Currently, 'bcachefs set-fs-option' requires all devices to be specified
when setting options on an offline multidevice filesystem - it can't yet
scan for the rest of the filesystem members.
We do need to fix this, but the scan code is written in Rust, so that
either means a lot of ugly FFI code or rewriting cmd_set_option() in
Rust - neither of which are happening today.
So as an interim hack, add a --dev-idx option: this can be specified
(multiple times if desired) for indicating which devices the device
specific options should be applied to.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2aeeac7785