Add comment for merge block workflow

.github/workflows/template_merge_block.yml

@@ -7,18 +7,48 @@ on:
         required: false
         type: string
         default: do not merge
+      comment:
+        required: false
+        type: boolean
+        default: true
 
 jobs:
   do-not-merge:
-
     name: Check
     runs-on: ubuntu-22.04
 
-    # contains(search, item) is not case-sensitive
-    # Therefore 'Do Not Merge' and 'DO NOT MERGE' will also match
-    # see https://docs.github.com/en/actions/learn-github-actions/expressions#contains
     steps:
-      - name: fail if label exists
+      - name: Find Comment
+        if: ${{ inputs.comment }} && contains(github.event.pull_request.labels.*.name, inputs.label)
+        uses: peter-evans/find-comment@v3.1.0
+        id: comment
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          body-includes: The merge is blocked. Remove the label '${{ inputs.label }}' to proceed.
+
+      - name: Comment on PR
+        if: ${{ inputs.comment }} && contains(github.event.pull_request.labels.*.name, inputs.label) && steps.comment.outputs.comment-id == ''
+        uses: peter-evans/create-or-update-comment@v4.0.0
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            ⚠️ **The merge is blocked.**
+
+            Remove the label '${{ inputs.label }}' to proceed.
+
+      - name: Delete Comment
+        if: ${{ inputs.comment }} && !contains(github.event.pull_request.labels.*.name, inputs.label) && steps.comment.outputs.comment-id != ''
+        uses: actions/github-script@v7.0.1
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            github.rest.issues.deleteComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: ${{ steps.comment.outputs.comment-id }}
+            })
+
+      - name: Fail if label exists to block merge
         if: contains(github.event.pull_request.labels.*.name, inputs.label)
         run: |
           echo "This PR has the label '${{ inputs.label }}'."

README.md

@@ -249,7 +249,10 @@ jobs:
     with:
       # optional: name of the label if the PR should not be merged, default: do not merge
       label: merge block
+      # optional: comment when the PR is blocked, default: true
+      comment: true
 ```
+
 </details>
 
 ### Release Drafter