A patch should be created against the last public release or, if practical, the latest code in CVS for the relevant source tree.

Instructions for obtaining a source tree from CVS are at http://httpd.apache.org/dev/anoncvs.txt

Here are instructions for easily obtaining diffs without using CVS:

[download httpd-2.0.48.tar.gz to /usr/local/src]

cd /usr/local/src
tar xvzf httpd-2.0.48.tar.gz
cp -ax httpd-2.0.48 httpd-2.0.48.new

[edit files in httpd-2.0.48.new/ and then test, test, test]

cd /usr/local/src
diff -ru httpd-2.0.48 httpd-2.0.48.new > my.unified.diff.patch