No mention of standby.signal in pg_ugprade docs

Hi,

I noticed that  standby.signal is not mentioned anywhere in the pg_upgrade document.

https://www.postgresql.org/docs/13/pgupgrade.html

I had trouble the first time I tried to start my secondary because it didn't connect to the primary / start streaming
untilI touched the signal  
file.  The signal file is obliterated during the rsync but there is no mention of putting it back or preserving it.


Here is what the docs currently read:

10. Upgrade streaming replication and log-shipping standby servers
...
e. Save configuration files

Save any configuration files from the old standbys' configuration directories you need to keep, e.g., postgresql.conf
(andany files included by it), postgresql.auto.conf, pg_hba.conf, because these will be overwritten or removed in the
nextstep. 



Maybe a mention of standby.signal would make sense under:

g. Configure streaming replication and log-shipping standby servers



Thanks for considering this change.


Dan Stoner