pgsql readme tweaks

landry and I have both hit semaphore limits with pg_upgrade from 17->18,
so I think it would be a good idea to make the sysctl section a bit more
forceful.

While in pkg-readme land, step 6 of the "non-pg_upgrade" upgrade notes
diffs the postgresql.conf from pg_upgrade, so let's have the user
install it, and step 3 of the pg_upgrade upgrade notes says "Upgrade
your PostgreSQL package with pkg_add" while actually having the user
install pg_upgrade, so I've changed that too.

Any comments / ok?

Index: Makefile
===================================================================
RCS file: /cvs/ports/databases/postgresql/Makefile,v
diff -u -p -r1.321 Makefile
--- Makefile	9 Jul 2026 07:31:35 -0000	1.321
+++ Makefile	6 Aug 2026 20:55:02 -0000
@@ -11,6 +11,8 @@ PREV_MAJOR=	17
 DISTNAME=	postgresql-${VERSION}
 PKGNAME-main=	postgresql-client-${VERSION}
 
+REVISION-server=0
+
 DPB_PROPERTIES=	parallel
 
 CATEGORIES=	databases
Index: pkg/README-server
===================================================================
RCS file: /cvs/ports/databases/postgresql/pkg/README-server,v
diff -u -p -r1.40 README-server
--- pkg/README-server	9 Jul 2026 07:31:35 -0000	1.40
+++ pkg/README-server	6 Aug 2026 20:55:02 -0000
@@ -54,17 +54,19 @@ certificate, or self-sign it:
 
 Restart PostgreSQL to allow these changes to take effect.
 
-Tuning for busy servers
-=======================
+SystemV semaphore tuning
+========================
 The default sizes in the GENERIC kernel for SysV semaphores are not
-large enough for PostgreSQL.  Adding the following in /etc/sysctl.conf
-should allow PostgreSQL to start:
+large enough for PostgreSQL.  Even smaller servers are likely to need
+them raised for defaults while running pg_upgrade.  Add the following
+in /etc/sysctl.conf, then reboot or also set them for the current run
+via sysctl(8).
 
 	kern.seminfo.semmni=256
 	kern.seminfo.semmns=2048
 
-While you can start PostgreSQL with smaller limits, it's probably
-not wise unless you are very resource constrained.
+While you may be able to start PostgreSQL with smaller limits in some
+situations, it's not wise unless you are very resource constrained.
 
 You may also want to tune the max_connections value in the
 postgresql.conf file to increase the number of connections to the
@@ -102,8 +104,11 @@ to the current version.
 3) Shutdown the server:
 # rcctl stop postgresql
 
-4) Upgrade your PostgreSQL package with pkg_add.
+4) Upgrade your PostgreSQL package with pkg_add. Even though you're not
+using pg_upgrade for the update, install it to provide an unmodified
+configuration file from a closer version for step 6.
 # pkg_add -ui postgresql-server
+# pkg_add postgresql-pg_upgrade
 
 5) Backup your old data directory and rename:
 # cd /var/postgresql && tar cf - data | gzip -1 > data.tar.gz
@@ -144,7 +149,7 @@ faster than a dump and reload, especiall
    enabled by default until PostgreSQL 18):
 # su _postgresql -c '/usr/local/bin/pg_checksums -e -D /var/postgresql/data'
 
-3) Upgrade your PostgreSQL package with pkg_add.
+3) Install the PostgreSQL pg_upgrade package with pkg_add.
 # pkg_add postgresql-pg_upgrade
 
 4) Backup your old data directory: