chore(ci): verify the PR title as part of linting (#18163)

This verifies the PR title as part of the lint step.

1 files changed, 47 insertions, 0 deletions

diff --git a/tools/verify_pr_title.js b/tools/verify_pr_title.js
new file mode 100644
index 000000000..be877bbfd
--- /dev/null
+++ b/tools/verify_pr_title.js
@@ -0,0 +1,47 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+const prTitle = Deno.args[0];
+
+if (prTitle == null) {
+  Deno.exit(0); // not a PR
+}
+
+console.log("PR title:", prTitle);
+
+// This is a release PR, so it's valid.
+if (/^[^\s]+\.[^\s]+\.[^\s]+$/.test(prTitle)) {
+  console.log("Valid.");
+  Deno.exit(0);
+}
+
+const validPrefixes = [
+  "chore",
+  "fix",
+  "feat",
+  "perf",
+  "ci",
+  "cleanup",
+  "docs",
+  "bench",
+  "build",
+  "refactor",
+  "test",
+  // allow Revert PRs because it allows us to remove the landed
+  // commit from the generated changelog
+  "Revert ",
+];
+
+if (validPrefixes.some((prefix) => prTitle.startsWith(prefix))) {
+  console.log("Valid.");
+} else {
+  console.error(
+    "The PR title must start with one of the following prefixes:\n",
+  );
+  for (const prefix of validPrefixes) {
+    console.error(`  - ${prefix}`);
+  }
+  console.error(
+    "\nPlease fix the PR title according to https://www.conventionalcommits.org " +
+      "then push an empty commit to reset the CI.",
+  );
+  Deno.exit(1);
+}