RFC: smart server protocol change for 0.16

[John Arbash Meinel]

Robert Collins wrote:
> One of the things I noticed while hacking on RemoteGraph was that error
> handling really needs to be improved a little. After chatting with
> Martin, we agreed that a nice improvement to the protocol would be that
> all responses have a success/fail prefix.
> 
> That is, rather than using 'ok' for boolean results and 'resultX' for
> non boolean, we'd return responses like:
> 'ok', 'True'
> or
> 'ok', 'resultX'
> for success, and
> 'error', 'ErrorClass', ...
> for errors.
> 
> This would make it unambigous about whether a given result is an error
> or not, and allow us to centralise the error handling as it would no
> longer be per-verb.
> 
> If we do this consistently, its a API break - but I think its a
> worthwhile one. We could add synonyms for all the current verbs which
> return the older style reponses, but personally I dont think thats worth
> it.
> 
> -Rob

I think this is much cleaner in the protocol, and worth breaking for.
Better to break now and get a nice protocol (before it is widespread)
than being hobbled from here out.

But if we are going to break, I think we should include things like the
client version that Martin has mentioned. (Of course, I've always been
in favor of versioned commands, so my view is a bit skewed in this regard).

John
=:->