It seems the standard Asciidoc way of specifying things like this is attribute lists (comma sepaated name=value pairs in square brackets), so the new block syntax is

////
[r, mycodechunk, echo = TRUE, results = "hide"]
x <- sin(pi / 1:10)
////

And the inline syntax for markdown works just as well for AsciiDoc.

`r x <- sin(pi / 1:10)`

pattern.R updated now.