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| author | Romain PELISSE <belaran@gmail.com> |
|---|---|
| date | Sat Sep 12 17:58:56 2009 +0200 (2009-09-12) |
| parents | 6b680d569bb4 f0110009e946 |
| children |
line source
1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
3 <chapter id="chap:template">
4 <?dbhtml filename="customizing-the-output-of-mercurial.html"?>
5 <title>Customizing the output of Mercurial</title>
7 <para id="x_578">Mercurial provides a powerful mechanism to let you control how
8 it displays information. The mechanism is based on templates.
9 You can use templates to generate specific output for a single
10 command, or to customize the entire appearance of the built-in web
11 interface.</para>
13 <sect1 id="sec:style">
14 <title>Using precanned output styles</title>
16 <para id="x_579">Packaged with Mercurial are some output styles that you can
17 use immediately. A style is simply a precanned template that
18 someone wrote and installed somewhere that Mercurial can
19 find.</para>
21 <para id="x_57a">Before we take a look at Mercurial's bundled styles, let's
22 review its normal output.</para>
24 &interaction.template.simple.normal;
26 <para id="x_57b">This is somewhat informative, but it takes up a lot of
27 space&emdash;five lines of output per changeset. The
28 <literal>compact</literal> style reduces this to three lines,
29 presented in a sparse manner.</para>
31 &interaction.template.simple.compact;
33 <para id="x_57c">The <literal>changelog</literal> style hints at the
34 expressive power of Mercurial's templating engine. This style
35 attempts to follow the GNU Project's changelog
36 guidelines<citation>web:changelog</citation>.</para>
38 &interaction.template.simple.changelog;
40 <para id="x_57d">You will not be shocked to learn that Mercurial's default
41 output style is named <literal>default</literal>.</para>
43 <sect2>
44 <title>Setting a default style</title>
46 <para id="x_57e">You can modify the output style that Mercurial will use
47 for every command by editing your <filename
48 role="special">~/.hgrc</filename> file, naming the style
49 you would prefer to use.</para>
51 <programlisting>[ui]
52 style = compact</programlisting>
54 <para id="x_57f">If you write a style of your own, you can use it by either
55 providing the path to your style file, or copying your style
56 file into a location where Mercurial can find it (typically
57 the <literal>templates</literal> subdirectory of your
58 Mercurial install directory).</para>
59 </sect2>
60 </sect1>
62 <sect1>
63 <title>Commands that support styles and templates</title>
65 <para id="x_580">All of Mercurial's
66 <quote><literal>log</literal>-like</quote> commands let you use
67 styles and templates: <command role="hg-cmd">hg
68 incoming</command>, <command role="hg-cmd">hg log</command>,
69 <command role="hg-cmd">hg outgoing</command>, and <command
70 role="hg-cmd">hg tip</command>.</para>
72 <para id="x_581">As I write this manual, these are so far the only commands
73 that support styles and templates. Since these are the most
74 important commands that need customizable output, there has been
75 little pressure from the Mercurial user community to add style
76 and template support to other commands.</para>
77 </sect1>
79 <sect1>
80 <title>The basics of templating</title>
82 <para id="x_582">At its simplest, a Mercurial template is a piece of text.
