Hi hackers:
I got a basebackup using pg_basebackup -R. After that, I created a restore point named test on primary, and set recovery_target_name to test, recovery_target_action to shutdown in standby datadir. I got a failure startup message after 'pg_ctl start -D $standby_datadir'. I think it is not a failure, and makes users nervous, especially for newbies.
My thought is to generate a recovery.done file if the postmaster receives exit code 3 from the startup process. When postmaster exits, pg_ctl will give a more friendly message to users.