Un-assigning this from digerata per request by him.

A workaround is entering a very high change list number in the field "First
change list to track" and clicking the flag "Force sync". In that case the
plugin only lists the changes after the given change number and still does a
complete sync.

What I did not understand before is that the field "First change list to track"
only deals with the change list in the hudson project. It does not have anything
to do with the synchronization of the project sources with the perforce server.

This issue can be closed now.

I've changed the computation of the first change list to track so that for new project/job it does not start from 0, but rather assumes that no changes should be
reported (i.e. not until there is a change introduced between two builds of the
job). This should hopefully address the original concern (too many changes).

It may still be of interest to have the feature: don't determine/save the changes
for builds of this project.