Subversion sometimes erroneously sets a pristine text ref-count to 0. This
issue is not about the causes of that error, but about further problems that
make it very hard to recover from such an error.
* 'cleanup' deletes pristines that have a ref-count of 0 without first
checking that the ref-count is correct.
* 'cleanup' errors out, leaving the WC locked, on finding a missing pristine.
See the dev@ email thread started on 2013-04-18 by Julian Foad, subject
"Pristine text missing - cleanup doesn't work", archived at e.g.
<http://svn.haxx.se/dev/archive-2013-04/0426.shtml>.
Major