On Sat, Dec 02, 2017 at 05:28:51PM +0100, Gábor Boskovits wrote:
> Sometimes while working in guix I run into problems because:
> 1. a tarball was removed or modified upstream
> 
> It would be great to have the ability to install the latest release in all
> the supported ways on all supported architectures, and have the ability do
> guix pull without problems.
> Last time I tried that it did not worked, because one of the upstream
> linux-libre tarballs was removed. It would be nice if we could afford to
> host the sources, so that at lesat a bare-bones guixsd suffered no such
> problems.

We actually do host the sources, but Guix usually tries fetching them
from upstream first, which can be annoying. We are discussing this here:

<https://bugs.gnu.org/28659>

> 2. some packages take very long time to build (notably guile)
> 
> It would be nice, if we could provide the substitutes that the current
> core-updates gnu-build-system needs. That would make development that needs
> to be done on core-updates much more pleasant to those who are working in a
> restricted hardware environment.

We use the core-updates branch like this:

1) For a couple months we just push changes to core packages to the
branch without worrying about if it works or not.
2) After some time, we try building the branch and fix everything that
is broken. Once that is done, we merge it into the master branch, which
is what `guix pull` uses by default.

So, for most of the life of a core-updates branch, it's likely that no
packages will be buildable, and thus we don't even try, so there are no
substitutes.

Once we start building it, substitutes are available in the normal way.