Wanted: contextual 'diff' program

[geoff at callan.UUCP]

>From time to time, I have seen bugfixes posted with "contextual" diff output.
For example:

5,8c6,9
	line 1
-	line 2
!	line 3
	line 4
---
	line 1
!	new version of line 3
+	line 3a
	line 4

Does anyone have a program to produce such output?  I would like to post some
fixes to the net, but don't really want to write that program just to post
them.
-- 

	Geoff Kuenning
	Callan Data Systems
	...!ihnp4!wlbr!callan!geoff
	...!ihnp4!wlbr!desint!geoff