* Support booting into another GRUB boot entry via ‘grub-reboot’.

This requires grub.conf to honour the saved_entry GRUB environment
  variable.

svn path=/nixos/trunk/; revision=27807

modules/installer/grub/grub-menu-builder.sh

@@ -59,8 +59,27 @@ GRUBEND
             cp -f @grub@/share/grub/unicode.pf2 /boot/grub/unicode.pf2
 	    cat > "$1" <<EOF
 # Automatically generated.  DO NOT EDIT THIS FILE!
-set default=@default@
-set timeout=@timeout@
+
+if [ -s \$prefix/grubenv ]; then
+  load_env
+fi
+
+# ‘grub-reboot’ sets a one-time saved entry, which we process here and
+# then delete.
+if [ "\${saved_entry}" ]; then
+  # The next line *has* to look exactly like this, otherwise KDM's
+  # reboot feature won't work properly with GRUB 2.
+  set default="\${saved_entry}"
+  set saved_entry=
+  set prev_saved_entry=
+  save_env saved_entry
+  save_env prev_saved_entry
+  set timeout=1
+else
+  set default=@default@
+  set timeout=@timeout@
+fi
+
 if loadfont $bootRoot/grub/unicode.pf2; then
   set gfxmode=640x480
   insmod gfxterm