83 Some of the text never changes, while other parts are
84 <emphasis>expanded</emphasis>, or replaced with new text, when
85 necessary.</para>
87 <para id="x_583">Before we continue, let's look again at a simple example of
88 Mercurial's normal output.</para>
90 &interaction.template.simple.normal;
92 <para id="x_584">Now, let's run the same command, but using a template to
93 change its output.</para>
95 &interaction.template.simple.simplest;
97 <para id="x_585">The example above illustrates the simplest possible
98 template; it's just a piece of static text, printed once for
99 each changeset. The <option
100 role="hg-opt-log">--template</option> option to the <command
101 role="hg-cmd">hg log</command> command tells Mercurial to use
102 the given text as the template when printing each
103 changeset.</para>
105 <para id="x_586">Notice that the template string above ends with the text
106 <quote><literal>\n</literal></quote>. This is an
107 <emphasis>escape sequence</emphasis>, telling Mercurial to print
108 a newline at the end of each template item. If you omit this
109 newline, Mercurial will run each piece of output together. See
110 <xref linkend="sec:template:escape"/> for more details
111 of escape sequences.</para>
113 <para id="x_587">A template that prints a fixed string of text all the time
114 isn't very useful; let's try something a bit more
115 complex.</para>
117 &interaction.template.simple.simplesub;
119 <para id="x_588">As you can see, the string
120 <quote><literal>{desc}</literal></quote> in the template has
121 been replaced in the output with the description of each
122 changeset. Every time Mercurial finds text enclosed in curly
123 braces (<quote><literal>{</literal></quote> and
124 <quote><literal>}</literal></quote>), it will try to replace the
125 braces and text with the expansion of whatever is inside. To
126 print a literal curly brace, you must escape it, as described in
127 <xref linkend="sec:template:escape"/>.</para>
128 </sect1>
130 <sect1 id="sec:template:keyword">
131 <title>Common template keywords</title>
133 <para id="x_589">You can start writing simple templates immediately using the
134 keywords below.</para>
136 <itemizedlist>
137 <listitem><para id="x_58a"><literal
138 role="template-keyword">author</literal>: String. The
139 unmodified author of the changeset.</para>
140 </listitem>
141 <listitem><para id="x_58b"><literal
142 role="template-keyword">branches</literal>: String. The
143 name of the branch on which the changeset was committed.
144 Will be empty if the branch name was
145 <literal>default</literal>.</para>
146 </listitem>
147 <listitem><para id="x_58c"><literal role="template-keyword">date</literal>:
148 Date information. The date when the changeset was
149 committed. This is <emphasis>not</emphasis> human-readable;
150 you must pass it through a filter that will render it
151 appropriately. See <xref
152 linkend="sec:template:filter"/> for more information
153 on filters. The date is expressed as a pair of numbers. The
154 first number is a Unix UTC timestamp (seconds since January
155 1, 1970); the second is the offset of the committer's
156 timezone from UTC, in seconds.</para>
157 </listitem>
158 <listitem><para id="x_58d"><literal role="template-keyword">desc</literal>:
159 String. The text of the changeset description.</para>
160 </listitem>
161 <listitem><para id="x_58e"><literal
162 role="template-keyword">files</literal>: List of strings.
163 All files modified, added, or removed by this
164 changeset.</para>
165 </listitem>
166 <listitem><para id="x_58f"><literal
167 role="template-keyword">file_adds</literal>: List of
168 strings. Files added by this changeset.</para>
169 </listitem>
170 <listitem><para id="x_590"><literal
171 role="template-keyword">file_dels</literal>: List of
172 strings. Files removed by this changeset.</para>
173 </listitem>
174 <listitem><para id="x_591"><literal role="template-keyword">node</literal>:
175 String. The changeset identification hash, as a
176 40-character hexadecimal string.</para>
177 </listitem>
178 <listitem><para id="x_592"><literal
179 role="template-keyword">parents</literal>: List of
180 strings. The parents of the changeset.</para>
181 </listitem>
182 <listitem><para id="x_593"><literal role="template-keyword">rev</literal>:
183 Integer. The repository-local changeset revision
184 number.</para>
185 </listitem>
186 <listitem><para id="x_594"><literal role="template-keyword">tags</literal>:
187 List of strings. Any tags associated with the
188 changeset.</para>
189 </listitem>
190 </itemizedlist>
192 <para id="x_595">A few simple experiments will show us what to expect when we
193 use these keywords; you can see the results below.</para>
195 &interaction.template.simple.keywords;
197 <para id="x_596">As we noted above, the date keyword does not produce
198 human-readable output, so we must treat it specially. This
199 involves using a <emphasis>filter</emphasis>, about which more
