Merge branch 'add-default-docs' into 'master'

Add usage of `default:`

Closes #63351

See merge request gitlab-org/gitlab-ce!30677

doc/ci/docker/using_docker_images.md

@@ -193,13 +193,14 @@ You can simply define an image that will be used for all jobs and a list of
 services that you want to use during build time:
 ```yaml
-image: ruby:2.2
-services:
-  - postgres:9.3
-before_script:
-  - bundle install
+default:
+  image: ruby:2.2
+  services:
+    - postgres:9.3
+  before_script:
+    - bundle install
 test:
   script:
@@ -209,8 +210,9 @@ test:
 It is also possible to define different images and services per job:
 ```yaml
-before_script:
-  - bundle install
+default:
+  before_script:
+    - bundle install
 test:2.1:
   image: ruby:2.1
@@ -231,18 +233,19 @@ Or you can pass some [extended configuration options](#extended-docker-configura
 for `image` and `services`:
 ```yaml
-image:
-  name: ruby:2.2
-  entrypoint: ["/bin/bash"]
-services:
-- name: my-postgres:9.4
-  alias: db-postgres
-  entrypoint: ["/usr/local/bin/db-postgres"]
-  command: ["start"]
-before_script:
-- bundle install
+default:
+  image:
+    name: ruby:2.2
+    entrypoint: ["/bin/bash"]
+  services:
+  - name: my-postgres:9.4
+    alias: db-postgres
+    entrypoint: ["/usr/local/bin/db-postgres"]
+    command: ["start"]
+  before_script:
+  - bundle install
 test:
   script:

doc/ci/yaml/README.md

@@ -119,6 +119,35 @@ The following table lists available parameters for jobs:
 NOTE: **Note:**
 Parameters `types` and `type` are [deprecated](#deprecated-parameters).
+## Setting default parameters
+
+Some parameters can be set globally as the default for all jobs using the
+`default:` keyword. Default parameters can then be overridden by job-specific
+configuration.
+
+The following job parameters can be defined inside a `default:` block:
+
+- [`image`](#image)
+- [`services`](#services)
+- [`before_script`](#before_script-and-after_script)
+- [`after_script`](#before_script-and-after_script)
+- [`cache`](#cache)
+
+In the following example, the `ruby:2.5` image is set as the default for all
+jobs except the `rspec 2.6` job, which uses the `ruby:2.6` image:
+
+```yaml
+default:
+  image: ruby:2.5
+
+rspec:
+  script: bundle exec rspec
+
+rspec 2.6:
+  image: ruby:2.6
+  script: bundle exec rspec
+```
+
 ## Parameter details
 The following are detailed explanations for parameters used to configure CI/CD pipelines.
@@ -239,8 +268,9 @@ It's possible to overwrite the globally defined `before_script` and `after_scrip
 if you set it per-job:
 ```yaml
-before_script:
-  - global before script
+default:
+  before_script:
+    - global before script
 job:
   before_script:
@@ -2550,18 +2580,39 @@ You can set it globally or per-job in the [`variables`](#variables) section.
 The following parameters are deprecated.
-### `types`
+### Globally-defined `types`
 CAUTION: **Deprecated:**
 `types` is deprecated, and could be removed in a future release.
 Use [`stages`](#stages) instead.
-### `type`
+### Job-defined `type`
 CAUTION: **Deprecated:**
 `type` is deprecated, and could be removed in one of the future releases.
 Use [`stage`](#stage) instead.
+### Globally-defined `image`, `services`, `cache`, `before_script`, `after_script`
+
+Defining `image`, `services`, `cache`, `before_script`, and
+`after_script` globally is deprecated. Support could be removed
+from a future release.
+
+Use [`default:`](#setting-default-parameters) instead. For example:
+
+```yaml
+default:
+  image: ruby:2.5
+  services:
+    - docker:dind
+  cache:
+    paths: [vendor/]
+  before_script:
+    - bundle install --path vendor/
+  after_script:
+    - rm -rf tmp/
+```
+
 ## Custom build directories
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-runner/merge_requests/1267) in Gitlab Runner 11.10