Probe using OPTIONS

[Jelmer Vernooij]

Hi Vincent,

As we discussed during UDS, I'd like to add a mechanism that allows
bzr-svn to do an OPTIONS request before the probing of the smart server
using a POST request to .bzr/smart hits in.

So far I've done this by moving the bzr-svn check before the bzr smart
server one. This is a bit hackish and it also means that the results of
the OPTIONS request done by bzr-svn are lost. ISTM the OPTIONS result
would also be useful for e.g. bzr-webdav?

Would it make sense to allow control formats to probe based on the
OPTIONS reply ?

Cheers,

Jelmer