Nixify repo

Using @tazjin's depot/default.nix to bootstrap this project. I'll be borrowing
his Nix idioms until I better understand Nix and have preferences of my own.

default.nix

@@ -0,0 +1,33 @@
+# At the time of this writing, this configuration was taken from @tazjin's
+# default.nix from his depot. I've added, changed, and removed that parts that I
+# don't need, and this is what remains.
+{ ... }@args:
+
+with builtins;
+
+let
+  fix = f: let x = f x; in x;
+
+  # Global configuration that all packages are called with.
+  config = pkgs: {
+    inherit pkgs;
+  };
+
+  readTree' = import /home/wpcarro/depot/nix/readTree {};
+
+  localPkgs = readTree: {
+    third_party   = readTree ./third_party;
+  };
+in fix(self: {
+  config = config self;
+
+  # Expose readTree for downstream repo consumers.
+  readTree = {
+    __functor = x: (readTree' x.config);
+    config = self.config;
+  };
+}
+
+# Add local packages as structured by readTree
+// (localPkgs (readTree' (self.config // { inherit (self) lib; })))
+)