Is there some way to write a working template that does what I'd like
it to do with this (nonworking) code?
As of [{{<includeonly>subst:</includeonly>FULLPAGENAME|oldid={{REVISIONID}}}}
this edit], this article uses content from {{{source}}}.
This is from [[Template:GFDLSource]]
As you can see, I'm trying to automatically stamp the article with a
link to the current revision.