spec(ci): beta ブランチ向けのGitHub Actions Workflowを追加 (MisskeyIO#538)

.github/workflows/docker-beta.yml

@@ -0,0 +1,51 @@
+name: Publish Docker image (beta)
+
+on:
+  push:
+    branches:
+      - beta
+    tags:
+      - "**"
+  workflow_dispatch:
+
+jobs:
+  push_to_registry:
+    name: Push Docker image to GitHub Container Registry
+    runs-on: ubuntu-22.04
+    if: github.repository == 'MisskeyIO/misskey'
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v4
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+        with:
+          platforms: linux/amd64
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/misskeyio/misskey
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Prepare image tags
+        run: |
+          echo "FORMATTED_BRANCH_NAME=$(echo ${{ github.ref_name }} | sed -e 's/\//-/g' )" >> $GITHUB_ENV
+      - name: Build and Push to GitHub Container Registry
+        uses: docker/build-push-action@v5
+        with:
+          builder: ${{ steps.buildx.outputs.name }}
+          context: .
+          push: true
+          platforms: ${{ steps.buildx.outputs.platforms }}
+          provenance: false
+          labels: ${{ env.FORMATTED_BRANCH_NAME }}
+          cache-from: type=registry,ref=ghcr.io/misskeyio/misskey:io-buildcache
+          cache-to: type=registry,ref=ghcr.io/misskeyio/misskey:io-buildcache,mode=max
+          tags: |
+            ghcr.io/misskeyio/misskey:beta
+            ghcr.io/misskeyio/misskey:${{ env.FORMATTED_BRANCH_NAME }}