1.1 --- a/en/template.tex	Mon Sep 04 10:58:09 2006 -0700
     1.2 +++ b/en/template.tex	Wed Sep 06 23:36:47 2006 -0700
     1.3 @@ -1,5 +1,288 @@
     1.4 -\chapter{Using templates to customise output}
     1.5 -\label{chap:templates}
     1.6 +\chapter{Customising the output of Mercurial}
     1.7 +\label{chap:template}
     1.8 +
     1.9 +Mercurial provides a powerful mechanism to let you control how it
    1.10 +displays information.  The mechanism is based on templates.  You can
    1.11 +use templates to generate specific output for a single command, or to
    1.12 +customise the entire appearance of the built-in web interface.
    1.13 +
    1.14 +\section{Using precanned output styles}
    1.15 +\label{sec:style}
    1.16 +
    1.17 +Packaged with Mercurial are some output styles that you can use
    1.18 +immediately.  A style is simply a precanned template that someone
    1.19 +wrote.
    1.20 +
    1.21 +Before we take a look at Mercurial's bundled styles, let's review its
    1.22 +normal output.
    1.23 +
    1.24 +\interaction{template.simple.normal}
    1.25 +
    1.26 +This is somewhat informative, but it takes up a lot of space---five
    1.27 +lines of output per changeset.  The \texttt{compact} style reduces
    1.28 +this to three lines, presented in a sparse manner.
    1.29 +
    1.30 +\interaction{template.simple.compact}
    1.31 +
    1.32 +The \texttt{changelog} style hints at the expressive power of
    1.33 +Mercurial's templating engine.  This style attempts to follow the GNU
    1.34 +Project's changelog guidelines\cite{web:changelog}.
    1.35 +
    1.36 +\interaction{template.simple.changelog}
    1.37 +
    1.38 +You will not be shocked to learn that Mercurial's default output style
    1.39 +is named \texttt{default}.
    1.40 +
    1.41 +\subsection{Setting an output style to use}
    1.42 +
    1.43 +You can modify the output style that Mercurial will use for every
    1.44 +command by editing your \hgrc\ file, naming the style you would
    1.45 +prefer to use.
    1.46 +
    1.47 +\begin{codesample2}
    1.48 +  [ui]
    1.49 +  style = compact
    1.50 +\end{codesample2}
    1.51 +
    1.52 +If you write a style of your own, you can use it by either providing
    1.53 +the path to your style file, or copying your style file into a
    1.54 +location where Mercurial can find it (typically the \texttt{templates}
    1.55 +subdirectory of your Mercurial install directory).
    1.56 +
    1.57 +\section{Commands that support styles and templates}
    1.58 +
    1.59 +All of Mercurial's ``\texttt{log}-like'' commands let you use styles
    1.60 +and templates: \hgcmd{incoming}, \hgcmd{log}, \hgcmd{outgoing}, and
    1.61 +\hgcmd{tip}.
    1.62 +
    1.63 +As I write this manual, these are so far the only commands that
    1.64 +support styles and templates.  Since these are the most important
    1.65 +commands that need customisable output, there has been little pressure
    1.66 +from the Mercurial user community to add style and template support to
    1.67 +other commands.
    1.68 +
    1.69 +\section{The basics of templating}
    1.70 +
    1.71 +At its simplest, a Mercurial template is a piece of text.  Some of the
    1.72 +text never changes, while other parts are \emph{expanded}, or replaced
    1.73 +with new text, when necessary.
    1.74 +
    1.75 +Before we continue, let's look again at a simple example of
    1.76 +Mercurial's normal output.
    1.77 +
    1.78 +\interaction{template.simple.normal}
    1.79 +
    1.80 +Now, let's run the same command, but using a template to change its
    1.81 +output.
    1.82 +
    1.83 +\interaction{template.simple.simplest}
    1.84 +
    1.85 +The example above illustrates the simplest possible template; it's
    1.86 +just a piece of static text, printed once for each changeset.  The
    1.87 +\hgopt{log}{--template} option to the \hgcmd{log} command tells
    1.88 +Mercurial to use the given text as the template when printing each
    1.89 +changeset.
