describe what p4publish does.

https://www.perforce.com/manuals/jenkins/Content/P4Jenkins/pipeline-snippet-generator-publish-assets.html#p4publish__P4_Publish

p4publish will:

• use the provided view to create a client
• "sync -k" all files in the client.   This sets the client metadata as having the latest revision of the files but leaves the current workspace files unchanged 
• "reconcile -e -a -f " all files in the client.  Any files changed or added by the build process should now be opened for edit or add.
• submit or shelve the files.