Fixes T3619. These URIs are valid:

git@domain.com:/path        (Git SCP-style implicit SSH)
ssh://git@domain.com/path   (Explicit SSH)

This URI, arrived at by adding "ssh://" to the front of an SCP-style URI, is not:

ssh://git@domain.com:/path

Detect URIs in this form and reject them. See T3619.

{F75486}

Also set some valid URIs.