200 in <xref linkend="sec:template:filter"/>.</para>
202 &interaction.template.simple.datekeyword;
203 </sect1>
205 <sect1 id="sec:template:escape">
206 <title>Escape sequences</title>
208 <para id="x_597">Mercurial's templating engine recognises the most commonly
209 used escape sequences in strings. When it sees a backslash
210 (<quote><literal>\</literal></quote>) character, it looks at the
211 following character and substitutes the two characters with a
212 single replacement, as described below.</para>
214 <itemizedlist>
215 <listitem><para id="x_598"><literal>\</literal>:
216 Backslash, <quote><literal>\</literal></quote>, ASCII
217 134.</para>
218 </listitem>
219 <listitem><para id="x_599"><literal>\n</literal>: Newline,
220 ASCII 12.</para>
221 </listitem>
222 <listitem><para id="x_59a"><literal>\r</literal>: Carriage
223 return, ASCII 15.</para>
224 </listitem>
225 <listitem><para id="x_59b"><literal>\t</literal>: Tab, ASCII
226 11.</para>
227 </listitem>
228 <listitem><para id="x_59c"><literal>\v</literal>: Vertical
229 tab, ASCII 13.</para>
230 </listitem>
231 <listitem><para id="x_59d"><literal>\{</literal>: Open curly
232 brace, <quote><literal>{</literal></quote>, ASCII
233 173.</para>
234 </listitem>
235 <listitem><para id="x_59e"><literal>\}</literal>: Close curly
236 brace, <quote><literal>}</literal></quote>, ASCII
237 175.</para>
238 </listitem></itemizedlist>
240 <para id="x_59f">As indicated above, if you want the expansion of a template
241 to contain a literal <quote><literal>\</literal></quote>,
242 <quote><literal>{</literal></quote>, or
243 <quote><literal>{</literal></quote> character, you must escape
244 it.</para>
245 </sect1>
247 <sect1 id="sec:template:filter">
248 <title>Filtering keywords to change their results</title>
250 <para id="x_5a0">Some of the results of template expansion are not
251 immediately easy to use. Mercurial lets you specify an optional
252 chain of <emphasis>filters</emphasis> to modify the result of
253 expanding a keyword. You have already seen a common filter,
254 <literal role="template-kw-filt-date">isodate</literal>, in
255 action above, to make a date readable.</para>
257 <para id="x_5a1">Below is a list of the most commonly used filters that
258 Mercurial supports. While some filters can be applied to any
259 text, others can only be used in specific circumstances. The
260 name of each filter is followed first by an indication of where
261 it can be used, then a description of its effect.</para>
263 <itemizedlist>
264 <listitem><para id="x_5a2"><literal
265 role="template-filter">addbreaks</literal>: Any text. Add
266 an XHTML <quote><literal><br/></literal></quote> tag
267 before the end of every line except the last. For example,
268 <quote><literal>foo\nbar</literal></quote> becomes
269 <quote><literal>foo<br/>\nbar</literal></quote>.</para>
270 </listitem>
271 <listitem><para id="x_5a3"><literal
272 role="template-kw-filt-date">age</literal>: <literal
273 role="template-keyword">date</literal> keyword. Render
274 the age of the date, relative to the current time. Yields a
275 string like <quote><literal>10
276 minutes</literal></quote>.</para>
277 </listitem>
278 <listitem><para id="x_5a4"><literal
279 role="template-filter">basename</literal>: Any text, but
280 most useful for the <literal
281 role="template-keyword">files</literal> keyword and its
282 relatives. Treat the text as a path, and return the
283 basename. For example,
284 <quote><literal>foo/bar/baz</literal></quote> becomes
285 <quote><literal>baz</literal></quote>.</para>
286 </listitem>
287 <listitem><para id="x_5a5"><literal
288 role="template-kw-filt-date">date</literal>: <literal
289 role="template-keyword">date</literal> keyword. Render a
290 date in a similar format to the Unix <literal
291 role="template-keyword">date</literal> command, but with
292 timezone included. Yields a string like <quote><literal>Mon
293 Sep 04 15:13:13 2006 -0700</literal></quote>.</para>
294 </listitem>
295 <listitem><para id="x_5a6"><literal
296 role="template-kw-filt-author">domain</literal>: Any text,
297 but most useful for the <literal
298 role="template-keyword">author</literal> keyword. Finds
299 the first string that looks like an email address, and
300 extract just the domain component. For example,
301 <quote><literal>Bryan O'Sullivan
302 <bos@serpentine.com></literal></quote> becomes
303 <quote><literal>serpentine.com</literal></quote>.</para>
304 </listitem>
305 <listitem><para id="x_5a7"><literal
306 role="template-kw-filt-author">email</literal>: Any text,
307 but most useful for the <literal
308 role="template-keyword">author</literal> keyword. Extract
309 the first string that looks like an email address. For
310 example, <quote><literal>Bryan O'Sullivan
311 <bos@serpentine.com></literal></quote> becomes
312 <quote><literal>bos@serpentine.com</literal></quote>.</para>
313 </listitem>
314 <listitem><para id="x_5a8"><literal
315 role="template-filter">escape</literal>: Any text.
