ci: Run Docker publish workflow on a schedule (meltano#6570)

.github/workflows/docker_publish.yml

@@ -1,12 +1,15 @@
 name: Docker Publish
 
 # This workflow will build and publish all public Docker images to the configured registry.
-# Set the input `dry-run` to `false` to skip pushing images to the registry.
+# Set the input `dry_run` to `false` to skip pushing images to the registry.
 
 on:
+  schedule:
+  # Weekly on Sunday at 04:45 UTC
+  - cron: '45 4 * * 0'
   workflow_dispatch:
     inputs:
-      dry-run:
+      dry_run:
         description: "Dry run (skip push step)"
         type: boolean
         required: true
@@ -20,12 +23,8 @@ on:
           - docker.io
 
 jobs:
-  public_docker_build:
+  build_meltano_image:
     runs-on: ubuntu-latest
-    env:
-      # Boolean values don't actually work so cast to 'true' and 'false'
-      # https://github.com/actions/runner/issues/1483
-      DRY_RUN_STR: ${{ format('{0}', github.event.inputs.dry-run) || 'true' }}
 
     strategy:
       fail-fast: false
@@ -41,6 +40,18 @@ jobs:
           is-default-python: false
 
     steps:
+    - name: Set the workflow inputs
+      # This step makes it so that the same workflow inputs can be accessed
+      # regardless of what event triggered it.
+      env:
+        DEFAULT_DRY_RUN: "true"
+        DEFAULT_REGISTRY: "ghcr.io"
+      run: |
+        # Boolean values don't actually work so cast to 'true' and 'false'
+        # https://github.com/actions/runner/issues/1483
+        echo "dry_run=${{ format('{0}', github.event.inputs.dry_run) || env.DEFAULT_DRY_RUN }}" >> $GITHUB_ENV
+        echo "registry=${{ github.event.inputs.registry || env.DEFAULT_REGISTRY }}" >> $GITHUB_ENV
+
     - uses: actions/checkout@v3
 
     - name: Get Meltano version
@@ -51,25 +62,11 @@ jobs:
         poetry version --short
         echo "::set-output name=release-version::$(poetry version --short)"
 
-    # These exist to show if 'dry-run' flag is set as intended and correctly parsed from inputs
-    - name: Print dry-run message (if applicable)
-      if: ${{ env.DRY_RUN_STR == 'true' }}
-      run: |
-        echo "DRY_RUN=${{ github.event.inputs.dry-run }}"
-        echo "NOTE: This job is a dry run and will not publish any images."
-
-    - name: Print publish message (if applicable)
-      if: ${{ env.DRY_RUN_STR == 'false' }}
-      run: |
-        echo "DRY_RUN=${{ github.event.inputs.dry-run }}"
-        echo "NOTE: This job is planning to publish the docker images."
-        echo "⚠️ If this is not intended, please cancel this job."
-
     - name: Assemble image tags
       id: assemble-tags
       run: |
         # To save space, only publish the `latest` tag for each images to the GitHub registry
-        if [[ "${{ github.event.inputs.registry }}" != "ghcr.io" ]]; then
+        if [[ "${{ env.registry }}" != "ghcr.io" ]]; then
           echo "v${{ steps.get-meltano-version.outputs.release-version }}-python${{ matrix.python-version }}" >> tags
           [[ "${{ matrix.is-default-python }}" == "true" ]] && echo "SHA-${{ github.sha }}" >> tags
           [[ "${{ matrix.is-default-python }}" == "true" ]] && echo "v${{ steps.get-meltano-version.outputs.release-version }}" >> tags
@@ -89,22 +86,22 @@ jobs:
     - name: Set registry username and password
       id: user-and-pass
       run: |
-        if [[ "${{ github.event.inputs.registry }}" == "ghcr.io" ]]; then
+        if [[ "${{ env.registry }}" == "ghcr.io" ]]; then
           echo "::set-output name=username::${{ github.actor }}"
           echo "::set-output name=password::${{ secrets.GITHUB_TOKEN }}"
         fi
-        if [[ "${{ github.event.inputs.registry }}" == "docker.io" ]]; then
+        if [[ "${{ env.registry }}" == "docker.io" ]]; then
           echo "::set-output name=username::meltano"
           echo "::set-output name=password::${{ secrets.DOCKERHUB_TOKEN }}"
         fi
 
     - name: Build, scan, then conditionally push the Docker image for a given Python version
       uses: ./.github/actions/docker-build-scan-push
       with:
-        push: ${{ env.DRY_RUN_STR == 'false' }}
+        push: ${{ env.dry_run == 'false' }}
         token: ${{ secrets.GITHUB_TOKEN }}
         tags: ${{ steps.assemble-tags.outputs.tags }}
-        registry: ${{ github.event.inputs.registry }}
+        registry: ${{ env.registry }}
         username: ${{ steps.user-and-pass.outputs.username }}
         password: ${{ steps.user-and-pass.outputs.password }}
         python-version: ${{ matrix.python-version }}