I'd like to be able to open two windows in Emacs, select a region of text in each window, and get a comparison of the difference between the two selections.
This would be very handy for a large-scale maintenance project, where I'm working on a version tree with multiple branches, lots of copy/paste, and code that is being moved around sporadically.
I've found a paid-for tool that does provide this function (Ultracompare), but it's windows-specific, and I need a solution that runs on Solaris/Linux.