[bug#65866] [PATCH v2 5/8] build: Add dependency on Git.

[Simon Tournier]

Hi Ludo,

On Sat, 23 Sep 2023 at 00:28, Ludovic Courtès <ludo@gnu.org> wrote:
> * configure.ac: Check for ‘git’ and substitute ‘GIT’.
> * guix/config.scm.in (%git): New variable.
> * guix/self.scm (compiled-guix): Define ‘git’ and pass it to
> ‘make-config.scm’.
> (make-config.scm): Add #:git; emit a ‘%git’ variable.
> * doc/guix.texi (Requirements): Add it.

Moving the Git dependency to a daemon dependency tweaks a bit what we
control when “bootstrapping”, no?  Maybe I misread or misunderstand a
point.

Currently, the full bootstrap story requires the binary seed (well
documented in the manual :-)), running a Linux kernel and a Guix daemon.
And then, everything is built one after the other, resolving the chain
of dependencies.

And obviously, there is another chicken-or-the-egg problem barely
discussed.  For building something, we first need to communicate with
the world for fetching the source code to build. :-)

It is not Git specific and also happens with ’url-fetch’ – as reported
very early (see #22774 from 2016).  For instance, TLS is required before
Guix has built GnuTLS.  The chicken-or-the-egg had been solved by hiding
this dependency as a dependency of the daemon.  A hack.

Therefore, it means that the Reduced Binary Seed bootstrap is somehow
enlarged by what the Guix daemon depends on.

I mean, breaking the dependency cycles by introducing a dependency on
Git (as for fixing #63331) is not free of other dependencies.  It is
another hack when it could be avoided since the issue is about
Guile-GnuTLS.

It means we are doing a step back for a full bootstrap story, IMHO,
having a “builtin:git-download” makes less clear what are the hard
dependencies to what Guix is able to build from source starting from
almost nothing.

Cheers,
simon