ci: add pr update checker

.github/workflows/pr_checker.yaml

@@ -0,0 +1,136 @@
+name: 'PR Update Check'
+
+on:
+  workflow_dispatch: # Trigger manually until pr push check is done
+  push:
+    branches:
+      - master # whenever master changes
+  schedule:
+    - cron:  '0 0 * * *' # once a day
+
+env:
+  ECH_NODE_VERSION: '14.x'
+  BASE_COMMIT_LIMIT: 10
+  CONTEXT: 'PR Update Check'
+
+jobs:
+  fetch:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.save.outputs.json }}
+    steps:
+      - name: Fetch GH pulls
+        id: fetch
+        uses: octokit/[email protected]
+        with:
+          route: GET /repos/{repo}/pulls?state=open
+          repo: ${{ github.repository }}
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Store matrix
+        id: save
+        uses: nickofthyme/object-remap@v1
+        with:
+          include.*.number: ${{ toJSON(fromJSON(steps.fetch.outputs.data).*.number) }}
+          include.*.title: ${{ toJSON(fromJSON(steps.fetch.outputs.data).*.title) }}
+          include.*.head_sha: ${{ toJSON(fromJSON(steps.fetch.outputs.data).*.head.sha) }}
+          include.*.base_ref: ${{ toJSON(fromJSON(steps.fetch.outputs.data).*.base.ref) }}
+          include.*.base_sha: ${{ toJSON(fromJSON(steps.fetch.outputs.data).*.base.sha) }}
+
+  base-status-check:
+    name: "PR #${{ matrix.number }} - ${{ matrix.title }}"
+    runs-on: ubuntu-latest
+    needs: fetch
+    strategy:
+      matrix: ${{ fromJSON(needs.fetch.outputs.matrix) }}
+      fail-fast: false
+    steps:
+      - name: Set pending status
+        uses: hkusu/status-create-action@v1
+        with:
+          sha: ${{ matrix.headSha }}
+          state: pending
+          target-url: "https://github.com/elastic/elastic-charts/actions/runs/${{ github.run_id }}"
+          description: "Checking if PR is up-to-date"
+          context: ${{ env.CONTEXT }}
+      - name: Git base compare
+        id: base-compare
+        uses: octokit/[email protected]
+        with:
+          route: GET /repos/{repo}/compare/{basehead}
+          repo: ${{ github.repository }}
+          basehead: "${{ matrix.baseRef }}...${{ matrix.baseSha }}"
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+      - run: echo "${{ fromJSON(steps.base-compare.outputs.data).behind_by }}"
+      - run: echo "This pr is behind by ${{ fromJSON(steps.base-compare.outputs.data).behind_by }} commits"
+      - name: Set success status - in sync
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by == 0 }}
+        uses: hkusu/status-create-action@v1
+        with:
+          sha: ${{ matrix.headSha }}
+          state: success
+          target-url: "https://github.com/elastic/elastic-charts/actions/runs/${{ github.run_id }}"
+          description: PR is in up-to-date with upstream base
+          context: ${{ env.CONTEXT }}
+      - name: Git head compare
+        id: head-compare
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by > 0 }}
+        uses: octokit/[email protected]
+        with:
+          route: GET /repos/{repo}/compare/{basehead}
+          repo: ${{ github.repository }}
+          basehead: "${{ matrix.baseSha }}...${{ matrix.headSha }}"
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Check files changes
+        id: files-check
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by > 0 && fromJSON(steps.base-compare.outputs.data).behind_by <= env.BASE_COMMIT_LIMIT }}
+        shell: python
+        # TODO: find a better way to do this, possiblly custom action
+        run: |
+          import json
+          baseFiles = json.loads("""${{ toJSON(fromJSON(steps.base-compare.outputs.data).files.*.filename) }}""")
+          headFiles = json.loads("""${{ toJSON(fromJSON(steps.head-compare.outputs.data).files.*.filename) }}""")
+
+          # file intersection
+          files = list(filter(lambda x:x in baseFiles, headFiles))
+
+          hasStaleScreenshot = False
+
+          for file in files:
+              if file.startswith('integration/tests/__image_snapshots__/') and '/__diff_output__/' not in file:
+                  hasStaleScreenshot = True;
+
+          print(f"::set-output name=hasStaleScreenshot::{str(hasStaleScreenshot).lower()}")
+      - name: Print output
+        run: echo ${{ steps.files-check.outputs.hasStaleScreenshot == 'true' }}
+      - name: Set failed status - out of sync with stale vrt
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by > 0 && fromJSON(steps.base-compare.outputs.data).behind_by <= env.BASE_COMMIT_LIMIT && steps.files-check.outputs.hasStaleScreenshot == 'true' }}
+        uses: hkusu/status-create-action@v1
+        with:
+          sha: ${{ matrix.headSha }}
+          state: failure
+          target-url: "https://github.com/elastic/elastic-charts/actions/runs/${{ github.run_id }}"
+          description: "PR has stale VRT screenshots. Please merge with ${{ matrix.baseRef }}."
+          context: ${{ env.CONTEXT }}
+      - name: Set success status - not in sync but no stale vrt
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by > 0 && fromJSON(steps.base-compare.outputs.data).behind_by <= env.BASE_COMMIT_LIMIT && steps.files-check.outputs.hasStaleScreenshot != 'true' }}
+        uses: hkusu/status-create-action@v1
+        with:
+          sha: ${{ matrix.headSha }}
+          state: success
+          target-url: "https://github.com/elastic/elastic-charts/actions/runs/${{ github.run_id }}"
+          description: "PR is ${{ fromJSON(steps.base-compare.outputs.data).behind_by }} commits behind with no stale VRT screenshots."
+          context: ${{ env.CONTEXT }}
+      - name: Set failed status - exceeds synced limit
+        if: ${{ fromJSON(steps.base-compare.outputs.data).behind_by > env.BASE_COMMIT_LIMIT }}
+        uses: hkusu/status-create-action@v1
+        with:
+          sha: ${{ matrix.headSha }}
+          state: failure
+          target-url: "https://github.com/elastic/elastic-charts/actions/runs/${{ github.run_id }}"
+          description: "PR is ${{ fromJSON(steps.base-compare.outputs.data).behind_by }} commits behind. Please merge with ${{ matrix.baseRef }}."
+          context: ${{ env.CONTEXT }}
+
+