Side-by-side diff viewer, editor and merge preparer
tkdiff is a graphical front end to the diff program. It provides a side-by-side view of the differences between two text files, along with several innovative features such as diff bookmarks, a graphical map of differences for quick navigation, and a facility for slicing diff regions to achieve exactly the merge output desired.
Parsing, analyzing, and comparing source code across many languages
...The incremental part is important because files change often so we want to be able to parse just what's changed and not have to analyze the entire project again.