Do not ask for authentication when cloning a public repository

This pull request fixes issue #199 (closed) (anonymous HTTP[S] cloning does not work). I tracked the issue down to the following problem: When git clones via HTTP, ultimately, in the file , the function authorized_request? is called. The problem is that git_cmd is nil in that situation for the initial request, therefore the request is rejected and the server asks for authentication. The attached commit changes authorized_request? to treat nil as a DOWNLOAD command, and thus allow it without password for un-authenticated users.

This is a re-submitted version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/78 for master. However I do (of course) not run my production environment on master, and I don't have a second installation, so I couldn't test whether this patch is actually still needed.