Merge branch '2.8' into 3.0

* 2.8: (22 commits)
  Fix merge
  [HttpFoundation] Use UPSERT for sessions stored in PgSql >= 9.5
  [Console] fixed PHPDoc
  [travis] HHVM 3.12 LTS
  Fix feature detection for IE
  [Form] Fixed collapsed choice attributes
  [Console] added explanation of messages usage in a progress bar
  force enabling the external XML entity loaders
  [Yaml] properly count skipped comment lines
  [WebProfilerBundle] Fix invalid CSS style
  Added progressive jpeg to mime types guesser
  [Yaml] Fix wrong line number when comments are inserted in the middle of a block.
  Fixed singular of committee
  Do not inject web debug toolbar on attachments
  bumped Symfony version to 2.8.8
  updated VERSION for 2.8.7
  updated CHANGELOG for 2.8.7
  bumped Symfony version to 2.7.15
  updated VERSION for 2.7.14
  update CONTRIBUTORS for 2.7.14
  ...

Conflicts:
	CHANGELOG-2.7.md
	CHANGELOG-3.0.md
	src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
	src/Symfony/Component/HttpKernel/Kernel.php

Author: nicolas-grekas

HttpFoundation/DbalSessionHandler.php

@@ -180,7 +180,7 @@ public function write($sessionId, $data)
             $updateStmt->bindValue(':time', time(), \PDO::PARAM_INT);
             $updateStmt->execute();
 
-            // When MERGE is not supported, like in Postgres, we have to use this approach that can result in
+            // When MERGE is not supported, like in Postgres < 9.5, we have to use this approach that can result in
             // duplicate key errors when the same session is written simultaneously. We can just catch such an
             // error and re-execute the update. This is similar to a serializable transaction with retry logic
             // on serialization failures but without the overhead and without possible false positives due to
@@ -224,11 +224,11 @@ private function getMergeSql()
     {
         $platform = $this->con->getDatabasePlatform()->getName();
 
-        switch ($platform) {
-            case 'mysql':
+        switch (true) {
+            case 'mysql' === $platform:
                 return "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
                     "ON DUPLICATE KEY UPDATE $this->dataCol = VALUES($this->dataCol), $this->timeCol = VALUES($this->timeCol)";
-            case 'oracle':
+            case 'oracle' === $platform:
                 // DUAL is Oracle specific dummy table
                 return "MERGE INTO $this->table USING DUAL ON ($this->idCol = :id) ".
                     "WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
@@ -239,8 +239,11 @@ private function getMergeSql()
                 return "MERGE INTO $this->table WITH (HOLDLOCK) USING (SELECT 1 AS dummy) AS src ON ($this->idCol = :id) ".
                     "WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
                     "WHEN MATCHED THEN UPDATE SET $this->dataCol = :data, $this->timeCol = :time;";
-            case 'sqlite':
+            case 'sqlite' === $platform:
                 return "INSERT OR REPLACE INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time)";
+            case 'postgresql' === $platform && version_compare($this->con->getServerVersion(), '9.5', '>='):
+                return "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
+                    "ON CONFLICT ($this->idCol) DO UPDATE SET ($this->dataCol, $this->timeCol) = (:data, :time) WHERE $this->idCol = :id";
         }
     }
 }