directory_writer (#1) (#1549)

* directory_writer

* fixup: Format Python code with psf/black

* fixup: DIRECTORY.md

.github/workflows/directory_writer.yml

@@ -0,0 +1,25 @@
+# The objective of this GitHub Action is to add a new DIRECTORY.md file to a pull request if needed.
+name: directory_writer
+on: [pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 1
+      matrix:
+        python-version: [3.7]
+    steps:
+
+      - uses: actions/checkout@v1
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v1
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Update DIRECTORY.md
+        run: |
+          scripts/build_directory_md.py 2>&1 | tee DIRECTORY.md
+          git config --global user.name 'directory_writer'
+          git config --global user.email 'mrvnmchm@users.noreply.github.com'
+          git remote set-url origin https://x-access-token:${{ secrets.gh_token }}@github.com/$GITHUB_REPOSITORY
+          git checkout $GITHUB_HEAD_REF
+          if git diff-files --quiet; then echo 0; else git commit -am "fixup: DIRECTORY.md" && git push; fi