Re: btrfs-progs confusing message

[Konstantin Svist <fry.kun@gmail.com>]

On 04/21/2016 04:02 AM, Austin S. Hemmelgarn wrote:
> On 2016-04-20 16:23, Konstantin Svist wrote:
>> Pretty much all commands print out the usage message when no device is
>> specified:
>>
>> [root@host ~]# btrfs scrub start
>> btrfs scrub start: too few arguments
>> usage: btrfs scrub start [-BdqrRf] [-c ioprio_class -n ioprio_classdata]
>> <path>|<device>
>> ...
>>
>> However, balance doesn't
>>
>> [root@host ~]# btrfs balance start
>> ERROR: can't access 'start': No such file or directory
>
> And this is an example of why backwards comparability can be a pain.
> The original balance command was 'btrfs filesystem balance', and had
> no start, stop, or similar sub-commands.  This got changed to the
> current incarnation when the support for filters was added.  For
> backwards compatibility reasons, we decided to still accept balance
> with no arguments other than the path as being the same as running
> 'btrfs balance start' on that path, and then made the old name an
> alias to the new one, with the restriction that you can't pass in
> filters through that interface.  What is happening here is that
> balance is trying to interpret start as a path, not a command, hence
> the message about not being able to access 'start'.
>

So since this is still detected as an error, why not print usage info at
this point?