qemu-img: info: refresh options/--help

Add missing long options and --help output.
Also add -b short option for --backing-chain, and remove
now-unused OPTION_BACKING_CHAIN.

Reorder options for consistency.

While at it, remove unused option_index variable.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Message-ID: <20250531171609.197078-14-mjt@tls.msk.ru>
[kwolf: Fixed up help text formatting]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
1 file changed