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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 <chapter id="chap:template">
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4 <?dbhtml filename="customizing-the-output-of-mercurial.html"?>
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5 <title>Customising the output of Mercurial</title>
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6
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7 <para>Mercurial provides a powerful mechanism to let you control how
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8 it displays information. The mechanism is based on templates.
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9 You can use templates to generate specific output for a single
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10 command, or to customise the entire appearance of the built-in web
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11 interface.</para>
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12
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13 <sect1 id="sec:style">
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14 <title>Using precanned output styles</title>
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15
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16 <para>Packaged with Mercurial are some output styles that you can
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17 use immediately. A style is simply a precanned template that
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18 someone wrote and installed somewhere that Mercurial can
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19 find.</para>
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20
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21 <para>Before we take a look at Mercurial's bundled styles, let's
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22 review its normal output.</para>
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23
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24 &interaction.template.simple.normal;
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25
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26 <para>This is somewhat informative, but it takes up a lot of
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27 space&emdash;five lines of output per changeset. The
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28 <literal>compact</literal> style reduces this to three lines,
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29 presented in a sparse manner.</para>
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30
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31 &interaction.template.simple.compact;
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32
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33 <para>The <literal>changelog</literal> style hints at the
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34 expressive power of Mercurial's templating engine. This style
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35 attempts to follow the GNU Project's changelog
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36 guidelines<citation>web:changelog</citation>.</para>
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37
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38 &interaction.template.simple.changelog;
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39
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40 <para>You will not be shocked to learn that Mercurial's default
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41 output style is named <literal>default</literal>.</para>
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42
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43 <sect2>
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44 <title>Setting a default style</title>
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45
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46 <para>You can modify the output style that Mercurial will use
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47 for every command by editing your <filename role="special">
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48 /.hgrc</filename>\ file, naming the style you would prefer
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49 to use.</para>
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50
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51 <programlisting>[ui] style = compact</programlisting>
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52
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53 <para>If you write a style of your own, you can use it by either
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54 providing the path to your style file, or copying your style
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55 file into a location where Mercurial can find it (typically
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56 the <literal>templates</literal> subdirectory of your
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57 Mercurial install directory).</para>
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58
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59 </sect2>
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60 </sect1>
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61 <sect1>
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62 <title>Commands that support styles and templates</title>
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63
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64 <para>All of Mercurial's
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65 <quote><literal>log</literal>-like</quote> commands let you use
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66 styles and templates: <command role="hg-cmd">hg
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67 incoming</command>, <command role="hg-cmd">hg log</command>,
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68 <command role="hg-cmd">hg outgoing</command>, and <command
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69 role="hg-cmd">hg tip</command>.</para>
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70
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71 <para>As I write this manual, these are so far the only commands
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72 that support styles and templates. Since these are the most
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73 important commands that need customisable output, there has been
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74 little pressure from the Mercurial user community to add style
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75 and template support to other commands.</para>
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76
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77 </sect1>
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78 <sect1>
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79 <title>The basics of templating</title>
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80
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81 <para>At its simplest, a Mercurial template is a piece of text.
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82 Some of the text never changes, while other parts are
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83 <emphasis>expanded</emphasis>, or replaced with new text, when
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84 necessary.</para>
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85
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86 <para>Before we continue, let's look again at a simple example of
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87 Mercurial's normal output.</para>
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88
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89 &interaction.template.simple.normal;
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90
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91 <para>Now, let's run the same command, but using a template to
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92 change its output.</para>
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93
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94 &interaction.template.simple.simplest;
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95
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96 <para>The example above illustrates the simplest possible
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97 template; it's just a piece of static text, printed once for
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98 each changeset. The <option
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99 role="hg-opt-log">--template</option> option to the <command
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100 role="hg-cmd">hg log</command> command tells Mercurial to use
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101 the given text as the template when printing each
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102 changeset.</para>
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103
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104 <para>Notice that the template string above ends with the text
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105 <quote><literal>\n</literal></quote>. This is an
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106 <emphasis>escape sequence</emphasis>, telling Mercurial to print
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107 a newline at the end of each template item. If you omit this
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108 newline, Mercurial will run each piece of output together. See
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109 section <xref linkend="sec:template:escape"/> for more details
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110 of escape sequences.</para>
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111
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112 <para>A template that prints a fixed string of text all the time
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113 isn't very useful; let's try something a bit more
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114 complex.</para>
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115
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116 &interaction.template.simple.simplesub;
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117
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118 <para>As you can see, the string
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119 <quote><literal>{desc}</literal></quote> in the template has
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120 been replaced in the output with the description of each
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121 changeset. Every time Mercurial finds text enclosed in curly
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122 braces (<quote><literal>{</literal></quote> and
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123 <quote><literal>}</literal></quote>), it will try to replace the braces
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124 and text with the expansion of whatever is inside. To print a
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125 literal curly brace, you must escape it, as described in section
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126 <xref
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127 linkend="sec:template:escape"/>.</para>
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128
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129 </sect1>
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130 <sect1 id="sec:template:keyword">
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131 <title>Common template keywords</title>
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132
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133 <para>You can start writing simple templates immediately using the
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134 keywords below.</para>
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135
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136 <itemizedlist>
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137 <listitem><para><literal
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138 role="template-keyword">author</literal>: String. The
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139 unmodified author of the changeset.</para>
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140 </listitem>
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141 <listitem><para><literal
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142 role="template-keyword">branches</literal>: String. The
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143 name of the branch on which the changeset was committed.
