Race condition causing only the content in the latest of concurrent commits to be visible about boar HOT 2 OPEN

This is most certainly a bug. There is a mutex that is held while the session 
is being modified, but the problem is that the session is not locked until the 
actual commit starts. The list of files to commit are gathered before that 
happens, making your scenario possible. This will need fixing.

I have pushed a temporary fix in changeset 094ecd048538 that aborts the 
long-running commit if there has been any intervening commits. Not too bad user 
experience, the scan has already been completed and you just need to do an 
update and then try again. 

Final solution will probably be to lock the session for the duration of the 
commit.