Add the receiver-side --super / --no-super tri-state (Config->super_mode)
under the safe-subset + clear-refusal privilege model: FastSync never
elevates privileges, it only permits super-user attempts that are already
confined fd-relative below the authorized receive root.
- identity: privilege_super_permitted() gate (OFF=false, ON=true, AUTO follows
geteuid()==0); identity_apply_ownership/_link become no-ops when not
permitted; --super with no explicit identity policy implies raw numeric-id
preservation (explicit usermap/groupmap/chown/numeric-ids still win); warn
exactly once when --super is requested by a non-root receiver.
- file_receive: gate char/block device-node creation on the gate; FIFO/socket
handling is unchanged.
- wire: trailing super_mode int after the --iconv spec, validated 0..2 in
receive_privilege_options and validate_received_config; PROTOCOL_VERSION
2.17.0 -> 2.18.0; version-sensitive tests and docs updated.
- CLI: --super/--no-super parsed explicitly before the generic --no-* branch
(malformed --super=x rejected); usage text added.
- tests: config wire round-trip + invalid-value rejection, privilege-gate mode
unit test, CLI parse test, integration transfer + root-gated ownership
suppression/appliance tests.
- docs: RSYNC_COMPAT --super row + Wave E note, protocol mentions, README.