ci: add reusable merger workflow (#7)

.github/workflows/merger.yml

@@ -0,0 +1,36 @@
+name: Pull-request Merger
+
+on:
+  workflow_call:
+  issue_comment:
+    types: [created, edited]
+
+jobs:
+  merge:
+    if: |
+      (github.event.issue.pull_request) &&
+      (github.event.comment.author_association == 'OWNER') &&
+      (github.event.comment.body == '/merge')
+    runs-on: ubuntu-20.04
+    timeout-minutes: 1
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - name: Merge
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUM: ${{ github.event.issue.number }}
+        run: |
+          PR_JSON=$(gh pr view "${PR_NUM}" --json "title,body,labels" --repo "${GITHUB_REPOSITORY}")
+          PR_TITLE=$(echo "${PR_JSON}" | jq -r '.title')
+          PR_BODY=$(echo "${PR_JSON}" | jq -r '.body')
+          PR_LABELS=$(echo "${PR_JSON}" | jq -r '.labels[].name' | sed "s/^/- /g")
+          PR_MERGE_TITLE="${PR_TITLE} (#${PR_NUM})"
+          gh pr merge "${PR_NUM}" --squash \
+            --subject "${PR_MERGE_TITLE}" \
+            --repo "${GITHUB_REPOSITORY}" \
+            --body "${PR_BODY}
+
+          Labels:
+          ${PR_LABELS}"

README.md

@@ -273,3 +273,19 @@ jobs:
   hadolint:
     uses: peaceiris/workflows/.github/workflows/hadolint.yml@v0.14.0
 ```
+
+
+
+## Reusable pull-request merger workflow
+
+```yaml
+name: pull-request
+
+on:
+  issue_comment:
+    types: [created, edited]
+
+jobs:
+  merger:
+    uses: peaceiris/workflows/.github/workflows/merger.yml@v0.16.0
+```