Automated CRAN and Bioconductor Guix channels

This script creates the automated GNU Guix channel for CRAN packages and the automated GNU Guix channel for Bioconductor packages. Since Guix commit c329eeb3a8a87edfa21675ce67353778a3b24773 you can run it like this:

REPO=https://github.com/guix-science/guix-cran
# REPO=https://github.com/guix-science/guix-bioc
git clone $REPO output
mkdir -p cache/{description,contents}
guix repl import.scm output [guix-cran|guix-bioc] [cran|bioc]

The directory output will contain the updated channel if the import succeeded.