* Change find_disks: after mouting target root, check for
/etc/fstab in target, and abort upgrade if not found.
* Change upgrade to check if the target root has /etc.old
before renaming the target /etc -> /etc.old. If found, abort.
(may indicates a failed upgrade.)
* Add save_etc(). saves target /etc as /etc.old, then copies back
config files we might want during upgrade, in case target is current root.
* Fix logic that fscks and mounts disks. Use subroutines to
fsck with a warning message and ok() on continue. Same for doing mounts.
* Fix bug in extract_dist(). Do NOT do target prefixing on the dist_dir,
since we didn't do target prefixing when mounting it.
(At least, NFS does't.)
* Add function to sanity-check target root.
Call after upgrade/install is done.
* Change MSG_realdir to print the strerror() of any errors.
Change target_chdir() to check if chdir() returns -1 and return errno.
* Make sure /dev exists before cd'ing there and running MAKEDEV.
* Use target_fopen() and fprintf() to write network state to disk,
to avoid inadvertent shell escapes.
* Fix silly typo in append_to_target_file. (maybe add shell quotes?)
77221dcc6a