Why is Stackage currently stuck on cabal 1.18?

Question

At the moment (Oct 24th, 2014) cabal 1.18 ships with Stackage, while cabal 1.20 is out since April 2014. I expect there is a reason for this: I'm curious to what that reason may be and hope that by this question I can get it out on a place that Google indexes.

Answer 1

Because the ghc package- which cannot be upgraded- depends on Cabal-1.18. For more information, see https://www.fpcomplete.com/blog/2014/05/lenient-lower-bounds. For the same reason, Haskell Platform ships with Cabal 1.18, and GHC 7.10 is trying to get rid of the Cabal dependency in the ghc package (and, AFAIK, that's already landed in HEAD).