Logging the PostgreSQL version on startup is useful for two reasons:
There is a clear marker in the log file that a new postmaster is
beginning, and it's useful for tracking the server version across
startup while upgrading.

Author: Christoph Berg <christoph.berg@credativ.de>
Discussion: https://www.postgresql.org/message-id/flat/20181121144611.GJ15795@msg.credativ.de/