Compare folders and files easily, even live, to find differences in content and versions, with Meld
Meld is a free and convenient utility that lets you compare your files and folders easily. It’s not the first and I guess not the last program of this kind, but I always try such programs because none of them, so far as I know, was able to offer a perfect way of such comparisons — fast, simple, clear enough.
Meld’s interface is rather outdated, but, although not being pleasant, it is simple, featuring some default functions and letting you create complex comparisons if the default ones are not enough for you. You can use Meld for file comparisons, even watching comparisons live as you edit a file. You can configure even three-way differences to monitor. A regex filter is able to help you ignore differences you are not interested in.
You can monitor the creation of new of files and find missing or changed ones. The program lets you also merge two files using a common ancestor, or merge modifications of the same file that are made independently of each other.
If you need a program to compare files and directories, Meld is one you should try.