Add some structure files

Add initial files nixos.py and home-manager.py

src/nix_background_upgrade/home-manager.py

@@ -0,0 +1,15 @@
+"""
+Control upgrading home-manager configuration
+"""
+
+import subprocess
+
+
+def home_manager_switch() -> None:
+    """
+    Switch home-manager to new version
+
+    :returns: None
+    """
+    subprocess.Popen("which -a home-manager".split())
+    return

src/nix_background_upgrade/nixos.py

@@ -0,0 +1,15 @@
+"""
+Control upgrading NixOS configuration
+"""
+
+import subprocess
+
+
+def nixos_switch() -> None:
+    """
+    Switch NixOS system to new version
+
+    :returns: None
+    """
+    subprocess.Popen("which -a nixos-rebuild".split())
+    return