Follow-up from "Check if git is available before performing remediation."

The following discussion from gitlab-org/security-products/analyzers/container-scanning!2839 (merged) should be addressed:

• Add integration test for gitlab-org/security-products/analyzers/container-scanning!2839 (merged)

• @adamcohen started a discussion: (+1 comment)

  suggestion: it seems to me that we really need an integration test against an actual Docker image to ensure that this behaviour functions as expected. The current test stubs everything out, which only confirms that we're calling git with the expected arguments, but does not confirm that the given git commands will resolve the bug.