17/197: installer: Add completion predicate for disk task.

[Danny Milosavljevic]

dannym pushed a commit to branch wip-installer-2
in repository guix.

commit 4cfb89841beb309d57daf367299c8346979b48e3
Author: John Darrington <address@hidden>
Date:   Thu Dec 22 19:14:24 2016 +0100

    installer: Add completion predicate for disk task.
    
    * gnu/system/installer/new.scm (size-of-largest-disk): New procedure, and
    use it to make completion predicate for disk task.
---
 gnu/system/installer/new.scm | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gnu/system/installer/new.scm b/gnu/system/installer/new.scm
index 5d37e58..aa393b8 100644
--- a/gnu/system/installer/new.scm
+++ b/gnu/system/installer/new.scm
@@ -39,6 +39,7 @@
             (ice-9 format)
              (ice-9 match)
             (ice-9 pretty-print)
+             (srfi srfi-1)
             (srfi srfi-9))
 
 
@@ -56,11 +57,15 @@
 (define timezone-menu-title    (N_ "Set the time zone"))
 (define hostname-menu-title    (N_ "Set the host name"))
 
+(define (size-of-largest-disk)
+  (fold (lambda (disk prev) (max (disk-size disk) prev))
+        0 (volumes)))
+
 (define main-options
   `(
     (disk . ,(make-task partition-menu-title
                         '()
-                        (lambda () #f)
+                        (lambda () (< 12000 (size-of-largest-disk)))
                         (lambda (page)
                           (make-disk-page
                            page