316 Replace the special XML/XHTML characters
317 <quote><literal>&</literal></quote>,
318 <quote><literal><</literal></quote> and
319 <quote><literal>></literal></quote> with XML
320 entities.</para>
321 </listitem>
322 <listitem><para id="x_5a9"><literal
323 role="template-filter">fill68</literal>: Any text. Wrap
324 the text to fit in 68 columns. This is useful before you
325 pass text through the <literal
326 role="template-filter">tabindent</literal> filter, and
327 still want it to fit in an 80-column fixed-font
328 window.</para>
329 </listitem>
330 <listitem><para id="x_5aa"><literal
331 role="template-filter">fill76</literal>: Any text. Wrap
332 the text to fit in 76 columns.</para>
333 </listitem>
334 <listitem><para id="x_5ab"><literal
335 role="template-filter">firstline</literal>: Any text.
336 Yield the first line of text, without any trailing
337 newlines.</para>
338 </listitem>
339 <listitem><para id="x_5ac"><literal
340 role="template-kw-filt-date">hgdate</literal>: <literal
341 role="template-keyword">date</literal> keyword. Render
342 the date as a pair of readable numbers. Yields a string
343 like <quote><literal>1157407993
344 25200</literal></quote>.</para>
345 </listitem>
346 <listitem><para id="x_5ad"><literal
347 role="template-kw-filt-date">isodate</literal>: <literal
348 role="template-keyword">date</literal> keyword. Render
349 the date as a text string in ISO 8601 format. Yields a
350 string like <quote><literal>2006-09-04 15:13:13
351 -0700</literal></quote>.</para>
352 </listitem>
353 <listitem><para id="x_5ae"><literal
354 role="template-filter">obfuscate</literal>: Any text, but
355 most useful for the <literal
356 role="template-keyword">author</literal> keyword. Yield
357 the input text rendered as a sequence of XML entities. This
358 helps to defeat some particularly stupid screen-scraping
359 email harvesting spambots.</para>
360 </listitem>
361 <listitem><para id="x_5af"><literal
362 role="template-kw-filt-author">person</literal>: Any text,
363 but most useful for the <literal
364 role="template-keyword">author</literal> keyword. Yield
365 the text before an email address. For example,
366 <quote><literal>Bryan O'Sullivan
367 <bos@serpentine.com></literal></quote> becomes
368 <quote><literal>Bryan O'Sullivan</literal></quote>.</para>
369 </listitem>
370 <listitem><para id="x_5b0"><literal
371 role="template-kw-filt-date">rfc822date</literal>:
372 <literal role="template-keyword">date</literal> keyword.
