset}, because it can
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167 contain a record of changes to several files.
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168
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169 The fields in a record of output from \hgcmd{log} are as follows.
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170 \begin{itemize}
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171 \item[\texttt{changeset}] This field has the format of a number,
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172 followed by a colon, followed by a hexadecimal string. These are
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173 \emph{identifiers} for the changeset. There are two identifiers
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174 because the number is shorter and easier to type than the hex
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175 string.
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176 \item[\texttt{user}] The identity of the person who created the
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177 changeset. This is a free-form field, but it most often contains a
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178 person's name and email address.
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179 \item[\texttt{date}] The date and time on which the changeset was
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180 created, and the timezone in which it was created. (The date and
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181 time are local to that timezone; they display what time and date it
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182 was for the person who created the changeset.)
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183 \item[\texttt{summary}] The first line of the text message that the
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184 creator of the changeset entered to describe the changeset.
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185 \end{itemize}
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186 The default output printed by \hgcmd{log} is purely a summary; it is
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187 missing a lot of detail.
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188
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189 Figure~\ref{fig:tour-basic:history} provides a graphical representation of
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190 the history of the \dirname{hello} repository, to make it a little
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191 easier to see which direction history is ``flowing'' in. We'll be
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192 returning to this figure several times in this chapter and the chapter
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193 that follows.
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194
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195 \begin{figure}[ht]
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196 \centering
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197 \grafix{tour-history}
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198 \caption{Graphical history of the \dirname{hello} repository}
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199 \label{fig:tour-basic:history}
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200 \end{figure}
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201
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202 \subsection{Changesets, revisions, and talking to other
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203 people}
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204
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205 As English is a notoriously sloppy language, and computer science has
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206 a hallowed history of terminological confusion (why use one term when
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207 four will do?), revision control has a variety of words and phrases
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208 that mean the same thing. If you are talking about Mercurial history
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209 with other people, you will find that the word ``changeset'' is often
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210 compressed to ``change'' or (when written) ``cset'', and sometimes a
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211 changeset is referred to as a ``revision'' or a ``rev''.
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212
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213 While it doesn't matter what \emph{word} you use to refer to the
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214 concept of ``a~changeset'', the \emph{identifier} that you use to
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215 refer to ``a~\emph{specific} changeset'' is of great importance.
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216 Recall that the \texttt{changeset} field in the output from
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217 \hgcmd{log} identifies a changeset using both a number and a
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218 hexadecimal string.
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219 \begin{itemize}
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220 \item The revision number is \emph{only valid in that repository},
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221 \item while the hex string is the \emph{permanent, unchanging
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222 identifier} that will always identify that exact changeset in
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223 \emph{every} copy of the repository.
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224 \end{itemize}
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225 This distinction is important. If you send someone an email talking
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226 about ``revision~33'', there's a high likelihood that their
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227 revision~33 will \emph{not be the same} as yours. The reason for this
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228 is that a revision number depends on the order in which changes
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229 arrived in a repository, and there is no guarantee that the same
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230 changes will happen in the same order in different repositories.
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231 Three changes $a,b,c$ can easily appear in one repository as $0,1,2$,
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232 while in another as $1,0,2$.
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233
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234 Mercurial uses revision numbers purely as a convenient shorthand. If
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235 you need to discuss a changeset with someone, or make a record of a
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236 changeset for some other reason (for example, in a bug report), use
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237 the hexadecimal identifier.
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238
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239 \subsection{Viewing specific revisions}
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240
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241 To narrow the output of \hgcmd{log} down to a single revision, use the
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242 \hgopt{log}{-r} (or \hgopt{log}{--rev}) option. You can use either a
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243 revision number or a long-form changeset identifier, and you can
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244 provide as many revisions as you want. \interaction{tour.log-r}
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245
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246 If you want to see the history of several revisions without having to
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247 list each one, you can use \emph{range notation}; this lets you
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248 express the idea ``I want all revisions between $a$ and $b$,
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249 inclusive''.
