Use only tools from Nixpkgs in activation script

Note, we still pull in the user's `PATH` in case the user has defined
their own activation blocks that depend on additional tools.
Eventually this will be deprecated and removed.

See #99.

modules/home-environment.nix

@@ -248,6 +248,12 @@ in
         activationBinPaths = lib.makeBinPath [
           pkgs.bash
           pkgs.coreutils
+          pkgs.diffutils        # For `cmp` and `diff`.
+          pkgs.findutils
+          pkgs.gnugrep
+          pkgs.gnused
+          pkgs.ncurses          # For `tput`.
+          pkgs.nix
         ];
 
         sf = pkgs.writeText "activation-script" ''

modules/misc/news.nix

@@ -351,6 +351,25 @@ in
           before that date.
         '';
       }
+
+      {
+        time = "2017-10-20T12:15:27+00:00";
+        condition = with config.systemd.user;
+          services != {} || sockets != {} || targets != {} || timers != {};
+        message = ''
+          Home Manager's interaction with systemd is now done using
+          'systemctl' from Nixpkgs, not the 'systemctl' in '$PATH'.
+
+          If you are using a distribution whose systemd is
+          incompatible with the version in Nixpkgs then you can
+          override this behavior by adding
+
+              systemd.user.systemctlPath = "/usr/bin/systemctl"
+
+          to your configuration. Home Manager will then use your
+          chosen version.
+        '';
+      }
     ];
   };
 }

modules/programs/info.nix

@@ -64,6 +64,8 @@ in
       "${cfg.homeInfoDirLocation}\${INFOPATH:+:}\${INFOPATH}";
 
     home.activation.createHomeInfoDir = dagEntryAfter ["installPackages"] ''
+      oPATH=$PATH
+      export PATH="${lib.makeBinPath [ pkgs.gzip ]}''${PATH:+:}$PATH"
       $DRY_RUN_CMD mkdir -p "${cfg.homeInfoDirLocation}"
       $DRY_RUN_CMD rm -f "${cfg.homeInfoDirLocation}/dir"
       if [[ -d "${homeInfoPath}" ]]; then
@@ -71,6 +73,8 @@ in
           -exec $DRY_RUN_CMD ${infoPkg}/bin/install-info '{}' \
           "${cfg.homeInfoDirLocation}/dir" \;
       fi
+      export PATH="$oPATH"
+      unset oPATH
     '';
 
     home.packages = [ infoPkg ];

modules/services/polybar.nix

@@ -142,7 +142,7 @@ in
     home.activation.applyPolybar = dagEntryAfter [ "reloadSystemD" ] ''
       if [[ -v polybarChanged && -v DISPLAY ]]; then
         echo "Restarting polybar"
-        systemctl --user restart polybar.service
+        ${config.systemd.user.systemctlPath} --user restart polybar.service
       fi
     '';
   };

modules/systemd.nix

@@ -49,6 +49,17 @@ in
 
   options = {
     systemd.user = {
+      systemctlPath = mkOption {
+        default = "${pkgs.systemd}/bin/systemctl";
+        defaultText = "\${pkgs.systemd}/bin/systemctl";
+        type = types.str;
+        description = ''
+          Absolute path to the <command>systemctl</command> tool. This
+          option may need to be set if running Home Manager on a
+          non-NixOS distribution.
+        '';
+      };
+
       services = mkOption {
         default = {};
         type = types.attrs;
@@ -157,7 +168,7 @@ in
           local -a toRestart=( )
 
           for f in ''${maybeRestart[@]} ; do
-            if systemctl --quiet --user is-active "$f" \
+            if ${cfg.systemctlPath} --quiet --user is-active "$f" \
                && ! cmp --quiet \
                    "$oldUserServicePath/$f" \
                    "$newUserServicePath/$f" ; then
@@ -187,7 +198,7 @@ in
           fi
         }
 
-        $DRY_RUN_CMD systemctl --user daemon-reload
+        $DRY_RUN_CMD ${cfg.systemctlPath} --user daemon-reload
         systemdPostReload
       '';
     })