warn about month old stale PRs (#24615)

closes #20945

Author: eleanorjboyd

.github/workflows/stale-prs.yml

@@ -0,0 +1,51 @@
+name: Warn about month-old PRs
+
+on:
+  schedule:
+    - cron: '0 0 */2 * *' # Runs every other day at midnight
+
+jobs:
+  stale-prs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Warn about stale PRs
+        uses: actions/github-script@v4
+        with:
+          script: |
+            const { Octokit } = require("@octokit/rest");
+            const octokit = new Octokit({ auth: process.env.GITHUB_TOKEN });
+
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+            const staleTime = new Date();
+            staleTime.setMonth(staleTime.getMonth() - 1);
+
+            const prs = await octokit.pulls.list({
+              owner,
+              repo,
+              state: 'open'
+            });
+
+            for (const pr of prs.data) {
+              const comments = await octokit.issues.listComments({
+                owner,
+                repo,
+                issue_number: pr.number
+              });
+
+              const lastComment = comments.data.length > 0 ? new Date(comments.data[comments.data.length - 1].created_at) : new Date(pr.created_at);
+
+              if (lastComment < staleTime) {
+                await octokit.issues.createComment({
+                  owner,
+                  repo,
+                  issue_number: pr.number,
+                  body: 'This PR has been stale for over a month. Please update or close it.'
+                });
+              }
+            }
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}