automate internal release workflow.

.github/workflows/release-internal.yml

@@ -8,7 +8,7 @@
 #
 # When?
 #
-# Manual trigger.
+# Manual trigger or cron job every wednesday morning.
 
 name: "Release to Cloud"
 run-name: "Release to Cloud off of ${{ inputs.ref }}"
@@ -32,20 +32,45 @@ on:
         required: true
         default: false
 
+  schedule:
+    - cron: '0 13 * * 3' # Every Wednesday at 8:00 AM central time
+
 defaults:
   run:
     shell: bash
 
 jobs:
+  get-latest-release:
+    runs-on: ubuntu-latest
+    outputs:
+      latest_release: ${{ steps.get_latest_release.outputs.latest_release }}
+    steps:
+      - name: Get latest release
+        id: get_latest_release
+        run: |
+          latest_release=$(curl --silent "https://api.github.com/repos/${{ github.repository }}/releases/latest" | jq -r .tag_name)
+          echo "::set-output name=latest_release::$latest_release"
+
+  check-for-new-commits:
+    runs-on: ubuntu-latest
+    needs: get-latest-release
+    outputs:
+      new_commits: ${{ steps.check_new_commits.outputs.new_commits }}
+    steps:
+      - name: Check for new commits since last release
+        id: check_new_commits
+        run: |
+          last_release_date=$(curl --silent "https://api.github.com/repos/${{ github.repository }}/releases/tags/${{ needs.get-latest-release.outputs.latest_release }}" | jq -r .published_at)
+          new_commits=$(git rev-list --count --since="$last_release_date" ${{ inputs.ref }})
+          echo "::set-output name=new_commits::$new_commits"
+
   invoke-reusable-workflow:
+    if: needs.check-for-new-commits.output.new_commits != '0'
     name: "Build and Release Internally"
-
     uses: "dbt-labs/dbt-release/.github/workflows/internal-archive-release.yml@main"
-
     with:
       package_test_command: "${{ inputs.package_test_command }}"
       dbms_name: "bigquery"
       ref: "${{ inputs.ref }}"
       skip_tests: "${{ inputs.skip_tests }}"
-
     secrets: "inherit"