Stop and return error when target has not been created

[puengel]

Scenario

The expected target is never created. You can achieve this with the following sample build command.

build:
  container: 
    input: |
      ./Dockerfile
    cmd: |
      docker build ---tag image-name:latest . < Dockerfile
    target:
      image: some-other-name:latest

Problem

Even after completion of the cmd execution bob will keep running and wait for the target to be created. Can't stop execution with ctrl+c.

Possible Solution

After successful cmd execution has completed bob should expect the target to exist. If the target is still missing the task should be marked as failed and a message should be displayed telling "Target for task has not been created. This is probably not an issue with bob. Check the task logs for more details."

Optional: Add a delay after cmd execution to wait for the target. Could lead to additional build times..