#424 #512 #513 more ugly code to handle edge cases: moved things around in update_merge so unique collisions and deletions of them are done in separate functions now + merging links now uses its own thing instead of update_merge, making update_merge lean again as special cases are handled somewhere else + used the dedup fixture inside the new test cases so running them alone with the -k option makes them pass + refactored log merging to use insert_merge indirectly and added an exclusion Q filter to weed out self links in logs