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144 Will be empty if the branch name was
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145 <literal>default</literal>.</para>
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146 </listitem>
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147 <listitem><para><literal role="template-keyword">date</literal>:
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148 Date information. The date when the changeset was
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149 committed. This is <emphasis>not</emphasis> human-readable;
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150 you must pass it through a filter that will render it
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151 appropriately. See section <xref
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152 linkend="sec:template:filter"/> for more information
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153 on filters. The date is expressed as a pair of numbers. The
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154 first number is a Unix UTC timestamp (seconds since January
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155 1, 1970); the second is the offset of the committer's
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156 timezone from UTC, in seconds.</para>
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157 </listitem>
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158 <listitem><para><literal role="template-keyword">desc</literal>:
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159 String. The text of the changeset description.</para>
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160 </listitem>
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161 <listitem><para><literal
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162 role="template-keyword">files</literal>: List of strings.
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163 All files modified, added, or removed by this
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164 changeset.</para>
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165 </listitem>
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166 <listitem><para><literal
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167 role="template-keyword">file_adds</literal>: List of
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168 strings. Files added by this changeset.</para>
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169 </listitem>
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170 <listitem><para><literal
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171 role="template-keyword">file_dels</literal>: List of
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172 strings. Files removed by this changeset.</para>
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173 </listitem>
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174 <listitem><para><literal role="template-keyword">node</literal>:
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175 String. The changeset identification hash, as a
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176 40-character hexadecimal string.</para>
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177 </listitem>
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178 <listitem><para><literal
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179 role="template-keyword">parents</literal>: List of
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180 strings. The parents of the changeset.</para>
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181 </listitem>
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182 <listitem><para><literal role="template-keyword">rev</literal>:
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183 Integer. The repository-local changeset revision
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184 number.</para>
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185 </listitem>
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186 <listitem><para><literal role="template-keyword">tags</literal>:
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187 List of strings. Any tags associated with the
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188 changeset.</para>
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189 </listitem></itemizedlist>
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190
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191 <para>A few simple experiments will show us what to expect when we
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192 use these keywords; you can see the results below.</para>
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193
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194 &interaction.template.simple.keywords;
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195
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196 <para>As we noted above, the date keyword does not produce
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197 human-readable output, so we must treat it specially. This
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198 involves using a <emphasis>filter</emphasis>, about which more
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199 in section <xref
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200 linkend="sec:template:filter"/>.</para>
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201
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202 &interaction.template.simple.datekeyword;
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203
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204 </sect1>
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205 <sect1 id="sec:template:escape">
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206 <title>Escape sequences</title>
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207
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208 <para>Mercurial's templating engine recognises the most commonly
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209 used escape sequences in strings. When it sees a backslash
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210 (<quote><literal>\</literal></quote>) character, it looks at the
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211 following character and substitutes the two characters with a
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212 single replacement, as described below.</para>
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213
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214 <itemizedlist>
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215 <listitem><para><literal>\textbackslash\textbackslash</literal>:
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216 Backslash, <quote><literal>\</literal></quote>, ASCII
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217 134.</para>
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218 </listitem>
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219 <listitem><para><literal>\textbackslash n</literal>: Newline,
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220 ASCII 12.</para>
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221 </listitem>
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222 <listitem><para><literal>\textbackslash r</literal>: Carriage
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223 return, ASCII 15.</para>
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224 </listitem>
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225 <listitem><para><literal>\textbackslash t</literal>: Tab, ASCII
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226 11.</para>
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227 </listitem>
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228 <listitem><para><literal>\textbackslash v</literal>: Vertical
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229 tab, ASCII 13.</para>
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230 </listitem>
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231 <listitem><para><literal>\textbackslash {</literal>: Open curly
