Consolidate git file logic in lintStagedFiles task

We limit the amount of moving parts when it comes to parsing our staged
files in git by reusing the files_to_commit utility rather than the
now-defunct collectStagedFiles task.

Fixes #5781

tasks/collect_staged_filenames.js

@@ -1,28 +0,0 @@
-import { resolve } from 'path';
-import SimpleGit from 'simple-git';
-import { promisify } from 'bluebird';
-
-const root = resolve(__dirname, '..');
-const simpleGit = new SimpleGit(root);
-const diff = promisify(simpleGit.diff, simpleGit);
-
-export default function (grunt) {
-  grunt.registerTask('collectStagedFiles', function () {
-    diff(['--name-status', '--cached'])
-    .then(output => {
-      const files = output
-      .split('\n')
-      .map(line => line.trim().split('\t'))
-      .map(parts => {
-        const status = parts.shift();
-        if (status === 'D' || status === 'U') return;
-        return parts.join('\t').trim();
-      })
-      .filter(Boolean);
-
-      grunt.log.ok(files.length + ' staged files');
-      grunt.config.set('stagedFiles', files);
-    })
-    .nodeify(this.async());
-  });
-};

tasks/lint_staged_files.js

@@ -1,17 +1,20 @@
 import { resolve } from 'path';
+import { isStaged, getFilename } from './utils/files_to_commit';
 
 const root = resolve(__dirname, '..');
 
 export default function (grunt) {
   grunt.registerTask('lintStagedFiles', function () {
-    grunt.task.requires('collectStagedFiles');
+    grunt.task.requires('collectFilesToCommit');
 
     // match these patterns
     var patterns = grunt.config.get('eslint.source.files.src');
     if (!patterns) grunt.fail.warn('eslint file pattern is not defined');
 
     const files = grunt.config
-    .get('stagedFiles')
+    .get('filesToCommit')
+    .filter(isStaged)
+    .map(getFilename)
     .map(file => resolve(root, file))
     .filter(file => grunt.file.isMatch(patterns, file));
 

tasks/precommit.js

@@ -1,7 +1,6 @@
 export default function (grunt) {
   grunt.registerTask('precommit', [
     'collectFilesToCommit',
-    'collectStagedFiles',
     'checkAddedFilenames',
     'lintStagedFiles'
   ]);

tasks/utils/files_to_commit.js

@@ -1,5 +1,6 @@
 import SimpleGit from 'simple-git';
 import { promisify } from 'bluebird';
+import { includes } from 'lodash';
 
 export default function filesToCommit(path) {
   const simpleGit = new SimpleGit(path);
@@ -30,3 +31,11 @@ export function isAdded(file) {
 export function isDeleted(file) {
   return file.status === 'D';
 }
+
+export function isUnmerged(file) {
+  return file.status === 'U';
+}
+
+export function isStaged(file) {
+  return !isDeleted(file) && !isUnmerged(file);
+}