mbbill/undotree — pull request #13 by inkarkat (2012-11-28 10:11:31+00:00)
Title: ENH: Differentate between added and changed text.

Instead of using the "UnderLined" highlight group for both changes and added lines, extract the distinction from the diff output and use either one of the default "DiffAdd" or "DiffChange" highlight groups. (People who prefer the old way can set both new config variables to the same old value.)
Also, linking to a new "UndotreeChangedText" highlight group is superfluous. Just use the original configured highlight group names in the matchadd().