Move the rule to run a bit later, after
the standard udev rules have called blkid.
Don't run blkid manually, and run probe-bcache
as a fallback which can be patched out in a
package that depends on util-linux 2.24+.
probe-bcache: bail if libblkid finds anything
Preserve our last-resort safety check here
in case earlier rules fail to call blkid.
Fail if the device has any leftover superblock or partition table label.
Add a --wipe-bcache flag to overwrite bcache superblocks and recommend
wipefs for non-bcache superblocks.
Once the device is safe to write, always zero immediately before the
bcache superblock.
Make sure errors go to stderr. Use pkg-config.
