Subversion 1.5 servers should be able to reject commits from clients that
don't have merge ingo
See this thread:
And this note Daniel Rall sent to me which doesn't appear in the mailing lists
Mark and I discussed this yesterday.
With ra_svn, we'd use its "capabilities" API. However, since Karl has
genericized this API to extend to the DAV RA layers, we might as well
use it there as well.
Ideally, this will also make it eaiser to identify Subversion clients that
speak the protocol, but don't use the same User-Agent string (e.g. SVNKit).