Check that all new files are snake cased

We removed the snake case check during precommit because it was
interfering with us getting features merged when dealing with legacy
files, but we do want to verify that any new files added have snake
cased names.

Fixes #5781

tasks/collect_files_to_commit.js

@@ -0,0 +1,15 @@
+import filesToCommit from './utils/files_to_commit';
+import { resolve } from 'path';
+
+const root = resolve(__dirname, '..');
+
+export default function registerCollectFilesToCommit(grunt) {
+  grunt.registerTask('collectFilesToCommit', function () {
+    filesToCommit(root)
+    .then(files => {
+      grunt.log.ok(`${files.length} files with changes to commit`);
+      grunt.config.set('filesToCommit', files);
+    })
+    .nodeify(this.async());
+  });
+};