bug#47664: CRAN importer does not parse “Remotes” field.

[Ricardo Wurmus <rekado@elephly.net>]

The CRAN importer can be used to import packages from CRAN and
Bioconductor, but also from arbitrary git and hg repositories.
Especially for code published as a git/hg repository the “Remotes” field
of the DESCRIPTION file can be important.

The bedtorch[1] package, for example, has a DESCRIPTION file like this:

--8<---------------cut here---------------start------------->8---
Package: bedtorch
Type: Package
Title: R package for fast BED-file manipulation
Version: 0.1.8
Authors@R: 
    person(given = "Haizi",
           family = "Zheng",
           role = c("aut", "cre"),
           email = "haizi.zh@gmail.com")
Description: The goal of bedtorch is to provide a fast BED file manipulation tool suite native in R.
License: MIT + file LICENSE
Encoding: UTF-8
LazyData: true
Roxygen: list(markdown = TRUE)
RoxygenNote: 7.1.1
Depends:
    R (>= 4.0)
Imports: 
    stringr,
    dplyr,
    purrr,
    tidyr,
    data.table,
    R.utils,
    assertthat,
    Rcpp,
    Rhtslib12,
    RCurl
Suggests: 
    testthat (>= 3.0.0),
    devtools (>= 2.3.0),
    zoo
Config/testthat/edition: 3
URL: https://github.com/haizi-zh/bedtorch
BugRePORTS: https://github.com/haizi-zh/bedtorch/issues
BiocType: Software
Remotes: 
    haizi-zh/Rhtslib12
LinkingTo: 
    Rcpp,
    Rhtslib12
SystemRequirements: GNU make
--8<---------------cut here---------------end--------------->8---

The “Remotes” field specifies the origin for the Rhtslib fork.  The
importer should probably try to import the packages from the “Remotes”
field first.

-- 
Ricardo