Add --fast flag, that can enable less expensive, but also less thurough versions of some commands.
* Add --fast flag, that can enable less expensive, but also less thurough
versions of some commands.
* fsck: In fast mode, avoid checking checksums.
* unused: In fast mode, just show all existing temp files as unused,
and avoid expensive scan for other unused content.
It compiles. It sorta works. Several subcommands are FIXME marked and
broken, because things that used to accept separate --backend and --key
params need to be changed to accept just a --key that encodes all the key
info, now that there is metadata in keys.
