web commit by intrigeri: initial pedigree plugin proposal

doc/todo/pedigree_plugin.mdwn

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+After realizing (thanks to
+[[Allow_TITLE_to_include_part_of_the_path_in_addition_to_the_basename]])
+that I needed some kind of "parentlinks on steroids", I wrote a new
+plugin, called pedigree.
+
+This plugin provides a bunch of loops that one can use in his/her
+`HTML::Template`'s to iterate over all or a subset of a page's
+parents. Inside these loops, half a dozen variables are made
+available, in addition to `PAGE` and `URL` that are already provided
+by parentlinks.
+
+Amongst many possibilities, one can e.g. simply use this plugin to
+give every parent link a different `class=` attribute, depending
+either on its depth in the path leading to the current page, or on its
+distance to it.
+
+The code and documentation (including simple and complex usage
+examples) are in the 'pedigree' Git branch in this repo:
+
+	git://repo.or.cz/ikiwiki/intrigeri.git
+
+Seems there is also a [gitweb](http://repo.or.cz/w/ikiwiki/intrigeri.git).
+
+Any opinions on the idea/design/implementation?
+
+What needs to be changed so that it's possible to include it in
+mainline ikiwiki?
+
+(I'll try never to rebase this branch, but writing this plugin has
+been a pretext for me to start learning Git, so...)