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232 brace, <quote><literal>{</literal></quote>, ASCII
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233 173.</para>
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234 </listitem>
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235 <listitem><para><literal>\textbackslash }</literal>: Close curly
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236 brace, <quote><literal>}</literal></quote>, ASCII
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237 175.</para>
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238 </listitem></itemizedlist>
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239
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240 <para>As indicated above, if you want the expansion of a template
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241 to contain a literal <quote><literal>\</literal></quote>,
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242 <quote><literal>{</literal></quote>, or
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243 <quote><literal>{</literal></quote> character, you must escape
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244 it.</para>
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245
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246 </sect1>
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247 <sect1 id="sec:template:filter">
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248 <title>Filtering keywords to change their results</title>
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249
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250 <para>Some of the results of template expansion are not
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251 immediately easy to use. Mercurial lets you specify an optional
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252 chain of <emphasis>filters</emphasis> to modify the result of
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253 expanding a keyword. You have already seen a common filter,
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254 <literal role="template-kw-filt-date">isodate</literal>, in
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255 action above, to make a date readable.</para>
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256
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257 <para>Below is a list of the most commonly used filters that
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258 Mercurial supports. While some filters can be applied to any
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259 text, others can only be used in specific circumstances. The
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260 name of each filter is followed first by an indication of where
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261 it can be used, then a description of its effect.</para>
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262
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263 <itemizedlist>
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264 <listitem><para><literal
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265 role="template-filter">addbreaks</literal>: Any text. Add
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266 an XHTML <quote><literal><br/></literal></quote> tag
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267 before the end of every line except the last. For example,
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268 <quote><literal>foo\nbar</literal></quote> becomes
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269 <quote><literal>foo<br/>\nbar</literal></quote>.</para>
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270 </listitem>
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271 <listitem><para><literal
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272 role="template-kw-filt-date">age</literal>: <literal
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273 role="template-keyword">date</literal> keyword. Render
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274 the age of the date, relative to the current time. Yields a
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275 string like <quote><literal>10
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276 minutes</literal></quote>.</para>
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277 </listitem>
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278 <listitem><para><literal
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279 role="template-filter">basename</literal>: Any text, but
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280 most useful for the <literal
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281 role="template-keyword">files</literal> keyword and its
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282 relatives. Treat the text as a path, and return the
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283 basename. For example,
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284 <quote><literal>foo/bar/baz</literal></quote> becomes
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285 <quote><literal>baz</literal></quote>.</para>
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286 </listitem>
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287 <listitem><para><literal
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288 role="template-kw-filt-date">date</literal>: <literal
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289 role="template-keyword">date</literal> keyword. Render a
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290 date in a similar format to the Unix <literal
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291 role="template-keyword">date</literal> command, but with
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292 timezone included. Yields a string like <quote><literal>Mon
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293 Sep 04 15:13:13 2006 -0700</literal></quote>.</para>
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294 </listitem>
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295 <listitem><para><literal
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296 role="template-kw-filt-author">domain</literal>: Any text,
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297 but most useful for the <literal
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298 role="template-keyword">author</literal> keyword. Finds
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299 the first string that looks like an email address, and
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300 extract just the domain component. For example,
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301 <quote><literal>Bryan O'Sullivan
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302 <bos@serpentine.com></literal></quote> becomes
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303 <quote><literal>serpentine.com</literal></quote>.</para>
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304 </listitem>
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305 <listitem><para><literal
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306 role="template-kw-filt-author">email</literal>: Any text,
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307 but most useful for the <literal
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308 role="template-keyword">author</literal> keyword. Extract
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309 the first string that looks like an email address. For
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310 example, <quote><literal>Bryan O'Sullivan
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311 <bos@serpentine.com></literal></quote> becomes
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312 <quote><literal>bos@serpentine.com</literal></quote>.</para>
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313 </listitem>
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314 <listitem><para><literal
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315 role="template-filter">escape</literal>: Any text.
