diffutils is "[a] group of utilities that displays difference between and among text files. 'diff' outputs the difference between two files in any of several formats. If the files are identical, it normally produces no ouput; if they are binary (non-text) it normally reports only that they are different. 'cmp' shows the offsets and files numbers where two files differ; it can also show, side by side, all the characters that differ between the two files. 'sdiff' merges two files interactively. 'diff3' shows differences among three files. If two people have made independent changes to a common original, diff3 reports that difference between the original and the two changed versions, and can produce a merged file that contains both persons' changes along with warnings about conflicts." (from http://directory.fsf.org/diffutils.html)
The ipk of diffutils does not install cmp by default -- cmp is provided by Busybox, and is likely sufficient for most purposes. If you want to install the heavyweight cmp provided by the diffutils package, you'll need to get the CVS source (
This package should probably be bundled with make, m4, and patch.