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.

tasks/check_added_filenames.js

@@ -0,0 +1,18 @@
+import { isAdded, getFilename } from './utils/files_to_commit';
+
+export default function registerCheckAddedFilenames(grunt) {
+  grunt.registerTask('checkAddedFilenames', function () {
+    grunt.task.requires('collectFilesToCommit');
+
+    const invalid = grunt.config
+    .get('filesToCommit')
+    .filter(isAdded)
+    .map(getFilename)
+    .filter(name => name.match(/[A-Z \-]/))
+    .reduce((all, name) => `${all}  ${name}\n`, '');
+
+    if (invalid) {
+      grunt.fail.fatal(`Filenames must use snake_case.\n${invalid}`);
+    }
+  });
+}

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());
+  });
+};

tasks/precommit.js

@@ -1,6 +1,8 @@
 export default function (grunt) {
   grunt.registerTask('precommit', [
+    'collectFilesToCommit',
     'collectStagedFiles',
+    'checkAddedFilenames',
     'lintStagedFiles'
   ]);
 };

tasks/utils/files_to_commit.js

@@ -0,0 +1,32 @@
+import SimpleGit from 'simple-git';
+import { promisify } from 'bluebird';
+
+export default function filesToCommit(path) {
+  const simpleGit = new SimpleGit(path);
+  const gitDiff = promisify(simpleGit.diff, simpleGit);
+
+  return gitDiff(['--name-status', '--cached'])
+  .then(output => {
+    return output
+    .split('\n')
+    .map(line => line.trim().split('\t'))
+    .filter(parts => parts.length === 2)
+    .map(parts => {
+      const status = parts.shift();
+      const name = parts.join('\t').trim();
+      return { status, name };
+    });
+  });
+};
+
+export function getFilename(file) {
+  return file.name;
+}
+
+export function isAdded(file) {
+  return file.status === 'A';
+};
+
+export function isDeleted(file) {
+  return file.status === 'D';
+}