GL_TOKEN

Document that GL_TOKEN must be defined as a CI Variable in the project using the pipeline or in an ancestor group. The token can either be a personal access token or a group access token. I think it only needs to have repository write privileges, but I haven't tested this. I've given mine all privileges. The token should be masked, available only to protected branches, and expanding.

Here are some references:

• https://docs.gitlab.com/ee/ci/variables/
• https://docs.gitlab.com/ee/user/profile/personal_access_tokens.html
• https://docs.gitlab.com/ee/user/group/settings/group_access_tokens.html