Retroactively filing so as to be considered for backport.

mvn -f subversion-plugin/pom.xml hpi:run does not work: you will not get the version under development, but rather 1.26. (Via jenkins-test-harness; not even the 1.34 bundled in Jenkins 1.466 WAR!) The console shows:

... hudson.PluginManager$1$3$1 isDuplicate
INFO: Ignoring .../subversion-plugin/./work/plugins/subversion.hpl because .../subversion-plugin/./work/plugins/subversion.jpi is already loaded

If you change the parent POM to 1.513, it works, because this regression (from https://github.com/jenkinsci/jenkins/commit/32d5c23 in 1.448) was fixed in https://github.com/jenkinsci/jenkins/commit/7547681a24fadab2a909729413b9f16da90b2d16 in 1.512 then https://github.com/jenkinsci/jenkins/commit/5aa4af75c2c4c66541f1fd24ef82c5d46a79940d in 1.513.