Diff Match and Patch: Google's open source text synchronization library

See also:

http://news.ycombinator.com/item?id=430320

That's where I first read about this.

Looks really useful, although I wonder is it really necessary for the C++ version to depend on Qt? Qt is a pretty huge library.

I love this library. Really well implemented, and fast. Great to unload this from the backend of a webapp into js too.