[Buildroot] [PATCH] package/rustc: allow cargo sub packages to download using 'git'

[Yann E. MORIN <yann.morin.1998@free.fr>]

Guillaume, All,

+Thomas for reference to his series
+Thomas +Arnout +Peter for their insight, toward the end

On 2021-02-21 08:51 +0100, guillaume.bressaix at gmail.com spake thusly:
> From: "Guillaume W. Bres" <guillaume.bressaix@gmail.com>
> 
> Adding this simple command to the general cargo configuration
> will allow sub packages (with their own cargo.toml file)
> to resolve dependencies using 'git'. Without this,
> we only support builtin packages or manually downloaded
> packages refered to with a local full path.

In fact, we explicitly do not want that to happen, because this means
that downloads happen during the build, not during the actual download
step. This prevents reproducible archives and thus reproducible builds,
and means that the output of legal-info is missing pieces.

There is a work in progress to support vendoring in the various
language-specific package managers like cargo, see this series from
Thomas:

    http://lists.busybox.net/pipermail/buildroot/2020-December/298802.html

The idea is that we manage the vendoring as part of the download step,
so that we can get totally off-line builds, and so that we can have
(slightly more) reproducible builds (as long as the archive is cached
locally or on a site-local mirror), and so that we can do a exhaustive
legal-info.

However, we have found a major roadblock for this, and we still have no
clear idea how to solve it.

The aforementioned series works pretty well, if one does not use primary
or backup mirrors. This is because the archive is (most probably) named
after the package and its version, but its content will be different when
we download it from the mirrors, compared to when we download it from
upstream: the upstream one will not be vendored, while the mirrored one
will.

This would cause quite a conflict, and we still do not see how to fix
that. Yet. I have a few ideas floating around in my head for now, but
that's not ready for primetime yet...

Of course, until this is solved, I don't know how to workaround the
vendoring problem imposed on us by those damn language-specific package
managers...

Maybe we could allow such a hack as yours for now, but really I have
little sympathy for those language-specific package managers. :-(

Regards,
Yann E. MORIN.

> Signed-off-by: Guillaume W. Bres <guillaume.bressaix@gmail.com>
> ---
>  package/rustc/cargo-config.in | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/package/rustc/cargo-config.in b/package/rustc/cargo-config.in
> index 47fad026be..be4c401f97 100644
> --- a/package/rustc/cargo-config.in
> +++ b/package/rustc/cargo-config.in
> @@ -1,2 +1,5 @@
>  [target. at RUSTC_TARGET_NAME@]
>  linker = "@CROSS_PREFIX at gcc"
> +
> +[net]
> +git-fetch-with-cli = true
> -- 
> 2.20.1
> 
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