CRAN URL checks

CRAN Repository Maintainers

The CRAN submission checks run by R CMD check --as-cran check the availability of URLs in files including DESCRIPTION, CITATION, NEWS.Rd, NEWS.md, README.md, and the .Rd help pages and HTML files in inst/doc. These notes explain the checks.

They are only done if the build of R in use supports a suitably recent version of libcurl: most should.