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316 Replace the special XML/XHTML characters
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317 <quote><literal>&</literal></quote>,
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318 <quote><literal><</literal></quote> and
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319 <quote><literal>></literal></quote> with XML
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320 entities.</para>
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321 </listitem>
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322 <listitem><para><literal
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323 role="template-filter">fill68</literal>: Any text. Wrap
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324 the text to fit in 68 columns. This is useful before you
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325 pass text through the <literal
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326 role="template-filter">tabindent</literal> filter, and
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327 still want it to fit in an 80-column fixed-font
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328 window.</para>
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329 </listitem>
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330 <listitem><para><literal
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331 role="template-filter">fill76</literal>: Any text. Wrap
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332 the text to fit in 76 columns.</para>
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333 </listitem>
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334 <listitem><para><literal
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335 role="template-filter">firstline</literal>: Any text.
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336 Yield the first line of text, without any trailing
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337 newlines.</para>
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338 </listitem>
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339 <listitem><para><literal
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340 role="template-kw-filt-date">hgdate</literal>: <literal
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341 role="template-keyword">date</literal> keyword. Render
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342 the date as a pair of readable numbers. Yields a string
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343 like <quote><literal>1157407993
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344 25200</literal></quote>.</para>
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345 </listitem>
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346 <listitem><para><literal
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347 role="template-kw-filt-date">isodate</literal>: <literal
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348 role="template-keyword">date</literal> keyword. Render
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349 the date as a text string in ISO 8601 format. Yields a
|
bos@559
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350 string like <quote><literal>2006-09-04 15:13:13
|
bos@559
|
351 -0700</literal></quote>.</para>
|
bos@559
|
352 </listitem>
|
bos@559
|
353 <listitem><para><literal
|
bos@559
|
354 role="template-filter">obfuscate</literal>: Any text, but
|
bos@559
|
355 most useful for the <literal
|
bos@559
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356 role="template-keyword">author</literal> keyword. Yield
|
bos@559
|
357 the input text rendered as a sequence of XML entities. This
|
bos@559
|
358 helps to defeat some particularly stupid screen-scraping
|
bos@559
|
359 email harvesting spambots.</para>
|
bos@559
|
360 </listitem>
|
bos@559
|
361 <listitem><para><literal
|
bos@559
|
362 role="template-kw-filt-author">person</literal>: Any text,
|
bos@559
|
363 but most useful for the <literal
|
bos@559
|
364 role="template-keyword">author</literal> keyword. Yield
|
bos@559
|
365 the text before an email address. For example,
|
bos@559
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366 <quote><literal>Bryan O'Sullivan
|
bos@559
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367 <bos@serpentine.com></literal></quote> becomes
|
bos@559
|
368 <quote><literal>Bryan O'Sullivan</literal></quote>.</para>
|
bos@559
|
369 </listitem>
|
bos@559
|
370 <listitem><para><literal
|
bos@559
|
371 role="template-kw-filt-date">rfc822date</literal>:
|
bos@559
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372 <literal role="template-keyword">date</literal> keyword.
|
bos@559
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373 Render a date using the same format used in email headers.
|
bos@559
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374 Yields a string like <quote><literal>Mon, 04 Sep 2006
|
bos@559
|
375 15:13:13 -0700</literal></quote>.</para>
|
bos@559
|
376 </listitem>
|
bos@559
|
377 <listitem><para><literal
|
bos@559
|
378 role="template-kw-filt-node">short</literal>: Changeset
|
bos@559
|
379 hash. Yield the short form of a changeset hash, i.e. a
|
bos@559
|
380 12-character hexadecimal string.</para>
|
bos@559
|
381 </listitem>
|
bos@559
|
382 <listitem><para><literal
|
bos@559
|
383 role="template-kw-filt-date">shortdate</literal>: <literal
|
bos@559
|
384 role="template-keyword">date</literal> keyword. Render
|
bos@559
|
385 the year, month, and day of the date. Yields a string like
|
bos@559
|
386 <quote><literal>2006-09-04</literal></quote>.</para>
|
bos@559
|
387 </listitem>
|
bos@559
|
388 <listitem><para><literal role="template-filter">strip</literal>:
|
bos@559
|
389 Any text. Strip all leading and trailing whitespace from
|
bos@559
|
390 the string.</para>
|
bos@559
|
391 </listitem>
|
bos@559
|
392 <listitem><para><literal
|
bos@559
|
393 role="template-filter">tabindent</literal>: Any text.
