Callbacks, prompts, etc. for issue 2779

Fer yer reference: http://subversion.tigris.org/issues/show_bug.cgi?id=2779

I've got Subversion on the issue-2779-dev branch able to follow redirects
from the server without user verification, with a hard-coded limit as to the
number of hops to follow before quitting, and with notification to the
client that the (or, each) redirection has occurred. I don't like the
hard-coded limit, and I don't like the hard-coded decision to always follow
redirects at all.

My original plan to add a ~/.subversion/servers configuration bit for
whether or not to honor server redirects. In fact, I could fix both of my
"don't likes" above by naming the flag max-redirects and giving it a numeric
value (0 means don't follow, other positive integers serve to allow with
limits the automatic redirection).

However, it was suggested that the client actually prompt the user when such
an event occurs for what to do.

I'm not fully sold on one approach or another, but I'm wondering two things:

a) What do folks think about the various approaches?

b) If the prompting approach is preferred, what's a reasonable way to do
this? The notification function cannot serve as a prompt. We could add a
redirection_callback_func to the likes of svn_client_update,
svn_client_checkout, svn_client_switch, svn_client_relocate, etc., but that
seems like such a really weird concept to expose at the API level. We could
introduce a custom prompting function in the client context baton. *shrug*
 Got suggestions?

-- 
C. Michael Pilato <cmpilato@red-bean.com> | http://cmpilato.blogspot.com/