Merge pull request '#7: Docker build command' (#10) from feature/7-docker into master

Reviewed-on: #10

docker/action.yaml

@@ -0,0 +1,33 @@
+name: build & push
+description: build & push OCI container images to the Gitea registry
+
+inputs:
+  name:
+    description: image name
+    required: true
+  tags:
+    description: newline-separated list of tags to tag the image
+    required: true
+  containerfile:
+    description: target container file to build
+    required: false
+    default: Containerfile
+
+runs:
+  using: composite
+  steps:
+    - shell: bash
+      run: |
+        repo_url="${{ gitea.event.repository.html_url }}"
+        repo_host="${repo_url#https://}"
+        repo_host="${repo_host%%/*}"
+        docker login --username acti-bot --password ${ACTI_BOT_TOKEN} ${repo_host}
+
+        docker build -f ${{ inputs.containerfile }} -t img-${{ gitea.run_id }} .
+        while IFS= read -r tag; do
+          [[ -z "$tag" ]] && continue
+
+          image="${repo_host}/${{ gitea.repository }}/${{ inputs.name }}:$tag"
+          docker tag img-${{ gitea.run_id }} $image
+          docker push $image
+        done <<< "${{ inputs.tags }}"