Improve version reporting in pgbench.

Commit 547f04e7 caused pgbench to start printing its version number,
which seems like a fine idea, but it needs a bit more work:
* Print the server version number too, when different.
* Print the PG_VERSION string, not some reconstructed approximation.

This patch copies psql's well-tested code for the same purpose.

Discussion: https://postgr.es/m/1226654.1624036821@sss.pgh.pa.us

src/bin/pgbench/pgbench.c

@@ -63,6 +63,7 @@
 #include "common/username.h"
 #include "fe_utils/cancel.h"
 #include "fe_utils/conditional.h"
+#include "fe_utils/string_utils.h"
 #include "getopt_long.h"
 #include "libpq-fe.h"
 #include "pgbench.h"
@@ -5493,6 +5494,37 @@ printSimpleStats(const char *prefix, SimpleStats *ss)
 	}
 }
 
+/* print version banner */
+static void
+printVersion(PGconn *con)
+{
+	int			server_ver = PQserverVersion(con);
+	int			client_ver = PG_VERSION_NUM;
+
+	if (server_ver != client_ver)
+	{
+		const char *server_version;
+		char		sverbuf[32];
+
+		/* Try to get full text form, might include "devel" etc */
+		server_version = PQparameterStatus(con, "server_version");
+		/* Otherwise fall back on server_ver */
+		if (!server_version)
+		{
+			formatPGVersionNumber(server_ver, true,
+								  sverbuf, sizeof(sverbuf));
+			server_version = sverbuf;
+		}
+
+		printf(_("%s (%s, server %s)\n"),
+			   "pgbench", PG_VERSION, server_version);
+	}
+	/* For version match, only print pgbench version */
+	else
+		printf("%s (%s)\n", "pgbench", PG_VERSION);
+	fflush(stdout);
+}
+
 /* print out results */
 static void
 printResults(StatsData *total,
@@ -5506,7 +5538,6 @@ printResults(StatsData *total,
 	double		bench_duration = PG_TIME_GET_DOUBLE(total_duration);
 	double		tps = ntx / bench_duration;
 
-	printf("pgbench (PostgreSQL) %d.%d\n", PG_VERSION_NUM / 10000, PG_VERSION_NUM % 100);
 	/* Report test parameters. */
 	printf("transaction type: %s\n",
 		   num_scripts == 1 ? sql_script[0].desc : "multiple scripts");
@@ -6334,6 +6365,9 @@ main(int argc, char **argv)
 	if (con == NULL)
 		exit(1);
 
+	/* report pgbench and server versions */
+	printVersion(con);
+
 	pg_log_debug("pghost: %s pgport: %s nclients: %d %s: %d dbName: %s",
 				 PQhost(con), PQport(con), nclients,
 				 duration <= 0 ? "nxacts" : "duration",

src/bin/pgbench/t/001_pgbench_with_server.pl

@@ -100,7 +100,7 @@ pgbench(
 	'no such database');
 
 pgbench(
-	'-S -t 1', 1, [qr{^$}],
+	'-S -t 1', 1, [],
 	[qr{Perhaps you need to do initialization}],
 	'run without init');