We created a perforce "jenkins_user" with only READ permissions on the repository and discovered that the default "Auto cleanup and sync" populate option silently fails. Here's what the build log shows:

P4 Task: tidying workspace to match have list.
(p4):cmd:... p4 reconcile -n -a -e -d -l -f C:\Jenkins\jobs\45027_Real_Time_MR_Interface_main\wo___
p4 reconcile -n -a -e -d -l -f C:\Jenkins\jobs\45027_Real_Time_MR_Interface_main\workspace/...

You don't have permission for this operation.

(p4):stop:8
duration: (15ms)

P4 Task: syncing files at change: 15452

Note the permission failure is not acted upon: the plugin goes on to sync files, etc. But previous build files remain in the workspace and cause trouble. It is not a clean build.

I would be happy to use "Forced clean and sync" instead, but then I run into JENKINS-32518!