image_builds: simplify the tags

We can use docker labels to pass the metadata we want
and make the tag simpoler.

also small fixup, make it so buildah it uses chroot isolation
and update the base image

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-ci/-/merge_requests/308>

.gitlab-ci.yml

@@ -25,7 +25,7 @@ test manifest:
         - "junit.xml"
 
 .base:
-  image: 'registry.fedoraproject.org/fedora:31'
+  image: 'registry.fedoraproject.org/fedora:32'
   extends:
     - '.global_ci_policy'
   tags: ['gstreamer']
@@ -35,42 +35,58 @@ test manifest:
   variables:
     STORAGE_DRIVER: 'vfs'
     BUILDAH_FORMAT: 'docker'
+    BUILDAH_ISOLATION: 'chroot'
     GIT_STRATEGY: fetch
   script:
     - export DATE=$(date +"%Y-%m-%d")
-    - export IMAGE="${CI_REGISTRY_IMAGE}/${ARCH}/${TAG}"
-    - export _UID="${IMAGE}:${DATE}-${CI_JOB_ID}"
-    - export LATEST="${IMAGE}:latest"
+    - export IMAGE="$CI_REGISTRY_IMAGE/${ARCH:=amd64}/$TAG"
+    - export _UID="$IMAGE:$DATE-$GST_UPSTREAM_BRANCH"
+    - export LATEST="$IMAGE:latest"
 
     - dnf install -y buildah runc
     # Newer versions of podman/buildah try to set overlayfs mount options when
     # using the vfs driver, and this causes errors.
     - sed -i '/^mountopt =.*/d' /etc/containers/storage.conf
 
-    - buildah bud --build-arg DEFAULT_BRANCH=${GST_UPSTREAM_BRANCH} -f ${DOCKERFILE} -t ${LATEST} ${CONTEXT_DIR}
+    - echo "Building image $_UID"
+
+    - >
+      buildah bud
+      --build-arg DEFAULT_BRANCH=$GST_UPSTREAM_BRANCH
+      --arch=${ARCH:=amd64}
+      --label ci.job_id=$CI_JOB_ID
+      --label pipeline.url=$CI_PIPELINE_URL
+      --label git.ref_name=$CI_COMMIT_REF_NAME
+      --label git.sha=$CI_COMMIT_SHA
+      --label gitlab.project_path=$CI_PROJECT_PATH
+      --label gitlab.project_url=$CI_PROJECT_URL
+      -f $DOCKERFILE
+      -t $IMAGE
+      $CONTEXT_DIR
+
+    - buildah login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
 
     # If we are in a fork, push the image to the reigstry regardless the branch
     - |
       if [ "$CI_PROJECT_NAMESPACE" != "gstreamer" ]; then
-        buildah login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
-        buildah push ${LATEST}
+        # Tag the image with the git ref
+        buildah tag $_UID $LATEST
+        # Only push the :latest so with each push the previous
+        # image in the forked registry gets overrwritten
+        # to avoid bloating the registry and making
+        # pruning easier for the gitlab admins
+        buildah push $LATEST
       fi
 
     # Push the images to the upstream registry
     - |
       if [ "$CI_PROJECT_NAMESPACE" = "gstreamer" ]; then
-        # Tag the image with the git ref
-        buildah tag ${LATEST} ${_UID}-${CI_COMMIT_REF_NAME}
-        # Push the tags
-        buildah login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
-        buildah push ${_UID}-${CI_COMMIT_REF_NAME}
-        buildah push ${LATEST}
+        buildah push $_UID
       fi
 
 alpine amd64 manifest builder docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "build-manifest"
     CONTEXT_DIR: "docker/build_manifest/"
     DOCKERFILE: "docker/build_manifest/Dockerfile"
@@ -79,7 +95,6 @@ alpine amd64 manifest builder docker:
 test manifest amd64 docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "test-manifest"
     CONTEXT_DIR: "docker/test_manifest/"
     DOCKERFILE: "docker/test_manifest/Dockerfile"
@@ -88,7 +103,6 @@ test manifest amd64 docker:
 gst-indent amd64 docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "gst-indent"
     CONTEXT_DIR: "docker/indent/"
     DOCKERFILE: "docker/indent/Dockerfile"
@@ -97,7 +111,6 @@ gst-indent amd64 docker:
 fedora amd64 docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "fedora"
     CONTEXT_DIR: "docker/fedora/"
     DOCKERFILE: "docker/fedora/Dockerfile"
@@ -106,7 +119,6 @@ fedora amd64 docker:
 cerbero fedora amd64 docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "cerbero-fedora"
     CONTEXT_DIR: "docker/cerbero/"
     DOCKERFILE: "docker/cerbero/Dockerfile-fedora"
@@ -115,7 +127,6 @@ cerbero fedora amd64 docker:
 android docker:
   stage: "build docker"
   variables:
-    ARCH: "amd64"
     TAG: "android"
     CONTEXT_DIR: "docker/android/"
     DOCKERFILE: "docker/android/Dockerfile"