Add a generalised variant of 'topHandler'.
Don't die if some deps weren't reinstalled.
Use globalInstallDirs as the sandbox location.

Reverts 7b2e3630f2ada8a56bf9100144e1bb9acbe6dc6a. Instead of temporarily setting
'configUserInstall' to 'False' in various places, we now just check that we're
not in a sandbox when deciding whether we should use 'rootCmd'.
Add an '--only' flag for 'build', 'test' and 'bench'.

Allows to skip the automatic reinstallation of add-source deps.
Merge pull request #1327 from 23Skidoo/skip-add-source-check

Add an '--only' flag for 'build', 'test', 'bench' and 'run'.
cabal-install: put the Paths_cabal_install.hs and Paths_Cabal.hs in place as expected
disable hackage's preferred-versions (as we don't use it when merge ebuilds)

hackage.haskell.org/00-index.tar contains preferred-versions for some interesting
packages. For now it's 'base-3'.

Otherwise depends generated by hackport differ from ones pulled by ./Setup.hs.
cabal/cabal-install: renamed D.C.Exception -> D.C.ExceptionCI to avoid clash with Cabal's one

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Fix error messages with "cabal update" -> "hackport update" Same fix as marty.rosenberg@gmail.com once did for cabal-install-0.8.2, which we now are replacing.
cabal/cabal-install: renamed D.C.Exception -> D.C.ExceptionCI to avoid clash with Cabal's one

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
forbid cabal to check for self updates