|
bos@559
|
394 Yield the text, with every line except the first starting
|
bos@559
|
395 with a tab character.</para>
|
bos@559
|
396 </listitem>
|
bos@559
|
397 <listitem><para><literal
|
bos@559
|
398 role="template-filter">urlescape</literal>: Any text.
|
bos@559
|
399 Escape all characters that are considered
|
bos@559
|
400 <quote>special</quote> by URL parsers. For example,
|
bos@559
|
401 <literal>foo bar</literal> becomes
|
bos@559
|
402 <literal>foo%20bar</literal>.</para>
|
bos@559
|
403 </listitem>
|
bos@559
|
404 <listitem><para><literal
|
bos@559
|
405 role="template-kw-filt-author">user</literal>: Any text,
|
bos@559
|
406 but most useful for the <literal
|
bos@559
|
407 role="template-keyword">author</literal> keyword. Return
|
bos@559
|
408 the <quote>user</quote> portion of an email address. For
|
bos@559
|
409 example, <quote><literal>Bryan O'Sullivan
|
bos@559
|
410 <bos@serpentine.com></literal></quote> becomes
|
bos@559
|
411 <quote><literal>bos</literal></quote>.</para>
|
bos@559
|
412 </listitem></itemizedlist>
|
bos@559
|
413
|
bos@567
|
414 &interaction.template.simple.manyfilters;
|
bos@559
|
415
|
bos@559
|
416 <note>
|
bos@559
|
417 <para> If you try to apply a filter to a piece of data that it
|
bos@559
|
418 cannot process, Mercurial will fail and print a Python
|
bos@559
|
419 exception. For example, trying to run the output of the
|
bos@559
|
420 <literal role="template-keyword">desc</literal> keyword into
|
bos@559
|
421 the <literal role="template-kw-filt-date">isodate</literal>
|
bos@559
|
422 filter is not a good idea.</para>
|
bos@559
|
423 </note>
|
bos@559
|
424
|
bos@559
|
425 <sect2>
|
bos@559
|
426 <title>Combining filters</title>
|
bos@559
|
427
|
bos@559
|
428 <para>It is easy to combine filters to yield output in the form
|
bos@559
|
429 you would like. The following chain of filters tidies up a
|
bos@559
|
430 description, then makes sure that it fits cleanly into 68
|
bos@559
|
431 columns, then indents it by a further 8 characters (at least
|
bos@559
|
432 on Unix-like systems, where a tab is conventionally 8
|
bos@559
|
433 characters wide).</para>
|
bos@559
|
434
|
bos@567
|
435 &interaction.template.simple.combine;
|
bos@559
|
436
|
bos@559
|
437 <para>Note the use of <quote><literal>\t</literal></quote> (a
|
bos@559
|
438 tab character) in the template to force the first line to be
|
bos@559
|
439 indented; this is necessary since <literal
|
bos@559
|
440 role="template-keyword">tabindent</literal> indents all
|
bos@559
|
441 lines <emphasis>except</emphasis> the first.</para>
|
bos@559
|
442
|
bos@559
|
443 <para>Keep in mind that the order of filters in a chain is
|
bos@559
|
444 significant. The first filter is applied to the result of the
|
bos@559
|
445 keyword; the second to the result of the first filter; and so
|
bos@559
|
446 on. For example, using <literal>fill68|tabindent</literal>
|
bos@559
|
447 gives very different results from
|
bos@559
|
448 <literal>tabindent|fill68</literal>.</para>
|
bos@559
|
449
|
bos@559
|
450
|
bos@559
|
451 </sect2>
|
bos@559
|
452 </sect1>
|
bos@559
|
453 <sect1>
|
bos@559
|
454 <title>From templates to styles</title>
|
bos@559
|
455
|
bos@559
|
456 <para>A command line template provides a quick and simple way to
|
bos@559
|
457 format some output. Templates can become verbose, though, and
|
bos@559
|
458 it's useful to be able to give a template a name. A style file
