Version 1.506 of Jenkins and version 1.44 of the Mercurial plugin.

My users were having the issue that, when working against a repository that has an hg hook that triggers a Jenkins job, running hg push from a console would cause the process to hang permanently, until it was killed. I tracked down the issue to a NullPointerException that was not handled by handleNotifyCommit.

This only occurs if there is at least one Jenkins project that (A) has Source Code Management enabled and (B) does not have a Repository URL entered. This is a situation that shouldn't happen – there's no use case for it – but in an environment where we let individual developers control their own Jenkins projects, mistakes happen. Everyone in the organization should not suffer because of another developer's mistake.