Inject backend defaults in modules

[mudler]

#101

[mudler]

@viccuad probably dbb9c9f should apply to other cases too, otherwise whatever we generated during the steps gets ignored and only module's default gets applied

[viccuad]

Thanks for looking into this, and sorry for needing some time before answering!

In theory, backend options do override some modules.
Example, for the global default options and modules/common:

modules/common/defaults.sh contains:

# Default versions in case the are undefined in the backend:
HELM_VERSION="${HELM_VERSION:-v2.16.1}"
KUBECTL_VERSION="${KUBECTL_VERSION:-v1.17.0}"
BAZEL_VERSION="${BAZEL_VERSION:-1.1.0}"

Yet, if any of those vars are defined on the backend, they will take precedence. This is achieved by the first line of the code on modules/common/deps.sh:

. "$ROOT_DIR/backend/$BACKEND/defaults.sh"
. ./defaults.sh
. ../../include/common.sh
. .envrc

This is cumbersome, but at least people reading modules/common/deps.sh and that snippet get an idea of the loading preference. Yet it doesn't use a compiled <buildir>/defaults.sh.

I would like to have a simpler approach, and maybe yours from this PR is it. I would love to save only changed options passed by env var on a different, <buildir>/custom_options.sh, that makes reviewing clusters way easier.

Can you think of an easier way to achieve this?