`rsync` host support and SSH key authentication
An rsync host is of the form git@git.gitlab.arm.com:bazel/git.git. This is the common form for social git platforms such as GitLab, Github and Bitbucket.
i.e. if the first colon is found and // does not follow it, then we assume it is an rsync host. We plonk ssh:// on the front and change the : over to a /.
Edited by Matthew Clarkson