373 Render a date using the same format used in email headers.
374 Yields a string like <quote><literal>Mon, 04 Sep 2006
375 15:13:13 -0700</literal></quote>.</para>
376 </listitem>
377 <listitem><para id="x_5b1"><literal
378 role="template-kw-filt-node">short</literal>: Changeset
379 hash. Yield the short form of a changeset hash, i.e. a
380 12-character hexadecimal string.</para>
381 </listitem>
382 <listitem><para id="x_5b2"><literal
383 role="template-kw-filt-date">shortdate</literal>: <literal
384 role="template-keyword">date</literal> keyword. Render
385 the year, month, and day of the date. Yields a string like
386 <quote><literal>2006-09-04</literal></quote>.</para>
387 </listitem>
388 <listitem><para id="x_5b3"><literal role="template-filter">strip</literal>:
389 Any text. Strip all leading and trailing whitespace from
390 the string.</para>
391 </listitem>
392 <listitem><para id="x_5b4"><literal
393 role="template-filter">tabindent</literal>: Any text.
394 Yield the text, with every line except the first starting
395 with a tab character.</para>
396 </listitem>
397 <listitem><para id="x_5b5"><literal
398 role="template-filter">urlescape</literal>: Any text.
399 Escape all characters that are considered
400 <quote>special</quote> by URL parsers. For example,
401 <literal>foo bar</literal> becomes
402 <literal>foo%20bar</literal>.</para>
403 </listitem>
404 <listitem><para id="x_5b6"><literal
405 role="template-kw-filt-author">user</literal>: Any text,
406 but most useful for the <literal
407 role="template-keyword">author</literal> keyword. Return
408 the <quote>user</quote> portion of an email address. For
409 example, <quote><literal>Bryan O'Sullivan
410 <bos@serpentine.com></literal></quote> becomes
411 <quote><literal>bos</literal></quote>.</para>
412 </listitem>
413 </itemizedlist>
415 &interaction.template.simple.manyfilters;
417 <note>
418 <para id="x_5b7"> If you try to apply a filter to a piece of data that it
419 cannot process, Mercurial will fail and print a Python
420 exception. For example, trying to run the output of the
421 <literal role="template-keyword">desc</literal> keyword into
422 the <literal role="template-kw-filt-date">isodate</literal>
423 filter is not a good idea.</para>
424 </note>
426 <sect2>
427 <title>Combining filters</title>
429 <para id="x_5b8">It is easy to combine filters to yield output in the form
430 you would like. The following chain of filters tidies up a
431 description, then makes sure that it fits cleanly into 68
432 columns, then indents it by a further 8 characters (at least
433 on Unix-like systems, where a tab is conventionally 8
434 characters wide).</para>
436 &interaction.template.simple.combine;
438 <para id="x_5b9">Note the use of <quote><literal>\t</literal></quote> (a
439 tab character) in the template to force the first line to be
440 indented; this is necessary since <literal
441 role="template-keyword">tabindent</literal> indents all
442 lines <emphasis>except</emphasis> the first.</para>
444 <para id="x_5ba">Keep in mind that the order of filters in a chain is
445 significant. The first filter is applied to the result of the
446 keyword; the second to the result of the first filter; and so
447 on. For example, using <literal>fill68|tabindent</literal>
448 gives very different results from
449 <literal>tabindent|fill68</literal>.</para>
450 </sect2>
451 </sect1>
453 <sect1>
454 <title>From templates to styles</title>
456 <para id="x_5bb">A command line template provides a quick and simple way to
457 format some output. Templates can become verbose, though, and
458 it's useful to be able to give a template a name. A style file
459 is a template with a name, stored in a file.</para>
461 <para id="x_5bc">More than that, using a style file unlocks the power of
462 Mercurial's templating engine in ways that are not possible
463 using the command line <option
464 role="hg-opt-log">--template</option> option.</para>
466 <sect2>
467 <title>The simplest of style files</title>
469 <para id="x_5bd">Our simple style file contains just one line:</para>
471 &interaction.template.simple.rev;
473 <para id="x_5be">This tells Mercurial, <quote>if you're printing a
474 changeset, use the text on the right as the
475 template</quote>.</para>
476 </sect2>
478 <sect2>
479 <title>Style file syntax</title>
481 <para id="x_5bf">The syntax rules for a style file are simple.</para>
483 <itemizedlist>
484 <listitem><para id="x_5c0">The file is processed one line at a
