The po plugin's protection against processing loops (i.e. the
alreadyfiltered stuff) is playing against us: the template plugin
triggers a filter hooks run with the very same ($page, $destpage)
arguments pair that is used to identify an already filtered page.

Processing an included template can then mark the whole translation
page as already filtered, which prevented `po_to_markup` to be called on
the PO content.

Symptoms: the unprocessed gettext file goes unfiltered to the
generated HTML.

This has been fixed in my po branch.

> My commit dcd57dd5c9f3265bb7a78a5696b90976698c43aa updates the
> bugfix in a much more elegant manner. Its main disadvantage is to
> add an (optional) argument to IkiWiki::filter. Please review.

-- [[intrigeri]]

>> Hmm. Don't like adding a fourth positional parameter to that (or
>> any really) function.
>>
>> I think it's quite possible that some of the directives that are
>> calling filter do so unnecessarily. For example, conditional,
>> cutpaste, more, and toggle each re-filter text that comes from the
>> page and so has already been filtered. They could probably drop
>> the filtering. template likewise does not need to filter the 
>> parameters passed into it. Does it need to filter the template output?
>> Well, it allows the (deprecated) embed plugin to work on template
>> content, but that's about it.
>>
>> Note also that the only other plugin to provide a filter, txt,
>> could also run into similar problems as po has, in theory (it looks at
>> the page parameter and assumes the content is for the whole page).
>>
>> [[!template id=gitbranch branch=origin/filter-full author="[[joey]]"]]
>> So, I've made a filter-full branch, where I attempt to fix this
>> by avoiding unnecessary filtering. Can you check it and merge it into
>> your po branch and remove your other workarounds so I can merge?
>> --[[Joey]]

>>> I merged your filter-full branch into my po branch and reverted my
>>> other workarounds. According to my tests this works ok. I'm glad
>>> you found this solution, as I didn't like changing the filter
>>> prototype. I believe you can now merge this code. --[[intrigeri]]

[[!tag patch done]]