Do not require username/password with no_push: true

[colinhoglund]

This updates all binaries and the plugin to skip authentication mechanisms when no_push: true. This allows pipelines to perform builds without requiring secrets, which can be useful during pull_request events, for example.

This was tested with the following public image

---
kind: pipeline
name: default

steps:
  - name: publish
    image: colinhoglund/kaniko-ecr
    settings:
      no_push: true

There is also a commit with a bit of linting.

[colinhoglund]

Hey @shubham149, looking for feedback on this PR when you get a chance.

[shubham149]

There is one concern. If the dockerfile itself uses a private base image, then docker build will fail.

[colinhoglund]

There is one concern. If the dockerfile itself uses a private base image, then docker build will fail.

Thanks @shubham149, good point. I updated the conditionals slightly to always setup auth when credentials are defined.

This pipeline will skip auth mechanisms altogether:

---
kind: pipeline
name: no-push

steps:
  - name: publish
    image: colinhoglund/kaniko
    settings:
      no_push: true

  - name: publish-gcr
    image: colinhoglund/kaniko-gcr
    settings:
      no_push: true

  - name: publish-ecr
    image: colinhoglund/kaniko-ecr
    settings:
      no_push: true

This pipeline will setup auth, but still pass the --no-push flag:

---
kind: pipeline
name: no-push-with-auth

steps:
  - name: publish
    image: colinhoglund/kaniko
    settings:
      no_push: true
      username: something
      password: something

  - name: publish-gcr
    image: colinhoglund/kaniko-gcr
    settings:
      no_push: true
      json_key: something

  - name: publish-ecr
    image: colinhoglund/kaniko-ecr
    settings:
      no_push: true
      registry: public.ecr.aws/my-registry
      access_key: something
      secret_key: something