Adds support for gitlab install in subfolder

Since gitlab can be hosted on any url also subdirectories should be
supported. (e.g https://mycompany.com/gitlab).
This supports only http and https protocols since the gitlab api url
is derived from the package repository url. And the ssh protocol doesn't
support folders this way.

src/Composer/Repository/Vcs/GitLabDriver.php

@@ -70,7 +70,7 @@ class GitLabDriver extends VcsDriver
      */
     public function initialize()
     {
-        if (!preg_match('#^((https?)://([^/]+)/|git@([^:]+):)([^/]+)/(.+?)(?:\.git|/)?$#', $this->url, $match)) {
+        if (!preg_match('#^((https?)://([0-9a-zA-Z\./]+)/|git@([^:]+):)([^/]+)/(.+?)(?:\.git|/)?$#', $this->url, $match)) {
             throw new \InvalidArgumentException('The URL provided is invalid. It must be the HTTP URL of a GitLab project.');
         }
 

tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php

@@ -217,4 +217,14 @@ JSON;
             array('http://example.com/foo/bar', false),
         );
     }
+
+    public function testGitlabSubDirectory()
+    {
+        $url = 'https://mycompany.com/gitlab/mygroup/myproject';
+        $apiUrl = 'https://mycompany.com/gitlab/api/v3/projects/mygroup%2Fmyproject';
+
+        $driver  = new GitLabDriver(array('url' => $url), $this->io->reveal(), $this->config, $this->process->reveal(), $this->remoteFilesystem->reveal());
+        $driver->initialize();
+        $this->assertEquals($apiUrl, $driver->getApiUrl(), 'API URL is derived from the repository URL');
+    }
 }