Update a newly-created '.config' file with some predefined values

[Roman Storozhenko]

Hello everybody,

I have a host machine and I have a VM machine running CentOS 7 with 3.x. There is
a kernel source tree on the host. I have made 'make menuconfig',
populated all options that I want to have in my custom kernel and as a
result got a '.config' file. Then I copied a centos-default distro config file from my VM's
'boot' catalog to my host's kernel source tree catalog. So now I have
two files in my source tree: '.config' and '.config.old'. I am able to
see difference between them using the following command:

    scripts/diffconfig .config.old .config | less

But is there anyway to update values in '.config' file with the
apropriate values from '.config.old' file?
I just want to make sure that all modules will be included in a
new custom kernel.

Thanks in advance,
Roman