chore: Enable auto-merge for dependabot PRs (#169)

Author: dreamorosi

Diff for: .github/workflows/auto-merge.yml

@@ -0,0 +1,68 @@
+name: Dependabot PR auto-merge
+
+on:
+  workflow_run:
+    workflows: [on-pull-request]
+    types: ["completed"]
+
+jobs:
+  auto-merge:
+    name: Auto-merge
+    runs-on: ubuntu-latest
+    # Run this only when the previous workflow was successfull & the initial actor was dependabot
+    if: ${{ github.event.workflow_run.conclusion == 'success' && github.actor == 'dependabot[bot]' }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Download PR artifact
+        uses: actions/[email protected]
+        with:
+          script: |
+            const fs = require('fs');
+
+            // Get all artifacts
+            const artifacts = await github.actions.listWorkflowRunArtifacts({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               run_id: ${{github.event.workflow_run.id }},
+            });
+            
+            // Identify the artifact of the PR
+            const matchArtifact = artifacts.data.artifacts.filter((artifact) => {
+              return artifact.name == "pr"
+            })[0];
+            
+            // Download the actual artifact
+            const download = await github.actions.downloadArtifact({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               artifact_id: matchArtifact.id,
+               archive_format: 'zip',
+            });
+            
+            // Write it to disk
+            fs.writeFileSync('${{github.workspace}}/pr.zip', Buffer.from(download.data));
+      - name: Unzip artifact
+        run: unzip pr.zip
+      - name: Merge PR
+        uses: actions/github-script@v3
+        with:
+          script: |
+            const fs = require('fs');
+            const pullNumber = Number(fs.readFileSync('./NR'));
+            
+            // Create a review
+            github.pulls.createReview({
+              owner: context.payload.repository.owner.login,
+              repo: context.payload.repository.name,
+              pull_number: pullNumber,
+              event: 'APPROVE'
+            })
+            
+            // Merge PR
+            github.pulls.merge({
+              owner: context.payload.repository.owner.login,
+              repo: context.payload.repository.name,
+              pull_number: pullNumber,
+              merge_method: 'squash'
+            })
+          github-token: ${{ secrets.GITHUB_TOKEN }}