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250 \interaction{tour.log.range}
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251 Mercurial also honours the order in which you specify revisions, so
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252 \hgcmdargs{log}{-r 2:4} prints $2,3,4$ while \hgcmdargs{log}{-r 4:2}
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253 prints $4,3,2$.
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254
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255 \subsection{More detailed information}
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256
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257 While the summary information printed by \hgcmd{log} is useful if you
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258 already know what you're looking for, you may need to see a complete
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259 description of the change, or a list of the files changed, if you're
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260 trying to decide whether a changeset is the one you're looking for.
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261 The \hgcmd{log} command's \hggopt{-v} (or \hggopt{--verbose})
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262 option gives you this extra detail.
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263 \interaction{tour.log-v}
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264
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265 If you want to see both the description and content of a change, add
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266 the \hgopt{log}{-p} (or \hgopt{log}{--patch}) option. This displays
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267 the content of a change as a \emph{unified diff} (if you've never seen
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268 a unified diff before, see section~\ref{sec:mq:patch} for an overview).
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269 \interaction{tour.log-vp}
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270
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271 \section{All about command options}
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272
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273 Let's take a brief break from exploring Mercurial commands to discuss
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274 a pattern in the way that they work; you may find this useful to keep
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275 in mind as we continue our tour.
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276
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277 Mercurial has a consistent and straightforward approach to dealing
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278 with the options that you can pass to commands. It follows the
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279 conventions for options that are common to modern Linux and Unix
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280 systems.
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281 \begin{itemize}
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282 \item Every option has a long name. For example, as we've already
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283 seen, the \hgcmd{log} command accepts a \hgopt{log}{--rev} option.
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284 \item Most options have short names, too. Instead of
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285 \hgopt{log}{--rev}, we can use \hgopt{log}{-r}. (The reason that
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286 some options don't have short names is that the options in question
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287 are rarely used.)
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288 \item Long options start with two dashes (e.g.~\hgopt{log}{--rev}),
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289 while short options start with one (e.g.~\hgopt{log}{-r}).
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290 \item Option naming and usage is consistent across commands. For
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291 example, every command that lets you specify a changeset~ID or
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292 revision number accepts both \hgopt{log}{-r} and \hgopt{log}{--rev}
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293 arguments.
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294 \end{itemize}
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295 In the examples throughout this book, I use short options instead of
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296 long. This just reflects my own preference, so don't read anything
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297 significant into it.
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298
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299 Most commands that print output of some kind will print more output
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300 when passed a \hggopt{-v} (or \hggopt{--verbose}) option, and less
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301 when passed \hggopt{-q} (or \hggopt{--quiet}).
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302
|
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bos@91
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303 \section{Making and reviewing changes}
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304
|
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bos@91
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305 Now that we have a grasp of viewing history in Mercurial, let's take a
|
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306 look at making some changes and examining them.
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307
|
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bos@91
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308 The first thing we'll do is isolate our experiment in a repository of
|
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309 its own. We use the \hgcmd{clone} command, but we don't need to
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bos@91
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310 clone a copy of the remote repository. Since we already have a copy
|
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311 of it locally, we can just clone that instead. This is much faster
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312 than cloning over the network, and cloning a local repository uses
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313 less disk space in most cases, too.
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314 \interaction{tour.reclone}
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315 As an aside, it's often good practice to keep a ``pristine'' copy of a
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316 remote repository around, which you can then make temporary clones of
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317 to create sandboxes for each task you want to work on. This lets you
|
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318 work on multiple tasks in parallel, each isolated from the others
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319 until it's complete and you're ready to integrate it back. Because
|
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320 local clones are so cheap, there's almost no overhead to cloning and
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321 destroying repositories whenever you want.
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322
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323 In our \dirname{my-hello} repository, we have a file
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bos@91
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324 \filename{hello.c} that contains the classic ``hello, world'' program.
