minikube start --image-repository=xxx does not work with ports in URL

[dmpe]

Hi there,
I have identified an issue whereby I consider this to be a regression, because it was certainly working in some of the past minikube releases (a number of releases back, cannot find this now easily).

With https://github.com/kubernetes/minikube/blob/v1.19.0/cmd/minikube/cmd/start_test.go minikube 1.19 there is now a TestValidateImageRepository. This checks for different formatting of the registry URL.

Our nexus3 docker registry has this format: nexus.devops.firm.com:6666. We use this type of URL everywhere else successfully and no known issues have been observed with this format. However, we started to transition to using nexus registry "everywhere", i.e. also for minikube and when installing minikube from scratch with following:

Steps to reproduce the issue:

1. minikube start --image-repository=nexus.devops.firm.com:6666 --driver=none --delete-on-failure=true

We get this error:

 minikube v1.20.0 on Centos 7.9.2009
* Using the none driver based on user configuration
  - The --image-repository flag your provided contains Scheme: nexus.devops.firm.com, it will be as a domian, removed automatically
* Using image repository

I.e. 6666 is stripped, hence the internal URL is ignored and hence it falls back to the assumption that VM in question has access to the internet (which in our case does not and hence we found out about this).

Full output of failed command:

Cannot post because a lot of private details (username, etc.). Sorry. But I am willing to test previews/rc/beta versions and maybe even contribute :)

[dmpe]

/assign

[RA489]

/kind support