crea shenvs, añade infrastructura para paquetes

pkgs/default.nix

@@ -0,0 +1,32 @@
+pkgs:
+with pkgs.lib; let
+  inherit (pkgs) buildEnv callPackage writeTextDir;
+
+  importAll = { root, exclude ? [] }:
+
+    # adapted from http://chriswarbo.net/projects/nixos/useful_hacks.html
+    let
+      basename = removeSuffix ".nix";
+
+      isMatch = name: type: (hasSuffix ".nix" name || type == "directory")
+                         && ! elem name (map basename exclude);
+
+      entry = name: _: {
+        name = basename name;
+        value = import (root + "/${name}");
+      };
+    in
+      mapAttrs' entry (filterAttrs isMatch (readDir root))
+
+in {
+  shenvs = let
+    build = name: { paths, enter ? null }: buildEnv {
+      name = "shenv-${name}";
+      paths = (optional (enter != null) (writeTextDir "lib/shenv/enter" enter))
+            ++ paths;
+    };
+  in mapAttrs (name: shenv: build name (shenv pkgs)) (importAll {
+    root = ../shenvs;
+    exclude = [ "config" ];
+  });
+}