package updater: operate on package structs, not names?

[Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de>]

Hi Guix,

I noticed a flaw in the CRAN updater.  The ‘latest-release’ procedure is
called with the result of ‘(package-name package)’.  The problem here is
that Guix package names follow much stricter naming rules than the
upstream packages.

Here are a couple of examples of R package names and their related Guix
package names:

    GenomicRanges —> r-genomic-ranges
    data.table    —> r-data-table
    formatR       –> r-formatr
    DBI           —> r-dbi

When we only pass the Guix name to ‘latest-release’, the updater won’t
know how to find the package and its upstream version because the names
don’t match.

There are two ways to approach this: we change the Guix package names to
closely match those of the upstream packages, or we pass the complete
package structure to ‘latest-release’.  The latter approach would allow
the CRAN updater to extract the appropriate name from the tarball URI.

We have the same problem for Ruby gems, I think, so I think that it
generally would be a good idea to pass the whole package object to
‘latest-release’.  Those updaters that only need the package name can
just reduce it by calling ‘(package-name package)’ themselves.

What do you think?

~~ Ricardo