MDEV-20428: "Start binlog_dump" message doesn't indicate GTID position

Problem:
=======
The "Start binlog_dump" message hasn't been updated to include the slave's
requested GTID position:

20:05:05 139836760311552 [Note] Start binlog_dump to slave_server(2), pos(, 4)

For diagnostic purposes, it would be helpful if the GTID position were
included.

Fix:
===
Imporve "Start binlog_dump" print message to include "using_gtid" and
"GTID position" requested by slave.

Ex:
[Note] Start binlog_dump to slave_server(2), pos(, 4), using_gtid(1),
  gtid('1-1-201,2-2-100')

[Note] Start binlog_dump to slave_server(3), pos('mariadb-bin.004142',
  507988273), using_gtid(0), gtid('')

mysql-test/suite/rpl/r/rpl_binlog_dump_slave_gtid_state_info.result

+include/master-slave.inc
+[connection master]
+SET GLOBAL LOG_WARNINGS=2;
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=current_pos;
+include/start_slave.inc
+"Test Case 1: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('')"
+FOUND /using_gtid\(1\), gtid\(\'\'\)/ in mysqld.1.err
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=no;
+include/start_slave.inc
+"Test Case 2: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(0), gtid('')"
+FOUND /using_gtid\(0\), gtid\(\'\'\)/ in mysqld.1.err
+CREATE TABLE t (f INT) ENGINE=INNODB;
+INSERT INTO t VALUES(10);
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=slave_pos;
+include/start_slave.inc
+"Test Case 3: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('0-1-2')"
+FOUND /using_gtid\(1\), gtid\(\'0-1-2\'\)/ in mysqld.1.err
+SET @@SESSION.gtid_domain_id=10;
+INSERT INTO t VALUES(20);
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=slave_pos;
+include/start_slave.inc
+"Test Case 4: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('0-1-2,10-1-1')"
+FOUND /using_gtid\(1\), gtid\(\'0-1-2,10-1-1\'\)/ in mysqld.1.err
+"===== Clean up ====="
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=no;
+include/start_slave.inc
+DROP TABLE t;
+SET GLOBAL LOG_WARNINGS=default;
+include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_binlog_dump_slave_gtid_state_info.test

+# ==== Purpose ====
+#
+# Test verifies that Start binlog_dump message will report GTID position
+# requested by slave when log_warnings > 1.
+#
+# ==== Implementation ====
+#
+# Steps:
+#    0 - Have LOG_WARNINGS=2
+#    1 - On a fresh slave server which has not replicated any GTIDs execute
+#        "CHANGE MASTER TO MASTER_USE_GTID=current_pos;" command. Start the
+#        slave.
+#    2 - In Master error log verify that pattern "using_gtid(1), gtid('')" is
+#        present.
+#    3 - On slave server do STOP SLAVE and execute "CHANGE MASTER TO
+#        MASTER_USE_GTID=no;" command. Start the slave threads.
+#    4 - In Master error log verify that pattern "using_gtid(0), gtid('')" is
+#        present.
+#    5-  Execute a DDL and DML on master server. This will generated two GTIDs
+#        on the master server ('0-1-2'). Sync the slave server with master.
+#    6 - On slave do STOP SLAVE and execute "CHANGE MASTER TO
+#        MASTER_USE_GTID=slave_pos;" command. Start slave threads.
+#    7 - In Master error verify that pattern "using_gtid(1), gtid('0-1-2')" is
+#        present.
+#    8 - On Master change domain ID to 10 and execute a DML operation. It will
+#        generate a GTID 10-1-1.
+#    9 - On slave do STOP SLAVE and execute "CHANGE MASTER TO
+#        MASTER_USE_GTID=slave_pos;" command. Start slave threads.
+#    10 -In Master error verify that pattern "using_gtid(1),
+#        gtid('0-1-2,10-1-1')" is present.
+#
+# ==== References ====
+#
+# MDEV-20428: "Start binlog_dump" message doesn't indicate GTID position
+#
+
+--source include/have_binlog_format_mixed.inc
+--source include/have_innodb.inc
+--source include/master-slave.inc
+
+--connection master
+SET GLOBAL LOG_WARNINGS=2;
+
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=current_pos;
+--source include/start_slave.inc
+
+--connection master
+# Check error log for correct messages.
+let $log_error_= `SELECT @@GLOBAL.log_error`;
+if(!$log_error_)
+{
+    # MySQL Server on windows is started with --console and thus
+    # does not know the location of its .err log, use default location
+    let $log_error_ = $MYSQLTEST_VARDIR/log/mysqld.1.err;
+}
+--echo "Test Case 1: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('')"
+--let SEARCH_FILE=$log_error_
+--let SEARCH_RANGE=-50000
+--let SEARCH_PATTERN=using_gtid\(1\), gtid\(\'\'\)
+--source include/search_pattern_in_file.inc
+
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=no;
+--source include/start_slave.inc
+
+--connection master
+--echo "Test Case 2: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(0), gtid('')"
+--let SEARCH_FILE=$log_error_
+--let SEARCH_RANGE=-50000
+--let SEARCH_PATTERN=using_gtid\(0\), gtid\(\'\'\)
+--source include/search_pattern_in_file.inc
+CREATE TABLE t (f INT) ENGINE=INNODB;
+INSERT INTO t VALUES(10);
+save_master_pos;
+
+--connection slave
+sync_with_master;
+
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=slave_pos;
+--source include/start_slave.inc
+
+--connection master
+--echo "Test Case 3: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('0-1-2')"
+--let SEARCH_FILE=$log_error_
+--let SEARCH_RANGE=-50000
+--let SEARCH_PATTERN=using_gtid\(1\), gtid\(\'0-1-2\'\)
+--source include/search_pattern_in_file.inc
+SET @@SESSION.gtid_domain_id=10;
+INSERT INTO t VALUES(20);
+save_master_pos;
+
+--connection slave
+sync_with_master;
+
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=slave_pos;
+--source include/start_slave.inc
+
+--connection master
+--echo "Test Case 4: Start binlog_dump to slave_server(#), pos(master-bin.000001, ###), using_gtid(1), gtid('0-1-2,10-1-1')"
+--let SEARCH_FILE=$log_error_
+--let SEARCH_RANGE=-50000
+--let SEARCH_PATTERN=using_gtid\(1\), gtid\(\'0-1-2,10-1-1\'\)
+--source include/search_pattern_in_file.inc
+
+--echo "===== Clean up ====="
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=no;
+--source include/start_slave.inc
+
+--connection master
+DROP TABLE t;
+SET GLOBAL LOG_WARNINGS=default;
+--source include/rpl_end.inc

sql/sql_repl.cc

@@ -2027,9 +2027,13 @@ static int init_binlog_sender(binlog_send_info *info,
     });
 
   if (global_system_variables.log_warnings > 1)
+  {
     sql_print_information(
-        "Start binlog_dump to slave_server(%lu), pos(%s, %lu)",
-        thd->variables.server_id, log_ident, (ulong)*pos);
+        "Start binlog_dump to slave_server(%lu), pos(%s, %lu), "
+        "using_gtid(%d), gtid('%s')", thd->variables.server_id,
+        log_ident, (ulong)*pos, info->using_gtid_state,
+        connect_gtid_state.c_ptr_quick());
+  }
 
 #ifndef DBUG_OFF
   if (opt_sporadic_binlog_dump_fail && (binlog_dump_count++ % 2))