Missing gist revision api endpoint

Author: acrobat

doc/gists.md

@@ -37,6 +37,12 @@ $gists = $github->api('gists')->all();
 $gist = $github->api('gists')->show(1);
 ```
 
+#### Get a specific revision of a gist
+
+```php
+$gist = $github->api('gists')->show(1, 'd189dbd4c5d96442db74ebcb62bb38e661a0c8ce');
+```
+
 #### Get commits for a single gist
 
 ```php

lib/Github/Api/Gists.php

@@ -51,6 +51,11 @@ public function show($number)
         return $this->get('/gists/'.rawurlencode($number));
     }
 
+    public function revision($number, $sha)
+    {
+        return $this->get('/gists/'.rawurlencode($number).'/'.rawurlencode($sha));
+    }
+
     public function create(array $params)
     {
         if (!isset($params['files']) || (!is_array($params['files']) || 0 === count($params['files']))) {

test/Github/Tests/Api/GistsTest.php

@@ -52,6 +52,22 @@ public function shouldShowGist()
         $this->assertEquals($expectedArray, $api->show(123));
     }
 
+    /**
+     * @test
+     */
+    public function shouldShowGistWithSpecificReference()
+    {
+        $expectedArray = ['id' => '123', 'sha' => 'd189dbd4c5d96442db74ebcb62bb38e661a0c8ce'];
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('/gists/123/d189dbd4c5d96442db74ebcb62bb38e661a0c8ce')
+            ->will($this->returnValue($expectedArray));
+
+        $this->assertEquals($expectedArray, $api->revision(123, 'd189dbd4c5d96442db74ebcb62bb38e661a0c8ce'));
+    }
+
     /**
      * @test
      */