If I am attempting to configure a new job, I may repeatedly build the HEAD revision of a project many times util the configuration is tuned to build correctly. Currently, the 'clean update' method does not clean up the local workspace if the repository has not changed since the last job run, so there are stale files left over from a prior failed build. The 'clean update' should still remove all non-versioned files even if the repository hasn't changed since the last job run.