When viewVC is configured with multiple repositories, it expects the repository
to be specified in the URL it's asked for. It refers to the repository as the
"root".

My viewvc has the option root_as_url_component = 1 enabled.

Svn URL: svn://server/project/foo/blah
svn info ->
.. Repository Root: svn://server/project ..

ViewSVN URL in job configuration: http://svn/viewvc/

Actual URL generated by Hudson: http://server/viewvc/?rev=30&view=revision
URL generated by ViewVC itself: http://server/viewvc/project?
view=revision&revision=30

Note also that a Hudson job can refer to multiple svn urls, that is, a job could
be doing something like:

svn co svn://server/tools/blah
svn co svn://server/src/baz
blah/go.sh baz

That is, the viewvc url can't be set to either http://server/viewvc/tools or
http://server/viewvc/src.

ViewVC 1.1.2
Hudson ver. 1.328
Sun Java6 / Tomcat6 / Linux2.6 / svn1.6 / etc.