"Could not load digger config" Error on PRs

[noralutz]

Recently upgraded both the Digger backend and Workflow runner from version 0.4.6 to vLatest (0.6.20 at that time) and immediately started receiving this comment on all PRs post-merge:

❌ Could not load digger config, error:
Checking the backend, this error appears to not be new, and was happening pre-update, but was potentially swallowed and not commented. This occurs on all PRs closed in the repo, even ones that do not affect any terraform code, so it is quite disturbing to developers who do not know why this message appears.

Notably, on the backend I see these errors corresponding to branches that the PR recently closed and deleted:

PlainClone error: couldn't find remote ref "refs/heads/branch_name"
github.go:682: Error cloning and loading config: couldn't find remote ref "refs/heads/branch_name"

I assume this is some issue with the Digger backend attempting to check out the branch upon PR merge, but we automatically delete branches on PR merge, so they will always be deleted. Could this be related to #1155?

[noralutz]

@motatoes tagging as requested