feat: introduce variable for additional docker/buildah push arguments

Signed-off-by: Carl-Christian Sautter <mail@c-sautter.de>

README.md

@@ -298,13 +298,14 @@ This job builds the image and publishes it to the _snapshot_ repository.
 It is bound to the `package-build` stage, and uses the following variables:
 
 | Input / Variable                                                        | Description                                                                                                                                                                                                                                                                       | Default value                  |
-| ----------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------ |
+|-------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------|
 | `build-args` / `DOCKER_BUILD_ARGS`                                      | Additional `docker/kaniko/buildah` `build` arguments                                                                                                                                                                                                                              | _(none)_                       |
 | `registry-mirror` / `DOCKER_REGISTRY_MIRROR`                            | URL of a Docker registry mirror to use during the image build (instead of default `https://index.docker.io`) <br>:warning: Used by the `kaniko` and `dind` options only                                                                                                           | _(none)_                       |
 | `container-registries-config-file` / `CONTAINER_REGISTRIES_CONFIG_FILE` | The [`registries.conf`](https://www.redhat.com/sysadmin/manage-container-registries) configuration to be used<br>:warning: Used by the `buildah` build only                                                                                                                       | _(none)_                       |
 | `metadata` / `DOCKER_METADATA`                                          | Additional `docker build`/`kaniko` arguments to set label                                                                                                                                                                                                                         | OCI Image Format Specification |
 | `kaniko-snapshot-image-cache` / `KANIKO_SNAPSHOT_IMAGE_CACHE`           | Snapshot image repository that will be used to store cached layers (leave empty to use default: snapshot image repository + `/cache`)<br>:warning: Used by the `kaniko` build only                                                                                                | _none_ (default cache path)    |
 | `build-cache-disabled` / `DOCKER_BUILD_CACHE_DISABLED`                  | Set to `true` to disable the build cache.<br/>Cache can typically be disabled when there is a network latency between the container registry and the runner.                                                                                                                      | _none_ (i.e cache enabled)     |
+| `push-args` / `DOCKER_PUSH_ARGS`                                        | Additional `push` arguments for [docker](https://docs.docker.com/reference/cli/docker/image/push/) or [buildah](https://github.com/containers/buildah/blob/main/docs/buildah-push.1.md) (executed right after `build`).<br>Ex: `--compression-format zstd --compression-level 20` | _(none)_                       |
 
 This job produces _output variables_ that are propagated to downstream jobs (using [dotenv artifacts](https://docs.gitlab.com/ee/ci/pipelines/job_artifacts.html#artifactsreportsdotenv)):
 

kicker.json

@@ -120,6 +120,11 @@
       "description": "Set to `true` to disable the build cache.",
       "type": "boolean",
       "advanced": true
+    },
+    {
+      "name": "DOCKER_PUSH_ARGS",
+      "description": "Additional docker/buildah `push` arguments (executed right after `build`).\n\nEx: `--compression-format zstd --compression-level 20`",
+      "advanced": true
     }
   ],
   "features": [

templates/gitlab-ci-docker.yml

@@ -79,6 +79,9 @@ spec:
     build-args:
       description: Additional docker/kaniko/buildah build arguments
       default: ''
+    push-args:
+      description: Additional docker/buildah `push` arguments (executed right after `build`)
+      default: ''
     build-cache-disabled:
       description: Disable the build cache
       type: boolean
@@ -285,6 +288,7 @@ variables:
   DOCKER_REGISTRY_MIRROR: $[[ inputs.registry-mirror ]]
   CONTAINER_REGISTRIES_CONFIG_FILE: $[[ inputs.container-registries-config-file ]]
   KANIKO_SNAPSHOT_IMAGE_CACHE: $[[ inputs.kaniko-snapshot-image-cache ]]
+  DOCKER_PUSH_ARGS: $[[ inputs.push-args ]]
   DOCKER_HADOLINT_DISABLED: $[[ inputs.hadolint-disabled ]]
   DOCKER_HADOLINT_ARGS: $[[ inputs.hadolint-args ]]
   DOCKER_HEALTHCHECK_DISABLED: $[[ inputs.healthcheck-disabled ]]
@@ -800,7 +804,7 @@ docker-dind-build:
       fi
     # Build using cache if exist
     - echo $DOCKER_METADATA $DOCKER_BUILD_ARGS "$(docker_context_path)" | xargs docker build --file "$DOCKER_FILE" ${dind_cache_args} --tag $DOCKER_SNAPSHOT_IMAGE --build-arg http_proxy="$http_proxy" --build-arg https_proxy="$https_proxy" --build-arg no_proxy="$no_proxy"
-    - docker push $DOCKER_SNAPSHOT_IMAGE
+    - docker push $DOCKER_PUSH_ARGS $DOCKER_SNAPSHOT_IMAGE
     # Display the size of each layer
     - docker history $DOCKER_SNAPSHOT_IMAGE
     # Display the total size of the image
@@ -843,7 +847,7 @@ docker-buildah-build:
       buildah version
     # build and push image
     - echo $DOCKER_METADATA $DOCKER_BUILD_ARGS "$(docker_context_path)" | xargs buildah build --file "$DOCKER_FILE" --tag $DOCKER_SNAPSHOT_IMAGE $buildah_cache_args --build-arg http_proxy="$http_proxy" --build-arg https_proxy="$https_proxy" --build-arg no_proxy="$no_proxy"
-    - buildah push --digestfile .img-digest.txt "$DOCKER_SNAPSHOT_IMAGE"
+    - buildah push --digestfile .img-digest.txt $DOCKER_PUSH_ARGS "$DOCKER_SNAPSHOT_IMAGE"
     # display digest of the resulting image
     - cat .img-digest.txt
     # create dotenv file