http://docs.kde.org/
PrevFolder Comparison and Merge with KDiff3Next

Starting Folder Comparison Or Merge

This is very similar to the single file merge and comparison. You just have to specify folders on the command line or in the file-open dialog.

Compare/Merge two folders: 

   kdiff3 folder1 folder2
   kdiff3 folder1 folder2 -o destdir

If no destination folder is specified, then KDiff3 will use folder2.

Compare/Merge three folders: 

   kdiff3 folder1 folder2 folder3
   kdiff3 folder1 folder2 folder3 -o destdir

When three folders are merged then folder1 is used as the base for the merge. If no destination folder is specified, then KDiff3 will use folder3 as the destination folder for the merge.

Note that only the comparison starts automatically, not the merge. For this you first must select a menu entry or the F7 key. (More details later.)