.github/workflows/request-reviews.yml: Add workflow

Adds a new GitHub workflow to automatically add reviewers to pull
requests when they are opened, reopened, synchronized, and if a draft
pull request is marked as ready for review. The workflow will not
run on draft pull requests.

The workflow is meant to be simple to understand and modify, relying
on existing logic in GetMaintainer.py to determine the relevant
reviewers and using simple Python GitHub REST API wrappers with the
default GitHub token for authentication.

Future changes may optimize the workflow.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>

.github/workflows/request-reviews.yml

@@ -0,0 +1,73 @@
+
+# This workflow automatically adds the appropriate reviewers to a pull request.
+#
+# The workflow directly reuses logic in the BaseTools/Scripts/GetMaintainer.py script
+# to determine the appropriate reviewers, so it matches what a user would see running
+# the script locally.
+#
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+
+name: Add Pull Request Reviewers
+
+on:
+  pull_request:
+    branches:
+      - master
+    types: [opened, ready_for_review, reopened, synchronize]
+
+env:
+  GET_MAINTAINER_REL_PATH: "BaseTools/Scripts/GetMaintainer.py"
+
+jobs:
+  auto-request-review:
+    name: Add Pull Request Reviewers
+    # Do not run on draft PRs and only run on PRs in the tianocore organization
+    if: ${{ github.event.pull_request.draft == false && github.repository_owner == 'tianocore' }}
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+      issues: write
+      pull-requests: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+
+      - name: Install PIP Modules
+        run: pip install edk2-pytool-library edk2-pytool-extensions requests
+
+      - name: Add Reviewers to Pull Request
+        shell: python
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          ORG_NAME: ${{ github.repository_owner }}
+          PR_NUMBER: ${{ github.event.number}}
+          REPO_NAME: ${{ github.event.pull_request.base.repo.name }}
+          TARGET_BRANCH: ${{ github.event.pull_request.base.ref }}
+          WORKSPACE_PATH: ${{ github.workspace }}
+        run: |
+            import os
+            import sys
+            sys.path.append(os.path.join(os.environ['WORKSPACE_PATH'], ".github"))
+            from scripts import GitHub
+
+            WORKSPACE_PATH = os.environ['WORKSPACE_PATH']
+            GET_MAINTAINER_LOCAL_PATH = os.path.join(WORKSPACE_PATH, os.environ['GET_MAINTAINER_REL_PATH'])
+
+            reviewers = GitHub.get_reviewers_for_current_branch(WORKSPACE_PATH, GET_MAINTAINER_LOCAL_PATH, f"origin/{os.environ['TARGET_BRANCH']}")
+            if not reviewers:
+                print("::notice title=No Reviewers Found!::No reviewers found for this PR.")
+                sys.exit(1)
+
+            print(f"::notice title=Reviewer List::Reviewers found for PR {os.environ['PR_NUMBER']}:\n{', '.join(reviewers)}")
+
+            GitHub.add_reviewers_to_pr(os.environ['GH_TOKEN'], os.environ['ORG_NAME'], os.environ['REPO_NAME'], os.environ['PR_NUMBER'], reviewers)