Comment 6 for bug 1250375

As discussed on IRC, the problem with reading the GTID info from xtrabackup_binlog_info is that it would require XtraBackup-specific changes to wsrep/mysqld part of PXC. And Galera developers prefer all SST methods to be identical (in this case, identically ugly).

So we will implement this request. But, as this is a PXC 5.6 specific hack, this is how it should work:

- in write_galera_info(), get Executed_Gtid_Set in the same way it is done in write_binlog_info()
- *if* Executed_Gtid_Set is defined (this automatically restricts functionality changes to PXC 5.6 with GTID enabled), do the following:
- execute FLUSH BINARY LOGS to create an empty log file
- get the current binary log file name from SHOW MASTER STATUS
- get the binary logs base directory by splitting the directory name from 'log_bin_basename'. Use File::Basename::dirname($mysql{vars}->{log_bin_basename}->{Value}.
- store $log_bin_dir/$log_bin_file into the backup

I don't think we need a new option to control that functionality.