patch applied (cabal-install): Take nub by package id when making a dep graph

[Duncan Coutts]

Tue Feb 26 18:17:06 PST 2008  Duncan Coutts <duncan at haskell.org>
  * Take nub by package id when making a dep graph
  and give more detailed error messages for internal error conditions.
  Fixes a problem where installing a set of packages where several depended
  on the same package would give us a ResolvedDependency list containing
  multiple copies of that package. The DepGraph was expecting unique packages.
  Resolving package deps and generating install plans needs more thought
  and better specified invariants.

    M ./Hackage/DepGraph.hs -6 +19

View patch online:

  http://darcs.haskell.org/cabal-install/_darcs/patches/20080227021706-adfee-52e72b3334c86884bc88091249e585578bc67137.gz