gitk: (un)interesting files/hunks diffs

Hello *,

      when viewing a merge diff in gitk it discards all files that merge
      cleanly (the whole file). It could be usefull to list the files in the
      file list with the color of the corresponding "winning" parent.

      Another thing that could be usefull is to make the (un)interesting
      test at the hunk level, so you could clearly see only the edits
      made manually during the merge.

      Thanks.

      Santi