allow host to be encoded in remote spec

[kevinushey]

So that someone could write e.g.

[email protected]::user/repo

to indicate that gitlab-server.com should be used as a custom host.

[jimhester]

This is probably a good idea, though we still have some issues with how to handle credentials when you have different hosts on the same type of remote.

[edpeyton]

@jimhester is there a plan to implement this feature in the near future? Or is there an alternative?

Currently I'm having to overwrite the remotes:::extra_deps in the remotes namespace to force the extra$host to our internal Gitlab server (to not default to gitlab.com - which seems to happen always) for our Gitlab repositories, which is undesirable.