Add changelog and docs

changelogs/unreleased/44447-expose-deploy-token-to-ci-cd.yml

+---
+title: Expose Deploy Token data as environment varialbes on CI/CD jobs
+merge_request: 18414
+author:
+type: added

doc/ci/variables/README.md

@@ -87,6 +87,8 @@ future GitLab releases.**
 | **GITLAB_USER_LOGIN**           | 10.0   | all    | The login username of the user who started the job |
 | **GITLAB_USER_NAME**            | 10.0   | all    | The real name of the user who started the job |
 | **RESTORE_CACHE_ATTEMPTS**      | 8.15   | 1.9    | Number of attempts to restore the cache running a job |
+| **CI_DEPLOY_USER**              | 10.8   | all    | Name of the GitLab Deploy Token. Only present if the Project has a [GitLab Deploy Token][gitlab-deploy-token] related.|
+| **CI_DEPLOY_PASSWORD**          | 10.8   | all    | Token of the Gitlab Deploy Token. Only present if the Project has a [GitLab Deploy Token][gitlab-deploy-token] related.|
 
 ## 9.0 Renaming
 
@@ -562,3 +564,4 @@ These variables are also not supported in a contex of a
 [subgroups]: ../../user/group/subgroups/index.md
 [builds-policies]: ../yaml/README.md#only-and-except-complex
 [dynamic-environments]: ../environments.md#dynamic-environments
+[gitlab-deploy-token]: ../../user/project/deploy_tokens/index.md

doc/user/project/deploy_tokens/index.md

@@ -71,6 +71,15 @@ docker login registry.example.com -u <username> -p <deploy_token>
 Just replace `<username>` and `<deploy_token>` with the proper values. Then you can simply 
 pull images from your Container Registry.
 
+### GitLab Deploy Token
+
+> [Introduced][ce-18414] in GitLab 10.8.
+
+There's a special case when it comes to Deploy Tokens, if a user creates one
+named `gitlab-deploy-token`, their information will be automatically exposed
+as environment variables.
+
 [ce-17894]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17894
 [ce-11845]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11845
+[ce-18414]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18414
 [container registry]: ../container_registry.md