Support newer versions of hermes (#155)

The npm hermes-engine appears to be behind the actual hermes releases (as of writing, stuck on v11 where v13 is available). Switch the hermes downloader to look up the version via the github releases API, and fix up the URL predictor to support a change in the download URL format.

engines/hermes/get-latest-version.js

@@ -15,20 +15,14 @@
 
 const get = require('../../shared/get.js');
 
-const getLatestVersion = (os) => {
-	const url = 'https://registry.npmjs.org/hermes-engine';
-	return new Promise(async (resolve, reject) => {
-		try {
-			const response = await get(url, {
-				json: true,
-			});
-			const data = response.body;
-			const version = data['dist-tags'].latest;
-			resolve(version);
-		} catch (error) {
-			reject(error);
-		}
+const getLatestVersion = async (os) => {
+	const url = 'https://api.github.com/repos/facebook/hermes/releases/latest';
+	const response = await get(url, {
+		json: true,
 	});
+	const data = response.body;
+	const version = data.tag_name.replace(/^v/, ''); // Strip prefix.
+	return version;
 };
 
 module.exports = getLatestVersion;

engines/hermes/predict-url.js

@@ -35,7 +35,10 @@ const predictFileName = (os) => {
 
 const predictUrl = (version, os) => {
 	const fileName = predictFileName(os);
-	const url = `https://github.com/facebook/hermes/releases/download/v${version}/hermes-cli-${fileName}-v${version}.tar.gz`;
+	const majorVersion = parseInt(version.split('.')[0]);
+	const minorVersion = parseInt(version.split('.')[1]);
+	const suffix = majorVersion > 0 || minorVersion >= 13 ? '' : `-v${version}`;
+	const url = `https://github.com/facebook/hermes/releases/download/v${version}/hermes-cli-${fileName}${suffix}.tar.gz`;
 	return url;
 };