Pardiff -- convert standard diff output to a parallel format

History:

I wrote pardiff to emulate the /PARALLEL option of the diff command in
the VMS operating system. This option caused the file differences to be
output in a side-by-side format. Pardiff provides a very similar function,
but is implemented as a post-process to diff.

Pardiff was originally developed on a Sun workstation (I don't recall
the OS version) circa 1992. It was subsequently ported to DOS, where it has
served under native DOS, and "DOS boxes" under Windows 3.1, 95, and NT.

Usage:

Pardiff is a post-processor for diff output, so it simply reads from
stdin and writes to stdout. A typical usage is:

    % diff file1 file2 | pardiff | more

This particular command is implemented as a shell script, called diffp,  that
is included with the pardiff distribution. Therefore, the above command can
be run as:

    % diffp file1 file2

Features:

Pardiff has only one feature, which is that it is smart enough (under
UNIX-like OSs) to automatically detect the width of the output terminal
and adjust it's column formatting accordingly.

Problems:

The section divider formatting is incorrect for line numbers with six or
more digits.

TAB characters can throw off the formatting.
