Carry over changesets from previous builds

This fixes the problem that changes from previous builds didn't get recorded when they were aborted o.s.l.t.

Unfortunately, I also included a different change in the same commit: that the list of affected files is limited to 20 in JIRA issues. While I principally think that this could be a useful feature, we should at least make it configurable in some way (disable or configure amount of files)