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