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325 Let's use the ancient and venerable \command{sed} command to edit this
|
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326 file so that it prints a second line of output. (I'm only using
|
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327 \command{sed} to do this because it's easy to write a scripted example
|
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328 this way. Since you're not under the same constraint, you probably
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329 won't want to use \command{sed}; simply use your preferred text editor to
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330 do the same thing.)
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bos@91
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331 \interaction{tour.sed}
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332
|
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333 Mercurial's \hgcmd{status} command will tell us what Mercurial knows
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334 about the files in the repository.
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bos@91
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335 \interaction{tour.status}
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336 The \hgcmd{status} command prints no output for some files, but a line
|
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337 starting with ``\texttt{M}'' for \filename{hello.c}. Unless you tell
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338 it to, \hgcmd{status} will not print any output for files that have
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339 not been modified.
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340
|
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bos@91
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341 The ``\texttt{M}'' indicates that Mercurial has noticed that we
|
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342 modified \filename{hello.c}. We didn't need to \emph{inform}
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343 Mercurial that we were going to modify the file before we started, or
|
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bos@97
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344 that we had modified the file after we were done; it was able to
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345 figure this out itself.
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346
|
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347 It's a little bit helpful to know that we've modified
|
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348 \filename{hello.c}, but we might prefer to know exactly \emph{what}
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349 changes we've made to it. To do this, we use the \hgcmd{diff}
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350 command.
|
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bos@91
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351 \interaction{tour.diff}
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352
|
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bos@91
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353 \section{Recording changes in a new changeset}
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354
|
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bos@91
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355 We can modify files, build and test our changes, and use
|
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356 \hgcmd{status} and \hgcmd{diff} to review our changes, until we're
|
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357 satisfied with what we've done and arrive at a natural stopping point
|
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358 where we want to record our work in a new changeset.
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359
|
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bos@91
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360 The \hgcmd{commit} command lets us create a new changeset; we'll
|
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bos@91
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361 usually refer to this as ``making a commit'' or ``committing''.
|
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362
|
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bos@102
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363 \subsection{Setting up a username}
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364
|
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bos@174
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365 When you try to run \hgcmd{commit} for the first time, it is not
|
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bos@174
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366 guaranteed to succeed. Mercurial records your name and address with
|
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bos@174
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367 each change that you commit, so that you and others will later be able
|
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bos@174
|
368 to tell who made each change. Mercurial tries to automatically figure
|
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bos@174
|
369 out a sensible username to commit the change with. It will attempt
|
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bos@174
|
370 each of the following methods, in order:
|
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bos@174
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371 \begin{enumerate}
|
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bos@174
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372 \item If you specify a \hgopt{commit}{-u} option to the \hgcmd{commit}
|
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|
373 command on the command line, followed by a username, this is always
|
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|
374 given the highest precedence.
|
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bos@174
|
375 \item If you have set the \envar{HGUSER} environment variable, this is
|
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bos@174
|
376 checked next.
|
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bos@174
|
377 \item If you create a file in your home directory called
|
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bos@174
|
378 \sfilename{.hgrc}, with a \rcitem{ui}{username} entry, that will be
|
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bos@174
|
379 used next. To see what the contents of this file should look like,
|
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bos@174
|
380 refer to section~\ref{sec:tour-basic:username} below.
|
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bos@174
|
381 \item If you have set the \envar{EMAIL} environment variable, this
|
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bos@174
|
382 will be used next.
|
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bos@174
|
383 \item Mercurial will query your system to find out your local user
|
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bos@174
|
384 name and host name, and construct a username from these components.
|
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bos@174
|
385 Since this often results in a username that is not very useful, it
|
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bos@174
|
386 will print a warning if it has to do this.
