Add Automerge workflow (#605)

* Add Automerge workflow

The automerge workflow will check for complete and approved pull requests and will merge them automatically.

Sources:
- For the python script to execute the merge: https://raw.githubusercontent.com/dapr/dapr/master/.github/scripts/automerge.py (only changed the label from "automerge" to "auto-merge")
- https://raw.githubusercontent.com/dapr/dapr/master/.github/workflows/dapr-bot-schedule.yml (only copied the automerge part, not the prune_stale part as that was not part of the issue.

Resolves https://github.com/dapr/java-sdk/issues/603

* Update automerge-bot.yml

* Update automerge-bot.yml

Co-authored-by: Artur Souza <artursouza.ms@outlook.com>

.github/scripts/automerge.py

@@ -0,0 +1,60 @@
+# ------------------------------------------------------------
+# Copyright (c) Microsoft Corporation and Dapr Contributors.
+# Licensed under the MIT License.
+# ------------------------------------------------------------
+
+# This script automerges PRs
+
+import os
+
+from github import Github
+
+
+g = Github(os.getenv("GITHUB_TOKEN"))
+repo = g.get_repo(os.getenv("GITHUB_REPOSITORY"))
+maintainers = [m.strip() for m in os.getenv("MAINTAINERS").split(',')]
+
+def fetch_pulls(mergeable_state):
+    return [pr for pr in repo.get_pulls(state='open', sort='created') \
+        if pr.mergeable_state == mergeable_state and 'auto-merge' in [l.name for l in pr.labels]]
+
+def is_approved(pr):
+    approvers = [r.user.login for r in pr.get_reviews() if r.state == 'APPROVED' and r.user.login in maintainers]
+    return len([a for a in approvers if repo.get_collaborator_permission(a) in ['admin', 'write']]) > 0
+
+# First, find a PR that can be merged
+pulls = fetch_pulls('clean')
+print(f"Detected {len(pulls)} open pull requests in {repo.name} to be automerged.")
+merged = False
+for pr in pulls:
+    if is_approved(pr):
+        # Merge only one PR per run.
+        print(f"Merging PR {pr.html_url}")
+        try:
+            pr.merge(merge_method='squash')
+            merged = True
+            break
+        except:
+            print(f"Failed to merge PR {pr.html_url}")
+
+if len(pulls) > 0 and not merged:
+    print("No PR was automerged.")
+
+# Now, update all PRs that are behind.
+pulls = fetch_pulls('behind')
+print(f"Detected {len(pulls)} open pull requests in {repo.name} to be updated.")
+for pr in pulls:
+    if is_approved(pr):
+        # Update all PRs since there is no guarantee they will all pass.
+        print(f"Updating PR {pr.html_url}")
+        try:
+            pr.update_branch()
+        except:
+            print(f"Failed to update PR {pr.html_url}")
+
+pulls = fetch_pulls('dirty')
+print(f"Detected {len(pulls)} open pull requests in {repo.name} to be automerged but are in dirty state.")
+for pr in pulls:
+    print(f"PR is in dirty state: {pr.html_url}")
+
+print("Done.")

.github/workflows/automerge-bot.yml

@@ -0,0 +1,26 @@
+# ------------------------------------------------------------
+# Copyright (c) Microsoft Corporation and Dapr Contributors.
+# Licensed under the MIT License.
+# ------------------------------------------------------------
+
+name: dapr-java-sdk-automerge-bot
+
+on:
+  schedule:
+    - cron: '*/30 * * * *'
+  workflow_dispatch:
+jobs:
+  automerge:
+    if: github.repository_owner == 'dapr'
+    name: Automerge and update PRs.
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+      - name: Install dependencies
+        run: pip install PyGithub
+      - name: Automerge and update
+        env:
+          MAINTAINERS: artursouza,mukundansundar
+          GITHUB_TOKEN: ${{ secrets.DAPR_BOT_TOKEN }}
+        run: python ./.github/scripts/automerge.py