ci: deploy to ghcr on push (#3435)

publish and tag docker images continuously to ghcr.io. adds custom
tagging so we can retain every commit. it's technically possible to do
this on docker hub, but in order to have custom tags, you need to set up
a regular user and log in/push via that user. the authentication is much
cleaner in github actions for ghcr.

(note docker hub pulls for releases are still staying the same, this is
just an alternative form of retention going forward).

.github/workflows/ghcr.yml

@@ -0,0 +1,73 @@
+name: Deploy docker image to ghcr
+
+# Deploy docker image to ghcr on pushes to master and all releases/tags.
+# Note releases to docker hub are managed separately in another process
+# (github sends webhooks to docker hub which triggers the build there).
+# This workflow is an alternative form of retention for docker images
+# which also allows us to tag and retain every single commit to master.
+
+on:
+  push:
+    tags:
+      - '*'
+    branches:
+      - master
+  release:
+    types: [released]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  deploy-ghcr:
+
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+            # need to fetch unshallow so that setuptools_scm can infer the version
+            fetch-depth: 0
+
+      - uses: actions/setup-python@v4
+        name: Install python
+        with:
+          python-version: "3.11"
+          cache: "pip"
+
+      - name: Generate vyper/version.py
+        run: |
+          pip install .
+          echo "VYPER_VERSION=$(PYTHONPATH=. python vyper/cli/vyper_compile.py --version)" >> "$GITHUB_ENV"
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          flavor: |
+            latest=true
+          tags: |
+            type=ref,event=branch
+            type=ref,event=tag
+            type=raw,value=${{ env.VYPER_VERSION }}
+
+      - name: Login to ghcr.io
+        uses: docker/login-action@v2
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}