|
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bos@174
|
387 \end{enumerate}
|
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bos@174
|
388 If all of these mechanisms fail, Mercurial will fail, printing an
|
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bos@174
|
389 error message. In this case, it will not let you commit until you set
|
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bos@174
|
390 up a username.
|
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bos@174
|
391
|
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bos@174
|
392 You should think of the \envar{HGUSER} environment variable and the
|
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bos@174
|
393 \hgopt{commit}{-u} option to the \hgcmd{commit} command as ways to
|
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bos@174
|
394 \emph{override} Mercurial's default selection of username. For normal
|
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bos@174
|
395 use, the simplest and most robust way to set a username for yourself
|
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bos@174
|
396 is by creating a \sfilename{.hgrc} file; see below for details.
|
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bos@102
|
397
|
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bos@102
|
398 \subsubsection{Creating a Mercurial configuration file}
|
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bos@174
|
399 \label{sec:tour-basic:username}
|
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bos@102
|
400
|
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bos@102
|
401 To set a user name, use your favourite editor to create a file called
|
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bos@102
|
402 \sfilename{.hgrc} in your home directory. Mercurial will use this
|
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bos@102
|
403 file to look up your personalised configuration settings. The initial
|
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bos@102
|
404 contents of your \sfilename{.hgrc} should look like this.
|
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bos@102
|
405 \begin{codesample2}
|
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bos@102
|
406 # This is a Mercurial configuration file.
|
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bos@102
|
407 [ui]
|
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bos@102
|
408 username = Firstname Lastname <email.address@domain.net>
|
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bos@102
|
409 \end{codesample2}
|
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bos@102
|
410 The ``\texttt{[ui]}'' line begins a \emph{section} of the config file,
|
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bos@102
|
411 so you can read the ``\texttt{username = ...}'' line as meaning ``set
|
|
bos@102
|
412 the value of the \texttt{username} item in the \texttt{ui} section''.
|
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bos@102
|
413 A section continues until a new section begins, or the end of the
|
|
bos@102
|
414 file. Mercurial ignores empty lines and treats any text from
|
|
bos@102
|
415 ``\texttt{\#}'' to the end of a line as a comment.
|
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bos@102
|
416
|
|
bos@102
|
417 \subsubsection{Choosing a user name}
|
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bos@102
|
418
|
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bos@102
|
419 You can use any text you like as the value of the \texttt{username}
|
|
bos@102
|
420 config item, since this information is for reading by other people,
|
|
bos@102
|
421 but for interpreting by Mercurial. The convention that most people
|
|
bos@102
|
422 follow is to use their name and email address, as in the example
|
|
bos@102
|
423 above.
|
|
bos@102
|
424
|
|
bos@102
|
425 \begin{note}
|
|
bos@102
|
426 Mercurial's built-in web server obfuscates email addresses, to make
|
|
bos@102
|
427 it more difficult for the email harvesting tools that spammers use.
|
|
bos@102
|
428 This reduces the likelihood that you'll start receiving more junk
|
|
bos@102
|
429 email if you publish a Mercurial repository on the web.
|
|
bos@102
|
430 \end{note}
|
|
bos@102
|
431
|
|
bos@91
|
432 \subsection{Writing a commit message}
|
|
bos@91
|
433
|
|
bos@91
|
434 When we commit a change, Mercurial drops us into a text editor, to
|
|
bos@91
|
435 enter a message that will describe the modifications we've made in
|
|
bos@91
|
436 this changeset. This is called the \emph{commit message}. It will be
|
|
bos@91
|
437 a record for readers of what we did and why, and it will be printed by
|
|
bos@91
|
438 \hgcmd{log} after we've finished committing.
|
|
bos@91
|
439 \interaction{tour.commit}
|
|
bos@91
|
440
|
|
bos@91
|
441 The editor that the \hgcmd{commit} command drops us into will contain
|
|
bos@91
|
442 an empty line, followed by a number of lines starting with
|
|
bos@91
|
443 ``\texttt{HG:}''.
