Ikiwiki's preprocessor parser cannot deal with arbitrary nested preprocesor
directives. It's possible to nest a directive with single quoted values
inside a triple-quoted value of a directive, but that's all.

It's not possible to unambiguously parse nested quotes, so to support
nesting, a new syntax would be needed. Maybe something xml-like?

> You can, however, unambiguously parse nested square brackets, and I think
> that would solve the problem, as long as you never allow the contents of a
> directive to contain a *partial* directive, which seems reasonable to me.
>
> For example, I *think* you can unambiguously parse the following:
>
>     \[[if test="enabled(template) and templates/foo" then="""
>     [[template id=foo content="""Flying Purple People Eater"""]]
>     """]]
>
> --[[JoshTriplett]]
d><td class='form'><form method='get'>
<select name='h' onchange='this.form.submit();'>
<option value='master' selected='selected'>master</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Unnamed repository; edit this file 'description' to name the repository.</td><td class='sub right'>Jonas Smedegaard</td></tr></table>
<table class='tabs'><tr><td>
<a href='/notmuch/?h=master'>summary</a><a href='/notmuch/refs/?h=master'>refs</a><a href='/notmuch/log/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>log</a><a href='/notmuch/tree/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>tree</a><a class='active' href='/notmuch/commit/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>commit</a><a href='/notmuch/diff/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>diff</a></td><td class='form'><form class='right' method='get' action='/notmuch/log/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys'>
<input type='hidden' name='h' value='master'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/notmuch/commit/?h=master'>root</a>/<a href='/notmuch/commit/tags?h=master'>tags</a>/<a href='/notmuch/commit/tags/41?h=master'>41</a>/<a href='/notmuch/commit/tags/41/71?h=master'>71</a>/<a href='/notmuch/commit/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de?h=master'>20170214053440.54B21358D@lxp5.free-owl.de</a>/<a href='/notmuch/commit/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>sys</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='h' value='master'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Jonas Smedegaard &lt;dr@jones.dk&gt;</td><td class='right'>2023-06-27 09:35:08 +0200</td></tr>
<tr><th>committer</th><td>Jonas Smedegaard &lt;dr@jones.dk&gt;</td><td class='right'>2023-06-27 09:35:08 +0200</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/notmuch/commit/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master&amp;id=fd54908da2b05c526dd3bee9b6dcd093214a220d'>fd54908da2b05c526dd3bee9b6dcd093214a220d</a> (<a href='/notmuch/patch/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?id=fd54908da2b05c526dd3bee9b6dcd093214a220d'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/notmuch/tree/?h=master'>c69c845069c99d1d01044f6fafda7c08433329c6</a> /<a href='/notmuch/tree/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/notmuch/commit/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master&amp;id=ba46132213560cf3335d53560d519c0ec0190da2'>ba46132213560cf3335d53560d519c0ec0190da2</a> (<a href='/notmuch/diff/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master&amp;id2=ba46132213560cf3335d53560d519c0ec0190da2'>diff</a>)</td></tr></table>
<div class='commit-subject'><span class='decoration'><a class='branch-deco' href='/notmuch/log/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>master</a></span></div><div class='commit-msg'></div><div class='diffstat-header'><a href='/notmuch/diff/?h=master'>Diffstat</a> (limited to 'tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys')</div><table summary='diffstat' class='diffstat'><tr><td class='mode'>-rw-r--r--</td><td class='add'><a href='/notmuch/diff/tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys?h=master'>tags/41/71/20170214053440.54B21358D@lxp5.free-owl.de/sys</a></td><td class='right'>0</td><td class='graph'><table summary='file diffstat' width='0%'><tr><td class='add' style='width: -nan%;'/><td class='rem' style='width: -nan%;'/><td class='none' style='width: -nan%;'/></tr></table></td></tr>
</table><div class='diffstat-summary'>1 files changed, 0 insertions, 0 deletions</div><table summary='diff' class='diff'><tr><td>