Over the years, I've been a big fan of a GNOME app, Meld, used for comparing 2-3 files or directories. I just ran into the weird situation, though, where I wanted to merge two source project directories (one an updated upstream, the other a modified local version) and Meld kept insisting the two directories were identical. Weird. They're different via 'diff' on the command line. Given I run KDE, I found there's a comparable app, KDiff3 for KDE... installed it in 5 sec, and it's doing the bizzo!