Documentation for HTTP:*AUTO-EXPORT*

When non-null, :GET and :HEAD methods auto-export static URLs
when they have a parent that is exported with a directory export type.
When *auto-export* is :ON-DEMAND, pathnames in exported directories are
exported as URLs when they are first accessed over HTTP rather than at export time.
This feature trades a fast start up of the server for a small additional time when
the URL is first accessed. If the value is T, all URLs are exported at export time.