anchor.diff:  `_<system-registry>_` is defined as a service with the name `docker-registry`
   running in OpenShift.
   
  -. Define a build with a strategy that consumes the image stream:
  +. If an image stream is the base image for the build, set the from field in the
  +build strategy to point to the image stream:
   +
   ====
   
  
positive.code: the build that is created uses the `*immutableid*` resolved from the
  `*ImageStream*` referenced by the `*Strategy*`. This ensures that builds
  are performed using consistent image tags for ease of reproduction.
  
  [#using-docker-credentials-for-pushing-and-pulling-images]
  == Using Docker Credentials for Pushing and Pulling Images
  
negative.code: In this case, the `*sourceStrategy*` definition is consuming the `latest` tag of
  the image stream named `ruby-20-centos7` located within this namespace.
  
  . Define a build with one or more triggers that point to image streams:
  +
  ====
  
  ----
  {
    "type": "imageChange", <1>
    "imageChange": {}
  }
  {
    "type": "imagechange", <2>
    "imageChange": {
       "from": {
         "kind": "ImageStreamTag",
         "name": "custom-image:latest"
       }
    }
  }
  ----
  
  <1> An image change trigger that monitors the `*ImageStream*` and
  `*Tag*` as defined by the build strategy's `*from*` field. The `*imageChange*` part
  must be empty.
  <2> An image change trigger that monitors an arbitrary image stream. The `*imageChange*`
  part in this case must include a `*from*` field that references the `*ImageStreamTag*` to monitor.
  ====
  
  When using an image change trigger for the strategy image stream, the generated build
  is supplied with an immutable Docker tag that points to the latest image corresponding
  to that tag. This new image reference will be used by the strategy
  when it executes for the build. For other image change triggers that do not
  reference the strategy image stream, a new build will be started, but the build
  strategy will not be updated with a unique image reference.
  
  In the example above that has an image change trigger for the strategy, the resulting build will be:
  
  ====
  
  ----
  