Change single-transaction so no more SUPER privilege is needed. Closes …

…ifsnop#54.

Previously, mysqldump-php modified global variables to guarantee transaction.
Now mysqldump-php only sets session variables, so no SUPER privilege is
needed.
start_transaction() has been splitted in two, (setup & start) so it should
be easier to implement a check to query the current transaction level. If
it is not REPEATABLE-READ, set it. Currenlty we are enforcing it.

README.md

@@ -216,8 +216,6 @@ To dump a database, you need the following privileges :
   - If any table has one or more triggers.
 - **LOCK TABLES**
   - If "lock tables" option was enabled.
-- **SUPER**
-  - If "single-transaction" option was enabled.
 
 Use **SHOW GRANTS FOR user@host;** to know what privileges user has. See the following link for more information:
 

src/Ifsnop/Mysqldump/Mysqldump.php

@@ -609,6 +609,7 @@ function prepareListValues($tableName)
         );
 
         if ($this->dumpSettings['single-transaction']) {
+            $this->dbHandler->exec($this->typeAdapter->setup_transaction());
             $this->dbHandler->exec($this->typeAdapter->start_transaction());
         }
 
@@ -969,6 +970,11 @@ public function show_columns()
         return "pragma table_info(${args[0]})";
     }
 
+    public function setup_transaction()
+    {
+        return "";
+    }
+
     public function start_transaction()
     {
         return "BEGIN EXCLUSIVE";
@@ -1278,10 +1284,14 @@ public function show_columns()
         return "SHOW COLUMNS FROM `${args[0]}`;";
     }
 
+    public function setup_transaction()
+    {
+        return "SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+    }
+
     public function start_transaction()
     {
-        return "SET GLOBAL TRANSACTION ISOLATION LEVEL REPEATABLE READ; " .
-            "START TRANSACTION";
+        return "START TRANSACTION";
     }
 
     public function commit_transaction()

tests/test.php

@@ -15,7 +15,7 @@
     'compress' => IMysqldump\Mysqldump::NONE,
     'no-data' => false,
     'add-drop-table' => true,
-    'single-transaction' => false,
+    'single-transaction' => true,
     'lock-tables' => true,
     'add-locks' => true,
     'extended-insert' => false,