callr sets the repos
option in subprocesses, to make sure that
a CRAN mirror is set up. This is because the subprocess cannot bring
up the menu of CRAN mirrors for the user to choose from.
default_repos()
Named character vector, the default value of the repos
option in callr subprocesses.
default_repos()#> MPN #> "https://mpn.metworx.com/snapshots/stable/2021-05-16" #> CRAN #> "https://mpn.metworx.com/snapshots/stable/2021-05-16"