[arch-haskell] Adding another data file for dependency "hints"

[Peter Simons]

Hi Magnus,

 > Now you make me think that I might have missed something, but surely
 > parsec version 2.2 wouldn't satisfy the former, but would satisfy the
 > latter.

yes, this is true, of course.

It is impossible to map that Cabal expression to Pacman without losing
some information. In this particular case, that restriction is lost. If
a version 2.2 of parsec were to come out, and if we were to decide to
ship that version, then we'd have to update the email-validate PKGBUILD
in order to fix the build.

Now, the alternative is to encode the Cabal expression in question as
('parsec>=2.1.0' 'parsec<2.2'). That choice means that email-validate
won't build anymore if we decide to upgrade to parsec 3.

In a way, both solutions are equally inaccurate, so we can choose either
one. I just happen to prefer the first solution because I feel that an
upgrade to parsec 3 is far more likely to occur than an upgrade to 2.2,
simply because parsec 3 exists, but parsec 2.2 does not.

Does that make sense?

Take care,
Peter