installer: Offer NM, Connman, and DHCP to non-desktop installs.

* gnu/installer/services.scm (%system-services): Add NetworkManager,
Connman, and the DHCP client.
* gnu/installer/newt/services.scm (run-networking-cbt-page): Add
'network-management?' parameter and honor it.
(run-services-page): Adjust call accordingly.

gnu/installer/newt/services.scm

@@ -45,13 +45,20 @@ choose the one to use on the log-in screen.")
       (condition
        (&installer-step-abort))))))
 
-(define (run-networking-cbt-page)
-  "Run a page allowing the user to select networking services."
+(define (run-networking-cbt-page network-management?)
+  "Run a page allowing the user to select networking services.  When
+NETWORK-MANAGEMENT? is true, include network management services like
+NetworkManager."
   (run-checkbox-tree-page
-   #:info-text (G_ "You can now select networking services to run on your
+   #:info-text (G_ "You can now select networking services to run on your \
 system.")
    #:title (G_ "Network service")
-   #:items (filter networking-system-service? %system-services)
+   #:items (filter (let ((types (if network-management?
+                                    '(network-management networking)
+                                    '(networking))))
+                     (lambda (service)
+                       (memq (system-service-type service) types)))
+                   %system-services)
    #:item->text system-service-name
    #:checkbox-tree-height 5
    #:exit-button-callback-procedure
@@ -61,5 +68,8 @@ system.")
        (&installer-step-abort))))))
 
 (define (run-services-page)
-  (append (run-desktop-environments-cbt-page)
-          (run-networking-cbt-page)))
+  (let ((desktop (run-desktop-environments-cbt-page)))
+    ;; When the user did not select any desktop services, and thus didn't get
+    ;; '%desktop-services', offer network management services.
+    (append desktop
+            (run-networking-cbt-page (null? desktop)))))

gnu/installer/services.scm

@@ -69,7 +69,21 @@
      (system-service
       (name "Tor anonymous network router")
       (type 'networking)
-      (snippet '(service tor-service-type))))))
+      (snippet '(service tor-service-type)))
+
+     ;; Network connectivity management.
+     (system-service
+      (name "NetworkManager network connection manager")
+      (type 'network-management)
+      (snippet '(service network-manager-service-type)))
+     (system-service
+      (name "Connman network connection manager")
+      (type 'network-management)
+      (snippet '(service connman-service-type)))
+     (system-service
+      (name "DHCP client")
+      (type 'network-management)
+      (snippet '(service dhcp-client-service))))))
 
 (define (desktop-system-service? service)
   "Return true if SERVICE is a desktop environment service."