Merge branch 'docs/refactor-ci-variables' into 'master'

Refactor CI variables docs

See merge request !7751

doc/ci/README.md

@@ -11,7 +11,8 @@
 - [Configure a Runner, the application that runs your builds](runners/README.md)
 - [Use Docker images with GitLab Runner](docker/using_docker_images.md)
 - [Use CI to build Docker images](docker/using_docker_build.md)
-- [Use variables in your `.gitlab-ci.yml`](variables/README.md)
+- [CI Variables](variables/README.md) - Learn how to use variables defined in
+  your `.gitlab-ci.yml` or secured ones defined in your project's settings
 - [Use SSH keys in your build environment](ssh_keys/README.md)
 - [Trigger builds through the API](triggers/README.md)
 - [Build artifacts](../user/project/builds/artifacts.md)
@@ -25,4 +26,6 @@
 
 ## Breaking changes
 
-- [New CI build permissions model](../user/project/new_ci_build_permissions_model.md) Read about what changed in GitLab 8.12 and how that affects your builds. There's a new way to access your Git submodules and LFS objects in builds.
+- [New CI build permissions model](../user/project/new_ci_build_permissions_model.md)
+  Read about what changed in GitLab 8.12 and how that affects your builds.
+  There's a new way to access your Git submodules and LFS objects in builds.

doc/ci/yaml/README.md

@@ -406,14 +406,20 @@ except master.
 ### job variables
 
 It is possible to define build variables using a `variables` keyword on a job
-level. It works basically the same way as its global-level equivalent but
-allows you to define job-specific build variables.
+level. It works basically the same way as its [global-level equivalent](#variables)
+but allows you to define job-specific build variables.
 
 When the `variables` keyword is used on a job level, it overrides global YAML
-build variables and predefined variables.
+build variables and predefined variables. To turn off global defined variables
+in your job, define an empty array:
 
-Build variables priority is defined in
-[variables documentation](../variables/README.md).
+```yaml
+job_name:
+  variables: []
+```
+
+Build variables priority is defined in the
+[variables documentation][variables].
 
 ### tags