repmgr: add --help output and documentation for --wait-sync

README.md

@@ -540,6 +540,18 @@ standby's upstream server is the replication cluster master. While of limited
 use in a simple master/standby replication cluster, this information is required
 to effectively manage cascading replication (see below).
 
+* * *
+
+> *TIP*: depending on your environment and workload, it may take some time for
+> the standby's node record to propagate from the master to the standby. Some
+> actions (such as starting `repmgrd`) require that the standby's node record
+> is present and up-to-date to function correctly - by providing the option
+> `--wait-sync` to the `repmgr standby register` command, `repmgr` will wait
+> until the record is synchronised before exiting. An optional timeout (in
+> seconds) can be added to this option (e.g. `--wait-sync=60`).
+
+* * *
+
 ### Using Barman to clone a standby
 
 `repmgr standby clone` also supports Barman, the Backup and

repmgr.c

@@ -5571,6 +5571,8 @@ do_help(void)
 			 "                                        PostgreSQL data directory\n"));
 	printf(_("  -w, --wal-keep-segments             (standby clone) minimum value for the GUC\n" \
 			 "                                        wal_keep_segments (default: %s)\n"), DEFAULT_WAL_KEEP_SEGMENTS);
+	printf(_("  --wait-sync[=VALUE]                 (standby register) wait for the node record to synchronise to the\n"\
+			 "                                        standby (optional timeout in seconds)\n"));
 	printf(_("  -W, --wait                          (standby follow) wait for a master to appear\n"));
 	printf(_("  -m, --mode                          (standby switchover) shutdown mode (\"fast\" - default, \"smart\" or \"immediate\")\n"));
 	printf(_("  -C, --remote-config-file            (standby switchover) path to the configuration file on\n" \