    1.90 +
    1.91 +Notice that the template string above ends with the text
    1.92 +``\Verb+\n+''.  This is an \emph{escape sequence}, telling Mercurial
    1.93 +to print a newline at the end of each template item.  If you omit this
    1.94 +newline, Mercurial will run each piece of output together.  See
    1.95 +section~\ref{sec:template:escape} for more details of escape sequences.
    1.96 +
    1.97 +A template that prints a fixed string of text all the time isn't very
    1.98 +useful; let's try something a bit more complex.
    1.99 +
   1.100 +\interaction{template.simple.simplesub}
   1.101 +
   1.102 +As you can see, the string ``\Verb+{desc}+'' in the template has been
   1.103 +replaced in the output with the description of each changeset.  Every
   1.104 +time Mercurial finds text enclosed in curly braces (``\texttt{\{}''
   1.105 +and ``\texttt{\}}''), it will try to replace the braces and text with
   1.106 +the expansion of whatever is inside.  To print a literal curly brace,
   1.107 +you must escape it, as described in section~\ref{sec:template:escape}.
   1.108 +
   1.109 +\section{Basic template keywords}
   1.110 +\label{sec:template:keyword}
   1.111 +
   1.112 +You can start writing simple templates immediately using the keywords
   1.113 +below.
   1.114 +
   1.115 +\begin{itemize}
   1.116 +\item[\tplkword{author}] String.  The unmodified author of the changeset.
   1.117 +\item[\tplkword{date}] Date information.  The date when the changeset
   1.118 +  was committed.  This is \emph{not} human-readable; you must pass it
   1.119 +  through a filter that will render it appropriately.  See
   1.120 +  section~\ref{sec:template:filter} for more information on filters.
   1.121 +  The date is expressed as a pair of numbers.  The first number is a
   1.122 +  Unix UTC timestamp (seconds since January 1, 1970); the second is
   1.123 +  the offset of the committer's timezone from UTC, in seconds.
   1.124 +\item[\tplkword{desc}] String.  The text of the changeset description.
   1.125 +\item[\tplkword{files}] List of strings.  All files modified, added, or
   1.126 +  removed by this changeset.
   1.127 +\item[\tplkword{file\_adds}] List of strings.  Files added by this
   1.128 +  changeset.
   1.129 +\item[\tplkword{file\_dels}] List of strings.  Files removed by this
   1.130 +  changeset.
   1.131 +\item[\tplkword{node}] String.  The changeset identification hash, as a
   1.132 +  40-character hexadecimal string.
   1.133 +\item[\tplkword{parents}] List of strings.  The parents of the
   1.134 +  changeset.
   1.135 +\item[\tplkword{rev}] Integer.  The repository-local changeset revision
   1.136 +  number.
   1.137 +\item[\tplkword{tags}] List of strings.  Any tags associated with the
   1.138 +  changeset.
   1.139 +\end{itemize}
   1.140 +
   1.141 +A few simple experiments will show us what to expect when we use these
   1.142 +keywords; you can see the results in
   1.143 +figure~\ref{fig:template:keywords}.
   1.144 +
   1.145 +\begin{figure}
   1.146 +  \interaction{template.simple.keywords}
   1.147 +  \caption{Template keywords in use}
   1.148 +  \label{fig:template:keywords}
   1.149 +\end{figure}
   1.150 +
   1.151 +As we noted above, the date keyword does not produce human-readable
   1.152 +output, so we must treat it specially.  This involves using a
   1.153 +\emph{filter}, about which more in section~\ref{sec:template:filter}.
   1.154 +
   1.155 +\interaction{template.simple.datekeyword}
   1.156 +
   1.157 +\section{Escape sequences}
   1.158 +\label{sec:template:escape}
   1.159 +
   1.160 +Mercurial's templating engine recognises the most commonly used escape
   1.161 +sequences in strings.  When it sees a backslash (``\Verb+\+'')
   1.162 +character, it looks at the following character and substitutes the two
   1.163 +characters with a single replacement, as described below.
   1.164 +
   1.165 +\begin{itemize}
   1.166 +\item[\Verb+\textbackslash\textbackslash+] Backslash, ``\Verb+\+'',
   1.167 +  ASCII~134.
   1.168 +\item[\Verb+\textbackslash n+] Newline, ASCII~12.
