Redirect loop if repo URL has `.git/` on the end

Zendesk issue: https://gitlab.zendesk.com/agent/tickets/14498

The following 3 URLs work to access a project:

• https://gitlab.com/gitlab-org/gitlab-ce
• https://gitlab.com/gitlab-org/gitlab-ce/
• https://gitlab.com/gitlab-org/gitlab-ce.git

However, the following results in an endless redirect

• https://gitlab.com/gitlab-org/gitlab-ce.git/

cc/ @rdavila Can you take a look, please?