Allow getting merge requests which would close an issue

lib/Gitlab/Api/Issues.php

@@ -213,4 +213,14 @@ public function awardEmoji($project_id, $issue_iid)
     {
         return $this->get($this->getProjectPath($project_id, 'issues/'.$this->encodePath($issue_iid).'/award_emoji'));
     }
+
+    /**
+    * @param int $project_id
+    * @param int $issue_iid
+    * @return mixed
+    */
+    public function closedByMergeRequests($project_id, $issue_iid)
+    {
+        return $this->get($this->getProjectPath($project_id, 'issues/'.$this->encodePath($issue_iid)).'/closed_by');
+    }
 }

test/Gitlab/Tests/Api/IssuesTest.php

@@ -290,6 +290,26 @@ public function shouldGetIssueAwardEmoji()
         $this->assertEquals($expectedArray, $api->awardEmoji(1, 2));
     }
 
+    /**
+     * @test
+     */
+    public function shouldGetIssueClosedByMergeRequests()
+    {
+        $expectedArray = array(
+            array('id' => 1, 'iid' => '1111', 'title' => 'Just saving the world'),
+            array('id' => 2, 'iid' => '1112', 'title' => 'Adding new feature to get merge requests that close an issue'),
+        );
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('projects/1/issues/2/closed_by')
+            ->will($this->returnValue($expectedArray))
+        ;
+
+        $this->assertEquals($expectedArray, $api->closedByMergeRequests(1, 2));
+    }
+
     protected function getApiClass()
     {
         return 'Gitlab\Api\Issues';