Find and copy files between two directories

I need a recommendation for software, script, 开发者_StackOverflow中文版whatever tool which would let me easily find and copy files from source directory to destination, which copies/replaces the file only when the destination directory doesn't contain the specified file or it contains the file with different content (eg. using hash comparision). Thanks in advance. Kris

I have found Meld on Ubuntu to do just that, but at the end of the day I have created small java utility using apache utils to resolve my problem