485 time.</para>
486 </listitem>
487 <listitem><para id="x_5c1">Leading and trailing white space are
488 ignored.</para>
489 </listitem>
490 <listitem><para id="x_5c2">Empty lines are skipped.</para>
491 </listitem>
492 <listitem><para id="x_5c3">If a line starts with either of the characters
493 <quote><literal>#</literal></quote> or
494 <quote><literal>;</literal></quote>, the entire line is
495 treated as a comment, and skipped as if empty.</para>
496 </listitem>
497 <listitem><para id="x_5c4">A line starts with a keyword. This must start
498 with an alphabetic character or underscore, and can
499 subsequently contain any alphanumeric character or
500 underscore. (In regexp notation, a keyword must match
501 <literal>[A-Za-z_][A-Za-z0-9_]*</literal>.)</para>
502 </listitem>
503 <listitem><para id="x_5c5">The next element must be an
504 <quote><literal>=</literal></quote> character, which can
505 be preceded or followed by an arbitrary amount of white
506 space.</para>
507 </listitem>
508 <listitem><para id="x_5c6">If the rest of the line starts and ends with
509 matching quote characters (either single or double quote),
510 it is treated as a template body.</para>
511 </listitem>
512 <listitem><para id="x_5c7">If the rest of the line <emphasis>does
513 not</emphasis> start with a quote character, it is
514 treated as the name of a file; the contents of this file
515 will be read and used as a template body.</para>
516 </listitem></itemizedlist>
517 </sect2>
518 </sect1>
520 <sect1>
521 <title>Style files by example</title>
523 <para id="x_5c8">To illustrate how to write a style file, we will construct a
524 few by example. Rather than provide a complete style file and
525 walk through it, we'll mirror the usual process of developing a
526 style file by starting with something very simple, and walking
527 through a series of successively more complete examples.</para>
529 <sect2>
530 <title>Identifying mistakes in style files</title>
532 <para id="x_5c9">If Mercurial encounters a problem in a style file you are
533 working on, it prints a terse error message that, once you
534 figure out what it means, is actually quite useful.</para>
536 &interaction.template.svnstyle.syntax.input;
538 <para id="x_5ca">Notice that <filename>broken.style</filename> attempts to
539 define a <literal>changeset</literal> keyword, but forgets to
540 give any content for it. When instructed to use this style
541 file, Mercurial promptly complains.</para>
543 &interaction.template.svnstyle.syntax.error;
545 <para id="x_5cb">This error message looks intimidating, but it is not too
546 hard to follow.</para>
548 <itemizedlist>
549 <listitem><para id="x_5cc">The first component is simply Mercurial's way
550 of saying <quote>I am giving up</quote>.</para>
551 <programlisting>___abort___: broken.style:1: parse error</programlisting>
552 </listitem>
553 <listitem><para id="x_5cd">Next comes the name of the style file that
554 contains the error.</para>
555 <programlisting>abort: ___broken.style___:1: parse error</programlisting>
556 </listitem>
557 <listitem><para id="x_5ce">Following the file name is the line number
558 where the error was encountered.</para>
559 <programlisting>abort: broken.style:___1___: parse error</programlisting>
560 </listitem>
561 <listitem><para id="x_5cf">Finally, a description of what went
562 wrong.</para>
563 <programlisting>abort: broken.style:1: ___parse error___</programlisting>
564 </listitem>
565 <listitem><para id="x_5d0">The description of the problem is not always
566 clear (as in this case), but even when it is cryptic, it
567 is almost always trivial to visually inspect the offending
568 line in the style file and see what is wrong.</para>
569 </listitem>
570 </itemizedlist>
571 </sect2>
573 <sect2>
574 <title>Uniquely identifying a repository</title>
576 <para id="x_5d1">If you would like to be able to identify a Mercurial
577 repository <quote>fairly uniquely</quote> using a short string
578 as an identifier, you can use the first revision in the
579 repository.</para>
581 &interaction.template.svnstyle.id;
583 <para id="x_5d2">This is likely to be unique, and so it is
584 useful in many cases. There are a few caveats.</para>
585 <itemizedlist>
586 <listitem><para id="x_5d3">It will not work in a completely empty
587 repository, because such a repository does not have a
588 revision zero.</para>
589 </listitem>
590 <listitem><para id="x_5d4">Neither will it work in the (extremely rare)
