So with checkpointing we write the checkpoint to both A and B and verify they match before using the checkpoint
What happens if the src of the replication is read only? As far as I can tell couch will just checkout a checkpoint_commit_error and carry on from the start, The only improvement I can think of is the user specifies they know the src is read only and to only use the target checkpoint, we can 'possibly' make that happen automatically if the src specifically fails the write due to permissions.
