Switch to extended Nixpkg's lib

This change makes use of the `extend` function inside `lib` to inject
a new `hm` field containing the Home Manager library functions. This
simplifies use of the Home Manager library in the modules and reduces
the risk of accidental infinite recursion.

PR #994

doc/default.nix

@@ -1,18 +1,20 @@
-{ pkgs }:
+{
+  # Note, this should be "the standard library" + HM extensions.
+  lib
+, pkgs
+}:
 
 let
 
-  lib = pkgs.lib;
-
   nmdSrc = pkgs.fetchFromGitLab {
     name = "nmd";
     owner = "rycee";
     repo = "nmd";
-    rev = "9751ca5ef6eb2ef27470010208d4c0a20e89443d";
-    sha256 = "0rbx10n8kk0bvp1nl5c8q79lz1w0p1b8103asbvwps3gmqd070hi";
+    rev = "b437898c2b137c39d9c5f9a1cf62ec630f14d9fc";
+    sha256 = "18j1nh53cfpjpdiwn99x9kqpvr0s7hwngyc0a93xf4sg88ww93lq";
   };
 
-  nmd = import nmdSrc { inherit pkgs; };
+  nmd = import nmdSrc { inherit lib pkgs; };
 
   # Make sure the used package is scrubbed to avoid actually
   # instantiating derivations.
@@ -29,7 +31,10 @@ let
 
   hmModulesDocs = nmd.buildModulesDocs {
     modules =
-      import ../modules/modules.nix { inherit lib pkgs; }
+      import ../modules/modules.nix {
+        inherit lib pkgs;
+        check = false;
+      }
       ++ [ scrubbedPkgsModule ];
     moduleRootPaths = [ ./.. ];
     mkModuleUrl = path:

doc/release-notes/rl-2003.adoc

@@ -36,6 +36,39 @@ home.file = {
 Support for the list form will be removed in Home Manager version
 20.09.
 
+* The `lib` function attribute given to modules is now enriched with
+an attribute `hm` containing extra library functions specific for Home
+Manager. More specifically, `lib.hm` is now the same as `config.lib`
+and should be the preferred choice since it is more robust.
++
+Therefore, if your configuration makes use of, for example,
+`config.lib.dag` to create activation script blocks, it is recommended
+to change to `lib.hm.dag`.
++
+Note, in the unlikely case that you are
++
+** using Home Manager's NixOS or nix-darwin module,
+** have made your own Home Manager module containing an top-level
+   option named `config` or `options`, and
+** assign to this option in your system configuration inside a plain
+   attribute set, i.e., without a function argument,
+
++
+then you must update your configuration to perform the option
+assignment inside a `config` attribute. For example, instead of
++
+[source,nix]
+----
+home-manager.users.jane = { config = "foo"; };
+----
++
+use
++
+[source,nix]
+----
+home-manager.users.jane = { config.config = "foo"; };
+----
+
 [[sec-release-20.03-state-version-changes]]
 === State Version Changes