Reorganize and update nixpkgs upstreams

This patch does a few things:

1. Switches from nixpkgs-unstable to nixos-unstable{,-small}, simply because
   nixpkgs-unstable is not in cache.nixos.org, but nixos-unstable is, and -small
   is the same but requires all tests to pass. So we should prefer
   nixos-unstable-small, whenever possible.

2. Reorganizes the nixpkgs import code such that Nixpkgs.nix returns an attrset
   of all the nixpkgs that I want to use, rather than putting other nixpkgs
   branches into the main one as an overlay. This is much simpler and explicit,
   but it meant I had to change a lot of usages throughtout the nix codebase.

3. As a consequence of 2, moves the overlays into separate files so they can be
   re-used across nixpkgs branches.

1 files changed, 44 insertions, 0 deletions

diff --git a/Biz/Bild/Haskell.nix b/Biz/Bild/Haskell.nix
new file mode 100644
index 0000000..2c0529a
--- /dev/null
+++ b/Biz/Bild/Haskell.nix
@@ -0,0 +1,44 @@
+_self: super:
+
+let
+  ghcCompiler = "ghc924";
+  buildCabal = sel: name: sel.callCabal2nix name super.sources.${name} { };
+  buildCabalSubdir = sel:
+    { name, src ? super.sources.${name}, subdir ? name }:
+    sel.callCabal2nix name (src + "/${subdir}") { };
+in rec {
+
+  haskell = super.haskell // {
+    packages = super.haskell.packages // {
+      "${ghcCompiler}" = super.haskell.packages."${ghcCompiler}".override
+        (_old: {
+          overrides = with super.pkgs.haskell.lib;
+            sel: sup:
+            super.overridePinnedDeps (buildCabal sel) // {
+              acid-state =
+                dontCheck sup.acid-state; # mac: "too many open files"
+              clay = doJailbreak sup.clay;
+              envy = doJailbreak sup.envy;
+              fast-tags =
+                sup.fast-tags.overrideAttrs (old: old // { patches = [ ]; });
+              generic-data = dontCheck
+                sup.generic-data; # https://github.com/Lysxia/generic-data/issues/56
+              readable =
+                doJailbreak sup.readable; # why is this even being built?
+              servant-auth = doJailbreak (buildCabalSubdir sel {
+                name = "servant-auth";
+                subdir = "servant-auth/servant-auth";
+              });
+              servant-server = doJailbreak sup.servant-server;
+              stripe-core = doJailbreak sup.stripe-core;
+              stripe-haskell = dontCheck sup.stripe-haskell;
+              stripe-http-client =
+                doJailbreak (dontCheck sup.stripe-http-client);
+              temporary = dontCheck sup.temporary;
+              wai-middleware-metrics = dontCheck sup.wai-middleware-metrics;
+            };
+        });
+    };
+  };
+
+}