pg_basebackup -F plain -R overwrites postgresql.auto.conf

Hi,

I found that pg_basebackup -F plain -R *overwrites* postgresql.auto.conf
taken from the primary server with new primary_conninfo setting,
while pg_basebackup -F tar -R just *appends* it into the file. I think that
this is a bug and pg_basebackup -F plain -R should *append* the setting.
Thought?

I attached the patch to fix the bug. This patch should be back-patch to
v12.

Regards,

-- 
Fujii Masao
NTT DATA CORPORATION
Advanced Platform Technology Group
Research and Development Headquarters