false is not a valid variable

Summary

According to the documentation https://docs.gitlab.com/ee/ci/yaml/#git-checkout you should set

variables:
  GIT_STRATEGY: clone
  GIT_CHECKOUT: false

But Gitlab then detects an invalid YAML syntax because. The YAML-Lint says: "variables config should be a hash of key value pairs"

variables:
  GIT_STRATEGY: clone
  GIT_CHECKOUT: "false"

is working.

Either fix documentation or change YAML validation.