Get the filename or datasource location that this content was loaded from.
Datasource locations look like this:
proto:protocol-specific-location-data, e.g. file:blah/foo.txt or
http://webmake.taint.org/index.html.
Expand a content item, as if in a curly-bracket content reference. If the
content item has not been expanded before, the current output file will be
noted as the content item's ''main'' URL.
The metadatum is converted to its native type, e.g. score is return as an
integer, title as a string, etc. If the metadatum is not provided, the
default value for that item, defined in HTML::WebMake::Metadata, is used.
Note that this method should only be called from a deferred reference, as
metadata often isn't available until all the normal content references in the
current page have been expanded.
Returns the content item's declaration order. This is a number representing
when the content item was first encountered in the WebMake file; earlier
content items have a lower declaration order. Useful for sorting.
Get a content item's URL. The URL is defined as the first page listed in the
WebMake file's out tags which refers to that item of content.
Note that, in some cases, the content item may not have been referred to yet by
the time it's get_url() method is called. In this case, WebMake will insert a
symbolic tag, hold the file in memory, and defer writing the file in question
until all other output files have been processed and the URL has been found.