ci: generate preview by pr

Author: SergioRibera

.github/workflows/gen_preview.yml

@@ -0,0 +1,44 @@
+name: Generate Image Preview
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+    paths:
+      - 'content/**'
+
+# cancel in-progress runs on new commits to same PR (github.event.number)
+concurrency:
+  group: gen_preview_image${{ github.workflow }}-${{ github.event.number || github.sha }}
+  cancel-in-progress: true
+
+jobs:
+  generate-preview:
+    runs-on: ubuntu-latest
+    name: Generate Preview Image
+    permissions:                # Job-level permissions configuration starts here
+      contents: write           # 'write' access to repository contents
+      pull-requests: write      # 'write' access to pull requests
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false # otherwise, the token used is the GITHUB_TOKEN, instead of your personal access token.
+          fetch-depth: 0 # otherwise, there would be errors pushing refs to the destination repository.
+      # Download bin of gen_preview
+      # TODO
+
+      - name: Get changed files
+        run: |
+          files=$(git --no-pager diff --name-only FETCH_HEAD $(git merge-base FETCH_HEAD main))
+          preview ./crates/preview/assets/bg_preview.png ./public/previews $files
+      - name: Commit changes
+        run: |
+          git config --global user.name 'github-actions[bot]'
+          git config --global user.email 'github-actions[bot]@users.noreply.github.com'
+          git add -A
+          git commit -m "chore: generate opengraph image" || echo "No changes to commit"
+
+      - uses: ad-m/github-push-action@master
+        with:
+          branch: ${{ github.head_ref }}
+