feat: Add workflow to mirror issue labels to pull requests

Author: frasermolyneux

.github/workflows/mirror-issue-labels.yml

@@ -0,0 +1,87 @@
+name: Mirror Issue Labels to PR
+
+on:
+  pull_request:
+    types: [opened, reopened, ready_for_review]
+
+permissions: {}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  mirror:
+    name: Mirror linked issue labels to PR
+    if: >-
+      contains(github.event.pull_request.labels.*.name, 'coding-agent') ||
+      github.event.pull_request.user.login == 'Copilot' ||
+      github.actor == 'copilot-swe-agent[bot]'
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      issues: read
+    steps:
+      - name: Copy labels from linked issue(s)
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const body = context.payload.pull_request.body || '';
+
+            // Strip HTML comments and fenced code blocks before matching, so
+            // example "Closes #N" lines in template guidance don't trigger.
+            const stripped = body
+              .replace(/<!--[\s\S]*?-->/g, '')
+              .replace(/```[\s\S]*?```/g, '');
+
+            // Match "Closes #N", "Fixes #N", "Resolves #N" (case-insensitive,
+            // with optional ing/d/s suffixes). Only same-repo references are mirrored.
+            const pattern = /\b(?:close[sd]?|fix(?:e[sd])?|resolve[sd]?)\s+#(\d+)\b/gi;
+            const issueNumbers = new Set();
+            let m;
+            while ((m = pattern.exec(stripped)) !== null) {
+              issueNumbers.add(parseInt(m[1], 10));
+            }
+
+            if (issueNumbers.size === 0) {
+              core.info('No "Closes #N" references found in PR body; nothing to mirror.');
+              return;
+            }
+
+            const prNumber = context.payload.pull_request.number;
+            const existingLabels = new Set(
+              (context.payload.pull_request.labels || []).map(l => l.name)
+            );
+
+            const toAdd = new Set();
+            for (const num of issueNumbers) {
+              try {
+                const { data: issue } = await github.rest.issues.get({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: num,
+                });
+                for (const label of issue.labels || []) {
+                  const name = typeof label === 'string' ? label : label.name;
+                  if (!name) continue;
+                  if (existingLabels.has(name)) continue;
+                  toAdd.add(name);
+                }
+              } catch (err) {
+                core.warning(`Failed to fetch issue #${num}: ${err.message}`);
+              }
+            }
+
+            if (toAdd.size === 0) {
+              core.info('Linked issue(s) had no new labels to mirror.');
+              return;
+            }
+
+            const labels = Array.from(toAdd);
+            await github.rest.issues.addLabels({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: prNumber,
+              labels,
+            });
+            core.info(`Mirrored ${labels.length} label(s) to PR: ${labels.join(', ')}`);