We are currently using NetBSD/i386 very happily. We use a customised kernel,
because we have a number of PCI/ISA cards produced in-house, and so we write
device drivers for them for NetBSD. So, at the moment, we take a generic
/usr/src/sys tree, add a few of our own files, and then add a few lines to
conf.h, conf.c, files.pci, and those sorts of files so that the system will
"see" the new devices when compiling a kernel.

So, we can make these changes under, let's say 1.5, and create .patch files
for all files we modified. This makes it quite easy for any other developers
here to modify their generic /sys tree in the same way by applying the
.patches. All good and well.

The problem now arises: NetBSD 1.5.1 comes out, with all sorts of new
features, bugfixes, bells and whistles :) So now we want to upgrade to it,
and include all our own drivers and customizations. I obviously can't use
the .patch file anymore, because it changes from 1.5 to our customized, and
will probably get way confused if the source has changed between 1.5 and
1.5.1.

Do we have to make all the changes in each file manually again, and generate
new .patch files? Is there any way to perhaps use the previous .patch files
(say, in conjunction with a 1.5->1.5.1 .patch) to get a 1.5.1 version, with
our customizations?

This used to be a simple process, as we only had to change 10 or so files,
but we are looking more like 100 files to change now, so it becomes very
non-trivial!

Thanks
 Bruce