--dirs accepted any path and fed it to `find -delete` running as root,
with no confirmation: `--clean --dirs /home` removed every file in /home
past the age threshold, and `--dirs /` did it system-wide.
Now refuses protected directories, comparing the readlink -f resolved
path so a symlink or /tmp/../home cannot smuggle one through, and
requires absolute paths. Anything outside the /tmp,/var/tmp defaults
also needs an interactive confirmation -- or --yes, so unattended use
stays possible; without a tty and without --yes it refuses rather than
hanging in cron.
usage() sliced fixed line numbers (head -22 | tail -n +18) and had
already outgrown them, truncating --help mid-list at --age. So --dirs,
the one option that could destroy a system, was the one option --help
never mentioned. Replaced with a sed range that tracks the comment block
wherever it moves.
The first version of the protected-path check let "/" through: it
compared against "${p%/}", which turns the "/" entry into an empty
string that matches nothing. Caught by testing the guard against the
paths it exists to stop, rather than assuming it worked.