installer: Add dry-run?

This allows running the installer without root privileges.  Do something like

    ./pre-inst-env guix repl
    ,use (guix)
    ,use (gnu installer)
    (installer-program #:dry-run? #t)
    ,build $1
    =>
    "/gnu/store/...-installer-program"

and run

    /gnu/store/...-installer-program

* gnu/installer/newt.scm (locale-page): Add #:dry-run? parameter.
(keymap-page): Likewise.
* gnu/installer/newt/keymap.scm (run-keymap-page): Likewise.
* gnu/installer/steps.scm (run-installer-steps): Likewise.  Use it to skip
writing to socket.
* gnu/installer/newt/final.scm (run-final-page): Rename to...
(run-final-page-install): ...this.
(dry-run-final-page, run-final-page): New procedures.
* gnu/installer/parted.scm (bootloader-configuration): Cater for empty user
partitions.
* gnu/installer/utils.scm (dry-run-command): New procedure.
* gnu/installer.scm (compute-locale-step): Add #:dry-run? parameter.  Use it
to avoid actually applying locale.
(compute-keymap-step): Add dry-run? parameter.  Pass it to
keymap-page.
(installer-program): Add #:dry-run? parameter.  If #:true
avoid writing to /proc, use dry-run-command, skip sync and reboot, and pass
dry-run? to...
(installer-steps): ...here.  Add #:dry-run? parameter.  Use it to disable
skip network, substitutes, partitioning pages, and pass it to...
compute-locale-step, compute-keymap-step, and final-page.

Change-Id: I0ff4c3b0a0c69539af617c27ba37654beed44619

1 files changed, 16 insertions, 13 deletions

diff --git a/gnu/installer/parted.scm b/gnu/installer/parted.scm
index e59df3d8e6..b36b238d8b 100644
--- a/gnu/installer/parted.scm
+++ b/gnu/installer/parted.scm
@@ -1461,19 +1461,22 @@ from (gnu system mapped-devices) and return it."
 
 (define (bootloader-configuration user-partitions)
   "Return the bootloader configuration field for USER-PARTITIONS."
-  (let* ((root-partition (find root-user-partition?
-                               user-partitions))
-         (root-partition-disk (user-partition-disk-file-name root-partition)))
-    `((bootloader-configuration
-       ,@(if (efi-installation?)
-             `((bootloader grub-efi-bootloader)
-               (targets (list ,(default-esp-mount-point))))
-             `((bootloader grub-bootloader)
-               (targets (list ,root-partition-disk))))
-
-       ;; XXX: Assume we defined the 'keyboard-layout' field of
-       ;; <operating-system> right above.
-       (keyboard-layout keyboard-layout)))))
+  (let ((root-partition (find root-user-partition? user-partitions)))
+    (match user-partitions
+      (() '())
+      (_
+       (let ((root-partition-disk (user-partition-disk-file-name
+                                   root-partition)))
+         `((bootloader-configuration
+            ,@(if (efi-installation?)
+                  `((bootloader grub-efi-bootloader)
+                    (targets (list ,(default-esp-mount-point))))
+                  `((bootloader grub-bootloader)
+                    (targets (list ,root-partition-disk))))
+
+            ;; XXX: Assume we defined the 'keyboard-layout' field of
+            ;; <operating-system> right above.
+            (keyboard-layout keyboard-layout))))))))
 
 (define (user-partition-missing-modules user-partitions)
   "Return the list of kernel modules missing from the default set of kernel