On [[todo/auto-create_tag_pages_according_to_a_template]], [[chrysn]]
suggests:

> Instead of creating a file that gets checked in into the RCS, the
> source files could be left out and the output files be written as
> long as there is no physical source file (think of a virtual underlay).
> Something similar would be required to implement alias directive,
> which couldn't be easily done by writing to the RCS as the page's
> contents can change depending on which other pages claim it as an alias.

`add_autofile` could be adapted to do this, or a similar API could be
added.

This would also be useful for autoindex, as suggested on
[[plugins/autoindex/discussion]]. I'd also like to use it for
[[plugins/contrib/album]].

One refinement I'd suggest is that if the transient page is edited,
its transient contents are evaluated and used as the initial
content for the edit box; after that, it'd become a static page. --[[smcv]]