fix: Allow specifying files in a github actions config file

[m-wynn]

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Description

If you want to run checkov on multiple files or directories from a github action, you have to hack in the list of input directory or files like:

 - name: Run Checkov action
   id: checkov
   uses: bridgecrewio/checkov-action@master
   with:
     file: foo.tf -f bar.tf -f baz.tf
     # or
     directory: prod -d dev -d staging

This technically works but has a few downsides. It'll fail if an file has a space in it, and if you're using DOWNLOAD_EXTERNAL_MODULES it will delete things you did not expect.

A much more robust alternative is using the .checkov.yaml with:

file:
  - foo.tf
  - bar.tf
  - baz.tf
# or
directory:
  - prod
  - dev
  - staging

In the github action, directory defaults to . but you can pass in directory: ''. As the code is now, this will still call checkov -d --output=... which causes an error.

This is probably not a breaking change because: if both $INPUT_FILE and $INPUT_DIRECTORYare empty (directory has explicitly been set to empty string in bridgecrewio/checkov-action, or a custom github action has been used):

• Before this change: Error with checkov: error: argument -d/--directory: expected one argument and exit 2.
• After this change: Either use the files defined in INPUT_CONFIG_FILE or print the logo / version and exit 0.

Fixes bridgecrewio/checkov-action#22

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

[m-wynn]

You can kinda test this via:

GITHUB_ACTIONS=true GITHUB_ENV=/dev/null GITHUB_OUTPUT=/dev/null INPUT_DIRECTORY='' INPUT_CONFIG_FILE=config.yaml ./github_action_resources/entrypoint.sh