Warn on archiving git directory

What does this MR do?

Add a warning printed when .git directory is used in artifacts/cache operations.

Why was this MR needed?

Please see gitlab-ce#32320 for a reference.

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Related to gitlab-ce#32320