back out r66983 as it breaks several packages

git-svn-id: https://svn.r-project.org/R/trunk@66985 00db46b3-68df-0310-9c12-caf00c1e9a41
Fix problem in computation on additional repositories.

git-svn-id: https://svn.r-project.org/R/trunk@66987 00db46b3-68df-0310-9c12-caf00c1e9a41