fix(init): do not require re-init after explicit init on clean directory

[jaymecd]

Description

Running terragrunt plan --terragrunt-no-auto-init on clean directory just after terragrunt init, raises confusing warning that init is needed.

On 1st clean init previousVersion is always empty, therefore no need to mark it as init required again and this warning is misleading.

How-to reproduce:

$ rm -rf .terragrunt-cache/

$ terragrunt init
INFO[0000] Downloading Terraform configurations from ...
Initializing the backend...
... 
Terraform has been successfully initialized!
...

$ terragrunt plan --terragrunt-no-auto-init
WARN[0000] Detected that init is needed, but Auto-Init is disabled. Continuing with further actions, but subsequent terraform commands may fail.  prefix=[/path/to/stack]
...

Workaround:

terraform {
  after_hook "cleanup_init_required_file" {
    commands = ["init"]
    execute  = ["sh", "-ec", "find . -type f -name .terragrunt-init-required -delete"]
  }
}

TODOs

Read the Gruntwork contribution guidelines.

• Run the relevant tests successfully, including pre-commit checks.
• Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes (draft)

Added / Removed / Updated [X].

Removed warning when using no-auto-init flag after explicit init on clean directory.

[denis256]

Noticed failing test:

    download_source_test.go:378: 
        	Error Trace:	/home/circleci/project/cli/commands/terraform/download_source_test.go:378
        	            				/home/circleci/project/cli/commands/terraform/download_source_test.go:238
        	Error:      	Should be true
        	Test:       	TestDownloadTerraformSourceIfNecessaryRemoteUrlOverrideSource
--- FAIL: TestDownloadTerraformSourceIfNecessaryRemoteUrlOverrideSource (2.72s)