reduce built docker image layers

.gitlab-ci.yml

@@ -19,7 +19,7 @@ build:
   stage: build
   script:
     - apk add --no-cache bash
-    - /bin/bash -n gitlab-ci-*
+    - /bin/bash -n overlay/usr/share/gitlab-ci-common overlay/usr/bin/gitlab-ci-*
     - echo Building ${RELEASE_IMAGE}
     - docker build -t $TEST_IMAGE .
     - docker push $TEST_IMAGE

Dockerfile

@@ -29,15 +29,6 @@ RUN mkdir -p /usr/share/man/man1 \
 	&& apt-mark auto $build_deps \
 	&& rm -rf /var/lib/apt/lists/*
 
-COPY gitlab-ci-common /usr/share/
-COPY gitlab-ci-add-pages-repo /usr/bin/
-COPY gitlab-ci-aptly /usr/bin/
-COPY gitlab-ci-autopkgtest /usr/bin/
-COPY gitlab-ci-entrypoint /usr/bin/
-COPY gitlab-ci-git-buildpackage /usr/bin/
-COPY gitlab-ci-git-buildpackage-all /usr/bin/
-COPY gitlab-ci-lintian /usr/bin/
-COPY gitlab-ci-enable-sid /usr/bin/
-COPY gitlab-ci-enable-experimental /usr/bin/
+ADD overlay /
 
 ENTRYPOINT ["/usr/bin/gitlab-ci-entrypoint"]