docs: some extension for flakes users

PR nix-community#1655

README.md

@@ -113,6 +113,13 @@ Currently the easiest way to install Home Manager is as follows:
     . "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
     ```
 
+    or this when managing home configuration together with system
+    configuration
+
+    ```bash
+    . "/etc/profiles/per-user/$USER/etc/profile.d/hm-session-vars.sh"
+    ```
+
     to your `~/.profile` file.
 
 If instead of using channels you want to run Home Manager from a Git
@@ -344,6 +351,10 @@ as follows:
 Note, the Home Manager library is exported by the flake under
 `lib.hm`.
 
+When using flakes, switch to new configurations as you do for the
+whole system (e. g. `nixos-rebuild switch --flake <path>`) instead of
+using the `home-manager` command line tool.
+
 Releases
 --------
 

doc/installation.adoc

@@ -79,8 +79,14 @@ configuration then you must source the
 [source,bash]
 $HOME/.nix-profile/etc/profile.d/hm-session-vars.sh
 +
-file in your shell configuration. Unfortunately, we currently only
-support POSIX.2-like shells such as
+file in your shell configuration. Alternatively source
++
+[source,bash]
+/etc/profiles/per-user/$USER/etc/profile.d/hm-session-vars.sh
++
+when managing home configuration together with system configuration.
++
+Unfortunately, we currently only support POSIX.2-like shells such as
 https://www.gnu.org/software/bash/[Bash] or
 http://zsh.sourceforge.net/[Z shell].
 +