lp:697174: Do not put absolute path in status variable binlog_snapshot_file.

Omit the directory part to make the output the same as SHOW MASTER STATUS.

mysql-test/suite/binlog/r/binlog_consistent.result

@@ -6,7 +6,7 @@ File	Position	Binlog_Do_DB	Binlog_Ignore_DB
 master-bin.000001	241		
 SHOW STATUS LIKE 'binlog_snapshot_%';
 Variable_name	Value
-binlog_snapshot_file	./master-bin.000001
+binlog_snapshot_file	master-bin.000001
 binlog_snapshot_position	241
 BEGIN;
 INSERT INTO t1 VALUES (0, "");
@@ -37,7 +37,7 @@ a	b
 0	
 SHOW STATUS LIKE 'binlog_snapshot_%';
 Variable_name	Value
-binlog_snapshot_file	./master-bin.000001
+binlog_snapshot_file	master-bin.000001
 binlog_snapshot_position	540
 SHOW MASTER STATUS;
 File	Position	Binlog_Do_DB	Binlog_Ignore_DB
@@ -59,7 +59,7 @@ a	b
 0	
 SHOW STATUS LIKE 'binlog_snapshot_%';
 Variable_name	Value
-binlog_snapshot_file	./master-bin.000001
+binlog_snapshot_file	master-bin.000001
 binlog_snapshot_position	540
 SHOW MASTER STATUS;
 File	Position	Binlog_Do_DB	Binlog_Ignore_DB
@@ -67,7 +67,7 @@ master-bin.000002	106
 COMMIT;
 SHOW STATUS LIKE 'binlog_snapshot_%';
 Variable_name	Value
-binlog_snapshot_file	./master-bin.000002
+binlog_snapshot_file	master-bin.000002
 binlog_snapshot_position	106
 SHOW MASTER STATUS;
 File	Position	Binlog_Do_DB	Binlog_Ignore_DB

sql/log.cc

@@ -6650,6 +6650,18 @@ static struct st_mysql_sys_var *binlog_sys_vars[]=
 #endif
 
 
+/*
+  Copy out the non-directory part of binlog position filename for the
+  `binlog_snapshot_file' status variable, same way as it is done for
+  SHOW MASTER STATUS.
+*/
+static void
+set_binlog_snapshot_file(const char *src)
+{
+  int dir_len = dirname_length(src);
+  strmake(binlog_snapshot_file, src + dir_len, sizeof(binlog_snapshot_file)-1);
+}
+
 /*
   Copy out current values of status variables, for SHOW STATUS or
   information_schema.global_status.
@@ -6666,21 +6678,21 @@ TC_LOG_BINLOG::set_status_variables(THD *thd)
   else
     trx_data= NULL;
 
+  bool have_snapshot=
+    (trx_data && 0 != strcmp(trx_data->last_commit_pos_file, ""));
   pthread_mutex_lock(&LOCK_commit_ordered);
   binlog_status_var_num_commits= this->num_commits;
   binlog_status_var_num_group_commits= this->num_group_commits;
-  if (!trx_data || 0 == strcmp(trx_data->last_commit_pos_file, ""))
+  if (!have_snapshot)
   {
-    strmake(binlog_snapshot_file, last_commit_pos_file,
-            sizeof(binlog_snapshot_file)-1);
+    set_binlog_snapshot_file(last_commit_pos_file);
     binlog_snapshot_position= last_commit_pos_offset;
   }
   pthread_mutex_unlock(&LOCK_commit_ordered);
 
-  if (trx_data && 0 != strcmp(trx_data->last_commit_pos_file, ""))
+  if (have_snapshot)
   {
-    strmake(binlog_snapshot_file, trx_data->last_commit_pos_file,
-            sizeof(binlog_snapshot_file)-1);
+    set_binlog_snapshot_file(trx_data->last_commit_pos_file);
     binlog_snapshot_position= trx_data->last_commit_pos_offset;
   }
 }