misc: only run scheduled publish job if there are new commits (GoogleChrome#14145)

Author: connorjclark

.github/workflows/publish.yml

@@ -5,9 +5,27 @@ on:
   workflow_dispatch: {}
 
 jobs:
+  check_date:
+    runs-on: ubuntu-latest
+    outputs:
+      should_run: ${{ steps.should_run.outputs.should_run }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: print latest_commit
+        run: echo ${{ github.sha }}
+
+      - id: should_run
+        continue-on-error: true
+        if: ${{ github.event_name == 'schedule' }}
+        run: test -z $(git rev-list --after="1 day" ${{ github.sha }}) && echo "::set-output name=should_run::false"
+
   publish:
-    # Prevent forks from running this job.
-    if: (github.event_name == 'schedule' && github.repository == 'GoogleChrome/lighthouse') || (github.event_name != 'schedule')
+    # Prevent scheduled job from running if...
+    # 1) this is a fork
+    # 2) there has not been a change in the last day
+    if: |
+      github.event_name != 'schedule' ||
+      (github.repository == 'GoogleChrome/lighthouse' && ${{ needs.check_date.outputs.should_run != 'false' }})
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v1