591 case where a repository is a merge of two or more formerly
592 independent repositories, and you still have those
593 repositories around.</para>
594 </listitem></itemizedlist>
595 <para id="x_5d5">Here are some uses to which you could put this
596 identifier:</para>
597 <itemizedlist>
598 <listitem><para id="x_5d6">As a key into a table for a database that
599 manages repositories on a server.</para>
600 </listitem>
601 <listitem><para id="x_5d7">As half of a {<emphasis>repository
602 ID</emphasis>, <emphasis>revision ID</emphasis>} tuple.
603 Save this information away when you run an automated build
604 or other activity, so that you can <quote>replay</quote>
605 the build later if necessary.</para>
606 </listitem>
607 </itemizedlist>
608 </sect2>
610 <sect2>
611 <title>Listing files on multiple lines</title>
613 <para id="x_714">Suppose we want to list the files changed by a changeset,
614 one per line, with a little indentation before each file
615 name.</para>
617 &interaction.ch10-multiline.go;
618 </sect2>
620 <sect2>
621 <title>Mimicking Subversion's output</title>
623 <para id="x_5d8">Let's try to emulate the default output format used by
624 another revision control tool, Subversion.</para>
626 &interaction.template.svnstyle.short;
628 <para id="x_5d9">Since Subversion's output style is fairly simple, it is
629 easy to copy-and-paste a hunk of its output into a file, and
630 replace the text produced above by Subversion with the
631 template values we'd like to see expanded.</para>
633 &interaction.template.svnstyle.template;
635 <para id="x_5da">There are a few small ways in which this template deviates
636 from the output produced by Subversion.</para>
637 <itemizedlist>
638 <listitem><para id="x_5db">Subversion prints a <quote>readable</quote>
639 date (the <quote><literal>Wed, 27 Sep 2006</literal></quote> in the
640 example output above) in parentheses. Mercurial's
641 templating engine does not provide a way to display a date
642 in this format without also printing the time and time
643 zone.</para>
644 </listitem>
645 <listitem><para id="x_5dc">We emulate Subversion's printing of
646 <quote>separator</quote> lines full of
647 <quote><literal>-</literal></quote> characters by ending
648 the template with such a line. We use the templating
649 engine's <literal role="template-keyword">header</literal>
650 keyword to print a separator line as the first line of
651 output (see below), thus achieving similar output to
652 Subversion.</para>
653 </listitem>
654 <listitem><para id="x_5dd">Subversion's output includes a count in the
655 header of the number of lines in the commit message. We
656 cannot replicate this in Mercurial; the templating engine
657 does not currently provide a filter that counts the number
658 of lines the template generates.</para>
659 </listitem></itemizedlist>
660 <para id="x_5de">It took me no more than a minute or two of work to replace
661 literal text from an example of Subversion's output with some
662 keywords and filters to give the template above. The style
663 file simply refers to the template.</para>
665 &interaction.template.svnstyle.style;
667 <para id="x_5df">We could have included the text of the template file
668 directly in the style file by enclosing it in quotes and
669 replacing the newlines with
670 <quote><literal>\n</literal></quote> sequences, but it would
671 have made the style file too difficult to read. Readability
672 is a good guide when you're trying to decide whether some text
673 belongs in a style file, or in a template file that the style
674 file points to. If the style file will look too big or
675 cluttered if you insert a literal piece of text, drop it into
676 a template instead.</para>
677 </sect2>
678 </sect1>
679 </chapter>
681 <!--
682 local variables:
683 sgml-parent-document: ("00book.xml" "book" "chapter")
684 end:
685 -->