BUG #17325: Unexpected streaming replication protocol bytes for IDENTIFY_SYSTEM command

The following bug has been logged on the website:

Bug reference:      17325
Logged by:          Greg Rychlewski
Email address:      greg.rychlewski@gmail.com
PostgreSQL version: 13.0
Operating system:   x86_64-apple-darwin18.7.0
Description:

Hi,

I ran the following command and captured the packets with wire shark:

psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"

The timeline ID returned from psql is displayed as 1. Based on the protocol
docs, I was expecting the packets to correspond to an int32 value of 1, but
I am seeing them coming as the string "1". I see following (values are
hexadecimal):

00 00 00 01 for the length 
31 for the value

Thanks,
Greg