Do not overwrite existing favicons

app/models/favicon.php

@@ -31,6 +31,15 @@ function store_favicon($mime_type, $blob)
     }
 
     $hash = sha1($blob);
+    $favicon_id = Database::getInstance('db')
+        ->table(TABLE)
+        ->eq('hash', $hash)
+        ->findOneColumn('id');
+
+    if ($favicon_id) {
+        return $favicon_id;
+    }
+
     if (file_put_contents(get_favicon_filename($hash, $mime_type), $blob) === false) {
         return false;
     }

tests/unit/FaviconModelTest.php

@@ -90,7 +90,7 @@ class FaviconModelTest extends BaseTest
         $this->assertCreateFeed($this->buildFeed());
 
         self::$functions
-            ->expects($this->any())
+            ->expects($this->once())
             ->method('file_put_contents')
             ->with(
                 $this->stringEndsWith('data/favicons/57978a20204f7af6967571041c79d907a8a8072c.png'),