hook files?The files in this directory are levergaed by Docker Cloud (cloud.docker.com) in support of autmatically building VOLTHA containers on the Docker Cloud infrastructure.
At issue is that for the automated builds Docker Cloud does not set docker build arguments. You can set environment variables via the automated build UI, but in order to make these values visible during the building of containers they must be converted to docker build arguments set via the --build-arg command line option.
To achieve this a custom build hook must be created. This hook will replace the stardard build command on Docker Cloud and augment the command by setting build arguments. This is the build file in this directory.
Full documentation on hooks that can be used with Docker Cloud automated builds can be found at https://docs.docker.com/docker-cloud/builds/advanced/.