patch applied (cabal-install): Hide the installed instance when installing the local package.

[Duncan Coutts]

Tue May  6 06:32:36 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Hide the installed instance when installing the local package.
  Otherwise the dependency resolver may decide to pick the installed
  instance of the package but we really do want to install the local
  version. So to remove that choice from the dep resolver we just
  delete it from the installed package index.

    M ./Hackage/Install.hs -3 +5

View patch online:
http://darcs.haskell.org/cabal-install/_darcs/patches/20080506133236-adfee-72ba13b38c8300483a9eadf3d209e821e2129125.gz