Merge branch 'patch-29' into 'master'

Better job naming (avoid conflicts with other jobs)

See merge request gitlab-org/gitlab!17218

changelogs/unreleased/patch-29.yml

+---
+title: Better job naming for Docker.gitlab-ci.yml
+merge_request: 17218
+author: luca.orlandi@gmail.com
+type: other

lib/gitlab/ci/templates/Docker.gitlab-ci.yml

-build-master:
+docker-build-master:
   # Official docker image.
   image: docker:latest
   stage: build
@@ -12,7 +12,7 @@ build-master:
   only:
     - master
 
-build:
+docker-build:
   # Official docker image.
   image: docker:latest
   stage: build