3.2. Dockerfile source

When you supply a dockerfile value, the content of this field is written to disk as a file named dockerfile. This is done after other input sources are processed, so if the input source repository contains a Dockerfile in the root directory, it is overwritten with this content.

The source definition is part of the spec section in the BuildConfig:

source:
  dockerfile: "FROM centos:7\nRUN yum install -y httpd"