remotes 2.4.0 breaks installation of private company GitLab repo

[jr-leary7]

With remotes 2.2.0, the following lines worked to install a company R package I maintain from GitLab to local:

remotes::install_git(url = "https://gitlab.company.com/user/package.git", 
                                  credentials = git2r::(username = "user", password = "password"))

However, as of remotes 2.4.0 that code results in the following error:

Error: Failed to install 'unknown package' from Git:
    Line starting '<DOCTYPE html> ...' is malformed!

From the reading I've done my limited understanding is that somehow the request is getting sent to a GitLab login page, and thus the file it's retrieving is the HTML of that page. I confirmed this morning that the install worked for a user with devtools v2.3.2 and remotes v2.2.0, but it does not work for me on devtools v2.4.1 and remotes v2.4.0.

[rnorberg]

This change introduced the issue. The problem is that remote_package_name.git2r_remote is trying to download the package DESCRIPTION file (to determine the package name), but the call to download in remote_package_name.git2r_remote doesn't get passed the credentials supplied by the user to install_git.

The result is that instead of downloading the package's DESCRIPTION file, you download GitLab's login page if the package repo isn't public.

[rnorberg]

#628 resolves this by amending remote_package_name.git2r_remote to return NA_character_ instead of throwing an error.

I proposed #633 to actually pass credentials supplied to install_git's credentials argument on to the (internal) download function.

Whether #633 is accepted or not, I think this issue can be marked as resolved.