   1.169 +\item[\Verb+\textbackslash r+] Carriage return, ASCII~15.
   1.170 +\item[\Verb+\textbackslash t+] Tab, ASCII~11.
   1.171 +\item[\Verb+\textbackslash v+] Vertical tab, ASCII~13.
   1.172 +\item[\Verb+\textbackslash \{+] Open curly brace, ``\Verb+{+'', ASCII~173.
   1.173 +\item[\Verb+\textbackslash \}+] Close curly brace, ``\Verb+}+'', ASCII~175.
   1.174 +\end{itemize}
   1.175 +
   1.176 +As indicated above, if you want the expansion of a template to contain
   1.177 +a literal ``\Verb+\+'', ``\Verb+{+'', or ``\Verb+{+'' character, you
   1.178 +must escape it.
   1.179 +
   1.180 +\section{Filtering expanded keywords}
   1.181 +\label{sec:template:filter}
   1.182 +
   1.183 +Some of the results of template expansion are not entirely easy to
   1.184 +use.  Mercurial lets you specify an optional chain of \emph{filters}
   1.185 +to modify the result of expanding a keyword.  You have already seen a
   1.186 +common filter, \tplkwfilt{date}{isodate}, in action above, to make a
   1.187 +date readable.
   1.188 +
   1.189 +\begin{itemize}
   1.190 +\item[\tplfilter{addbreaks}] Any text. Add an XHTML ``\Verb+<br/>+''
   1.191 +  tag before the end of every line except the last.  For example,
   1.192 +  ``\Verb+foo\nbar+'' becomes ``\Verb+foo<br/>\nbar+''.
   1.193 +\item[\tplkwfilt{date}{age}] \tplkword{date} keyword.  Render the
   1.194 +  age of the date, relative to the current time.  Yields a string like
   1.195 +  ``\Verb+10 minutes+''.
   1.196 +\item[\tplfilter{basename}] Any text, but most useful for the
   1.197 +  \tplkword{files} keyword and its relatives.  Treat the text as a
   1.198 +  path, and return the basename. For example, ``\Verb+foo/bar/baz+''
   1.199 +  becomes ``\Verb+baz+''.
   1.200 +\item[\tplkwfilt{date}{date}] \tplkword{date} keyword.  Render a date
   1.201 +  in a similar format to the Unix \tplkword{date} command, but with
   1.202 +  timezone included.  Yields a string like
   1.203 +  ``\Verb+Mon Sep 04 15:13:13 2006 -0700+''.
   1.204 +\item[\tplkwfilt{author}{domain}] Any text, but most useful for the
   1.205 +  \tplkword{author} keyword.  Finds the first string that looks like
   1.206 +  an email address, and extract just the domain component.  For
   1.207 +  example, ``\Verb+Bryan O'Sullivan <bos@serpentine.com>+'' becomes
   1.208 +  ``\Verb+serpentine.com+''.
   1.209 +\item[\tplkwfilt{author}{email}] Any text, but most useful for the
   1.210 +  \tplkword{author} keyword.  Extract the first string that looks like
   1.211 +  an email address.  For example,
   1.212 +  ``\Verb+Bryan O'Sullivan <bos@serpentine.com>+'' becomes
   1.213 +  ``\Verb+bos@serpentine.com+''.
   1.214 +\item[\tplfilter{escape}] Any text.  Replace the special XML/XHTML
   1.215 +  characters ``\Verb+&+'', ``\Verb+<+'' and ``\Verb+>+'' with
   1.216 +  XML entities.
   1.217 +\item[\tplfilter{fill68}] Any text.  Wrap the text to fit in 68
   1.218 +  columns.  This is useful before you pass text through the
   1.219 +  \tplfilter{tabindent} filter, and still want it to fit in an
   1.220 +  80-column fixed-font window.
   1.221 +\item[\tplfilter{fill76}] Any text.  Wrap the text to fit in 76
   1.222 +  columns.
   1.223 +\item[\tplfilter{firstline}] Any text.  Yield the first line of text,
   1.224 +  without any trailing newlines.
   1.225 +\item[\tplkwfilt{date}{hgdate}] \tplkword{date} keyword.  Render the
   1.226 +  date as a pair of readable numbers.  Yields a string like
   1.227 +  ``\Verb+1157407993 25200+''.
