WITH DOCKER breaks with EARTHLY_DOCKERD_CACHE_DATA: parameter not set

[alexcb]

What went wrong?

using older versions of earthly cli, like v0.8.9 along with a satellite running v0.8.10, would fail to run any WITH DOCKER commands:

/var/earthly/dockerd-wrapper.sh: 80: EARTHLY_DOCKERD_CACHE_DATA: parameter not set

What should have happened?

The dockerd wrapper script should have supplied a default value when no value was passed from the earthly cli, e.g.

EARTHLY_DOCKERD_CACHE_DATA=${EARTHLY_DOCKERD_CACHE_DATA:-"false"}

should have been included (and was since added under #4121)

What earthly version?

v0.8.9 (or earlier) cli and a satellite running v0.8.10

Buildkit Logs

No response

Other Helpful Information

This feature was initially implemented under #4064, which included a test for the feature; however no backwards compatibility test existed which is how this bug went undetected.

Action Item
Write a test that will use the existing earthly v0.8.0 binary against a version of buildkitd that's compiled from main to provide test coverage for backwards incompatibility issues.