add multi-arch builds for upstream and stable skopeo image via Travis

Travis is used, as it has native hardware to run the build for many
architectures (amd64, s390x, ppc64le). Docker is used as build and
manifest tool. `quay.io/skopeo/upstream:ma`, `quay.io/skopeo/stable:ma`
and `quay.io/containers/skopeo:ma` are specified as target multi-arch
upstream image.
Travis config file has 3 stages:
- local-build to do the local test for linux/amd64 and osx, as it was in
the initial code
- image-build-push to build and push images for specific architectures
(amd64, s390x, ppc64le)
- multi-arch-manifest-push to create and push manifest for multi-arch
image - `quay.io/skopeo/upstream:master`, `quay.io/skopeo/stable:v1.2.0`
and `quay.io/containers/skopeo:v1.2.0`

2 last stages are not done for pull request.

2 env variables specified in Travis settings are expected - QUAY_USERNAME and
QUAY_PASSWORD to push the images to quay.io.
As a result multi-arch images for 3 architectures are published.

Signed-off-by: Yulia Gaponenko <[email protected]>

.travis.yml

@@ -1,27 +1,74 @@
 language: go
 
-matrix:
-  include:
-  -  os: linux
-     sudo: required
-     services:
-       - docker
-  -  os: osx
-
 go:
   - 1.13.x
 
 notifications:
   email: false
 
-install:
-  # Ideally, the (brew update) should not be necessary and Travis would have fairly
-  # frequenstly updated OS images; that’s not been the case historically.
-  # In particular, explicitly unlink python@2, which has been removed from Homebrew
-  # since the last OS image build (as of July 2020), but the Travis OS still
-  # contains it, and it prevents updating of Python 3.
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update && brew unlink python@2 && brew install gpgme ; fi
-
-script:
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]];   then hack/travis_osx.sh ; fi
-  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then make vendor && ./hack/tree_status.sh && make local-cross && make check ; fi
+env:
+  global:
+    - REGISTRY=quay.io
+
+x_base_steps:
+  - &image-build-push
+    services:
+      - docker
+    os: linux
+    script:
+      - SOURCE_TYPE=upstream REPO=skopeo/upstream TAG=master make build-push-arch-container
+      - SOURCE_TYPE=stable REPO=skopeo/stable TAG=v1.2.0 EXTRA_REPO=containers/skopeo make build-push-arch-container
+
+stages:
+  - local-build
+  - name: image-build-push
+    if: type != pull_request AND branch = master
+  - name: multi-arch-manifest-push
+    if: type != pull_request AND branch = master
+
+jobs:
+  allow_failures:
+  - if: arch in (s390x, ppc64le)
+  include:
+    - stage: local-build
+      <<: *local-build
+      name: local build for osx
+      os: osx
+      install:
+        # Ideally, the (brew update) should not be necessary and Travis would have fairly
+        # frequently updated OS images; that's not been the case historically.
+        # In particular, explicitly unlink python@2, which has been removed from Homebrew
+        # since the last OS image build (as of July 2020), but the Travis OS still
+        # contains it, and it prevents updating of Python 3.
+      - brew update && brew unlink python@2 && brew install gpgme
+      script:
+      - hack/travis_osx.sh
+    - stage: local-build
+      <<: *local-build
+      name: local build for linux
+      os: linux
+      services:
+      - docker
+      script: 
+      - make vendor && ./hack/tree_status.sh && make local-cross && make check
+
+    - stage: image-build-push
+      <<: *image-build-push
+      name: image for amd64
+      arch: amd64
+
+    - stage: image-build-push
+      <<: *image-build-push
+      name: image for s390x
+      arch: s390x
+
+    - stage: image-build-push
+      <<: *image-build-push
+      name: image for ppc64le
+      arch: ppc64le
+
+    - stage: multi-arch-manifest-push
+      os: linux
+      script:
+      - SOURCE_TYPE=upstream REPO=skopeo/upstream TAG=master make push-ma-manifest
+      - SOURCE_TYPE=stable REPO=skopeo/stable TAG=v1.2.0 EXTRA_REPO=containers/skopeo make push-ma-manifest

Makefile

@@ -82,6 +82,14 @@ ifeq ($(DISABLE_CGO), 1)
 	override BUILDTAGS = exclude_graphdriver_devicemapper exclude_graphdriver_btrfs containers_image_openpgp
 endif
 
+ARCHES=amd64 s390x ppc64le
+MA_IMAGE := $(REGISTRY)/$(REPO):$(TAG)
+ARCH_IMAGE := $(MA_IMAGE)-$(GOARCH)
+ifneq ($(EXTRA_REPO),)
+EXTRA_MA_IMAGE := $(REGISTRY)/$(EXTRA_REPO):$(TAG)
+EXTRA_ARCH_IMAGE := $(EXTRA_MA_IMAGE)-$(GOARCH)
+endif
+
 #   make all DEBUG=1
 #     Note: Uses the -N -l go compiler options to disable compiler optimizations
 #           and inlining. Using these build options allows you to subsequently
@@ -135,6 +143,27 @@ local-cross: bin/skopeo.darwin.amd64 bin/skopeo.linux.arm bin/skopeo.linux.arm64
 build-container:
 	${CONTAINER_RUNTIME} build ${BUILD_ARGS} -t "$(IMAGE)" .
 
+# Build and ush container specific to arch
+build-push-arch-container:
+	${CONTAINER_RUNTIME} build -t "${ARCH_IMAGE}" contrib/skopeoimage/${SOURCE_TYPE}
+	echo "${QUAY_PASSWORD}" | ${CONTAINER_RUNTIME} login ${REGISTRY} -u "${QUAY_USERNAME}" --password-stdin
+	${CONTAINER_RUNTIME} push "${ARCH_IMAGE}"
+ifneq ($(EXTRA_REPO),)
+	${CONTAINER_RUNTIME} tag "${ARCH_IMAGE}" "${EXTRA_ARCH_IMAGE}"
+	${CONTAINER_RUNTIME} push "${EXTRA_ARCH_IMAGE}"
+endif
+
+# Push manifest to make multi-arch image
+push-ma-manifest:
+	echo "${QUAY_PASSWORD}" | docker login ${REGISTRY} -u "${QUAY_USERNAME}" --password-stdin
+	sudo chmod 0755 /etc/docker
+	DOCKER_CLI_EXPERIMENTAL="enabled" docker manifest create "${MA_IMAGE}" $(foreach arch,${ARCHES}, ${MA_IMAGE}-${arch})
+	DOCKER_CLI_EXPERIMENTAL="enabled" docker manifest push --purge "${MA_IMAGE}"
+ifneq ($(EXTRA_REPO),)
+	DOCKER_CLI_EXPERIMENTAL="enabled" docker manifest create "${EXTRA_MA_IMAGE}" $(foreach arch,${ARCHES}, ${EXTRA_MA_IMAGE}-${arch})
+	DOCKER_CLI_EXPERIMENTAL="enabled" docker manifest push --purge "${EXTRA_MA_IMAGE}"
+endif
+
 $(MANPAGES): %: %.md
 	sed -e 's/\((skopeo.*\.md)\)//' -e 's/\[\(skopeo.*\)\]/\1/' $<  | $(GOMD2MAN) -in /dev/stdin -out $@