merge wip-haskell?

[Ricardo Wurmus <rekado@elephly.net>]

Hey there,

wip-haskell contains commits that do a number of things aimed to reduce
the closure of packages:

1) make the “out” (and “lib”) output independent from “doc”
2) add a “doc” output to more packages
3) add a “static” output for all Haskell packages containing the “.a” files
4) change ghc-pandoc (and ghc-pandoc-citeproc) to use static linking

Number 1 required some smelly hackery: the generated configuration file
is edited to remove the “haddock-html” field.  One unfortunate effect of
doing this and moving the .haddock files is that there are now
complaints about unresolvable links in generated documentation.  I don’t
know if we can avoid this, but it seems like a small price to pay for
independent “doc” outputs.  (Otherwise we’d have to download huge “doc”
outputs even if we don’t want them.)

Number 3 required circumventing bug 41569.

Number 4 is by far the ugliest change of them all.  In order to
statically link packages we need to add all the “static” outputs of all
Haskell inputs *and* the “static” outputs of *their* Haskell inputs.
This is not easily accomplished, so I ended up using “package-closure”
on all direct inputs, and then filtered the result to packages with
names starting with “ghc-”.  If there was a more appropriate tool I’d
use it, but I don’t think it exists.

The result is a much reduced closure for ghc-pandoc and all packages
using it (such as R markdown).  We should probably rename “ghc-pandoc”
to “pandoc”, while we’re at it, because now the package contains the
executable.

I suppose we could change this so that “ghc-pandoc” is the usual library
package with a new “pandoc” package inheriting from “ghc-pandoc”.  I’ll
give that a try soon.

I’d be happy to hear your comments about all of this, and I’m looking
forward to merging this branch into “master” soon.

-- 
Ricardo