Declaring channel dependencies in the operating-system configuration

[Elais Player]

Hi Guix!

One thing that I've often found to be annoying was manually adding a

channels.scm file to systems, and I've come up with a solution that I'd like to

share.

For those interested in having their channels.scm be added as part of the system

generation process, just do the following.

Create an object representing a scheme file using the `scheme-file` procedure

(define %guix-channels

  (scheme-file

        "channels.scm"

        #~(cons* (channel

                        (name 'example)

                        (url "https://example.org/channel.git"))

                 %default-channels)))

Then add the file-like object to your system services using the

extra-special-file procedure. It symlinks a file from the store to

/etc/guix/channels.scm and makes the channels declared there available to all of

your systems users.

(operating-system

  ...

  (services

    (cons*

      (extra-special-file "/etc/guix/channels.scm"

                          %guix-channels)

      %base-services)))

I think this is a pretty neat solution for those of us who need to use custom

channels, but I was wondering if this is something that can be improved on and

added to the top level operating-system declaration.

Just like we can declare hosts for the operating system would it be a good idea

to declare (channels #~(cons* (channel ...))) too?

Would it make sense to add it as a configuration in guix-service-type?