Trigger the build workflow on PRs with a label

.github/scripts/cleanup-pr.cjs

@@ -0,0 +1,44 @@
+// Copyright 2025 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only
+// Please see LICENSE in the repository root for full details.
+
+// @ts-check
+
+/** @param {import('@actions/github-script').AsyncFunctionArguments} AsyncFunctionArguments */
+module.exports = async ({ github, context }) => {
+  const metadataJson = process.env.BUILD_IMAGE_MANIFEST;
+  if (!metadataJson) throw new Error("BUILD_IMAGE_MANIFEST is not defined");
+  /** @type {Record<string, {tags: string[]}>} */
+  const metadata = JSON.parse(metadataJson);
+
+  await github.rest.issues.removeLabel({
+    issue_number: context.issue.number,
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    name: "Z-Build-Workflow",
+  });
+
+  const tagListMarkdown = metadata.regular.tags
+    .map((tag) => `- \`${tag}\``)
+    .join("\n");
+
+  // Get the workflow run
+  const run = await github.rest.actions.getWorkflowRun({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    run_id: context.runId,
+  });
+
+  await github.rest.issues.createComment({
+    issue_number: context.issue.number,
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    body: `A build for this PR at commit <kbd>${context.sha}</kbd> has been created through the <kbd>Z-Build-Workflow</kbd> label by <kbd>${context.actor}</kbd>.
+
+Docker image is available at:
+${tagListMarkdown}
+
+Pre-built binaries are available through the [workflow run artifacts](${run.data.html_url}).`,
+  });
+};