Allow progress tracking of sub-commands - Mailing list pgsql-hackers

I've noticed several complaints about two commands trying to report their
progress at the same time, overwriting each other's output [1][2][3]. I posted
a prototype of an enhancement of the monitoring infrastructure that allows for
progress reporting of two commands w/o conflicts [4].

This is a new version that passes regression tests. I'll register it for the
upcoming CF.


[1] https://www.postgresql.org/message-id/5667.1774513434%40localhost
[2] https://www.postgresql.org/message-id/CALj2ACUgwSchK6jQ2CdKLBWUADTOE_zKdTff2Zg3E6hOuXKv-w%40mail.gmail.com
[3] https://www.postgresql.org/message-id/aj4gJQMba0kClQmj%40Mac
[4] https://www.postgresql.org/message-id/30939.1777888333%40localhost

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com