standby promote: enable "service_promote_command" in PostgreSQL 12

This enables the promote command generated internally by repmgr to
be overridden if desired, in the same way as for PostgreSQL 11 and
earlier.

HISTORY

@@ -1,4 +1,4 @@
-5.1     2019-??-??
+5.1     2020-??-??
         repmgr: remove BDR 2.x support
         repmgr: don't query upstream's data directory (Ian)
         repmgr: rename --recovery-conf-only to --replication-conf-only (Ian)
@@ -14,6 +14,7 @@
         repmgr: consolidate replication connection code (Ian)
         repmgr: check permissions for "pg_promote()" and fall back to pg_ctl
           if necessary (Ian)
+        repmgr: enable "service_promote_command" in PostgreSQL 12 (Ian)
 
 5.0     2019-10-15
         general: add PostgreSQL 12 support (Ian)

doc/appendix-release-notes.xml

@@ -97,6 +97,12 @@
             </para>
           </listitem>
 
+          <listitem>
+            <para>
+              <link linkend="repmgr-standby-promote"><command>repmgr standby promote</command></link>:
+              in PostgreSQL 12 and later, use <varname>service_promote_command</varname> if set.
+            </para>
+          </listitem>
 
           <listitem>
             <para>

doc/repmgr-standby-promote.xml

@@ -195,6 +195,23 @@
 		 </simpara>
 	   </listitem>
 
+       <listitem>
+        <indexterm>
+          <primary>service_promote_command</primary>
+          <secondary>with &quot;repmgr standby promote &quot;</secondary>
+        </indexterm>
+         <simpara>
+           <literal>service_promote_command</literal>:
+           a command which will be executed instead of <command>pg_ctl promote</command>
+           or (in PostgreSQL 12 and later) <function>pg_promote()</function>.
+         </simpara>
+         <simpara>
+           This is intended for systems which provide a package-level promote command,
+           such as Debian's <application>pg_ctlcluster</application>, to promote the
+           PostgreSQL from standby to primary.
+         </simpara>
+       </listitem>
+
 	  </itemizedlist>
 	</para>
 

repmgr-action-standby.c

@@ -2487,7 +2487,11 @@ _do_standby_promote_internal(PGconn *conn)
 		{
 			use_pg_promote = true;
 
-			if (can_execute_pg_promote(conn) == false)
+			if (config_file_options.service_promote_command[0] != '\0')
+			{
+				use_pg_promote = false;
+			}
+			else if (can_execute_pg_promote(conn) == false)
 			{
 				use_pg_promote = false;
 				log_info(_("user \"%s\" does not have permission to execute \"pg_promote()\", falling back to \"pg_ctl promote\""),