|
|
bos@91
|
444 \begin{codesample2}
|
|
bos@91
|
445 \emph{empty line}
|
|
bos@91
|
446 HG: changed hello.c
|
|
bos@91
|
447 \end{codesample2}
|
|
bos@91
|
448 Mercurial ignores the lines that start with ``\texttt{HG:}''; it uses
|
|
bos@91
|
449 them only to tell us which files it's recording changes to. Modifying
|
|
bos@91
|
450 or deleting these lines has no effect.
|
|
bos@91
|
451
|
|
bos@91
|
452 \subsection{Writing a good commit message}
|
|
bos@91
|
453
|
|
bos@91
|
454 Since \hgcmd{log} only prints the first line of a commit message by
|
|
bos@91
|
455 default, it's best to write a commit message whose first line stands
|
|
bos@91
|
456 alone. Here's a real example of a commit message that \emph{doesn't}
|
|
bos@91
|
457 follow this guideline, and hence has a summary that is not readable.
|
|
bos@91
|
458 \begin{codesample2}
|
|
bos@91
|
459 changeset: 73:584af0e231be
|
|
bos@91
|
460 user: Censored Person <censored.person@example.org>
|
|
bos@91
|
461 date: Tue Sep 26 21:37:07 2006 -0700
|
|
bos@91
|
462 summary: include buildmeister/commondefs. Add an exports and install
|
|
bos@91
|
463 \end{codesample2}
|
|
bos@91
|
464
|
|
bos@91
|
465 As far as the remainder of the contents of the commit message are
|
|
bos@91
|
466 concerned, there are no hard-and-fast rules. Mercurial itself doesn't
|
|
bos@91
|
467 interpret or care about the contents of the commit message, though
|
|
bos@91
|
468 your project may have policies that dictate a certain kind of
|
|
bos@91
|
469 formatting.
|
|
bos@91
|
470
|
|
bos@91
|
471 My personal preference is for short, but informative, commit messages
|
|
bos@91
|
472 that tell me something that I can't figure out with a quick glance at
|
|
bos@91
|
473 the output of \hgcmdargs{log}{--patch}.
|
|
bos@91
|
474
|
|
bos@91
|
475 \subsection{Aborting a commit}
|
|
bos@91
|
476
|
|
bos@91
|
477 If you decide that you don't want to commit while in the middle of
|
|
bos@91
|
478 editing a commit message, simply exit from your editor without saving
|
|
bos@91
|
479 the file that it's editing. This will cause nothing to happen to
|
|
bos@91
|
480 either the repository or the working directory.
|
|
bos@91
|
481
|
|
bos@91
|
482 If we run the \hgcmd{commit} command without any arguments, it records
|
|
bos@91
|
483 all of the changes we've made, as reported by \hgcmd{status} and
|
|
bos@91
|
484 \hgcmd{diff}.
|
|
bos@91
|
485
|
|
bos@102
|
486 \subsection{Admiring our new handiwork}
|
|
bos@91
|
487
|
|
bos@91
|
488 Once we've finished the commit, we can use the \hgcmd{tip} command to
|
|
bos@91
|
489 display the changeset we just created. This command produces output
|
|
bos@91
|
490 that is identical to \hgcmd{log}, but it only displays the newest
|
|
bos@91
|
491 revision in the repository.
|
|
bos@91
|
492 \interaction{tour.tip}
|
|
bos@91
|
493 We refer to the newest revision in the repository as the tip revision,
|
|
bos@91
|
494 or simply the tip.
|
|
bos@91
|
495
|
|
bos@91
|
496 \section{Sharing changes}
|
|
bos@91
|
497
|
|
bos@91
|
498 We mentioned earlier that repositories in Mercurial are
|
|
bos@91
|
499 self-contained. This means that the changeset we just created exists
|
|
bos@91
|
500 only in our \dirname{my-hello} repository. Let's look at a few ways
|
|
bos@91
|
501 that we can propagate this change into other repositories.