   1.228 +\item[\tplkwfilt{date}{isodate}] \tplkword{date} keyword.  Render the
   1.229 +  date as a text string in ISO~8601 format.  Yields a string like
   1.230 +  ``\Verb+2006-09-04 15:13:13 -0700+''.
   1.231 +\item[\tplfilter{obfuscate}] Any text, but most useful for the
   1.232 +  \tplkword{author} keyword.  Yield the input text rendered as a
   1.233 +  sequence of XML entities.  This helps to defeat some particularly
   1.234 +  stupid screen-scraping email harvesting spambots.
   1.235 +\item[\tplkwfilt{author}{person}] Any text, but most useful for the
   1.236 +  \tplkword{author} keyword.  Yield the text before an email address.
   1.237 +  For example, ``\Verb+Bryan O'Sullivan <bos@serpentine.com>+''
   1.238 +  becomes ``\Verb+Bryan O'Sullivan+''.
   1.239 +\item[\tplkwfilt{date}{rfc822date}] \tplkword{date} keyword.  Render a
   1.240 +  date using the same format used in email headers.  Yields a string
   1.241 +  like ``\Verb+Mon, 04 Sep 2006 15:13:13 -0700+''.
   1.242 +\item[\tplkwfilt{node}{short}] Changeset hash.  Yield the short form
   1.243 +  of a changeset hash, i.e.~a 12-byte hexadecimal string.
   1.244 +\item[\tplkwfilt{date}{shortdate}] \tplkword{date} keyword.  Render
   1.245 +  the year, month, and day of the date.  Yields a string like
   1.246 +  ``\Verb+2006-09-04+''.
   1.247 +\item[\tplfilter{strip}] Any text.  Strip all leading and trailing
   1.248 +  whitespace from the string.
   1.249 +\item[\tplfilter{tabindent}] Any text.  Yield the text, with every line
   1.250 +  except the first starting with a tab character.
   1.251 +\item[\tplfilter{urlescape}] Any text.  Escape all characters that are
   1.252 +  considered ``special'' by URL parsers.  For example, \Verb+foo bar+
   1.253 +  becomes \Verb+foo%20bar+.
   1.254 +\item[\tplkwfilt{author}{user}] Any text, but most useful for the
   1.255 +  \tplkword{author} keyword.  Return the ``user'' portion of an email
   1.256 +  address.  For example,
   1.257 +  ``\Verb+Bryan O'Sullivan <bos@serpentine.com>+'' becomes
   1.258 +  ``\Verb+bos+''.
   1.259 +\end{itemize}
   1.260 +
   1.261 +\begin{figure}
   1.262 +  \interaction{template.simple.manyfilters}
   1.263 +  \caption{Template filters in action}
   1.264 +  \label{fig:template:filters}
   1.265 +\end{figure}
   1.266 +
   1.267 +\begin{note}
   1.268 +  If you try to apply a filter to a piece of data that it cannot
   1.269 +  process, Mercurial will fail and print a Python exception.  For
   1.270 +  example, trying to run the output of the \tplkword{desc} keyword
   1.271 +  into the \tplkwfilt{date}{isodate} filter is not a good idea.
   1.272 +\end{note}
   1.273 +
   1.274 +\subsection{Combining filters}
   1.275 +
   1.276 +It is easy to combine filters to yield output in the form you would
   1.277 +like.  The following chain of filters tidies up a description, then
   1.278 +makes sure that it fits cleanly into 68 columns, then indents it by a
   1.279 +further 8~characters (at least on Unix-like systems, where a tab is
   1.280 +conventionally 8~characters wide).
   1.281 +
   1.282 +\interaction{template.simple.combine}
   1.283 +
   1.284 +Note the use of ``\Verb+\t+'' (a tab character) in the template to
   1.285 +force the first line to be indented; this is necessary since
   1.286 +\tplkword{tabindent} indents all lines \emph{except} the first.
   1.287 +
   1.288 +Keep in mind that the order of filters in a chain is significant.
   1.289 +Using \Verb+fill68|tabindent+ gives very different results from
   1.290 +\Verb+tabindent|fill68+.
   1.291  
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