diffutils 2.8 and -u/-U options

[Ignacio Goyret]

May I ask what was the rationale behind disallowing -NUM altogether?
I understand the desire to follow POSIX whims, but this move broke a
bunch of tools that do not know anything about the new -U and -C options
(eg, rcsdiff, cvs diff, etc).

Is there an environment variable that one can set to make diff ignore
these POSIX silliness and revert to previous behavior, where a '-u'
followed by a number set the context size?

Alternatively, how about expanding the -u (and -c) options to take
an optional numeric argument?