remove the fixed filename extension in one-liner

You can use

ruby -e 'print "file: #{File.basename(ARGF.filename, '"'.*'"')}"' test.adoc

The File.basename with the second argument set to .* returns file name without any extensions, but you need to quote the single quotes correctly in order to keep syntax right.

In '"'.*'"', the first ' closes the currently open ' before print, then "'.*'" adds '.*' to the line of code, then ' re-starts the code line to be closed with the trailing '.