What does "Warning : There are multiple branch changesets here" mean?

We use Jenkins as our CI-engine, which knows how to monitor a git repository. For some reason I usually see

Started by user anonymous
Building in workspace /var/lib/jenkins/jobs/X/workspace
Checkout:workspace / /var/lib/jenkins/jobs/X/workspace - hudson.remoting.LocalChannel@844d88
Using strategy: Default
Last Built Revision: Revision 8422864a9745535d808435bd33ece764fd250358 (origin/HEAD, origin/master)
Fetching changes from 1 remote Git repository
Fetching upstream changes from gitosis@...
Seen branch in repository origin/HEAD
Seen branch in repository origin/master
Commencing build of Revision c1e71af117df3cd63da972f361ad260af6f16bf5 (origin/HEAD, origin/master)
Checking out Revision c1e71af117df3cd63da972f361ad260af6f16bf5 (origin/HEAD, origin/master)
Warning : There are multiple branch changesets here
Parsing POMs
Modules changed, recalculating dependency graph

My question is, what does the "Warning : There are multiple branch changesets here" line actually_mean_?