How do you diff a directory for only files of a specific type?

Question

I have a question about the diff command if I want a recursive directory diff but only for a specific file type, how to do that?

I tried using the exclude option but can

Answer 1

If you want to differ sources and keep it simple:

diff -rqx "*.a" -x "*.o" -x "*.d" ./PATH1 ./PATH2 | grep "\.cpp " | grep "^Files"

Remove the last grep if you want to get the files which exist in only one of the paths.