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>.