ci: add pr comment workflow with artifacts

Add pr comment workflow with artifacts.

Signed-off-by: Melg Eight <public.melg8@gmail.com>

.github/workflows/pr_comment.yml

@@ -0,0 +1,72 @@
+# SPDX-FileCopyrightText: © 2022 Melg Eight <public.melg8@gmail.com>
+#
+# SPDX-License-Identifier: MIT
+
+---
+name: Comment on pull request
+# yamllint disable-line rule:truthy
+on:
+  workflow_run:
+    workflows: ["Checks"]
+    types: [completed]
+jobs:
+  pr_comment:
+    if: github.event.workflow_run.event == 'pull_request' &&
+      github.event.workflow_run.conclusion == 'success'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v5
+        with:
+          script: |
+            async function upsertComment(owner,
+                                         repo, issue_number, purpose, body) {
+              const {data: comments} = await github.rest.issues.listComments(
+                {owner, repo, issue_number});
+
+              const marker = `<!-- bot: ${purpose} -->`;
+              body = marker + "\n" + body;
+
+              const existing = comments.filter((c) => c.body.includes(marker));
+              if (existing.length > 0) {
+                const last = existing[existing.length - 1];
+                core.info(`Updating comment ${last.id}`);
+                await github.rest.issues.updateComment({
+                  owner, repo,
+                  body,
+                  comment_id: last.id,
+                });
+              } else {
+                core.info(`Creating a comment in issue / PR #${issue_number}`);
+                await github.rest.issues.createComment(
+                      {issue_number, body, owner, repo});
+              }
+            }
+
+            const {owner, repo} = context.repo;
+            const run_id = ${{github.event.workflow_run.id}};
+
+            const pull_requests = ${{ toJSON(
+                                  github.event.workflow_run.pull_requests) }};
+            if (!pull_requests.length) {
+              return core.error(
+                     "This workflow doesn't match any pull requests!");
+            }
+
+            const artifacts = await github.paginate(
+              github.rest.actions.listWorkflowRunArtifacts,
+              {owner, repo, run_id});
+            if (!artifacts.length) {
+              return core.error(`No artifacts found`);
+            }
+            let body = `Download the artifacts for this pull request:\n`;
+            for (const art of artifacts) {
+              body += `\n* [${art.name}.zip](
+              https://nightly.link/${owner}/${repo}/actions/artifacts/${art.id}.zip)`;
+            }
+
+            core.info("Review thread message body:", body);
+
+            for (const pr of pull_requests) {
+              await upsertComment(owner, repo, pr.number,
+                "nightly-link", body);
+            }