List<Revision> revisions = ae.getData(SVNRevisionGraph.SELECTED_REVISIONS);
int selectionSize = (revisions == null) ? 0 : revisions.size();
if (selectionSize == 2) {
graph.compareFileRevisions(revisions.get(0), revisions.get(1));
} else if (selectionSize == 1) {
Revision currentRevision = ae.getData(SVNRevisionGraph.CURRENT_REVISION);
graph.compareFileRevisions(revisions.get(0), currentRevision);
}
}