question or RFE on diff -r handling non-same files: show new/older when they "differ"

[L A Walsh]

I was doing a "diff -rq ./src ./dev
to find areas of 'dev' that hadn't been rolled into src when I
realized some patches had gone into src directly.  Rather than
just telling me files "differed", it really would be useful,
sometimes, to know which of two files under a recursive
tree-diff was newer, older or had the same last mtime.

Is there a switch for this in diff that would accomplish this,
or does this fall into an RFE?

Thanks!
-linda