How to compare files with same names in two different directories using a shell script

Before moving on to use SVN, I used to manage my project by simply keeping a /develop/ directory and editing and testing files there, then moving them to the /main/ directory. When I decided to move to SVN, I needed to be sure that the directories were indeed in sync.

So, what is a good way to write a shell script [ bash ] to recursively compare files with the same name in two different directories?

Note: The directory names used above are for sample only. I do not recommend storing your code in the top level :).