Private/Hidden tags

Tags starting with a dot '.' are now private.
They can only be seen and searched when logged in.

Fixes #315

tests/LinkDBTest.php

@@ -298,6 +298,7 @@ class LinkDBTest extends PHPUnit_Framework_TestCase
                 'css' => 1,
                 'Mercurial' => 1,
                 '-exclude' => 1,
+                '.hidden' => 1,
             ),
             self::$privateLinkDB->allTags()
         );
@@ -349,4 +350,22 @@ class LinkDBTest extends PHPUnit_Framework_TestCase
             count(self::$privateLinkDB->filter(LinkFilter::$FILTER_TAG, $tags, true, false))
         );
     }
+
+    /**
+     * Test hidden tags feature:
+     *  tags starting with a dot '.' are only visible when logged in.
+     */
+    public function testHiddenTags()
+    {
+        $tags = '.hidden';
+        $this->assertEquals(
+            1,
+            count(self::$privateLinkDB->filter(LinkFilter::$FILTER_TAG, $tags, true, false))
+        );
+
+        $this->assertEquals(
+            0,
+            count(self::$publicLinkDB->filter(LinkFilter::$FILTER_TAG, $tags, true, false))
+        );
+    }
 }

tests/Updater/UpdaterTest.php

@@ -239,7 +239,6 @@ class UpdaterTest extends PHPUnit_Framework_TestCase
         $this->assertEmpty($linkDB->filter(LinkFilter::$FILTER_TAG, 'exclude'));
         $updater = new Updater(array(), self::$configFields, $linkDB, true);
         $updater->updateMethodRenameDashTags();
-        var_dump($linkDB->filter(LinkFilter::$FILTER_TAG, 'exclude'));
         $this->assertNotEmpty($linkDB->filter(LinkFilter::$FILTER_TAG, 'exclude'));
     }
 }

tests/utils/ReferenceLinkDB.php

@@ -28,7 +28,7 @@ class ReferenceLinkDB
             'A free software media publishing platform',
             0,
             '20130614_184135',
-            'gnu media web'
+            'gnu media web .hidden'
         );
 
         $this->addLink(