|
bos@559
|
459 is a template with a name, stored in a file.</para>
|
bos@559
|
460
|
bos@559
|
461 <para>More than that, using a style file unlocks the power of
|
bos@559
|
462 Mercurial's templating engine in ways that are not possible
|
bos@559
|
463 using the command line <option
|
bos@559
|
464 role="hg-opt-log">--template</option> option.</para>
|
bos@559
|
465
|
bos@559
|
466 <sect2>
|
bos@559
|
467 <title>The simplest of style files</title>
|
bos@559
|
468
|
bos@559
|
469 <para>Our simple style file contains just one line:</para>
|
bos@559
|
470
|
bos@567
|
471 &interaction.template.simple.rev;
|
bos@559
|
472
|
bos@559
|
473 <para>This tells Mercurial, <quote>if you're printing a
|
bos@559
|
474 changeset, use the text on the right as the
|
bos@559
|
475 template</quote>.</para>
|
bos@559
|
476
|
bos@559
|
477 </sect2>
|
bos@559
|
478 <sect2>
|
bos@559
|
479 <title>Style file syntax</title>
|
bos@559
|
480
|
bos@559
|
481 <para>The syntax rules for a style file are simple.</para>
|
bos@559
|
482
|
bos@559
|
483 <itemizedlist>
|
bos@559
|
484 <listitem><para>The file is processed one line at a
|
bos@559
|
485 time.</para>
|
bos@559
|
486 </listitem>
|
bos@559
|
487 <listitem><para>Leading and trailing white space are
|
bos@559
|
488 ignored.</para>
|
bos@559
|
489 </listitem>
|
bos@559
|
490 <listitem><para>Empty lines are skipped.</para>
|
bos@559
|
491 </listitem>
|
bos@559
|
492 <listitem><para>If a line starts with either of the characters
|
bos@559
|
493 <quote><literal>#</literal></quote> or
|
bos@559
|
494 <quote><literal>;</literal></quote>, the entire line is
|
bos@559
|
495 treated as a comment, and skipped as if empty.</para>
|
bos@559
|
496 </listitem>
|
bos@559
|
497 <listitem><para>A line starts with a keyword. This must start
|
bos@559
|
498 with an alphabetic character or underscore, and can
|
bos@559
|
499 subsequently contain any alphanumeric character or
|
bos@559
|
500 underscore. (In regexp notation, a keyword must match
|
bos@559
|
501 <literal>[A-Za-z_][A-Za-z0-9_]*</literal>.)</para>
|
bos@559
|
502 </listitem>
|
bos@559
|
503 <listitem><para>The next element must be an
|
bos@559
|
504 <quote><literal>=</literal></quote> character, which can
|
bos@559
|
505 be preceded or followed by an arbitrary amount of white
|
bos@559
|
506 space.</para>
|
bos@559
|
507 </listitem>
|
bos@559
|
508 <listitem><para>If the rest of the line starts and ends with
|
bos@559
|
509 matching quote characters (either single or double quote),
|
bos@559
|
510 it is treated as a template body.</para>
|
bos@559
|
511 </listitem>
|
bos@559
|
512 <listitem><para>If the rest of the line <emphasis>does
|
bos@559
|
513 not</emphasis> start with a quote character, it is
|
bos@559
|
514 treated as the name of a file; the contents of this file
|
bos@559
|
515 will be read and used as a template body.</para>
|
bos@559
|
516 </listitem></itemizedlist>
|
bos@559
|
517
|
bos@559
|
518 </sect2>
|
bos@559
|
519 </sect1>
|
bos@559
|
520 <sect1>
|
bos@559
|
521 <title>Style files by example</title>
|
bos@559
|
522
|
bos@559
|
523 <para>To illustrate how to write a style file, we will construct a
|
bos@559
|
524 few by example. Rather than provide a complete style file and
|
bos@559
|
525 walk through it, we'll mirror the usual process of developing a
|
bos@559
|
526 style file by starting with something very simple, and walking
