az acr build-task show doesn't return nested step information

[SteveLasker]

az acr build-task show -n demo42quotesapi -o json
should return:

• image and tag values
• build-arg
• dockerfile

[djyou]

This has been supported as of this PR Azure/azure-cli#6241

Sample output:

{
    "alias": "MyBuildTask",
    "creationDate": "2018-04-20T07:42:31.108587+00:00",
    "id": "/subscriptions/3647315e-0c5b-4ce4-8739-b071e144b2c9/resourceGroups/MyRG/providers/Microsoft.ContainerRegistry/registries/MyRegistry/buildTasks/MyBuildTask",
    "location": "westus",
    "name": "MyBuildTask",
    "platform": {
        "cpu": 1,
        "osType": "Linux"
    },
    "properties": {
        "baseImageDependencies": null,
        "baseImageTrigger": "Runtime",
        "branch": "something",
        "buildArguments": [
            {
                "isSecret": false,
                "name": "k1",
                "value": "v1"
            }
        ],
        "contextPath": null,
        "dockerFilePath": "Dockerfile",
        "imageNames": [
            "hello:world:latest"
        ],
        "isPushEnabled": false,
        "noCache": false,
        "provisioningState": "Succeeded",
        "type": "Docker"
    },
    "provisioningState": "Succeeded",
    "resourceGroup": "MyRG",
    "sourceRepository": {
        "isCommitTriggerEnabled": true,
        "repositoryUrl": "https://github.com/some/repo",
        "sourceControlAuthProperties": null,
        "sourceControlType": "Github"
    },
    "status": "Disabled",
    "tags": null,
    "timeout": null,
    "type": "Microsoft.ContainerRegistry/registries/buildTasks"
}