Re: [Orchestration][RFC] A simple draft for channels

[Ricardo Wurmus <rekado@elephly.net>]

Pjotr Prins <pjotr.public12@thebird.nl> writes:

> On Mon, Mar 19, 2018 at 01:04:00PM +0100, Pjotr Prins wrote:
>> Maybe we should start thinking that a channel is simply an
>> architecture dependent Guix 'pack' of substitutes that includes the
>> pre-built Guix git repo. When deployed in a container we can inject
>> the keys. When this works we can design a pack repository, making the
>> channels searchable.
>
> Continuing my line of thought: a binary channel in my mind is now a
> compiled Guix package tree with Guix and possible adaptations (say a
> special package for Ruby). In other words, a special (timed) version
> of Guix sitting in /gnu/store/*named-guix-channel/bin/guix.

What you describe is essentially “guix pull”.  “guix pull” can already
use a different branch or a different repository.

It has at least two problems in this context:

1) it only keeps a link to the “latest” Guix.  There is no way to
   declare the use of a different variant of Guix.

2) it builds everything from source (Ludo’s branch for splitting the
   target of “guix pull” into several derivations addresses this)

Maybe we should address the first problem next and allow for not only
the latest Guix version to be retained.  This is not quite the same as a
regular profile, because these different variants of Guix surely would
provide colliding files.

The guix command would need to be changed to pick “latest” by default,
but use a different variant if specified.

The workflow would be something like that:

    # fetch Guix from somewhere and record as “foobar”
    guix pull --url=https://somewhere foobar

    # use that variant of Guix
    guix --variant=foobar build hello

I don’t think this should be the only mechanism through which people can
provide channels.  I wouldn’t want to have to essentially fork Guix.
For a user this is a problem, too, because channels would no longer be
composable (today I can compose multiple package collections with
GUIX_PACKAGE_PATH).

--
Ricardo

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