alternateAbsoluteLink() respects action parameter

fixes #275

code/extensions/SiteTreeSubsites.php

@@ -347,11 +347,15 @@ class SiteTreeSubsites extends DataExtension
         }
     }
 
-    public function alternateAbsoluteLink()
+    /**
+     * @param null $action
+     * @return string
+     */
+    public function alternateAbsoluteLink($action = null)
     {
         // Generate the existing absolute URL and replace the domain with the subsite domain.
         // This helps deal with Link() returning an absolute URL.
-        $url = Director::absoluteURL($this->owner->Link());
+        $url = Director::absoluteURL($this->owner->Link($action));
         if ($this->owner->SubsiteID) {
             $url = preg_replace('/\/\/[^\/]+\//', '//' . $this->owner->Subsite()->domain() . '/', $url);
         }

tests/php/SiteTreeSubsitesTest.php

@@ -3,7 +3,6 @@
 namespace SilverStripe\Subsites\Tests;
 
 use Page;
-use SilverStripe\Assets\FileNameFilter;
 use SilverStripe\CMS\Controllers\CMSMain;
 use SilverStripe\CMS\Controllers\ModelAsController;
 use SilverStripe\CMS\Model\SiteTree;
@@ -399,4 +398,33 @@ class SiteTreeSubsitesTest extends BaseSubsiteTest
             'Themes should be modified when Subsite has theme defined'
         );
     }
+
+    protected function provideAlternateAbsoluteLink()
+    {
+        return [
+            ['home', null, 'http://localhost/'],
+            ['home', 'myaction', 'http://localhost/home/myaction'],
+            ['contact', null, 'http://localhost/contact-us/'],
+            ['contact', 'myaction', 'http://localhost/contact-us/myaction'],
+            ['subsite1_home', null, 'http://subsite1.localhost/'],
+            ['subsite1_home', 'myaction', 'http://subsite1.localhost/home/myaction'],
+            ['subsite1_contactus', null, 'http://subsite1.localhost/contact-us/'],
+            ['subsite1_contactus', 'myaction', 'http://subsite1.localhost/contact-us/myaction']
+        ];
+    }
+
+    /**
+     * @dataProvider provideAlternateAbsoluteLink
+     * @param $fixture
+     * @param $expected
+     */
+    public function testAlternateAbsoluteLink($pageFixtureName, $action, $expectedAbsoluteLink)
+    {
+        /** @var Page $page */
+        $page = $this->objFromFixture('Page', $pageFixtureName);
+
+        $result = $page->AbsoluteLink($action);
+
+        $this->assertEquals($expectedAbsoluteLink, $result);
+    }
 }