refactor: sort branches

This makes the onboarding PR easier to understand by putting pin first, then minor, then major.

lib/workers/repository/updates/branchify.js

@@ -50,6 +50,10 @@ function branchifyUpgrades(config) {
   const branchList = config.repoIsOnboarded
     ? branches.map(upgrade => upgrade.branchName)
     : config.branchList;
+  const sortOrder = ['digest', 'pin', 'minor', 'major', 'lockFileMaintenance'];
+  branches.sort(
+    (a, b) => sortOrder.indexOf(a.type) - sortOrder.indexOf(b.type)
+  );
   return {
     ...config,
     errors: config.errors.concat(errors),