ci: Experimental workflow to update screenshots in a PR (#4991)

Untested. A workflow must exist in the main branch before a version of
it from any branch can be triggered.

.github/workflows/selenium-lab-tests.yaml

@@ -11,6 +11,18 @@ on:
       test_filter:
         description: "A filter to run a subset of the tests.  If empty, all tests will run."
         required: false
+  workflow_call:
+    # Allows for reuse from other workflows, such as "Update All Screenshots"
+    # workflow.
+    inputs:
+      pr:
+        description: "A PR number to build and test in the lab.  If empty, will build and test from main."
+        required: false
+      test_filter:
+        description: "A filter to run a subset of the tests.  If empty, all tests will run."
+        required: false
+      ignore_test_status:
+        description: "If true, ignore test failures and treat the workflow as a success."
   schedule:
     # Runs every night at 2am PST / 10am UTC, testing against the main branch.
     - cron: '0 10 * * *'
@@ -199,6 +211,11 @@ jobs:
             extra_flags="$extra_flags --filter $filter"
           fi
 
+          ignore_test_status="${{ github.event.inputs.ignore_test_status }}"
+          if [[ "$ignore_test_status" == "true" ]]; then
+            extra_flags="$extra_flags || true"
+          fi
+
           python3 build/test.py \
               --no-build \
               --reporters spec --spec-hide-passed \

.github/workflows/update-screenshots.yaml

@@ -0,0 +1,63 @@
+name: Update All Screenshots
+# Updates all screenshots on an existing PR, assuming permission has been given
+# to maintainers to make edits.
+
+on:
+  workflow_dispatch:
+    # Allows for manual triggering on PRs.  They should be reviewed first, to
+    # avoid malicious code executing in the lab.
+    inputs:
+      pr:
+        description: "A PR number to build and test in the lab, then update all the screenshots."
+        required: true
+
+jobs:
+  run-lab-tests:
+    name: Get Selenium Lab Screenshots
+    uses: ./.github/workflows/selenium-lab-tests.yaml
+    with:
+      pr: ${{ github.event.inputs.pr }}
+      test_filter: 'layout'
+      ignore_test_status: true
+
+  update-pr:
+    name: Update PR
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: refs/pull/${{ github.event.inputs.pr }}/head
+
+      - name: Get artifacts
+        uses: actions/download-artifact@v3
+
+      - name: Update screenshots
+        run: |
+          # Unpack screenshots from the lab.
+          for i in screenshots-*.zip; do
+            unzip -d test/test/assets/screenshots/ "$i"
+          done
+
+          # Update the official screenshots for any that has visibly changed.
+          # This is not a byte-for-byte comparison.
+          ./build/updateScreenshots.py
+
+          # Emulate the actions bot.
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+
+          # Update the PR.
+          git add test/test/assets/screenshots/*/*.png
+          git commit -m ':robot: Update all screenshots'
+
+          PR_API_URL="/repos/${{ github.repository }}/pulls/${{ github.event.inputs.pr }}"
+          REMOTE=$(gh api $GH_API_URL | jq -r .head.repo.html_url)
+          BRANCH=$(gh api $GH_API_URL | jq -r .head.ref)
+
+          git push "$REMOTE" "$BRANCH"
+
+      - name: Debug
+        uses: mxschmitt/[email protected]
+        with:
+          limit-access-to-actor: true
+        if: failure()