[feature request] add rsync as alternate option after first SD clone

[golfromeo-fr]

When a user has clone its SDcard to another SDcard, to limit wear leveling of SDcard cells, it would be nice to have an option to do "rsync" instead of full cloning.

for example, look at rsync in the scripts like
https://wiki.archlinux.org/index.php/Full_system_backup_with_rsync
https://github.com/igorpecovnik/lib/blob/2174692e6a494353c3c1054f97892fdaafc9fe38/scripts/nand-sata-install/usr/lib/nand-sata-install/nand-sata-install.sh

rsync -aAXv --exclude={"/dev/","/proc/","/sys/","/tmp/","/run/","/mnt/","/media/*","/lost+found"} / /path/to/backup/folder

Also doing a rsync just after the first clone may lower possible cloning issues with a live system.

[SpareSimian]

Add to the rsync options, --delete and --one-file-system. The latter can replace most of the excludes.