To use the LOCALPATCHES configuration directive in  GODI, first edit /path/to/godi/installation/etc/godi.conf and add

# Define LOCALPATCHES
LOCALPATCHES=${LOCALBASE}/localpatches

then

mkdir /path/to/godi/installation/localpatches

Let's say you want to apply a patch to godi-foobar package, create a directory called godi/godi-foobar under /path/to/godi/installation/localpatches with

mkdir /path/to/godi/installation/localpatches/godi/godi-foobar

and rename the patch you have put is that directory to patch-0x-patchname.

The patch must be generated with

diff -aur file.orig file > patch-0X-patchname

from the working directory, not the parent directory.

An example of a working localpatches sub-tree is available here :  http://people.grenouille.com/~fraggle/patches/godi/