Add support for S3 custom endpoint

[takmatsu]

For S3-compatible object storage (like minio),
this patch enable to use custom endpoint-url.

Fix #531

Usage:

apiVersion: v1
kind: Pod
metadata:
  name: kaniko
spec:
  containers:
  - name: kaniko
    image: REGISTRY/PROJECT/REPOSITORY:TAG
    args: ["--dockerfile=Dockerfile",
            "--context=s3://BUCKET/FILE",
            "--destination=REGISTRY/PROJECT/REPOSITORY:TAG"]
    env:
      - name: AWS_ACCESS_KEY_ID
        value: MINIO_ACCESS_KEY
      - name: AWS_SECRET_ACCESS_KEY
        value: MINIO_SECRET_KEY
      - name: AWS_REGION
        value: us-east-1
      - name: S3_ENDPOINT
        value: http://minio-server:9000
      - name: S3_FORCE_PATH_STYLE
        value: "true"
    volumeMounts:
      - name: docker-config
        mountPath: /kaniko/.docker/
  restartPolicy: Never
  volumes:
    - name: docker-config
      configMap:
        name: docker-config

[pennycoders]

Hi,

Is this PR going to be merged any time soon ?

Thanks,

Alex.

[takmatsu]

cc/ @priyawadhwa

[hegand]

+1

[priyawadhwa]

Thanks for adding this -- I'm not super familiar with S3 and I don't know that it's possible to add an integration test for this. Have you tested locally?

[takmatsu]

Sure, I have tested locally for both S3 and Custom endpoint(minio).
I think we can add integration tests as a code, but it needs some environments...

[priyawadhwa]

Yah so we don't have the setup to test with S3 -- but if it's working locally I think we can go ahead and add this change.