hub: For multiplexing GHC installations and providing development sandboxes

This package provides a utility for multiplexing multiple GHC and Haskell Platform installations, each selected by an environment variable or a work-tree configuration file.

The package also provides flexible development sandboxes (aka hubs) into which packages can be installed and subsequently erased. Commands are provided for (re)naming, annotating, replicating, swapping, archiving, locking and removing hubs. E.g.,

hub init

will create a hub based on the default GHC installation and associate the current directory with it. Any use of cabal or the GHC tools within this directory or it's descendants will work with correct tool chain and the private user-package database belonging to the hub.

The following would (i) download hexpat (ii) install it in a named 'hexpat-test' hub connected to the 2011.2.0.1 Haskell Platform, (iii) build the hexpat test suite with the same hub, and (iv) finally run the test suite.

cabal unpack hexpat
cd hexpat-*
hub init -s 2011.2.0.1 hexpat-test
cabal install
cd test
cabal install --bindir=.
./testsuite

This same 'hexpat-test' hub can be shared with other work trees.

The tool is intended to be provided as part of a distribution (like the JustHub Enterprise Linux distribution) but it can be configured with existing stock GHC installations without too much effort. Once installed and configured the hub command inter-operates seamlessly with the GHC tools (ghc, ghci, ghc-pkg, etc.) and Cabal-install.

For installation instructions, introductory material, FAQs, etc., see the home page http://justhub.org.