maintainers/scripts/haskell/regenerate-hackage-packages.sh: init

Introduces a script that can be used to update the Nix expressions for

the Haskell package set. In service of that, also

- introduces cabal2nix-latest, which pins the hackage2nix version used

- changes all-cabal-hashes to use fetchFromGitHub

- adds update-hackage.sh & update-cabal2nix-latest.sh & update-stackage.sh maintainer scripts

pkgs/data/misc/hackage/default.nix

@@ -1,6 +1,10 @@
+# Hackage database snapshot, used by maintainers/scripts/regenerate-hackage-packages.sh
+# and callHackage
 { fetchurl }:
-
+let
+  pin = builtins.fromJSON (builtins.readFile ./pin.json);
+in
 fetchurl {
-  url = "https://github.com/commercialhaskell/all-cabal-hashes/archive/d202e2aff06500ede787ed63544476f6d41e9eb7.tar.gz";
-  sha256 = "00hmclrhr3a2h9vshsl909g0zgymlamx491lkhwr5kgb3qx9sfh2";
+  inherit (pin) url sha256;
+  passthru.updateScript = ../../../../maintainers/scripts/haskell/update-hackage.sh;
 }

pkgs/data/misc/hackage/pin.json

@@ -0,0 +1,5 @@
+{
+  "commit": "f04ff9179e228b67aee1241fe8c6508f91e92fb5",
+  "url": "https://github.com/commercialhaskell/all-cabal-hashes/archive/f04ff9179e228b67aee1241fe8c6508f91e92fb5.tar.gz",
+  "sha256": "11k786zcj21hgjxd2fvfshllxdl1z252x01wvfs16wp66n720wly"
+}