|
|
bos@91
|
502
|
|
bos@91
|
503 \subsection{Pulling changes from another repository}
|
|
bos@91
|
504 \label{sec:tour:pull}
|
|
bos@91
|
505
|
|
bos@91
|
506 To get started, let's clone our original \dirname{hello} repository,
|
|
bos@91
|
507 which does not contain the change we just committed. We'll call our
|
|
bos@91
|
508 temporary repository \dirname{hello-pull}.
|
|
bos@91
|
509 \interaction{tour.clone-pull}
|
|
bos@91
|
510
|
|
bos@91
|
511 We'll use the \hgcmd{pull} command to bring changes from
|
|
bos@91
|
512 \dirname{my-hello} into \dirname{hello-pull}. However, blindly
|
|
bos@91
|
513 pulling unknown changes into a repository is a somewhat scary
|
|
bos@91
|
514 prospect. Mercurial provides the \hgcmd{incoming} command to tell us
|
|
bos@91
|
515 what changes the \hgcmd{pull} command \emph{would} pull into the
|
|
bos@91
|
516 repository, without actually pulling the changes in.
|
|
bos@91
|
517 \interaction{tour.incoming}
|
|
bos@91
|
518 (Of course, someone could cause more changesets to appear in the
|
|
bos@91
|
519 repository that we ran \hgcmd{incoming} in, before we get a chance to
|
|
bos@91
|
520 \hgcmd{pull} the changes, so that we could end up pulling changes that we
|
|
bos@91
|
521 didn't expect.)
|
|
bos@91
|
522
|
|
bos@91
|
523 Bringing changes into a repository is a simple matter of running the
|
|
bos@91
|
524 \hgcmd{pull} command, and telling it which repository to pull from.
|
|
bos@91
|
525 \interaction{tour.pull}
|
|
bos@91
|
526 As you can see from the before-and-after output of \hgcmd{tip}, we
|
|
bos@91
|
527 have successfully pulled changes into our repository. There remains
|
|
bos@92
|
528 one step before we can see these changes in the working directory.
|
|
bos@92
|
529
|
|
bos@92
|
530 \subsection{Updating the working directory}
|
|
bos@92
|
531
|
|
bos@92
|
532 We have so far glossed over the relationship between a repository and
|
|
bos@91
|
533 its working directory. The \hgcmd{pull} command that we ran in
|
|
bos@91
|
534 section~\ref{sec:tour:pull} brought changes into the repository, but
|
|
bos@91
|
535 if we check, there's no sign of those changes in the working
|
|
bos@91
|
536 directory. This is because \hgcmd{pull} does not (by default) touch
|
|
bos@91
|
537 the working directory. Instead, we use the \hgcmd{update} command to
|
|
bos@91
|
538 do this.
|
|
bos@91
|
539 \interaction{tour.update}
|
|
bos@91
|
540
|
|
bos@91
|
541 It might seem a bit strange that \hgcmd{pull} doesn't update the
|
|
bos@91
|
542 working directory automatically. There's actually a good reason for
|
|
bos@91
|
543 this: you can use \hgcmd{update} to update the working directory to
|
|
bos@91
|
544 the state it was in at \emph{any revision} in the history of the
|
|
bos@91
|
545 repository. If you had the working directory updated to an old
|
|
bos@91
|
546 revision---to hunt down the origin of a bug, say---and ran a
|
|
bos@91
|
547 \hgcmd{pull} which automatically updated the working directory to a
|
|
bos@91
|
548 new revision, you might not be terribly happy.
|
|
bos@91
|
549
|
|
bos@91
|
550 However, since pull-then-update is such a common thing to do,
|
|
bos@91
|
551 Mercurial lets you combine the two by passing the \hgopt{pull}{-u}
|
|
bos@91
|
552 option to \hgcmd{pull}.
