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

I used the following command to find the diff of all *.tmpl files between DIR1 and DIR2. In my case this didn't yield any false positives, but it may for you, depending on the contents of your DIRS.

diff --brief DIR1 DIR2 | grep tmpl