x86: preserve partition table on sysupgrade

With this patch sysupgrade will write directly to the partitions
instead of to the main disk.  The UUID is copied from the image
to the MBR as well.  This prevents the mbr from being completely
overwritten and losing the partition table.  The -p option has
been added to maintain the original behavior and overwite the
entire disk with the new image.  Tests have been added to ensure
that the image partitions match up with the active partitions.

Signed-off-by: Rob Mosher <nyt-openwrt@countercultured.net>

SVN-Revision: 48682

package/base-files/files/sbin/sysupgrade

@@ -10,6 +10,7 @@ export INTERACTIVE=0
 export VERBOSE=1
 export SAVE_CONFIG=1
 export SAVE_OVERLAY=0
+export SAVE_PARTITIONS=1
 export DELAY=
 export CONF_IMAGE=
 export CONF_BACKUP_LIST=0
@@ -29,6 +30,7 @@ while [ -n "$1" ]; do
 		-q) export VERBOSE="$(($VERBOSE - 1))";;
 		-n) export SAVE_CONFIG=0;;
 		-c) export SAVE_OVERLAY=1;;
+		-p) export SAVE_PARTITIONS=0;;
 		-b|--create-backup) export CONF_BACKUP="$2" NEED_IMAGE=1; shift;;
 		-r|--restore-backup) export CONF_RESTORE="$2" NEED_IMAGE=1; shift;;
 		-l|--list-backup) export CONF_BACKUP_LIST=1; break;;
@@ -62,6 +64,7 @@ upgrade-option:
 	-i           interactive mode
 	-c           attempt to preserve all changed files in /etc/
 	-n           do not save configuration over reflash
+	-p           do not attempt to restore the partition table after flash.
 	-T | --test
 	             Verify image and config .tar.gz but do not actually flash.
 	-F | --force