|
|
bos@91
|
553 \begin{codesample2}
|
|
bos@91
|
554 hg pull -u
|
|
bos@91
|
555 \end{codesample2}
|
|
bos@92
|
556 If you look back at the output of \hgcmd{pull} in
|
|
bos@92
|
557 section~\ref{sec:tour:pull} when we ran it without \hgopt{pull}{-u},
|
|
bos@92
|
558 you can see that it printed a helpful reminder that we'd have to take
|
|
bos@92
|
559 an explicit step to update the working directory:
|
|
bos@92
|
560 \begin{codesample2}
|
|
bos@92
|
561 (run 'hg update' to get a working copy)
|
|
bos@92
|
562 \end{codesample2}
|
|
bos@91
|
563
|
|
bos@91
|
564 To find out what revision the working directory is at, use the
|
|
bos@91
|
565 \hgcmd{parents} command.
|
|
bos@91
|
566 \interaction{tour.parents}
|
|
bos@101
|
567 If you look back at figure~\ref{fig:tour-basic:history}, you'll see
|
|
bos@101
|
568 arrows connecting each changeset. The node that the arrow leads
|
|
bos@101
|
569 \emph{from} in each case is a parent, and the node that the arrow
|
|
bos@101
|
570 leads \emph{to} is its child. The working directory has a parent in
|
|
bos@101
|
571 just the same way; this is the changeset that the working directory
|
|
bos@101
|
572 currently contains.
|
|
bos@101
|
573
|
|
bos@91
|
574 To update the working directory to a particular revision, give a
|
|
bos@91
|
575 revision number or changeset~ID to the \hgcmd{update} command.
|
|
bos@91
|
576 \interaction{tour.older}
|
|
bos@91
|
577 If you omit an explicit revision, \hgcmd{update} will update to the
|
|
bos@94
|
578 tip revision, as shown by the second call to \hgcmd{update} in the
|
|
bos@94
|
579 example above.
|
|
bos@91
|
580
|
|
bos@92
|
581 \subsection{Pushing changes to another repository}
|
|
bos@92
|
582
|
|
bos@92
|
583 Mercurial lets us push changes to another repository, from the
|
|
bos@92
|
584 repository we're currently visiting. As with the example of
|
|
bos@92
|
585 \hgcmd{pull} above, we'll create a temporary repository to push our
|
|
bos@92
|
586 changes into.
|
|
bos@92
|
587 \interaction{tour.clone-push}
|
|
bos@92
|
588 The \hgcmd{outgoing} command tells us what changes would be pushed
|
|
bos@92
|
589 into another repository.
|
|
bos@92
|
590 \interaction{tour.outgoing}
|
|
bos@92
|
591 And the \hgcmd{push} command does the actual push.
|
|
bos@92
|
592 \interaction{tour.push}
|
|
bos@92
|
593 As with \hgcmd{pull}, the \hgcmd{push} command does not update the
|
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bos@92
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594 working directory in the repository that it's pushing changes into.
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595 (Unlike \hgcmd{pull}, \hgcmd{push} does not provide a \texttt{-u}
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596 option that updates the other repository's working directory.)
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597
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598 What happens if we try to pull or push changes and the receiving
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599 repository already has those changes? Nothing too exciting.
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600 \interaction{tour.push.nothing}
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601
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602 \subsection{Sharing changes over a network}
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603
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604 The commands we have covered in the previous few sections are not
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605 limited to working with local repositories. Each works in exactly the
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606 same fashion over a network connection; simply pass in a URL instead
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607 of a local path.
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608 \interaction{tour.outgoing.net}
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609 In this example, we can see what changes we could push to the remote
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610 repository, but the repository is understandably not set up to let
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611 anonymous users push to it.
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612 \interaction{tour.push.net}
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613
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614 %%% Local Variables:
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615 %%% mode: latex
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616 %%% TeX-master: "00book"
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617 %%% End:
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