Limiting size of global package database

[Herbert Valerio Riedel]

Hello Michael,

On 2014-12-31 at 15:10:37 +0100, Michael Snoyman wrote:
> tl;dr: Now that ghc (the library) doesn't depend on Cabal (the library),
> can we remove Cabal from the global package database installed with GHC?

[...]

> For both of these reasons, I think we should limit the number of packages
> included in the global package database. One seemingly small step we could
> do on that front is not include extraneous packages. In GHC 7.10rc1, that
> includes Cabal and xhtml: 

btw, haskeline and terminfo should be considered as well, according to
your argument.

> both packages are in the global package database, but could just as
> easily be removed from there and installed by users. The motivation
> for that would be to avoid problem (1) above.

However, as for xhtml, haskeline and terminfo, we had to register/expose
them in the global pkg DB due to

  https://ghc.haskell.org/trac/ghc/ticket/8919

and as for Cabal, I have been told (maybe Duncan can weigh in...?) that
Haskell implementations need to provide it (together with a `*hc-pkg`
executable) in order to conform to the CABAL specification[1].


Cheers,
  hvr

 [1]: https://www.haskell.org/cabal/proposal/pkg-spec.pdf