|
bos@559
|
527 through a series of successively more complete examples.</para>
|
bos@559
|
528
|
bos@559
|
529 <sect2>
|
bos@559
|
530 <title>Identifying mistakes in style files</title>
|
bos@559
|
531
|
bos@559
|
532 <para>If Mercurial encounters a problem in a style file you are
|
bos@559
|
533 working on, it prints a terse error message that, once you
|
bos@559
|
534 figure out what it means, is actually quite useful.</para>
|
bos@559
|
535
|
bos@567
|
536 &interaction.template.svnstyle.syntax.input;
|
bos@559
|
537
|
bos@559
|
538 <para>Notice that <filename>broken.style</filename> attempts to
|
bos@559
|
539 define a <literal>changeset</literal> keyword, but forgets to
|
bos@559
|
540 give any content for it. When instructed to use this style
|
bos@559
|
541 file, Mercurial promptly complains.</para>
|
bos@559
|
542
|
bos@567
|
543 &interaction.template.svnstyle.syntax.error;
|
bos@559
|
544
|
bos@559
|
545 <para>This error message looks intimidating, but it is not too
|
bos@559
|
546 hard to follow.</para>
|
bos@559
|
547
|
bos@559
|
548 <itemizedlist>
|
bos@559
|
549 <listitem><para>The first component is simply Mercurial's way
|
bos@559
|
550 of saying <quote>I am giving up</quote>.</para>
|
bos@559
|
551 <programlisting>___abort___: broken.style:1: parse
|
bos@559
|
552 error</programlisting>
|
bos@559
|
553 </listitem>
|
bos@559
|
554 <listitem><para>Next comes the name of the style file that
|
bos@559
|
555 contains the error.</para>
|
bos@559
|
556 <programlisting>
|
bos@559
|
557 abort: ___broken.style___:1: parse error
|
bos@559
|
558 </programlisting>
|
bos@559
|
559 </listitem>
|
bos@559
|
560 <listitem><para>Following the file name is the line number
|
bos@559
|
561 where the error was encountered.</para>
|
bos@559
|
562 <programlisting>abort: broken.style:___1___: parse
|
bos@559
|
563 error</programlisting>
|
bos@559
|
564 </listitem>
|
bos@559
|
565 <listitem><para>Finally, a description of what went
|
bos@559
|
566 wrong.</para>
|
bos@559
|
567 <programlisting>abort: broken.style:1: ___parse
|
bos@559
|
568 error___</programlisting>
|
bos@559
|
569 </listitem>
|
bos@559
|
570 <listitem><para>The description of the problem is not always
|
bos@559
|
571 clear (as in this case), but even when it is cryptic, it
|
bos@559
|
572 is almost always trivial to visually inspect the offending
|
bos@559
|
573 line in the style file and see what is wrong.</para>
|
bos@559
|
574 </listitem></itemizedlist>
|
bos@559
|
575
|
bos@559
|
576 </sect2>
|
bos@559
|
577 <sect2>
|
bos@559
|
578 <title>Uniquely identifying a repository</title>
|
bos@559
|
579
|
bos@559
|
580 <para>If you would like to be able to identify a Mercurial
|
bos@559
|
581 repository <quote>fairly uniquely</quote> using a short string
|
bos@559
|
582 as an identifier, you can use the first revision in the
|
bos@567
|
583 repository.</para>
|
bos@567
|
584
|
bos@567
|
585 &interaction.template.svnstyle.id;
|
bos@567
|
586
|
bos@567
|
587 <para>This is not guaranteed to be unique, but it is
|
bos@567
|
588 nevertheless useful in many cases.</para>
|
bos@559
|
589 <itemizedlist>
|
bos@559
|
590 <listitem><para>It will not work in a completely empty
|
bos@559
|
591 repository, because such a repository does not have a
|
bos@559
|
592 revision zero.</para>
|
bos@559
|
593 </listitem>
|
bos@559
|
594 <listitem><para>Neither will it work in the (extremely rare)
