SVNAdaptor from Tigris

[Rod Widdowson]

> I'm fairly concerned also that it seems to be last tagged 9 years ago. The
> trunk has some activity, but there doesn't seem to be any real support of
> this as a stable library in its own right. That's a large red flag, I
> think.
> 
> I'm not sure it's worth the bother vs. just marking svnkit optional and
> excluding it from the release.

I don't have the experience to make the call, but that makes perfect sense
(I'll note that, for example log4shib gets changes at least every 6 months).

 For me, the Tigris code has the advantage that it is a clean interface but
the disadvantage of bringing all that JavaHL baggage over with it, but using
SVNKit has the significant advantage that we can "just" do a port from V2,
which means a better chance of doing what is current expected.  

I do think that we would need to fail the related Resource API (since that
is not the way we configure SVNKit), but that is a minor detail.

Unless people disagree I'll do a port of the V2 SVN resource (i.e. implement
a Spring Resource using SVNKit) and add some tests.

Just to confirm my understanding, the current plan is to add svnkit.jar to
the pom as "provided" ?

Rod