The second and third calls wouldn't have effect because server is null.So if we expose createMergedRegion() as public method, we can call it directly.
merged.openHRegion(reporter) is also called in RegionMergeTransaction#openMergedRegion.
Maybe we can also implement hbase shell bindings for online one.
Shell command of online region is already done(
1.We should fix the snapshot break caused by offline merge now
2.Do some easy alignment about the code of online merge and offline merge, since we plan to remove offline merge in a futuer moment