Maybe the following helps having around:

miyu% cat ~/bin/pkgdiff 
#!/bin/sh
echo '$NetBSD$'
echo ''
diff -u $@


 - Hubert

-- 
NetBSD - Better for your uptime than Viagra

---------- Forwarded message ----------
Date: Mon, 27 Dec 1999 21:00:42 -0800 (PST)
From: Thomas Klausner <wiz@netbsd.org>
To: source-changes@netbsd.org
Subject: CVS commit: pkgsrc


Module Name:	pkgsrc
Committed By:	wiz
Date:		Tue Dec 28 05:00:42 UTC 1999

Modified Files:
	pkgsrc/devel/gmp/patches: patch-aa

Log Message:
RCS tag added


To generate a diff of this commit:
cvs rdiff -r1.1 -r1.2 pkgsrc/devel/gmp/patches/patch-aa

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.