|
bos@559
|
595 case where a repository is a merge of two or more formerly
|
bos@559
|
596 independent repositories, and you still have those
|
bos@559
|
597 repositories around.</para>
|
bos@559
|
598 </listitem></itemizedlist>
|
bos@559
|
599 <para>Here are some uses to which you could put this
|
bos@559
|
600 identifier:</para>
|
bos@559
|
601 <itemizedlist>
|
bos@559
|
602 <listitem><para>As a key into a table for a database that
|
bos@559
|
603 manages repositories on a server.</para>
|
bos@559
|
604 </listitem>
|
bos@559
|
605 <listitem><para>As half of a {<emphasis>repository
|
bos@559
|
606 ID</emphasis>, <emphasis>revision ID</emphasis>} tuple.
|
bos@559
|
607 Save this information away when you run an automated build
|
bos@559
|
608 or other activity, so that you can <quote>replay</quote>
|
bos@559
|
609 the build later if necessary.</para>
|
bos@559
|
610 </listitem></itemizedlist>
|
bos@559
|
611
|
bos@559
|
612 </sect2>
|
bos@559
|
613 <sect2>
|
bos@559
|
614 <title>Mimicking Subversion's output</title>
|
bos@559
|
615
|
bos@559
|
616 <para>Let's try to emulate the default output format used by
|
bos@567
|
617 another revision control tool, Subversion.</para>
|
bos@567
|
618
|
bos@567
|
619 &interaction.template.svnstyle.short;
|
bos@559
|
620
|
bos@559
|
621 <para>Since Subversion's output style is fairly simple, it is
|
bos@559
|
622 easy to copy-and-paste a hunk of its output into a file, and
|
bos@559
|
623 replace the text produced above by Subversion with the
|
bos@567
|
624 template values we'd like to see expanded.</para>
|
bos@567
|
625
|
bos@567
|
626 &interaction.template.svnstyle.template;
|
bos@559
|
627
|
bos@559
|
628 <para>There are a few small ways in which this template deviates
|
bos@559
|
629 from the output produced by Subversion.</para>
|
bos@559
|
630 <itemizedlist>
|
bos@559
|
631 <listitem><para>Subversion prints a <quote>readable</quote>
|
ori@561
|
632 date (the <quote><literal>Wed, 27 Sep 2006</literal></quote> in the
|
bos@559
|
633 example output above) in parentheses. Mercurial's
|
bos@559
|
634 templating engine does not provide a way to display a date
|
bos@559
|
635 in this format without also printing the time and time
|
bos@559
|
636 zone.</para>
|
bos@559
|
637 </listitem>
|
bos@559
|
638 <listitem><para>We emulate Subversion's printing of
|
bos@559
|
639 <quote>separator</quote> lines full of
|
bos@559
|
640 <quote><literal>-</literal></quote> characters by ending
|
bos@559
|
641 the template with such a line. We use the templating
|
bos@559
|
642 engine's <literal role="template-keyword">header</literal>
|
bos@559
|
643 keyword to print a separator line as the first line of
|
bos@559
|
644 output (see below), thus achieving similar output to
|
bos@559
|
645 Subversion.</para>
|
bos@559
|
646 </listitem>
|
bos@559
|
647 <listitem><para>Subversion's output includes a count in the
|
bos@559
|
648 header of the number of lines in the commit message. We
|
bos@559
|
649 cannot replicate this in Mercurial; the templating engine
|
bos@559
|
650 does not currently provide a filter that counts the number
|
bos@559
|
651 of lines the template generates.</para>
|
bos@559
|
652 </listitem></itemizedlist>
|
bos@559
|
653 <para>It took me no more than a minute or two of work to replace
|
bos@559
|
654 literal text from an example of Subversion's output with some
|
bos@559
|
655 keywords and filters to give the template above. The style
|
bos@567
|
656 file simply refers to the template.</para>
|
bos@567
|
657
|
bos@567
|
658 &interaction.template.svnstyle.style;
|
bos@559
|
659
|
bos@559
|
660 <para>We could have included the text of the template file
|
bos@559
|
661 directly in the style file by enclosing it in quotes and
|
bos@559
|
662 replacing the newlines with
|
bos@559
|
663 <quote><literal>\n</literal></quote> sequences, but it would
|
bos@559
|
664 have made the style file too difficult to read. Readability
|
bos@559
|
665 is a good guide when you're trying to decide whether some text
|
bos@559
|
666 belongs in a style file, or in a template file that the style
|
bos@559
|
667 file points to. If the style file will look too big or
|
bos@559
|
668 cluttered if you insert a literal piece of text, drop it into
|
bos@559
|
669 a template instead.</para>
|
bos@559
|
670
|
bos@559
|
671 </sect2>
|
bos@559
|
672 </sect1>
|
bos@559
|
673 </chapter>
|
bos@559
|
674
|
bos@559
|
675 <!--
|
bos@559
|
676 local variables:
|
bos@559
|
677 sgml-parent-document: ("00book.xml" "book" "chapter")
|
bos@559
|
678 end:
|
bos@559
|
679 -->
|